(() => {
  "use strict";

  // Storage is namespaced per account so two people sharing a browser (or one
  // person logging out and back in as someone else) never see each other's
  // cached events/profile. currentUser is set by the auth gate before the app
  // boots, so these are only ever called once a user is known.
  let currentUser = null;
  // A guest is someone here on a share link (see "guest links" in the README):
  // the same data as the owner, minus everything under Settings that is the
  // owner's to decide. currentUser.id is the owner's either way, which is what
  // keeps the cache keys below pointing at the right data.
  const isGuest      = () => currentUser?.role === "guest";
  const guestLabel   = () => (isGuest() ? (currentUser.label || "") : "");
  const guestShareId = () => (isGuest() ? (currentUser.shareId || "") : "");

  // Who may change an already-logged event. The owner may change anything on
  // their own account; a guest may only touch what they logged themselves, so a
  // sitter can fix up their own entries and cannot rewrite or delete a single
  // one of the owner's. Keyed on the link id rather than its label, because two
  // links can easily carry the same label ("Sitter"). The server enforces the
  // same rule in Store.sync — this is what keeps the UI honest about it.
  const canEditEvent = (ev) => !isGuest() || ev.loggedByShare === guestShareId();
  const eventsKey    = () => `puppy-tracker:${currentUser.id}:events:v1`;
  const configKey    = () => `puppy-tracker:${currentUser.id}:config:v1`;
  const exercisesKey = () => `puppy-tracker:${currentUser.id}:exercises:v1`;
  const SYNC_URL = "api/events/sync";
  const SYNC_DEBOUNCE_MS = 1200;
  const SYNC_POLL_MS = 60_000;

  const EVENT_LABELS = {
    "sleep-start": "Sleep start",
    "sleep-end":   "Sleep end",
    "walk-start":  "Walk start",
    "walk-end":    "Walk end",
    "eat":         "Ate",
    "pee":         "Pee",
    "poo":         "Poo",
    "weight":      "Weight",
    "training":    "Training",
    "note":        "Note",
  };

  // ---------- photos: IndexedDB store ----------
  // Schema: object store `photos` keyed by `id`, value `{id, blob, uploaded}`.
  // - Photos taken locally are written with uploaded:false and queued for upload.
  // - Photos fetched from server are cached with uploaded:true (server is source-of-truth).
  const PHOTO_DB = "puppy-tracker";
  const PHOTO_STORE = "photos";
  let photoDB = null;

  function openPhotoDB() {
    if (photoDB) return Promise.resolve(photoDB);
    return new Promise((resolve, reject) => {
      const req = indexedDB.open(PHOTO_DB, 1);
      req.onupgradeneeded = (e) => {
        const db = e.target.result;
        if (!db.objectStoreNames.contains(PHOTO_STORE)) {
          db.createObjectStore(PHOTO_STORE, { keyPath: "id" });
        }
      };
      req.onsuccess = () => { photoDB = req.result; resolve(photoDB); };
      req.onerror   = () => reject(req.error);
    });
  }

  async function putPhoto(id, blob, uploaded) {
    const db = await openPhotoDB();
    return new Promise((resolve, reject) => {
      const tx = db.transaction(PHOTO_STORE, "readwrite");
      tx.objectStore(PHOTO_STORE).put({ id, blob, uploaded });
      tx.oncomplete = () => resolve();
      tx.onerror    = () => reject(tx.error);
    });
  }

  async function getPhoto(id) {
    const db = await openPhotoDB();
    return new Promise((resolve, reject) => {
      const tx  = db.transaction(PHOTO_STORE, "readonly");
      const req = tx.objectStore(PHOTO_STORE).get(id);
      req.onsuccess = () => resolve(req.result || null);
      req.onerror   = () => reject(req.error);
    });
  }

  async function getAllPhotos() {
    const db = await openPhotoDB();
    return new Promise((resolve, reject) => {
      const tx  = db.transaction(PHOTO_STORE, "readonly");
      const req = tx.objectStore(PHOTO_STORE).getAll();
      req.onsuccess = () => resolve(req.result || []);
      req.onerror   = () => reject(req.error);
    });
  }

  async function deletePhoto(id) {
    const db = await openPhotoDB();
    return new Promise((resolve, reject) => {
      const tx = db.transaction(PHOTO_STORE, "readwrite");
      tx.objectStore(PHOTO_STORE).delete(id);
      tx.oncomplete = () => resolve();
      tx.onerror    = () => reject(tx.error);
    });
  }

  // Resize an image File to a max dimension and return a JPEG Blob.
  function resizeImage(file, maxDim = 1600, quality = 0.85) {
    return new Promise((resolve, reject) => {
      const img = new Image();
      const url = URL.createObjectURL(file);
      img.onload = () => {
        URL.revokeObjectURL(url);
        const scale = Math.min(1, maxDim / Math.max(img.naturalWidth, img.naturalHeight));
        const w = Math.max(1, Math.round(img.naturalWidth  * scale));
        const h = Math.max(1, Math.round(img.naturalHeight * scale));
        const canvas = document.createElement("canvas");
        canvas.width = w; canvas.height = h;
        canvas.getContext("2d").drawImage(img, 0, 0, w, h);
        canvas.toBlob(
          (blob) => blob ? resolve(blob) : reject(new Error("toBlob returned null")),
          "image/jpeg",
          quality,
        );
      };
      img.onerror = () => { URL.revokeObjectURL(url); reject(new Error("image load failed")); };
      img.src = url;
    });
  }

  async function uploadPhotoBlob(id, blob) {
    const form = new FormData();
    form.append("id", id);
    form.append("file", blob, `${id}.jpg`);
    const res = await fetch("api/photos", { method: "POST", body: form });
    if (!res.ok) throw new Error(`upload HTTP ${res.status}`);
  }

  async function syncPhotos() {
    if (!navigator.onLine) return;
    const all = await getAllPhotos();
    for (const p of all) {
      if (p.uploaded) continue;
      try {
        await uploadPhotoBlob(p.id, p.blob);
        await putPhoto(p.id, p.blob, true);
      } catch (err) {
        console.warn("photo upload failed", p.id, err);
        // leave queued; next sync will retry
      }
    }
  }

  // Resolve a photoId to a displayable URL. Prefers local cache; falls back
  // to the server URL (the SW will cache it transparently). Returns null if
  // we have nothing and the server doesn't either.
  const photoURLCache = new Map(); // id -> object URL (lifetime = page session)
  async function photoSrc(id) {
    if (!id) return null;
    if (photoURLCache.has(id)) return photoURLCache.get(id);
    const local = await getPhoto(id);
    if (local && local.blob) {
      const url = URL.createObjectURL(local.blob);
      photoURLCache.set(id, url);
      return url;
    }
    // Fall back to server URL — let the browser/SW cache it. Also opportunistically
    // pull it into IndexedDB so cold-offline-loads still see it.
    if (navigator.onLine) {
      try {
        const res = await fetch(`api/photos/${encodeURIComponent(id)}`);
        if (res.ok) {
          const blob = await res.blob();
          await putPhoto(id, blob, true);
          const url = URL.createObjectURL(blob);
          photoURLCache.set(id, url);
          return url;
        }
      } catch (_) { /* fall through */ }
    }
    return null;
  }

  // crypto.randomUUID() is only exposed in secure contexts (HTTPS / localhost),
  // so over plain HTTP on the LAN we need a fallback. crypto.getRandomValues
  // is available everywhere; Math.random is the last resort.
  function uuid() {
    if (typeof crypto !== "undefined" && typeof crypto.randomUUID === "function") {
      return crypto.randomUUID();
    }
    if (typeof crypto !== "undefined" && typeof crypto.getRandomValues === "function") {
      const b = new Uint8Array(16);
      crypto.getRandomValues(b);
      b[6] = (b[6] & 0x0f) | 0x40; // version 4
      b[8] = (b[8] & 0x3f) | 0x80; // variant 10
      const h = [...b].map(x => x.toString(16).padStart(2, "0"));
      return `${h.slice(0,4).join("")}-${h.slice(4,6).join("")}-${h.slice(6,8).join("")}-${h.slice(8,10).join("")}-${h.slice(10,16).join("")}`;
    }
    return `x-${Date.now().toString(16)}-${Math.random().toString(16).slice(2, 10)}`;
  }

  // ---------- storage ----------
  // Internal "raw" storage includes deleted tombstones; UI uses live().
  function loadAll() {
    try {
      const raw = localStorage.getItem(eventsKey());
      if (!raw) return [];
      const parsed = JSON.parse(raw);
      if (!Array.isArray(parsed)) return [];
      // Backfill updatedAt for events written by an older client version.
      return parsed.map(e => ({
        ...e,
        updatedAt: Number.isFinite(e.updatedAt) ? e.updatedAt : (e.at || Date.now()),
      }));
    } catch {
      return [];
    }
  }

  function saveAll(events) {
    localStorage.setItem(eventsKey(), JSON.stringify(events));
  }

  function live() {
    return loadAll().filter(e => !e.deleted);
  }

  // ---------- config (puppy name + birthday) ----------
  // The shared profile lives on the host so every client sees the same values.
  // localStorage is just a cache for instant paint + offline; the server is the
  // source of truth, reconciled by last-write-wins on updatedAt (see syncConfig).
  function loadConfig() {
    try {
      const parsed = JSON.parse(localStorage.getItem(configKey()));
      if (!parsed || typeof parsed !== "object") return { name: "", birthday: "", pedigreeId: "", updatedAt: 0 };
      return {
        name: parsed.name || "",
        birthday: parsed.birthday || "",
        pedigreeId: parsed.pedigreeId || "",
        updatedAt: Number.isFinite(parsed.updatedAt) ? parsed.updatedAt : 0,
      };
    } catch {
      return { name: "", birthday: "", pedigreeId: "", updatedAt: 0 };
    }
  }

  function saveConfig(cfg) {
    localStorage.setItem(configKey(), JSON.stringify(cfg));
  }

  // Reconcile a local and a server profile. Name/birthday/updatedAt are plain
  // last-write-wins by timestamp. The pedigree id is sticky: a non-empty value
  // never loses to an empty one — so it can't be dropped by a clock race between
  // devices — and when both are set the newer profile's id wins with the rest.
  // (The server merge mirrors this, so a set id is only changed, never cleared,
  // by sync.)
  function reconcileConfig(local, server) {
    const base = server.updatedAt >= local.updatedAt ? server : local;
    return {
      name: base.name,
      birthday: base.birthday,
      pedigreeId: (local.pedigreeId && server.pedigreeId)
        ? base.pedigreeId
        : (local.pedigreeId || server.pedigreeId),
      updatedAt: base.updatedAt,
    };
  }
  function sameConfig(a, b) {
    return a.name === b.name && a.birthday === b.birthday
      && a.pedigreeId === b.pedigreeId && a.updatedAt === b.updatedAt;
  }

  // Age in whole days / weeks / calendar months from a "YYYY-MM-DD" birthday,
  // measured at `at` (defaults to now — pass a weigh-in's timestamp for its age
  // at that point). Returns null for a missing/invalid birthday or a date before it.
  function ageParts(birthday, at) {
    if (!birthday) return null;
    const [y, mo, d] = birthday.split("-").map(Number);
    if (!y || !mo || !d) return null;
    const birth = startOfDay(new Date(y, mo - 1, d));
    const ref   = startOfDay(new Date(Number.isFinite(at) ? at : Date.now()));
    if (birth > ref) return null;
    const days  = Math.floor((ref - birth) / 86_400_000);
    const weeks = Math.floor(days / 7);
    let months = (ref.getFullYear() - birth.getFullYear()) * 12 +
                 (ref.getMonth() - birth.getMonth());
    if (ref.getDate() < birth.getDate()) months--;
    if (months < 0) months = 0;
    // Whole weeks left over after the calendar months (so "N months and M weeks").
    const anchor = startOfDay(new Date(birth.getFullYear(),
                                       birth.getMonth() + months, birth.getDate()));
    const remWeeks = Math.floor((ref - anchor) / 86_400_000 / 7);
    return { days, weeks, months, remWeeks };
  }

  // e.g. "16 weeks (3 months and 3 weeks) old". Weeks are the headline unit while
  // the puppy is young; once it's 4+ months the week count is just noise, so we
  // drop it and lead with the months form ("4 months and 1 week old").
  function formatAge(birthday, at) {
    const a = ageParts(birthday, at);
    if (!a) return "";
    const wk = `${a.weeks} week${a.weeks === 1 ? "" : "s"}`;
    if (a.months < 1) return `${wk} old`;
    const mo = `${a.months} month${a.months === 1 ? "" : "s"}`;
    const rw = a.remWeeks > 0
      ? ` and ${a.remWeeks} week${a.remWeeks === 1 ? "" : "s"}` : "";
    const monthPhrase = `${mo}${rw}`;
    if (a.months >= 4) return `${monthPhrase} old`;
    return `${wk} (${monthPhrase}) old`;
  }

  // Compact one-line age for space-tight spots (header): keeps the weeks + months
  // breakdown but abbreviated — "16 wk · 3 mo 3 wk", "5 mo 2 wk", "3 wk".
  function formatAgeShort(birthday, at) {
    const a = ageParts(birthday, at);
    if (!a) return "";
    const wk = `${a.weeks} wk`;
    if (a.months < 1) return wk;
    const mo = `${a.months} mo${a.remWeeks > 0 ? ` ${a.remWeeks} wk` : ""}`;
    if (a.months >= 4) return mo;
    return `${wk} · ${mo}`;
  }

  // Weeks-only age for dense lists (weight rows): "16 wk".
  function formatAgeWeeks(birthday, at) {
    const a = ageParts(birthday, at);
    return a ? `${a.weeks} wk` : "";
  }

  // Rough age-based daily sleep goal (hours), for the trend chart's goal band:
  // 0–8 weeks 20–22h, 8–16 weeks 18–20h, then 16–18h to 6 months and 14–16h to
  // 12 months. No birthday (or an adult dog) → no goal.
  function sleepTargetFor(birthday) {
    const a = ageParts(birthday);
    if (!a) return null;
    if (a.weeks < 8)   return { lo: 20, hi: 22, label: "0–8 weeks" };
    if (a.weeks < 16)  return { lo: 18, hi: 20, label: "8–16 weeks" };
    if (a.months < 6)  return { lo: 16, hi: 18, label: "4–6 months" };
    if (a.months < 12) return { lo: 14, hi: 16, label: "6–12 months" };
    return null;
  }

  function addEvent(type, note, at, { photoId, weight, grams, exerciseId } = {}) {
    const events = loadAll();
    const now = Date.now();
    const ev = {
      id: uuid(),
      type,
      at: Number.isFinite(at) ? at : now,
      note: note || "",
      photoId: photoId || "",
      weight: Number.isFinite(weight) ? weight : undefined,
      grams: Number.isFinite(grams) ? grams : undefined,
      exerciseId: exerciseId || "",
      updatedAt: now,
      // Only set when logging through a guest link, and only so the badge and
      // the "you may edit this" check work before the first sync: the server
      // stamps both authoritatively on insert, and mergeSynced keeps our copy
      // when updatedAt ties, so without a local stamp neither would settle
      // until some later edit. Both sides compute the same values, so the two
      // never disagree.
      loggedBy: guestLabel(),
      loggedByShare: guestShareId(),
    };
    events.push(ev);
    saveAll(events);
    scheduleSync();
    render();
    return ev;
  }

  function updateEvent(id, patch) {
    const events = loadAll().map(e =>
      e.id === id ? { ...e, ...patch, updatedAt: Date.now() } : e
    );
    saveAll(events);
    scheduleSync();
    render();
  }

  function deleteEvent(id) {
    // Soft-delete so the deletion can propagate via sync.
    const events = loadAll().map(e =>
      e.id === id ? { ...e, deleted: true, updatedAt: Date.now() } : e
    );
    saveAll(events);
    scheduleSync();
    render();
  }

  // ---------- exercises (training definitions) ----------
  // User-defined training exercises ("Sit", "Leash walking", …), each with
  // optional instruction text. They sync like events: UUID ids, last-write-wins
  // on updatedAt, tombstoned deletes — but as their own collection, since they
  // are definitions rather than things that happened at a point in time.
  function loadExercises() {
    try {
      const parsed = JSON.parse(localStorage.getItem(exercisesKey()));
      return Array.isArray(parsed) ? parsed : [];
    } catch {
      return [];
    }
  }

  function saveExercises(list) {
    localStorage.setItem(exercisesKey(), JSON.stringify(list));
  }

  function liveExercises() {
    return loadExercises()
      .filter(x => !x.deleted)
      .sort((a, b) => (a.name || "").localeCompare(b.name || ""));
  }

  function addExercise(name, note) {
    const list = loadExercises();
    list.push({ id: uuid(), name, note: note || "", updatedAt: Date.now() });
    saveExercises(list);
    scheduleSync();
    render();
  }

  function updateExercise(id, patch) {
    saveExercises(loadExercises().map(x =>
      x.id === id ? { ...x, ...patch, updatedAt: Date.now() } : x
    ));
    scheduleSync();
    render();
  }

  function deleteExercise(id) {
    // Tombstone, like events. Logged training sessions keep referencing the id;
    // name lookups still resolve through the tombstone (see exerciseNames).
    saveExercises(loadExercises().map(x =>
      x.id === id ? { ...x, deleted: true, updatedAt: Date.now() } : x
    ));
    scheduleSync();
    render();
  }

  // id -> name across *all* exercises, tombstones included, so history rows for
  // a deleted exercise still show its name instead of a generic "Training".
  function exerciseNames() {
    return new Map(loadExercises().map(x => [x.id, x.name]));
  }

  // ---------- helpers ----------
  function ymd(date) {
    const y = date.getFullYear();
    const m = String(date.getMonth() + 1).padStart(2, "0");
    const d = String(date.getDate()).padStart(2, "0");
    return `${y}-${m}-${d}`;
  }

  function startOfDay(date) {
    const d = new Date(date);
    d.setHours(0, 0, 0, 0);
    return d;
  }

  function endOfDay(date) {
    const d = new Date(date);
    d.setHours(23, 59, 59, 999);
    return d;
  }

  // ---------- days that don't count ----------
  // Not every logged day is equally trustworthy: a day someone else had the
  // puppy produces a thin record that reads exactly like a real one, and then
  // drags down every average. Marking a day "not counted" keeps its data
  // untouched and fully visible on the day itself, but takes it out of
  // everything that aggregates across days.
  //
  // A mark is an ordinary event, the way a training session is: it rides the
  // existing sync with per-item last-write-wins and tombstones (un-marking is
  // just a delete), so it needs no table, endpoint or contract of its own.
  // Timestamped at noon so the day it lands on is unambiguous under the same
  // ymd() bucketing every other event uses.
  const EXCLUDED_TYPE = "day-excluded";

  // Behaviour is what a sparse logger distorts. A weigh-in and a note are
  // records of fact, so they keep counting even on a day that doesn't.
  const ALWAYS_COUNTS = new Set(["weight", "note"]);

  // Refreshed once per render() and read like chartDays() — the chart drawers
  // need to know which day slots to hatch, not just which events to drop.
  let excludedSet = new Set();

  function excludedDays(events) {
    return new Set(
      events.filter(e => e.type === EXCLUDED_TYPE).map(e => ymd(new Date(e.at)))
    );
  }

  const isExcluded = (date) => excludedSet.has(ymd(date));

  // The event list the cross-day panels see.
  function countedEvents(events) {
    if (excludedSet.size === 0) return events;
    return events.filter(e =>
      ALWAYS_COUNTS.has(e.type) || !excludedSet.has(ymd(new Date(e.at))));
  }

  // True if any part of [from, to] falls on an excluded day. Used to throw away
  // measurements that reach across one — see gapsBetween.
  function spansExcluded(from, to) {
    if (excludedSet.size === 0) return false;
    for (let d = startOfDay(new Date(from)); d.getTime() <= to; d.setDate(d.getDate() + 1)) {
      if (isExcluded(d)) return true;
    }
    return false;
  }

  function formatTime(ts) {
    return new Date(ts).toLocaleTimeString([], { hour: "2-digit", minute: "2-digit", hour12: false });
  }

  const pad2 = n => String(n).padStart(2, "0");
  function toDateInput(ts) {
    const d = new Date(ts);
    return `${d.getFullYear()}-${pad2(d.getMonth() + 1)}-${pad2(d.getDate())}`;
  }
  function toTimeInput(ts) {
    const d = new Date(ts);
    return `${pad2(d.getHours())}:${pad2(d.getMinutes())}`;
  }
  function fromDateTimeInputs(dateStr, timeStr) {
    if (!dateStr || !timeStr) return NaN;
    const [y, mo, d] = dateStr.split("-").map(Number);
    const [h, mi]    = timeStr.split(":").map(Number);
    const t = new Date(y, mo - 1, d, h, mi).getTime();
    return Number.isFinite(t) ? t : NaN;
  }

  function formatDuration(ms) {
    if (ms <= 0) return "0m";
    const totalMin = Math.round(ms / 60000);
    const h = Math.floor(totalMin / 60);
    const m = totalMin % 60;
    if (h === 0) return `${m}m`;
    return `${h}h ${m}m`;
  }

  // kg with up to 2 decimals, trailing zeros stripped (5.20 -> "5.2 kg").
  function formatWeight(kg) {
    return `${Math.round(kg * 100) / 100} kg`;
  }

  function formatRelative(ts) {
    if (!ts) return "—";
    const diff = Date.now() - ts;
    if (diff < 60_000) return "just now";
    if (diff < 3_600_000) return `${Math.floor(diff / 60_000)}m ago`;
    if (diff < 86_400_000) {
      const h = Math.floor(diff / 3_600_000);
      const m = Math.floor((diff % 3_600_000) / 60_000);
      return m ? `${h}h ${m}m ago` : `${h}h ago`;
    }
    const d = Math.floor(diff / 86_400_000);
    return `${d}d ago`;
  }

  function eventsForDay(events, day) {
    const from = startOfDay(day).getTime();
    const to = endOfDay(day).getTime();
    return events
      .filter(e => e.at >= from && e.at <= to)
      .sort((a, b) => a.at - b.at);
  }

  // Calculate sleep time within a given day. Sleep intervals are derived from
  // consecutive sleep-start → sleep-end pairs across the whole event log, and
  // clipped to the day window. Unmatched sleep-start = ongoing sleep (clipped to now).
  function sleepMsInRange(events, fromTs, toTs) {
    const sorted = [...events].sort((a, b) => a.at - b.at);
    const intervals = [];
    let openStart = null;
    for (const e of sorted) {
      if (e.type === "sleep-start" && openStart === null) {
        openStart = e.at;
      } else if (e.type === "sleep-end" && openStart !== null) {
        intervals.push([openStart, e.at]);
        openStart = null;
      }
    }
    if (openStart !== null) intervals.push([openStart, Date.now()]);

    let total = 0;
    for (const [start, end] of intervals) {
      const s = Math.max(start, fromTs);
      const ePt = Math.min(end, toTs);
      if (ePt > s) total += ePt - s;
    }
    return total;
  }

  // The newest of a set of boundary event types. For two events sharing the
  // same `at` (common once "now" events are minute-floored), the one logged
  // later (higher updatedAt) wins, so the tie resolves the same way everywhere
  // it's read.
  function latestOfTypes(events, types) {
    let latest = null;
    for (const e of events) {
      if (!types.includes(e.type)) continue;
      if (!latest ||
          e.at > latest.at ||
          (e.at === latest.at && (e.updatedAt || 0) > (latest.updatedAt || 0))) {
        latest = e;
      }
    }
    return latest;
  }

  // Current state derived from the *latest* sleep event. The single source of
  // truth for both the big clock and the "Currently" row.
  function currentSleepState(events) {
    const latest = latestOfTypes(events, ["sleep-start", "sleep-end"]);
    if (!latest) return { state: null, since: 0 };
    return {
      state: latest.type === "sleep-start" ? "asleep" : "awake",
      since: latest.at,
    };
  }

  // Same idea for walks: the newest walk boundary says whether one is running.
  function currentWalkState(events) {
    const latest = latestOfTypes(events, ["walk-start", "walk-end"]);
    if (!latest) return { walking: false, since: 0 };
    return { walking: latest.type === "walk-start", since: latest.at };
  }

  function formatCounter(ms) {
    if (ms < 0) ms = 0;
    const totalSec = Math.floor(ms / 1000);
    const h  = Math.floor(totalSec / 3600);
    const m  = Math.floor((totalSec % 3600) / 60);
    const s  = totalSec % 60;
    const pp = n => String(n).padStart(2, "0");
    return h > 0 ? `${h}:${pp(m)}:${pp(s)}` : `${m}:${pp(s)}`;
  }

  function lastEventOfType(events, type) {
    let latest = null;
    for (const e of events) {
      if (e.type === type && (!latest || e.at > latest.at)) latest = e;
    }
    return latest;
  }

  // Pair up boundary events into windows: every `openType` runs until the next
  // `closeType`. A trailing unmatched `openType` is an ongoing/open window,
  // measured to now. Only the two given types are considered, so the same scan
  // produces sleep windows, their inverse (wake windows) and walks.
  function pairWindows(events, openType, closeType) {
    const sorted = events
      .filter(e => e.type === openType || e.type === closeType)
      .sort((a, b) => a.at - b.at);
    const out = [];
    let open = null;
    for (const e of sorted) {
      if (e.type === openType) {
        open = e.at;
      } else if (open !== null) {
        out.push({ start: open, end: e.at, ongoing: false });
        open = null;
      }
    }
    if (open !== null) out.push({ start: open, end: Date.now(), ongoing: true });
    return out;
  }

  // Wake windows: time between a sleep-end and the next sleep-start. The final
  // sleep-end with no following sleep-start = ongoing/open wake window.
  function wakeWindows(events) {
    return pairWindows(events, "sleep-end", "sleep-start");
  }

  // Sleep windows: each sleep-start → next sleep-end pair. An unmatched
  // sleep-start = ongoing/open sleep window.
  function sleepWindows(events) {
    return pairWindows(events, "sleep-start", "sleep-end");
  }

  // Walks: each walk-start → next walk-end pair, ongoing while out.
  function walkWindows(events) {
    return pairWindows(events, "walk-start", "walk-end");
  }

  // Time spent walking inside [fromTs, toTs], clipping windows that straddle
  // the edges — the same treatment sleepMsInRange gives sleep.
  function walkMsInRange(events, fromTs, toTs) {
    let total = 0;
    for (const w of walkWindows(events)) {
      const s = Math.max(w.start, fromTs);
      const e = Math.min(w.end, toTs);
      if (e > s) total += e - s;
    }
    return total;
  }

  function sleepWindowsForDay(events, day) {
    const dayStart = startOfDay(day).getTime();
    const dayEnd   = endOfDay(day).getTime();
    const today    = ymd(new Date()) === ymd(day);
    // Keep the overlap filter so windows show on every day they touch, but
    // display the *actual* start/end — a sleep from 23:00 yesterday to 07:00
    // today should show as "23:00 – 07:00 (8h)", not clipped at midnight.
    return sleepWindows(events)
      .filter(w => w.start <= dayEnd && w.end >= dayStart)
      .map(w => ({ start: w.start, end: w.end, ongoing: w.ongoing && today }));
  }

  // Wake windows that overlap the given day, clipped to that day for display.
  // Only mark a window as "ongoing" if the selected day is today.
  function wakeWindowsForDay(events, day) {
    const dayStart = startOfDay(day).getTime();
    const dayEnd   = endOfDay(day).getTime();
    const today    = ymd(new Date()) === ymd(day);
    // Same untrimmed-times policy as sleep windows: show the real start/end
    // even if part of the window falls outside the selected day.
    return wakeWindows(events)
      .filter(w => w.start <= dayEnd && w.end >= dayStart)
      .map(w => ({ start: w.start, end: w.end, ongoing: w.ongoing && today }));
  }

  // Walks that overlap the given day. Same untrimmed-times policy as the sleep
  // and wake lists: a walk that crosses midnight shows its real start and end.
  function walkWindowsForDay(events, day) {
    const dayStart = startOfDay(day).getTime();
    const dayEnd   = endOfDay(day).getTime();
    const today    = ymd(new Date()) === ymd(day);
    return walkWindows(events)
      .filter(w => w.start <= dayEnd && w.end >= dayStart)
      .map(w => ({ start: w.start, end: w.end, ongoing: w.ongoing && today }));
  }

  // ---------- rendering ----------
  const dayPicker  = document.getElementById("day-picker");
  const eventList  = document.getElementById("event-list");
  const emptyState = document.getElementById("empty-state");
  const statusEl   = document.getElementById("online-status");

  function selectedDay() {
    const v = dayPicker.value;
    if (v) {
      const [y, m, d] = v.split("-").map(Number);
      return new Date(y, m - 1, d);
    }
    return new Date();
  }

  function renderStats(events) {
    const day = selectedDay();
    const from = startOfDay(day).getTime();
    const today = ymd(new Date()) === ymd(day);
    const to = today ? Date.now() : endOfDay(day).getTime();

    const sleepMs = sleepMsInRange(events, from, to);
    const awakeMs = Math.max(0, (to - from) - sleepMs);

    const dayEvents = eventsForDay(events, day);
    const count = (t) => dayEvents.filter(e => e.type === t).length;

    document.getElementById("stat-sleep").textContent = formatDuration(sleepMs);
    document.getElementById("stat-awake").textContent = formatDuration(awakeMs);
    document.getElementById("stat-meals").textContent = count("eat");
    const gramsTotal = dayEvents
      .filter(e => e.type === "eat" && Number.isFinite(e.grams))
      .reduce((s, e) => s + e.grams, 0);
    const gramsEl = document.getElementById("stat-meals-grams");
    gramsEl.textContent = gramsTotal > 0 ? `${Math.round(gramsTotal)} g` : "";
    gramsEl.hidden = !(gramsTotal > 0);
    // Walk time is a duration, not a count, so the tile leads with it and puts
    // "N walks" underneath — the day's exercise at a glance.
    document.getElementById("stat-walk").textContent = formatDuration(walkMsInRange(events, from, to));
    const walks = walkWindowsForDay(events, day).length;
    const walkCountEl = document.getElementById("stat-walk-count");
    walkCountEl.textContent = `${walks} walk${walks === 1 ? "" : "s"}`;
    walkCountEl.hidden = walks === 0;
    document.getElementById("stat-pees").textContent  = count("pee");
    document.getElementById("stat-poos").textContent  = count("poo");
    document.getElementById("stat-training").textContent = count("training");
  }

  // Gaps (ms) between consecutive events of `type` logged within the last
  // `days` days, sorted ascending. These intervals are what tell you how
  // often the puppy needs to go out. Defaults to the picked chart window, so
  // the 7d/14d/30d buttons widen the timing panel along with the charts —
  // read at call time, not at definition, so a change takes on the next render.
  function gapsBetween(events, type, days = chartDays()) {
    const cutoff = startOfDay(new Date());
    cutoff.setDate(cutoff.getDate() - (days - 1));
    const from = cutoff.getTime();
    const times = events
      .filter(e => e.type === type && e.at >= from)
      .map(e => e.at)
      .sort((a, b) => a - b);
    const gaps = [];
    for (let i = 1; i < times.length; i++) {
      // A gap reaching across a day that doesn't count is not a real gap: the
      // events in between were dropped, so Tuesday's last pee now sits next to
      // Thursday's first and the subtraction invents thirty hours. Discarding
      // the pair is the only honest answer — measuring it would blow out the
      // "longest" figure far worse than the sparse day this feature exists to
      // take out of the numbers.
      if (spansExcluded(times[i - 1], times[i])) continue;
      gaps.push(times[i] - times[i - 1]);
    }
    return gaps.sort((a, b) => a - b);
  }

  // Median is used for the "typical" gap because it ignores the single long
  // overnight gap each day, so it reflects real daytime frequency.
  function median(sorted) {
    if (sorted.length === 0) return null;
    const mid = Math.floor(sorted.length / 2);
    return sorted.length % 2 ? sorted[mid] : (sorted[mid - 1] + sorted[mid]) / 2;
  }

  // Each type gets a small range chart: a band spanning the shortest to the
  // typical gap over the window, and a marker for how long it has been since
  // the last one. The marker is free to sit outside the band — just went (left
  // of shortest) or overdue (right of typical) — which is the reading that
  // decides whether to take the puppy out now.
  const TIMING_ROWS = [
    { type: "pee", label: "Pees",  noun: "pee",  cls: "tm-pee" },
    { type: "poo", label: "Poos",  noun: "poo",  cls: "tm-poo" },
    { type: "eat", label: "Meals", noun: "meal", cls: "tm-eat" },
  ];

  function renderTiming(events) {
    for (const row of TIMING_ROWS) {
      const svg  = document.getElementById(`timing-chart-${row.type}`);
      const note = document.getElementById(`timing-note-${row.type}`);
      if (!svg || !note) continue;
      const gaps = gapsBetween(events, row.type);
      const last = lastEventOfType(events, row.type);
      drawTimingChart(svg, note, row, gaps, last ? Math.max(0, Date.now() - last.at) : null);
    }
  }

  function drawTimingChart(svg, note, row, gaps, since) {
    const typical  = median(gaps);
    const shortest = gaps[0] ?? null;
    const longest  = gaps[gaps.length - 1] ?? null;

    // Fewer than two events in the window means there is no gap to draw, so the
    // row falls back to a sentence rather than an axis with nothing on it.
    if (typical == null) {
      svg.innerHTML = "";
      svg.style.display = "none";
      note.hidden = false;
      note.textContent = since == null
        ? `No ${row.noun}s logged in the last ${chartDays()} days.`
        : `One ${row.noun} logged, ${formatDuration(since)} ago — log another to see the typical gap.`;
      return;
    }
    svg.style.display = "";
    note.hidden = true;

    const W = 320, H = 50, ML = 26, MR = 26;
    const innerW = W - ML - MR;
    const trackY = 20, trackH = 8;

    // Gaps are heavily skewed: one long overnight gap a night sits alongside
    // daytime gaps a tenth its length, and on a plain linear axis it squashes
    // the everyday range — the part you actually read — into the first tenth of
    // the track. So the axis is stretched, the way the sleep trend's is above
    // 10h: the typical gap is pinned to the middle, the shortest-to-typical
    // stretch gets the left half and typical-to-longest the right. Reading it
    // is then the same in every row — left of centre is sooner than usual,
    // right of centre is longer — however extreme that row's tail happens to be.
    const over = since != null && since > longest;
    const cur  = since == null ? null : Math.min(since, longest);

    const lo = Math.min(shortest, cur ?? shortest);
    const halfW = innerW / 2;
    const mid = ML + halfW;
    const xOf = (v) => {
      if (v <= typical) return typical > lo ? ML + ((v - lo) / (typical - lo)) * halfW : mid;
      return longest > typical ? mid + ((v - typical) / (longest - typical)) * halfW : mid;
    };

    // Two bands: the full spread of gaps in the window, and inside it the solid
    // stretch from the shortest to the typical one. Where the solid ends is the
    // median, so the boundary itself marks "typical" without another mark.
    const xShort = xOf(shortest), xTypical = xOf(typical), xLong = xOf(longest);
    const dot = (a, b) => b - a < trackH + 2;
    const bandRect = (cls, a, b, extra) => {
      const w = Math.max(trackH + 2, b - a);
      const x = dot(a, b) ? (a + b) / 2 - w / 2 : a;
      return `<rect class="${cls}" x="${x.toFixed(1)}" y="${trackY}" width="${w.toFixed(1)}" ` +
        `height="${trackH}" rx="${trackH / 2}">${extra}</rect>`;
    };

    const parts = [
      `<rect class="tm-track" x="${ML}" y="${trackY}" width="${innerW}" height="${trackH}" rx="${trackH / 2}"/>`,
      bandRect(`tm-range ${row.cls}`, xShort, xLong,
        `<title>${escapeText(`${formatDuration(shortest)}–${formatDuration(longest)} between ${row.noun}s over the last ${chartDays()} days`)}</title>`),
      bandRect(`tm-band ${row.cls}`, xShort, xTypical,
        `<title>${escapeText(`Typically ${formatDuration(typical)} between ${row.noun}s`)}</title>`),
    ];

    // Ticks tie the summary line under the track to the three points it names.
    const tickY = trackY + trackH + 5;
    const tick = (x) =>
      `<line class="tm-tick" x1="${x.toFixed(1)}" y1="${tickY}" x2="${x.toFixed(1)}" y2="${tickY + 4}"/>`;
    const labelY = tickY + 13;
    // Whitespace inside a <tspan> is at the mercy of XML normalisation (an
    // &#160; does not survive every renderer either), so the gap between a word
    // and its value is an explicit dx offset.
    const word = (w, dx) => `<tspan class="tm-word"${dx ? ` dx="${dx}"` : ""}>${w}</tspan>`;
    const val = (w, ms, dx) => `${word(w, dx)}<tspan dx="3">${escapeText(formatDuration(ms))}</tspan>`;

    // Three values will not fit as labels hung off their own points, so they
    // read as one centred line and the ticks carry the positions.
    if (longest - shortest < 60_000) {
      parts.push(tick(xTypical));
      parts.push(`<text x="${(W / 2).toFixed(1)}" y="${labelY}" text-anchor="middle">${val("typical", typical)}</text>`);
    } else {
      parts.push(tick(xShort), tick(xTypical), tick(xLong));
      parts.push(
        `<text x="${(W / 2).toFixed(1)}" y="${labelY}" text-anchor="middle">` +
        `${val("shortest", shortest)}${word("·", 4)}${val("typical", typical, 4)}` +
        `${word("·", 4)}${val("longest", longest, 4)}</text>`
      );
    }

    if (cur != null) {
      const x  = over ? W - MR : xOf(cur);
      const y1 = trackY - 5, y2 = trackY + trackH + 5;
      // Surface-coloured underlay: a ring that keeps the marker legible
      // wherever on the band it lands.
      parts.push(`<line class="tm-now-ring" x1="${x.toFixed(1)}" y1="${y1}" x2="${x.toFixed(1)}" y2="${y2}"/>`);
      parts.push(
        `<line class="tm-now" x1="${x.toFixed(1)}" y1="${y1}" x2="${x.toFixed(1)}" y2="${y2}">` +
        `<title>${escapeText(`${formatDuration(since)} since the last ${row.noun}`)}</title></line>`
      );
      if (over) {
        parts.push(
          `<path class="tm-over" d="M${(x + 5).toFixed(1)} ${trackY} ` +
          `L${(x + 12).toFixed(1)} ${trackY + trackH / 2} L${(x + 5).toFixed(1)} ${trackY + trackH} Z"/>`
        );
      }
      const anchor = x < ML + 55 ? "start" : (x > W - MR - 55 ? "end" : "middle");
      parts.push(
        `<text class="tm-now-label" x="${x.toFixed(1)}" y="11" text-anchor="${anchor}">` +
        `${escapeText(`${formatDuration(since)} ago`)}</text>`
      );
    }

    svg.innerHTML = parts.join("");
    svg.setAttribute("aria-label",
      `${row.label}: typically ${formatDuration(typical)} between ${row.noun}s, ` +
      `shortest ${formatDuration(shortest)}, longest ${formatDuration(longest)}` +
      (since == null ? "" : `, ${formatDuration(since)} since the last one`) + ".");
  }

  function renderLasts(events) {
    const setLast = (id, type) => {
      const ev = lastEventOfType(events, type);
      document.getElementById(id).textContent = ev
        ? `${formatTime(ev.at)} (${formatRelative(ev.at)})`
        : "—";
    };
    setLast("last-pee", "pee");
    setLast("last-poo", "poo");
    setLast("last-eat", "eat");

    const sortedSleep = events
      .filter(e => e.type === "sleep-start" || e.type === "sleep-end")
      .sort((a, b) => b.at - a.at);
    const lastSleep = sortedSleep[0];
    document.getElementById("last-sleep").textContent = lastSleep
      ? `${EVENT_LABELS[lastSleep.type]} at ${formatTime(lastSleep.at)} (${formatRelative(lastSleep.at)})`
      : "—";

    const lastWalk = latestOfTypes(events, ["walk-start", "walk-end"]);
    document.getElementById("last-walk").textContent = lastWalk
      ? `${EVENT_LABELS[lastWalk.type]} at ${formatTime(lastWalk.at)} (${formatRelative(lastWalk.at)})`
      : "—";
  }

  // Tracks the latest sleep transition so the 1-second tick can update the
  // counter without re-deriving from the event log.
  let bigClockState = null; // "asleep" | "awake" | null
  let bigClockSince = 0;

  // The counter renders twice: the big card at the top of the page and the
  // compact pill in the frozen day bar. The pill only *shows* once the big
  // card is scrolled out of sight (see updateBarClockMode); while the card is
  // visible the pill is invisible but keeps its slot so the bar never shifts.
  function updateBarClockMode() {
    const pill = document.getElementById("bar-clock");
    if (!bigClockState || pill.hidden) return;
    const card = document.getElementById("big-clock");
    const bar  = document.querySelector(".day-bar");
    // The card lives on the Today tab, so on any other tab it isn't on screen
    // at all and the pill is the only timer there is. Asked explicitly rather
    // than left to the rect: a hidden element measures as zeroes, which would
    // give the right answer here by coincidence rather than by rule.
    const cardOnThisTab = card.offsetParent !== null;
    const cardVisible = cardOnThisTab &&
      card.getBoundingClientRect().bottom > bar.getBoundingClientRect().bottom;
    pill.classList.toggle("standby", cardVisible);
  }

  function renderBigClock(events) {
    const card  = document.getElementById("big-clock");
    const label = document.getElementById("bc-label");
    const time  = document.getElementById("bc-time");
    const since = document.getElementById("bc-since");
    const pill  = document.getElementById("bar-clock");
    const icon  = document.getElementById("bar-clock-icon");
    const ptime = document.getElementById("bar-clock-time");
    const { state, since: ts } = currentSleepState(events);
    bigClockState = state;
    bigClockSince = ts;
    if (!state) {
      card.hidden = true;
      pill.hidden = true;
      return;
    }
    card.hidden = false;
    pill.hidden = false;
    card.classList.toggle("asleep", state === "asleep");
    card.classList.toggle("awake",  state === "awake");
    pill.classList.toggle("asleep", state === "asleep");
    pill.classList.toggle("awake",  state === "awake");
    label.textContent = state === "asleep" ? "Asleep for" : "Awake for";
    const counter = formatCounter(Date.now() - ts);
    time.textContent  = counter;
    ptime.textContent = counter;
    since.textContent = `since ${formatTime(ts)}`;
    icon.textContent = state === "asleep" ? "😴" : "☀️";
    const flip = state === "asleep" ? "Sleep end" : "Sleep start";
    pill.title = `${state === "asleep" ? "Asleep" : "Awake"} since ${formatTime(ts)} — tap to log ${flip.toLowerCase()}`;
    pill.setAttribute("aria-label", `${state === "asleep" ? "Asleep" : "Awake"} since ${formatTime(ts)}. Log ${flip.toLowerCase()}.`);
    updateBarClockMode();
  }

  function tickBigClock() {
    if (!bigClockState) return;
    const counter = formatCounter(Date.now() - bigClockSince);
    const time  = document.getElementById("bc-time");
    const ptime = document.getElementById("bar-clock-time");
    if (time)  time.textContent  = counter;
    if (ptime) ptime.textContent = counter;
  }

  function renderWindowList(listId, emptyId, windows, ongoingLabel, extraClass) {
    const list  = document.getElementById(listId);
    const empty = document.getElementById(emptyId);
    list.innerHTML = "";
    if (windows.length === 0) {
      empty.hidden = false;
      return;
    }
    empty.hidden = true;
    for (const w of windows) {
      // A window may bring its own class and label, which is how the merged
      // sleep/wake list states every row's kind. A single-kind list passes one
      // class and one label for the lot and only tags the open row, where
      // "Walking" is news rather than a repetition of the heading.
      const cls = w.cls || extraClass;
      const tag = w.tag || (w.ongoing ? ongoingLabel : "");
      const li = document.createElement("li");
      li.className = `ww ${cls}` + (w.ongoing ? " ongoing" : "");
      const range = document.createElement("span");
      range.className = "ww-range";
      range.textContent = w.ongoing
        ? `from ${formatTime(w.start)}`
        : `${formatTime(w.start)} – ${formatTime(w.end)}`;
      const dur = document.createElement("span");
      dur.className = "ww-dur";
      dur.textContent = formatDuration(w.end - w.start);
      li.appendChild(range);
      li.appendChild(dur);
      if (tag) {
        const tagEl = document.createElement("span");
        tagEl.className = "ww-tag";
        tagEl.textContent = tag;
        li.appendChild(tagEl);
      }
      list.appendChild(li);
    }
  }

  // Sleep and wake windows are the same boundaries read two ways — a wake
  // window is precisely the gap between two sleeps — so they alternate by
  // construction and sorting the two sets by start time interleaves them back
  // into the day's actual rhythm, "45 minutes asleep after two and a half hours
  // up" in one glance instead of a comparison between two lists.
  //
  // Newest first, like the history and notes logs: the row still running is
  // then the first one you see, and today's list grows downward from where you
  // are rather than pushing the current state further away with every window.
  function sleepWakeWindowsForDay(events, day) {
    return [
      ...sleepWindowsForDay(events, day).map(w => ({ ...w, cls: "sleep-ww", tag: "Asleep" })),
      ...wakeWindowsForDay(events, day).map(w => ({ ...w, cls: "wake-ww", tag: "Awake" })),
    ].sort((a, b) => b.start - a.start);
  }

  function renderSleepWake(events) {
    renderWindowList(
      "sleep-wake-list", "sleep-wake-empty",
      sleepWakeWindowsForDay(events, selectedDay()),
      "", "",
    );
  }

  function renderWalks(events) {
    const day = selectedDay();
    const windows = walkWindowsForDay(events, day);
    // Newest first, like every other list in the app, so a walk in progress is
    // the first row. Reversed here rather than in walkWindowsForDay, whose
    // other callers — the day's total and the history rails — read the windows
    // as a set and would only be made harder to follow by a display order.
    renderWindowList(
      "walk-list", "walk-empty",
      [...windows].reverse(),
      "Walking", "walk-ww",
    );

    // Total next to the heading, so a collapsed panel still answers "how much
    // did we walk?".
    const from = startOfDay(day).getTime();
    const to = ymd(new Date()) === ymd(day) ? Date.now() : endOfDay(day).getTime();
    const totalMs = walkMsInRange(events, from, to);
    document.getElementById("walk-total").textContent =
      windows.length ? `(${formatDuration(totalMs)})` : "";
  }

  // Which history rows sit inside a sleep or walk window, so the list can run a
  // dotted rail down the margin from a start row to its end row. It reuses the
  // windows the Sleep and Walks panels already draw, so a pair that crosses
  // midnight is treated the same way here as there. Rows logged in between — a
  // pee taken on a walk — fall inside the bracket, which is the point: the rail
  // says "this happened during that", not merely "these two are a pair".
  //
  // Roles are named for where the row sits in the *rendered* list, which runs
  // newest-first, so a span's chronologically last event is its top row. A span
  // whose boundary isn't itself a row here (an ongoing walk, or one that runs
  // past midnight) leaves that end open, and the rail runs off the list edge
  // rather than stopping at a row that didn't end anything.
  function historyRails(events, dayEvents, day) {
    const rails = new Map();
    const spans = [
      ...sleepWindowsForDay(events, day).map(w => ({ ...w, kind: "sleep" })),
      ...walkWindowsForDay(events, day).map(w => ({ ...w, kind: "walk" })),
    ];
    for (const span of spans) {
      const inside = dayEvents.filter(e => e.at >= span.start && e.at <= span.end);
      if (inside.length < 2) continue; // nothing to tie to
      const closedTop    = inside[inside.length - 1].at >= span.end;
      const closedBottom = inside[0].at <= span.start;
      inside.forEach((e, i) => {
        const role =
          i === inside.length - 1 ? (closedTop ? "top" : "mid")
          : i === 0 ? (closedBottom ? "bottom" : "mid")
          : "mid";
        // Sleep is added first, so the (in practice impossible) overlap of a
        // walk and a sleep paints as the walk.
        rails.set(e.id, { kind: span.kind, role });
      });
    }
    return rails;
  }

  function renderHistory(events) {
    const day = selectedDay();
    // The "not counted" mark is bookkeeping about the day, not something that
    // happened to the puppy, so it never appears as a row in the log.
    const chronological = eventsForDay(events, day).filter(e => e.type !== EXCLUDED_TYPE);
    const rails = historyRails(events, chronological, day);
    const dayEvents = [...chronological].reverse();
    const exNames = exerciseNames();
    eventList.innerHTML = "";
    if (dayEvents.length === 0) {
      emptyState.hidden = false;
      return;
    }
    emptyState.hidden = true;
    for (const ev of dayEvents) {
      let label = EVENT_LABELS[ev.type] || ev.type;
      if (ev.type === "training" && exNames.get(ev.exerciseId)) {
        label = `Training · ${exNames.get(ev.exerciseId)}`;
      }
      const li = document.createElement("li");
      li.className = "event";
      li.dataset.type = ev.type;
      li.dataset.id = ev.id;
      const rail = rails.get(ev.id);
      if (rail) li.classList.add("rail", `rail-${rail.kind}`, `rail-${rail.role}`);
      li.innerHTML = `
        <span class="dot"></span>
        <span class="time">${formatTime(ev.at)}</span>
        <span class="label">${escapeText(label)}</span>
        <span class="note"></span>
      `;
      // Logged through a guest link: say whose, so a row you don't remember
      // making has an explanation attached to it.
      if (ev.loggedBy) {
        const by = document.createElement("span");
        by.className = "by";
        by.textContent = ev.loggedBy;
        by.title = `Logged by ${ev.loggedBy} on a guest link`; // the badge is truncated
        li.querySelector(".label").after(by);
      }
      const noteEl = li.querySelector(".note");
      if (ev.type === "weight" && Number.isFinite(ev.weight)) {
        noteEl.textContent = ev.note ? `${formatWeight(ev.weight)} · ${ev.note}` : formatWeight(ev.weight);
      } else if (ev.type === "eat" && Number.isFinite(ev.grams) && ev.grams > 0) {
        const g = `${Math.round(ev.grams)} g`;
        noteEl.textContent = ev.note ? `${g} · ${ev.note}` : g;
      } else {
        noteEl.textContent = ev.note || "";
      }
      li.addEventListener("click", () => openEditDialog(ev));

      for (const pid of photoIdsOf(ev)) {
        const img = document.createElement("img");
        img.className = "thumb";
        img.alt = "photo";
        img.loading = "lazy";
        img.dataset.photoId = pid;
        img.addEventListener("click", (e) => {
          e.stopPropagation(); // don't open the edit dialog
          openLightbox(pid);
        });
        li.appendChild(img);
        photoSrc(pid).then(url => { if (url) img.src = url; });
      }

      eventList.appendChild(li);
    }
  }

  // Cross-day log of free-text notes (vaccinations, vet visits, milestones…),
  // newest first. Unlike History this ignores the day picker so the record is
  // always visible regardless of which day you're viewing.
  function renderNotes(events) {
    const notes = events
      .filter(e => e.type === "note")
      .sort((a, b) => b.at - a.at);
    const list  = document.getElementById("notes-list");
    const empty = document.getElementById("notes-empty");
    list.innerHTML = "";
    if (notes.length === 0) { empty.hidden = false; return; }
    empty.hidden = true;

    const birthday = loadConfig().birthday;
    for (const ev of notes) {
      const li = document.createElement("li");
      li.className = "event";
      li.dataset.type = "note";
      li.dataset.id = ev.id;
      const dateStr = new Date(ev.at).toLocaleDateString(undefined, { year: "numeric", month: "short", day: "numeric" });
      const age = formatAgeWeeks(birthday, ev.at);
      li.innerHTML = `
        <span class="dot"></span>
        <span class="note-date">${escapeText(age ? `${dateStr} · ${age}` : dateStr)}</span>
        <span class="note-text"></span>
      `;
      li.querySelector(".note-text").textContent = ev.note || "";
      li.addEventListener("click", () => openEditDialog(ev));

      for (const pid of photoIdsOf(ev)) {
        const img = document.createElement("img");
        img.className = "thumb";
        img.alt = "photo";
        img.loading = "lazy";
        img.dataset.photoId = pid;
        img.addEventListener("click", (e) => {
          e.stopPropagation();
          openLightbox(pid);
        });
        li.appendChild(img);
        photoSrc(pid).then(url => { if (url) img.src = url; });
      }

      list.appendChild(li);
    }
  }

  // ---------- lightbox ----------
  const lightbox      = document.getElementById("lightbox");
  const lightboxImg   = document.getElementById("lightbox-img");
  const lightboxClose = document.getElementById("lightbox-close");

  async function openLightbox(photoId) {
    const url = await photoSrc(photoId);
    if (!url) { alert("Photo not yet available (still uploading?)."); return; }
    lightboxImg.src = url;
    lightbox.showModal();
  }

  lightboxClose.addEventListener("click", () => lightbox.close());
  // Click on backdrop closes the lightbox too.
  lightbox.addEventListener("click", (e) => {
    if (e.target === lightbox) lightbox.close();
  });

  // ---------- chart window ----------
  // How many days the rolling charts cover. Device-global (like the theme),
  // picked via the 7d/14d/30d buttons in the charts card and applied to every
  // day-window chart: daily bars, sleep timeline, hour heatmap, training grid.
  const CHART_DAYS_KEY = "puppy-tracker:chart-days:v1";
  const CHART_DAY_CHOICES = [7, 14, 30];
  function chartDays() {
    const v = Number(localStorage.getItem(CHART_DAYS_KEY));
    return CHART_DAY_CHOICES.includes(v) ? v : 7;
  }
  function setChartDays(n) {
    try { localStorage.setItem(CHART_DAYS_KEY, String(n)); } catch { /* ignore */ }
    render();
  }

  // Which metrics the daily-counts chart shows. Device-global, toggled via the
  // checkboxes under the chart. At least one is always kept on so the chart is
  // never empty; an invalid/empty stored value falls back to all three.
  const COUNTS_METRICS_KEY = "puppy-tracker:counts-metrics:v1";
  const COUNTS_METRIC_KEYS = ["pees", "poos", "meals"];
  function countsMetrics() {
    let stored;
    try { stored = JSON.parse(localStorage.getItem(COUNTS_METRICS_KEY)); } catch { /* ignore */ }
    const on = Array.isArray(stored)
      ? COUNTS_METRIC_KEYS.filter(k => stored.includes(k))
      : [];
    return on.length ? on : COUNTS_METRIC_KEYS.slice();
  }
  function setCountsMetrics(keys) {
    // Never let the user hide everything — keep at least one metric visible.
    const on = COUNTS_METRIC_KEYS.filter(k => keys.includes(k));
    if (!on.length) { renderChartWindow(); return; } // restore the checkbox we just rejected
    try { localStorage.setItem(COUNTS_METRICS_KEY, JSON.stringify(on)); } catch { /* ignore */ }
    render();
  }

  // Sync every "(last N days)" header and the picker's active button.
  function renderChartWindow() {
    const n = chartDays();
    document.querySelectorAll("[data-chart-days-label]").forEach(el => {
      el.textContent = `(last ${n} days)`;
    });
    document.querySelectorAll(".chart-days-picker button").forEach(b => {
      b.classList.toggle("active", Number(b.dataset.days) === n);
    });
    const on = countsMetrics();
    document.querySelectorAll("#counts-metrics input[data-metric]").forEach(cb => {
      cb.checked = on.includes(cb.dataset.metric);
    });
  }

  // ---------- daily charts ----------
  function weeklyData(events) {
    const today = startOfDay(new Date());
    const now = Date.now();
    const days = [];
    for (let i = chartDays() - 1; i >= 0; i--) {
      const d = new Date(today);
      d.setDate(d.getDate() - i);
      const from = startOfDay(d).getTime();
      const to = (i === 0) ? now : endOfDay(d).getTime();
      // A day marked "not counted" keeps its slot on the axis — dropping it
      // would make consecutive bars stop being consecutive days — but carries
      // no figures. Zeroing them here rather than in each chart means every
      // axis maximum, total and tooltip downstream is already right, and the
      // drawers only have to decide what to paint in the empty slot.
      const excluded = isExcluded(d);
      const sleepMs = excluded ? 0 : sleepMsInRange(events, from, to);
      const dayEvents = excluded ? [] : eventsForDay(events, d);
      days.push({
        date: d,
        ymd: ymd(d),
        excluded,
        sleepHours: sleepMs / 3_600_000,
        pees:  dayEvents.filter(e => e.type === "pee").length,
        poos:  dayEvents.filter(e => e.type === "poo").length,
        meals: dayEvents.filter(e => e.type === "eat").length,
        grams: dayEvents
          .filter(e => e.type === "eat" && Number.isFinite(e.grams))
          .reduce((s, e) => s + e.grams, 0),
        walkMinutes: excluded ? 0 : walkMsInRange(events, from, to) / 60_000,
      });
    }
    return days;
  }

  // A day that doesn't count gets a hatched column where its bar would be, so
  // the gap reads as deliberate rather than as a day the puppy barely did
  // anything. Shared by all four daily bar charts, which differ only in height.
  function excludedSlot(d, x, barW, top, innerH) {
    const title = `${d.date.toLocaleDateString(undefined, { weekday: "long", month: "short", day: "numeric" })} — not counted`;
    return `<rect class="bar bar-excluded" data-day="${d.ymd}" x="${x}" y="${top}" ` +
      `width="${barW}" height="${innerH}" rx="3"><title>${escapeText(title)}</title></rect>`;
  }

  function dayLabel(date, isToday) {
    if (isToday) return "Today";
    return date.toLocaleDateString(undefined, { weekday: "short" });
  }

  // Wider windows can't fit a label under every bar: label today and every
  // 2nd (or 4th) day counting back from it, depending on the window.
  function showDayLabel(i, len) {
    const every = len <= 8 ? 1 : len <= 16 ? 2 : 4;
    return (len - 1 - i) % every === 0;
  }

  // Pick a chart Y maximum and tick count so every tick label is a clean
  // whole number (avoids 0, 0, 1, 1, 2 from rounding fractional steps):
  // 1-unit gridlines up to 10, 2-unit up to 20, 5-unit beyond.
  function niceAxis(rawMax) {
    if (!(rawMax > 0)) return { yMax: 1, steps: 1 };
    if (rawMax <= 10) {
      const m = Math.ceil(rawMax);
      return { yMax: m, steps: m };
    }
    if (rawMax <= 20) {
      const m = Math.ceil(rawMax / 2) * 2;
      return { yMax: m, steps: m / 2 };
    }
    const m = Math.ceil(rawMax / 5) * 5;
    return { yMax: m, steps: m / 5 };
  }

  // Magnitude-agnostic 0-based axis with a "nice" step, so tick labels stay
  // round whatever the daily totals are (tens of grams for a tiny puppy,
  // hundreds+ later; minutes walked likewise). Aims for ~10 segments so small
  // day-to-day differences still show.
  function niceAxisLinear(rawMax) {
    if (!(rawMax > 0)) return { yMax: 100, steps: 4 };
    const rawStep = rawMax / 10;
    const mag  = Math.pow(10, Math.floor(Math.log10(rawStep)));
    const norm = rawStep / mag;
    const step = (norm <= 1 ? 1 : norm <= 2 ? 2 : norm <= 2.5 ? 2.5 : norm <= 5 ? 5 : 10) * mag;
    const yMax = Math.ceil(rawMax / step) * step;
    return { yMax, steps: Math.max(1, Math.round(yMax / step)) };
  }

  // Sleep-specific axis: 1-hour granularity, capped at 24h/day. Shared by the
  // sleep bars and the trend chart; both thin out labels when steps get dense.
  function niceAxisSleepHours(rawMax) {
    if (!(rawMax > 0)) return { yMax: 2, steps: 2 };
    const m = Math.min(24, Math.max(2, Math.ceil(rawMax)));
    return { yMax: m, steps: m };
  }

  function escapeText(s) {
    return String(s).replace(/[&<>"']/g, c => (
      { "&": "&amp;", "<": "&lt;", ">": "&gt;", '"': "&quot;", "'": "&#39;" }[c]
    ));
  }

  function setChartSVG(svg, parts) {
    svg.innerHTML = parts.join("");
    svg.querySelectorAll(".bar[data-day]").forEach(b => {
      b.addEventListener("click", () => {
        dayPicker.value = b.dataset.day;
        render();
      });
    });
  }

  function drawSleepChart(days) {
    const svg = document.getElementById("chart-sleep");
    const W = 320, H = 160;
    const ML = 26, MR = 6, MT = 10, MB = 26;
    const innerW = W - ML - MR;
    const innerH = H - MT - MB;

    const rawMax = Math.max(...days.map(d => d.sleepHours));
    const { yMax, steps: ySteps } = niceAxisSleepHours(rawMax);

    const gap = days.length > 14 ? 2 : 4;
    const barW = (innerW - (days.length - 1) * gap) / days.length;

    // Label every 1h gridline; smaller text once the axis is dense so the
    // labels stay apart (this chart's plot area is shorter than the trend's).
    const yLabelCls = ySteps > 12 ? "y-dense" : "";
    const parts = [];
    for (let i = 0; i <= ySteps; i++) {
      const y = MT + innerH * (1 - i / ySteps);
      const v = Math.round(yMax * i / ySteps * 10) / 10;
      const vText = v % 1 === 0 ? v : v.toFixed(1);
      parts.push(`<line class="grid" x1="${ML}" y1="${y}" x2="${W - MR}" y2="${y}"/>`);
      parts.push(`<text class="${yLabelCls}" x="${ML - 4}" y="${y + 3}" text-anchor="end">${vText}h</text>`);
    }

    const selYmd = ymd(selectedDay());
    days.forEach((d, i) => {
      const isToday = i === days.length - 1;
      const isSel = d.ymd === selYmd;
      const x = ML + i * (barW + gap);
      const h = (d.sleepHours / yMax) * innerH;
      const y = MT + innerH - h;
      const title = `${d.date.toLocaleDateString(undefined, { weekday: "long", month: "short", day: "numeric" })} — ${d.sleepHours.toFixed(1)}h`;
      if (isSel) {
        parts.push(`<rect class="day-highlight" x="${(x - gap / 2).toFixed(1)}" y="${MT}" width="${(barW + gap).toFixed(1)}" height="${innerH}" rx="3"/>`);
      }
      if (d.excluded) {
        parts.push(excludedSlot(d, x, barW, MT, innerH));
      } else {
        parts.push(
          `<rect class="bar bar-sleep ${isToday ? "" : "bar-faded"}" data-day="${d.ymd}" ` +
          `x="${x}" y="${y}" width="${barW}" height="${Math.max(0, h)}" rx="3">` +
          `<title>${escapeText(title)}</title></rect>`
        );
      }
      // The selected day always gets a label (accent-colored), even on wide
      // windows that would otherwise skip it.
      if (showDayLabel(i, days.length) || isSel) {
        parts.push(
          `<text class="${isSel ? "day-label-sel" : ""}" x="${x + barW / 2}" y="${H - MB + 14}" text-anchor="middle">` +
          `${escapeText(dayLabel(d.date, isToday))}</text>`
        );
      }
    });

    setChartSVG(svg, parts);
  }

  function drawCountsChart(days) {
    const svg = document.getElementById("chart-counts");
    const W = 320, H = 180;
    const ML = 22, MR = 6, MT = 10, MB = 26;
    const innerW = W - ML - MR;
    const innerH = H - MT - MB;

    const series = [
      { key: "pees",  label: "Pees",  cls: "bar-pee" },
      { key: "poos",  label: "Poos",  cls: "bar-poo" },
      { key: "meals", label: "Meals", cls: "bar-eat" },
    ].filter(s => countsMetrics().includes(s.key));

    const rawMax = Math.max(0, ...days.flatMap(d => series.map(s => d[s.key])));
    const { yMax, steps: ySteps } = niceAxis(rawMax);

    const groupGap = days.length > 14 ? 2 : 4;
    const innerBarGap = days.length > 14 ? 0.5 : 1.5;
    const groupW = (innerW - (days.length - 1) * groupGap) / days.length;
    const barW = (groupW - (series.length - 1) * innerBarGap) / series.length;

    const parts = [];
    for (let i = 0; i <= ySteps; i++) {
      const y = MT + innerH * (1 - i / ySteps);
      const v = Math.round(yMax * i / ySteps);
      parts.push(`<line class="grid" x1="${ML}" y1="${y}" x2="${W - MR}" y2="${y}"/>`);
      parts.push(`<text x="${ML - 4}" y="${y + 3}" text-anchor="end">${v}</text>`);
    }

    const selYmd = ymd(selectedDay());
    days.forEach((d, i) => {
      const isToday = i === days.length - 1;
      const isSel = d.ymd === selYmd;
      const groupX = ML + i * (groupW + groupGap);

      if (isSel) {
        parts.push(`<rect class="day-highlight" x="${(groupX - groupGap / 2).toFixed(1)}" y="${MT}" width="${(groupW + groupGap).toFixed(1)}" height="${innerH}" rx="3"/>`);
      }
      if (d.excluded) {
        // One hatch across the whole group rather than three empty bars.
        parts.push(excludedSlot(d, groupX, groupW, MT, innerH));
      } else {
        series.forEach((s, j) => {
          const val = d[s.key];
          const x = groupX + j * (barW + innerBarGap);
          const h = (val / yMax) * innerH;
          const y = MT + innerH - h;
          const title = `${d.date.toLocaleDateString(undefined, { weekday: "long", month: "short", day: "numeric" })} — ${s.label}: ${val}`;
          parts.push(
            `<rect class="bar ${s.cls} ${isToday ? "" : "bar-faded"}" data-day="${d.ymd}" ` +
            `x="${x}" y="${y}" width="${barW}" height="${Math.max(0, h)}" rx="2">` +
            `<title>${escapeText(title)}</title></rect>`
          );
        });
      }

      if (showDayLabel(i, days.length) || isSel) {
        parts.push(
          `<text class="${isSel ? "day-label-sel" : ""}" x="${groupX + groupW / 2}" y="${H - MB + 14}" text-anchor="middle">` +
          `${escapeText(dayLabel(d.date, isToday))}</text>`
        );
      }
    });

    setChartSVG(svg, parts);
  }

  // Grams of food per day. Hidden entirely until any meal in the window has an
  // amount logged, so the weekly card doesn't grow an empty chart.
  function drawGramsChart(days) {
    const wrap = document.getElementById("grams-chart-wrap");
    const svg  = document.getElementById("chart-grams");
    if (!days.some(d => d.grams > 0)) { wrap.hidden = true; return; }
    wrap.hidden = false;

    const W = 320, H = 160;
    const ML = 34, MR = 6, MT = 10, MB = 26;
    const innerW = W - ML - MR;
    const innerH = H - MT - MB;

    const { yMax, steps: ySteps } = niceAxisLinear(Math.max(...days.map(d => d.grams)));

    const gap = days.length > 14 ? 2 : 4;
    const barW = (innerW - (days.length - 1) * gap) / days.length;

    const parts = [];
    for (let i = 0; i <= ySteps; i++) {
      const y = MT + innerH * (1 - i / ySteps);
      const v = yMax * i / ySteps;
      const vText = v % 1 === 0 ? v : v.toFixed(1);
      parts.push(`<line class="grid" x1="${ML}" y1="${y}" x2="${W - MR}" y2="${y}"/>`);
      parts.push(`<text x="${ML - 4}" y="${y + 3}" text-anchor="end">${vText}</text>`);
    }

    const selYmd = ymd(selectedDay());
    days.forEach((d, i) => {
      const isToday = i === days.length - 1;
      const isSel = d.ymd === selYmd;
      const x = ML + i * (barW + gap);
      const h = (d.grams / yMax) * innerH;
      const y = MT + innerH - h;
      const title = `${d.date.toLocaleDateString(undefined, { weekday: "long", month: "short", day: "numeric" })} — ${Math.round(d.grams)} g`;
      if (isSel) {
        parts.push(`<rect class="day-highlight" x="${(x - gap / 2).toFixed(1)}" y="${MT}" width="${(barW + gap).toFixed(1)}" height="${innerH}" rx="3"/>`);
      }
      if (d.excluded) {
        parts.push(excludedSlot(d, x, barW, MT, innerH));
      } else {
        parts.push(
          `<rect class="bar bar-eat ${isToday ? "" : "bar-faded"}" data-day="${d.ymd}" ` +
          `x="${x}" y="${y}" width="${barW}" height="${Math.max(0, h)}" rx="3">` +
          `<title>${escapeText(title)}</title></rect>`
        );
      }
      if (showDayLabel(i, days.length) || isSel) {
        parts.push(
          `<text class="${isSel ? "day-label-sel" : ""}" x="${x + barW / 2}" y="${H - MB + 14}" text-anchor="middle">` +
          `${escapeText(dayLabel(d.date, isToday))}</text>`
        );
      }
    });

    setChartSVG(svg, parts);
  }

  // Minutes walked per day. Hidden until there's a walk to show, like the
  // grams chart — no point in an empty panel for someone who doesn't log walks.
  function drawWalkChart(days) {
    const wrap = document.getElementById("walk-chart-wrap");
    const svg  = document.getElementById("chart-walk");
    if (!days.some(d => d.walkMinutes > 0)) { wrap.hidden = true; return; }
    wrap.hidden = false;

    const W = 320, H = 160;
    const ML = 30, MR = 6, MT = 10, MB = 26;
    const innerW = W - ML - MR;
    const innerH = H - MT - MB;

    const { yMax, steps: ySteps } = niceAxisLinear(Math.max(...days.map(d => d.walkMinutes)));

    const gap = days.length > 14 ? 2 : 4;
    const barW = (innerW - (days.length - 1) * gap) / days.length;

    const parts = [];
    for (let i = 0; i <= ySteps; i++) {
      const y = MT + innerH * (1 - i / ySteps);
      const v = yMax * i / ySteps;
      const vText = v % 1 === 0 ? v : v.toFixed(1);
      parts.push(`<line class="grid" x1="${ML}" y1="${y}" x2="${W - MR}" y2="${y}"/>`);
      parts.push(`<text x="${ML - 4}" y="${y + 3}" text-anchor="end">${vText}</text>`);
    }

    const selYmd = ymd(selectedDay());
    days.forEach((d, i) => {
      const isToday = i === days.length - 1;
      const isSel = d.ymd === selYmd;
      const x = ML + i * (barW + gap);
      const h = (d.walkMinutes / yMax) * innerH;
      const y = MT + innerH - h;
      const title = `${d.date.toLocaleDateString(undefined, { weekday: "long", month: "short", day: "numeric" })} — ${formatDuration(d.walkMinutes * 60_000)}`;
      if (isSel) {
        parts.push(`<rect class="day-highlight" x="${(x - gap / 2).toFixed(1)}" y="${MT}" width="${(barW + gap).toFixed(1)}" height="${innerH}" rx="3"/>`);
      }
      if (d.excluded) {
        parts.push(excludedSlot(d, x, barW, MT, innerH));
      } else {
        parts.push(
          `<rect class="bar bar-walk ${isToday ? "" : "bar-faded"}" data-day="${d.ymd}" ` +
          `x="${x}" y="${y}" width="${barW}" height="${Math.max(0, h)}" rx="3">` +
          `<title>${escapeText(title)}</title></rect>`
        );
      }
      if (showDayLabel(i, days.length) || isSel) {
        parts.push(
          `<text class="${isSel ? "day-label-sel" : ""}" x="${x + barW / 2}" y="${H - MB + 14}" text-anchor="middle">` +
          `${escapeText(dayLabel(d.date, isToday))}</text>`
        );
      }
    });

    setChartSVG(svg, parts);
  }

  function renderWeekly(events) {
    const days = weeklyData(events);
    drawSleepChart(days);
    drawCountsChart(days);
    drawWalkChart(days);
    drawGramsChart(days);
  }

  // ---------- pattern charts ----------

  // Where "now" falls in the day, 0..1 — the shared x for the charts that run
  // midnight to midnight.
  function nowDayFraction() {
    const now = new Date();
    return (now.getTime() - startOfDay(now).getTime()) / 86_400_000;
  }

  // Vertical "now" rule for those charts: ink over a surface-coloured underlay
  // so it stays legible whatever bar or cell it crosses, with a caret hung
  // above the track so it doesn't read as one more gridline. Append the parts
  // last so the rule sits on top; it ignores pointer events, so the rows and
  // cells underneath stay tappable.
  function nowRuleParts(x, yTop, yBottom) {
    const xs = x.toFixed(1);
    return [
      `<line class="now-rule-ring" x1="${xs}" y1="${yTop}" x2="${xs}" y2="${yBottom}"/>`,
      `<line class="now-rule" x1="${xs}" y1="${yTop}" x2="${xs}" y2="${yBottom}"/>`,
      `<path class="now-rule-cap" d="M${(x - 3).toFixed(1)} ${yTop - 4} ` +
      `L${(x + 3).toFixed(1)} ${yTop - 4} L${xs} ${yTop} Z"/>`,
    ];
  }

  // Actogram: one row per day (oldest at top), a midnight-to-midnight track
  // with the given windows shaded. Windows are clipped to each day, so one that
  // crosses midnight shows correctly split across two rows, and an open one
  // runs to now (both window builders already clip ongoing to Date.now()).
  // Sleep and walks are the same picture drawn from different windows, so the
  // drawing lives here once and each caller brings its windows and their fill.
  function drawActogram(svgId, windows, barCls) {
    const svg = document.getElementById(svgId);
    if (!svg) return;
    const N = chartDays();
    const W = 320;
    const ML = 44, MR = 8, MT = 16, MB = 4;
    const innerW = W - ML - MR;
    const rowGap = 2;
    // Fixed row height, chart grows with the window (13px × 14 days matches
    // the original 228-high viewBox; wider windows use thinner rows).
    const rowH = N > 14 ? 9 : 13;
    const H = MT + MB + N * rowH + (N - 1) * rowGap;
    svg.setAttribute("viewBox", `0 0 ${W} ${H}`);
    const dayMs = 86_400_000;

    const today = startOfDay(new Date());
    const xOf = (frac) => ML + frac * innerW;

    const parts = [];
    for (const hr of [0, 6, 12, 18, 24]) {
      const x = xOf(hr / 24);
      parts.push(`<line class="grid" x1="${x.toFixed(1)}" y1="${MT}" x2="${x.toFixed(1)}" y2="${H - MB}"/>`);
      const anchor = hr === 0 ? "start" : hr === 24 ? "end" : "middle";
      parts.push(`<text x="${x.toFixed(1)}" y="${MT - 5}" text-anchor="${anchor}">${hr}h</text>`);
    }

    const selYmd = ymd(selectedDay());
    for (let i = 0; i < N; i++) {
      const day = new Date(today);
      day.setDate(day.getDate() - (N - 1 - i)); // oldest at top, today at bottom
      const dayStart = startOfDay(day).getTime();
      const dayEnd = dayStart + dayMs;
      const isToday = ymd(day) === ymd(new Date());
      const isSel = ymd(day) === selYmd;
      const y = MT + i * (rowH + rowGap);

      parts.push(`<rect class="stl-track${isSel ? " stl-selected" : ""}" x="${ML}" y="${y.toFixed(1)}" width="${innerW}" height="${rowH.toFixed(1)}" rx="2"/>`);

      // A day that doesn't count keeps its row — the rows are a calendar, so
      // dropping one would misalign every day above it — but is hatched right
      // across instead of showing the sparse windows that made it untrustworthy.
      if (isExcluded(day)) {
        parts.push(`<rect class="bar-excluded" x="${ML}" y="${y.toFixed(1)}" width="${innerW}" height="${rowH.toFixed(1)}" rx="2"/>`);
      } else {
        for (const wdw of windows) {
          const s = Math.max(wdw.start, dayStart);
          const e = Math.min(wdw.end, dayEnd);
          if (e <= s) continue;
          const x = xOf((s - dayStart) / dayMs);
          const wpx = ((e - s) / dayMs) * innerW;
          parts.push(`<rect class="${barCls}" x="${x.toFixed(1)}" y="${y.toFixed(1)}" width="${Math.max(0.6, wpx).toFixed(1)}" height="${rowH.toFixed(1)}" rx="1.5"/>`);
        }
      }

      const label = isToday ? "Today" : `${day.toLocaleDateString(undefined, { weekday: "short" })} ${day.getDate()}`;
      parts.push(`<text class="stl-day ${isToday ? "stl-today" : ""}${isSel ? " stl-sel" : ""}" x="${ML - 6}" y="${(y + rowH / 2 + 3).toFixed(1)}" text-anchor="end">${escapeText(label)}</text>`);

      const dateText = day.toLocaleDateString(undefined, { weekday: "long", month: "short", day: "numeric" });
      const title = isExcluded(day) ? `${dateText} — not counted` : dateText;
      parts.push(`<rect class="bar stl-hit" data-day="${ymd(day)}" x="${ML}" y="${y.toFixed(1)}" width="${innerW}" height="${rowH.toFixed(1)}"><title>${escapeText(title)}</title></rect>`);
    }

    // The window always ends today, so one rule marks both the live edge of the
    // bottom row and the same time of day on every row above it.
    parts.push(...nowRuleParts(xOf(nowDayFraction()), MT, H - MB));

    setChartSVG(svg, parts); // wires the .bar[data-day] click → select that day
  }

  function renderSleepTimeline(events) {
    drawActogram("chart-sleep-timeline", sleepWindows(events), "stl-sleep");
  }

  // The walk patterns are only worth a panel once there is a walk to draw, so
  // both hide themselves rather than showing an empty day grid to someone who
  // doesn't track walks.
  function renderWalkPatterns(events) {
    const windows = walkWindows(events);
    const any = windows.length > 0;
    for (const key of ["walk-timeline", "walk-trend"]) {
      const section = document.querySelector(`section[data-panel="${key}"]`);
      if (section) section.hidden = !any;
    }
    if (!any) return;
    drawActogram("chart-walk-timeline", windows, "wtl-walk");
    renderWalkTrend(events);
  }

  // Cumulative minutes walked through the day, as a step per walk: flat while
  // the puppy is in, climbing only while a walk is on. Today and yesterday are
  // built from their own walk boundaries so the steps stay square; the average
  // is sampled hourly instead, since a mean over many days is a smooth
  // reference with no steps of its own to preserve.
  //
  // Unlike the sleep trend there is no projected tail. Sleep is a state the
  // puppy drifts back into, so "what the average day adds from here" is a fair
  // guess; walks are decisions, and projecting them would be predicting the
  // handler, not the dog.
  function walkTrendCurves(events) {
    const HOUR = 3_600_000, MIN = 60_000, DAY = 86_400_000;
    const windows = walkWindows(events); // an ongoing walk is already clipped to now
    const walkedMs = (from, to) => {
      let total = 0;
      for (const w of windows) {
        const s = Math.max(w.start, from);
        const e = Math.min(w.end, to);
        if (e > s) total += e - s;
      }
      return total;
    };
    const day = selectedDay();
    const isToday = ymd(day) === ymd(new Date());
    const dayAgo = (daysAgo) => {
      const d = startOfDay(day);
      d.setDate(d.getDate() - daysAgo);
      return d;
    };
    const dayStartTs = (daysAgo) => dayAgo(daysAgo).getTime();
    const pointsAt = (start, stops) =>
      stops.map(t => ({ x: (t - start) / HOUR, y: walkedMs(start, t) / MIN }));

    // Every boundary falling inside the day, plus the day's two ends, is a
    // corner of the step line. capTs (today only) ends it at "now".
    const curveFor = (start, capTs) => {
      const end = capTs != null ? capTs : start + DAY;
      const stops = new Set([start, end]);
      for (const w of windows) {
        if (w.end <= start || w.start >= end) continue;
        stops.add(Math.max(w.start, start));
        stops.add(Math.min(w.end, end));
      }
      return pointsAt(start, [...stops].sort((a, b) => a - b));
    };
    const hourlyFor = (start) => {
      const stops = [];
      for (let h = 0; h <= 24; h++) stops.push(start + h * HOUR);
      return pointsAt(start, stops);
    };
    const totalOf = (pts) => pts[pts.length - 1].y;

    const today = curveFor(dayStartTs(0), isToday ? Date.now() : null);
    // Same as the sleep trend: a day that doesn't count is dropped as a
    // comparison rather than drawn flat at zero.
    const prev = curveFor(dayStartTs(1));
    const yesterday = (!isExcluded(dayAgo(1)) && totalOf(prev) > 0) ? prev : null;

    // Mean of the last N days, skipping days that don't count and days with no
    // walk at all, so a gap in logging doesn't drag the average toward zero.
    const avgDays = chartDays();
    const dayCurves = [];
    for (let i = 1; i <= avgDays; i++) {
      if (isExcluded(dayAgo(i))) continue;
      const c = hourlyFor(dayStartTs(i));
      if (c[24].y > 0) dayCurves.push(c);
    }
    let avg = null;
    if (dayCurves.length > 0) {
      avg = [];
      for (let h = 0; h <= 24; h++) {
        avg.push({ x: h, y: dayCurves.reduce((s, c) => s + c[h].y, 0) / dayCurves.length });
      }
    }

    const fmtDay = (daysAgo) =>
      new Date(dayStartTs(daysAgo)).toLocaleDateString(undefined, { month: "short", day: "numeric" });
    return {
      today, yesterday, avg, avgDays,
      dayLabel: isToday ? "Today" : fmtDay(0),
      prevDayLabel: isToday ? "Yesterday" : fmtDay(1),
    };
  }

  function drawWalkTrendChart(curves) {
    const svg = document.getElementById("chart-walk-trend");
    if (!svg) return;
    const W = 320, H = 180;
    const ML = 30, MR = 8, MT = 10, MB = 22;
    const innerW = W - ML - MR;
    const innerH = H - MT - MB;

    const series = [
      // Reference lines first so today draws on top of them.
      { pts: curves.avg,       cls: "wtrend-avg",       label: `${curves.avgDays}-day average` },
      { pts: curves.yesterday, cls: "wtrend-yesterday", label: curves.prevDayLabel },
      { pts: curves.today,     cls: "wtrend-today",     label: curves.dayLabel },
    ].filter(s => s.pts && s.pts.length > 1);

    const rawMax = Math.max(...series.flatMap(s => s.pts.map(p => p.y)));
    const { yMax, steps } = niceAxisLinear(rawMax);
    // Minutes are linear all the way down, so no split axis: the sleep trend
    // stretches its top because the interesting hours cluster near a 16h goal,
    // while a walk total is as readable at 10 minutes as at 60.
    const xOf = (hour) => ML + (hour / 24) * innerW;
    const yOf = (v) => MT + innerH * (1 - v / yMax);

    const parts = [];
    for (let i = 0; i <= steps; i++) {
      const v = yMax * i / steps;
      const y = yOf(v);
      parts.push(`<line class="grid" x1="${ML}" y1="${y.toFixed(1)}" x2="${W - MR}" y2="${y.toFixed(1)}"/>`);
      parts.push(`<text x="${ML - 4}" y="${(y + 3).toFixed(1)}" text-anchor="end">${Math.round(v)}m</text>`);
    }
    for (const hr of [0, 6, 12, 18, 24]) {
      const x = xOf(hr);
      parts.push(`<line class="grid" x1="${x.toFixed(1)}" y1="${MT}" x2="${x.toFixed(1)}" y2="${MT + innerH}"/>`);
      const anchor = hr === 0 ? "start" : hr === 24 ? "end" : "middle";
      parts.push(`<text x="${x.toFixed(1)}" y="${H - MB + 14}" text-anchor="${anchor}">${pad2(hr)}</text>`);
    }

    for (const s of series) {
      const d = s.pts
        .map((p, i) => `${i === 0 ? "M" : "L"}${xOf(p.x).toFixed(1)} ${yOf(p.y).toFixed(1)}`)
        .join(" ");
      const last = s.pts[s.pts.length - 1];
      parts.push(
        `<path class="${s.cls}" d="${d}">` +
        `<title>${escapeText(`${s.label} — ${Math.round(last.y)} min walked`)}</title></path>`
      );
    }

    svg.innerHTML = parts.join("");
  }

  function renderWalkTrend(events) {
    const curves = walkTrendCurves(events);
    drawWalkTrendChart(curves);

    const chip = (id) => document.getElementById(id);
    const mins = (pts) => `${Math.round(pts[pts.length - 1].y)} min`;
    chip("legend-wtrend-today-text").textContent = `${curves.dayLabel} ${mins(curves.today)}`;

    const yLegend = chip("legend-wtrend-yesterday");
    yLegend.hidden = !curves.yesterday;
    if (curves.yesterday) {
      chip("legend-wtrend-yesterday-text").textContent = `${curves.prevDayLabel} ${mins(curves.yesterday)}`;
    }
    const aLegend = chip("legend-wtrend-avg");
    aLegend.hidden = !curves.avg;
    if (curves.avg) {
      chip("legend-wtrend-avg-text").textContent = `${curves.avgDays}-day avg ${mins(curves.avg)}`;
    }
  }

  // Which heatmap block is focused, remembered across re-renders so a background
  // sync doesn't wipe the block the user just tapped. The counts behind it are
  // recomputed every render, so the readout stays current.
  let hourCellSel = null; // `${type}-${hour}`, or null for nothing focused
  const HOUR_CELL_HINT = "Tap a block to see how many it counts.";

  // Hour-of-day heatmap: one row per event type, 24 cells shaded by how often
  // that event lands in each hour across the window. Reveals daily rhythm that
  // the median gap can't show (e.g. "always poos ~7am and ~6pm").
  function renderHourHeatmap(events) {
    const svg = document.getElementById("chart-hour-heatmap");
    if (!svg) return;
    const info = document.getElementById("hour-heatmap-info");
    const from = startOfDay(new Date(Date.now() - (chartDays() - 1) * 86_400_000)).getTime();

    const series = [
      { type: "pee", label: "Pees",  cls: "hm-pee", one: "pee",  many: "pees" },
      { type: "poo", label: "Poos",  cls: "hm-poo", one: "poo",  many: "poos" },
      { type: "eat", label: "Meals", cls: "hm-eat", one: "meal", many: "meals" },
    ];
    const counts = {};
    for (const s of series) counts[s.type] = new Array(24).fill(0);
    for (const e of events) {
      if (e.at < from) continue;
      if (counts[e.type]) counts[e.type][new Date(e.at).getHours()]++;
    }

    const W = 320, H = 120;
    const ML = 40, MR = 8, MT = 6, MB = 18;
    const innerW = W - ML - MR;
    const rowGap = 6;
    const rowH = (H - MT - MB - (series.length - 1) * rowGap) / series.length;
    const cellW = innerW / 24;

    // "3 meals between 07:00 and 08:00" — self-describing, so the same string
    // serves as the pointer tooltip and as the tap readout under the chart.
    const cellText = (s, h, c) =>
      `${c === 0 ? "No" : c} ${c === 1 ? s.one : s.many} between ` +
      `${pad2(h)}:00 and ${pad2((h + 1) % 24)}:00`;

    const parts = [];
    const hits = [];    // appended last so they sit above every row
    const details = {}; // cell key → readout text
    series.forEach((s, r) => {
      const y = MT + r * (rowH + rowGap);
      const max = Math.max(1, ...counts[s.type]);
      for (let h = 0; h < 24; h++) {
        const c = counts[s.type][h];
        const op = c === 0 ? 0.06 : 0.2 + 0.8 * (c / max);
        const x = ML + h * cellW;
        const key = `${s.type}-${h}`;
        details[key] = cellText(s, h, c);
        parts.push(
          `<rect class="hm-cell ${s.cls}" data-cell="${key}" x="${x.toFixed(1)}" y="${y.toFixed(1)}" ` +
          `width="${(cellW - 1).toFixed(1)}" height="${rowH.toFixed(1)}" rx="1.5" fill-opacity="${op.toFixed(2)}"/>`
        );
        // A cell is only ~12px wide on a phone, so the tap target claims the
        // spacing between cells and half the gap to the neighbouring rows.
        hits.push(
          `<rect class="hm-hit" data-cell="${key}" x="${x.toFixed(1)}" y="${(y - rowGap / 2).toFixed(1)}" ` +
          `width="${cellW.toFixed(1)}" height="${(rowH + rowGap).toFixed(1)}">` +
          `<title>${escapeText(details[key])}</title></rect>`
        );
      }
      parts.push(`<text x="${ML - 6}" y="${(y + rowH / 2 + 3).toFixed(1)}" text-anchor="end">${s.label}</text>`);
    });

    const yAxis = H - MB + 12;
    for (const hr of [0, 6, 12, 18]) {
      const x = ML + (hr / 24) * innerW;
      parts.push(`<text x="${x.toFixed(1)}" y="${yAxis}" text-anchor="${hr === 0 ? "start" : "middle"}">${hr}h</text>`);
    }
    parts.push(`<text x="${(ML + innerW).toFixed(1)}" y="${yAxis}" text-anchor="end">24h</text>`);

    svg.innerHTML = parts.concat(hits, nowRuleParts(ML + nowDayFraction() * innerW, MT, H - MB)).join("");

    // <title> tooltips only ever show on a pointer, which left phones with no
    // way to read a block's count. Tapping (or hovering) a block names it in
    // the caption under the chart.
    const cells = svg.querySelectorAll(".hm-cell[data-cell]");
    const focusCell = (key) => {
      hourCellSel = details[key] ? key : null;
      cells.forEach(c => c.classList.toggle("hm-active", c.dataset.cell === hourCellSel));
      if (info) info.textContent = hourCellSel ? details[hourCellSel] : HOUR_CELL_HINT;
    };
    svg.querySelectorAll(".hm-hit").forEach(hit => {
      const key = hit.dataset.cell;
      // Select, never toggle. A tap fires the emulated mouseenter and then the
      // click on the same block, so a toggle here selected on the first of the
      // pair and cleared on the second — the count only appeared on a later tap
      // that arrived without a fresh mouseenter. Selecting twice is a no-op.
      hit.addEventListener("click", () => focusCell(key));
      hit.addEventListener("mouseenter", () => focusCell(key));
    });
    focusCell(hourCellSel);
  }

  // ---------- sleep trend ----------
  // Cumulative hours slept as the selected day progresses: that day's running
  // total (up to now when it's today, else the full 24h) against the previous
  // day's full curve and the mean of the N full days before it, where N
  // follows the 7/14/30 chart-days picker.
  // Each curve is a list of { x: hour-of-day 0..24, y: cumulative hours }.
  function sleepTrendCurves(events) {
    const HOUR = 3_600_000;
    const windows = sleepWindows(events); // ongoing sleep already clipped to now
    const sleptMs = (from, to) => {
      let total = 0;
      for (const w of windows) {
        const s = Math.max(w.start, from);
        const e = Math.min(w.end, to);
        if (e > s) total += e - s;
      }
      return total;
    };
    const day = selectedDay();
    const isToday = ymd(day) === ymd(new Date());
    const dayAgo = (daysAgo) => {
      const d = startOfDay(day);
      d.setDate(d.getDate() - daysAgo);
      return d;
    };
    const dayStartTs = (daysAgo) => dayAgo(daysAgo).getTime();
    // capTs (today only) truncates the curve at "now" with a final fractional
    // point, so the line visibly ends where the day currently stands.
    const curveFor = (start, capTs) => {
      const pts = [];
      for (let h = 0; h <= 24; h++) {
        const to = start + h * HOUR;
        if (capTs != null && to >= capTs) {
          pts.push({ x: (capTs - start) / HOUR, y: sleptMs(start, capTs) / HOUR });
          break;
        }
        pts.push({ x: h, y: sleptMs(start, to) / HOUR });
      }
      return pts;
    };

    // A past day is complete, so its curve runs the full 24h uncapped.
    const today = curveFor(dayStartTs(0), isToday ? Date.now() : null);

    // A day that doesn't count is no comparison at all, so it is dropped
    // outright rather than drawn as a flat line at zero. Checked explicitly
    // rather than leaning on the "any sleep at all" guard below: a nap running
    // in from the previous, counted day would give an excluded day a non-zero
    // total and sneak it back in.
    const yesterdayCurve = curveFor(dayStartTs(1));
    const yesterday =
      (!isExcluded(dayAgo(1)) && yesterdayCurve[24].y > 0) ? yesterdayCurve : null;

    // Mean of the last N full days, skipping days that don't count and days
    // with no sleep at all, so a young log (or a tracking gap) doesn't drag the
    // average toward zero.
    const avgDays = chartDays();
    const dayCurves = [];
    for (let i = 1; i <= avgDays; i++) {
      if (isExcluded(dayAgo(i))) continue;
      const c = curveFor(dayStartTs(i));
      if (c[24].y > 0) dayCurves.push(c);
    }
    let avg = null;
    if (dayCurves.length > 0) {
      avg = [];
      for (let h = 0; h <= 24; h++) {
        avg.push({ x: h, y: dayCurves.reduce((s, c) => s + c[h].y, 0) / dayCurves.length });
      }
    }

    // Where today is likely to end up: continue today's line by adding what
    // the average day typically adds between now and midnight. That respects
    // the time-of-day rhythm (night sleep, nap clusters), unlike a linear
    // rate extrapolation, which overshoots wildly just after a long night.
    // No history → no average → no projection. Past days are already complete,
    // so there is nothing to project.
    let projected = null;
    if (avg && isToday) {
      const nowPt = today[today.length - 1];
      const avgAt = (x) => {
        const lo = Math.floor(x);
        const hi = Math.min(24, lo + 1);
        return avg[lo].y + (avg[hi].y - avg[lo].y) * (x - lo);
      };
      projected = [{ x: nowPt.x, y: nowPt.y }];
      for (let h = Math.ceil(nowPt.x); h <= 24; h++) {
        if (h <= nowPt.x) continue; // now landing exactly on an hour boundary
        projected.push({ x: h, y: nowPt.y + avgAt(h) - avgAt(nowPt.x) });
      }
    }

    // Labels follow the selection so a past day reads as its date, not "Today".
    const fmtDay = (daysAgo) =>
      new Date(dayStartTs(daysAgo)).toLocaleDateString(undefined, { month: "short", day: "numeric" });
    const dayLabel = isToday ? "Today" : fmtDay(0);
    const prevDayLabel = isToday ? "Yesterday" : fmtDay(1);

    return { today, yesterday, avg, avgDays, projected, dayLabel, prevDayLabel };
  }

  function drawSleepTrendChart(curves, target) {
    const svg = document.getElementById("chart-sleep-trend");
    if (!svg) return;
    const W = 320, H = 220;
    const ML = 26, MR = 8, MT = 10, MB = 22;
    const innerW = W - ML - MR;
    const innerH = H - MT - MB;

    const series = [
      // Reference lines first so today (and its projected tail) draw on top.
      { pts: curves.avg,       cls: "trend-avg",       label: `${curves.avgDays}-day average` },
      { pts: curves.yesterday, cls: "trend-yesterday", label: curves.prevDayLabel },
      { pts: curves.projected, cls: "trend-projected", label: "Projected end of day" },
      { pts: curves.today,     cls: "trend-today",     label: curves.dayLabel },
    ].filter(s => s.pts && s.pts.length > 1);

    // The axis must reach the goal band's top even when the data doesn't yet.
    const rawMax = Math.max(
      target ? target.hi : 0,
      ...series.flatMap(s => s.pts.map(p => p.y)),
    );
    const { yMax } = niceAxisSleepHours(rawMax);

    // The interesting detail sits near the goal, in the upper teens of hours,
    // so the y scale is piecewise: everything up to BREAK shares a compressed
    // slice of the height and the hours above it get all the rest. Linear
    // again while the axis is still too short for a split to mean anything.
    const BREAK = 10, LOW_FRAC = 0.26;
    const split = yMax > BREAK + 2;
    const frac = (v) => !split
      ? v / yMax
      : v <= BREAK
        ? (v / BREAK) * LOW_FRAC
        : LOW_FRAC + ((v - BREAK) / (yMax - BREAK)) * (1 - LOW_FRAC);
    const xOf = (hour) => ML + (hour / 24) * innerW;
    const yOf = (v) => MT + innerH * (1 - frac(v));

    // Gridlines: every 1h in the stretched region above the break, every 2h
    // in the compressed region below it (1h everywhere when linear).
    const yTicks = [];
    if (split) {
      for (let v = 0; v < BREAK; v += 2) yTicks.push(v);
      for (let v = BREAK; v <= yMax; v++) yTicks.push(v);
    } else {
      for (let v = 0; v <= yMax; v++) yTicks.push(v);
    }
    // Smaller text once the axis is dense so the labels stay apart.
    const yLabelCls = yTicks.length > 16 ? "y-dense" : "";
    const parts = [];

    // Age-based goal band, behind everything: today's projection should land
    // inside it by midnight.
    if (target) {
      const yTop = yOf(target.hi);
      const yBot = yOf(target.lo);
      parts.push(
        `<rect class="trend-goal" x="${ML}" y="${yTop.toFixed(1)}" ` +
        `width="${innerW}" height="${(yBot - yTop).toFixed(1)}">` +
        `<title>${escapeText(`Goal ${target.lo}–${target.hi}h (${target.label})`)}</title></rect>`
      );
    }
    for (const v of yTicks) {
      const y = yOf(v);
      parts.push(`<line class="grid" x1="${ML}" y1="${y.toFixed(1)}" x2="${W - MR}" y2="${y.toFixed(1)}"/>`);
      parts.push(`<text class="${yLabelCls}" x="${ML - 4}" y="${(y + 3).toFixed(1)}" text-anchor="end">${v}h</text>`);
    }
    for (const hr of [0, 6, 12, 18, 24]) {
      const x = xOf(hr);
      parts.push(`<line class="grid" x1="${x.toFixed(1)}" y1="${MT}" x2="${x.toFixed(1)}" y2="${MT + innerH}"/>`);
      const anchor = hr === 0 ? "start" : hr === 24 ? "end" : "middle";
      parts.push(`<text x="${x.toFixed(1)}" y="${H - MB + 14}" text-anchor="${anchor}">${pad2(hr)}</text>`);
    }

    for (const s of series) {
      const d = s.pts
        .map((p, i) => `${i === 0 ? "M" : "L"}${xOf(p.x).toFixed(1)} ${yOf(p.y).toFixed(1)}`)
        .join(" ");
      const last = s.pts[s.pts.length - 1];
      const title = `${s.label} — ${last.y.toFixed(1)}h slept`;
      parts.push(`<path class="${s.cls}" d="${d}"><title>${escapeText(title)}</title></path>`);
    }

    svg.innerHTML = parts.join("");
  }

  function renderSleepTrend(events) {
    const curves = sleepTrendCurves(events);
    const target = sleepTargetFor(loadConfig().birthday);
    drawSleepTrendChart(curves, target);
    // Drop legend chips for missing reference lines (no data for them yet),
    // keep the average chip's label in step with the chart-days picker, and
    // write each curve's slept-hours total into its chip.
    const chip = (id) => document.getElementById(id);
    const hrs = (pts) => `${pts[pts.length - 1].y.toFixed(1)}h`;
    chip("legend-trend-today-text").textContent = `${curves.dayLabel} ${hrs(curves.today)}`;
    const yLegend = chip("legend-trend-yesterday");
    yLegend.hidden = !curves.yesterday;
    if (curves.yesterday) {
      chip("legend-trend-yesterday-text").textContent = `${curves.prevDayLabel} ${hrs(curves.yesterday)}`;
    }
    const aLegend = chip("legend-trend-avg");
    aLegend.hidden = !curves.avg;
    if (curves.avg) {
      chip("legend-trend-avg-text").textContent = `${curves.avgDays}-day avg ${hrs(curves.avg)}`;
    }
    const pLegend = chip("legend-trend-projected");
    pLegend.hidden = !curves.projected;
    if (curves.projected) {
      // ✓ when the projection reaches at least the goal's lower bound.
      let mark = "";
      if (target) {
        const end = curves.projected[curves.projected.length - 1].y;
        mark = end >= target.lo ? " ✓" : " ▽";
        pLegend.title = end >= target.lo
          ? "On track for the sleep goal"
          : "Projected below the sleep goal";
      }
      chip("legend-trend-projected-text").textContent = `Projected ~${hrs(curves.projected)}${mark}`;
    }
    const gLegend = chip("legend-trend-goal");
    gLegend.hidden = !target;
    if (target) {
      chip("legend-trend-goal-text").textContent =
        `Goal ${target.lo}–${target.hi}h (${target.label})`;
    }
  }

  // ---------- weight ----------
  // Pick a "nice" kg axis that frames the data with a little headroom rather
  // than forcing 0-based (a puppy going 5→8 kg would otherwise look flat).
  function niceWeightAxis(min, max) {
    if (!(max > 0)) return { lo: 0, hi: 1, steps: 1 };
    if (min === max) { min = Math.max(0, min - 0.5); max = max + 0.5; }
    const span = max - min;
    let lo = Math.max(0, min - span * 0.15);
    let hi = max + span * 0.15;
    const rawStep = (hi - lo) / 4;
    const mag  = Math.pow(10, Math.floor(Math.log10(rawStep)));
    const norm = rawStep / mag;
    const step = (norm <= 1 ? 1 : norm <= 2 ? 2 : norm <= 2.5 ? 2.5 : norm <= 5 ? 5 : 10) * mag;
    lo = Math.floor(lo / step) * step;
    hi = Math.ceil(hi / step) * step;
    return { lo, hi, steps: Math.max(1, Math.round((hi - lo) / step)) };
  }

  // Human-readable detail for one weigh-in: date, weight, and the puppy's age
  // at that date (omitted if no birthday is configured).
  function weightPointInfo(w, birthday) {
    const dateStr = new Date(w.at).toLocaleDateString(undefined, { weekday: "short", month: "short", day: "numeric" });
    const age = formatAge(birthday, w.at);
    return `${dateStr} — ${formatWeight(w.weight)}${age ? ` · ${age}` : ""}`;
  }

  function drawWeightChart(weights, birthday) {
    const svg  = document.getElementById("chart-weight");
    const info = document.getElementById("weight-point-info");
    const W = 320, H = 180;
    const ML = 30, MR = 8, MT = 10, MB = 24;
    const innerW = W - ML - MR;
    const innerH = H - MT - MB;

    if (weights.length === 0) { svg.innerHTML = ""; info.textContent = ""; return; }

    const vals = weights.map(w => w.weight);
    const { lo, hi, steps } = niceWeightAxis(Math.min(...vals), Math.max(...vals));

    const t0 = weights[0].at;
    const t1 = weights[weights.length - 1].at;
    const tSpan = t1 - t0;
    const xOf = (t) => tSpan > 0 ? ML + ((t - t0) / tSpan) * innerW : ML + innerW / 2;
    const yOf = (v) => MT + innerH * (1 - (v - lo) / (hi - lo));

    const parts = [];
    for (let i = 0; i <= steps; i++) {
      const v = lo + (hi - lo) * i / steps;
      const y = yOf(v);
      parts.push(`<line class="grid" x1="${ML}" y1="${y}" x2="${W - MR}" y2="${y}"/>`);
      parts.push(`<text x="${ML - 4}" y="${y + 3}" text-anchor="end">${Math.round(v * 10) / 10}</text>`);
    }

    if (weights.length > 1) {
      const d = weights
        .map((w, i) => `${i === 0 ? "M" : "L"}${xOf(w.at).toFixed(1)} ${yOf(w.weight).toFixed(1)}`)
        .join(" ");
      parts.push(`<path class="weight-line" d="${d}"/>`);
    }

    // Visible dots, then larger transparent hit targets on top (easier to tap
    // on touch, and they carry the tooltip + click detail).
    weights.forEach(w => {
      parts.push(`<circle class="weight-dot" cx="${xOf(w.at).toFixed(1)}" cy="${yOf(w.weight).toFixed(1)}" r="3.5"/>`);
    });
    weights.forEach((w, i) => {
      const detail = weightPointInfo(w, birthday);
      parts.push(
        `<circle class="weight-hit" data-i="${i}" cx="${xOf(w.at).toFixed(1)}" cy="${yOf(w.weight).toFixed(1)}" r="10">` +
        `<title>${escapeText(detail)}</title></circle>`
      );
    });

    const fmtX = (t) => new Date(t).toLocaleDateString(undefined, { month: "short", day: "numeric" });
    parts.push(`<text x="${ML}" y="${H - MB + 16}" text-anchor="start">${escapeText(fmtX(t0))}</text>`);
    if (tSpan > 0) {
      parts.push(`<text x="${W - MR}" y="${H - MB + 16}" text-anchor="end">${escapeText(fmtX(t1))}</text>`);
    }

    svg.innerHTML = parts.join("");

    // Default the caption to the most recent weigh-in; hover/tap focuses a point.
    const hits = svg.querySelectorAll(".weight-hit");
    const focus = (i) => {
      info.textContent = weightPointInfo(weights[i], birthday);
      hits.forEach(h => h.classList.toggle("active", Number(h.dataset.i) === i));
    };
    hits.forEach(h => {
      const i = Number(h.dataset.i);
      h.addEventListener("mouseenter", () => focus(i));
      h.addEventListener("click", () => focus(i));
    });
    info.textContent = weightPointInfo(weights[weights.length - 1], birthday);
  }

  function renderWeight(events) {
    const weights = events
      .filter(e => e.type === "weight" && Number.isFinite(e.weight))
      .sort((a, b) => a.at - b.at);

    const empty    = document.getElementById("weight-empty");
    const latestEl = document.getElementById("weight-latest");
    const changeEl = document.getElementById("weight-change");
    const list     = document.getElementById("weight-list");

    const birthday = loadConfig().birthday;

    list.innerHTML = "";
    changeEl.classList.remove("up", "down");

    if (weights.length === 0) {
      empty.hidden = false;
      latestEl.textContent = "—";
      changeEl.textContent = "—";
      drawWeightChart([], birthday);
      return;
    }
    empty.hidden = true;

    const latest = weights[weights.length - 1];
    latestEl.textContent = formatWeight(latest.weight);

    if (weights.length >= 2) {
      const d = latest.weight - weights[weights.length - 2].weight;
      const rounded = Math.round(d * 100) / 100;
      const arrow = d > 0 ? "▲" : d < 0 ? "▼" : "▬";
      changeEl.textContent = `${arrow} ${d > 0 ? "+" : ""}${rounded} kg`;
      changeEl.classList.toggle("up", d > 0);
      changeEl.classList.toggle("down", d < 0);
    } else {
      changeEl.textContent = "—";
    }

    // Most-recent-first log; tap a row to edit that weigh-in.
    for (const w of [...weights].reverse()) {
      const li = document.createElement("li");
      li.className = "ww weight-ww";
      const date = document.createElement("span");
      date.className = "ww-range";
      const age = formatAgeWeeks(birthday, w.at);
      const dateStr = new Date(w.at).toLocaleDateString(undefined, { month: "short", day: "numeric" });
      date.textContent = age ? `${dateStr} · ${age}` : dateStr;
      const val = document.createElement("span");
      val.className = "ww-dur";
      val.textContent = formatWeight(w.weight);
      li.appendChild(date);
      li.appendChild(val);
      li.addEventListener("click", () => openEditDialog(w));
      list.appendChild(li);
    }

    drawWeightChart(weights, birthday);
  }

  // ---------- training ----------
  // Per-exercise stats plus a consistency heatmap. Everything here is rolling
  // (last session / last 7 days / streak / chart window) rather than scoped to
  // the day picker — the point is keeping the habit up, not reviewing one day.
  const expandedExercises = new Set(); // ids showing their instructions (per page load)

  function trainingStreakDays(times) {
    // Consecutive days with ≥1 session, counting back from today — or from
    // yesterday, so a streak isn't shown as broken before today's session
    // has had a chance to happen.
    const days = new Set(times.map(t => ymd(new Date(t))));
    const d = new Date();
    if (!days.has(ymd(d))) d.setDate(d.getDate() - 1);
    let streak = 0;
    while (days.has(ymd(d))) { streak++; d.setDate(d.getDate() - 1); }
    return streak;
  }

  function exerciseMeta(times) {
    if (times.length === 0) return "not yet trained";
    const weekFrom = startOfDay(new Date());
    weekFrom.setDate(weekFrom.getDate() - 6);
    const week = times.filter(t => t >= weekFrom.getTime()).length;
    const parts = [`last ${formatRelative(Math.max(...times))}`, `${week}× this week`];
    const streak = trainingStreakDays(times);
    if (streak >= 2) parts.push(`🔥 ${streak}-day streak`);
    return parts.join(" · ");
  }

  // Exercise × day grid: one row per exercise, one cell per day, opacity scaled
  // by that day's session count. Same idea as the hour heatmap, with days for
  // columns. Cells click through to the day picker via setChartSVG.
  function renderTrainingHeatmap(exercises, events) {
    const wrap = document.getElementById("training-chart-wrap");
    const svg  = document.getElementById("chart-training");
    if (exercises.length === 0) { wrap.hidden = true; return; }
    wrap.hidden = false;

    const N = chartDays();
    const from = startOfDay(new Date());
    from.setDate(from.getDate() - (N - 1));
    const dayList = [];
    const dayIndex = new Map(); // ymd -> column
    for (let i = 0; i < N; i++) {
      const d = new Date(from);
      d.setDate(d.getDate() + i);
      dayList.push(d);
      dayIndex.set(ymd(d), i);
    }
    const exIndex = new Map(exercises.map((x, i) => [x.id, i]));
    const counts = exercises.map(() => new Array(N).fill(0));
    for (const e of events) {
      if (e.type !== "training") continue;
      const r = exIndex.get(e.exerciseId);
      const c = dayIndex.get(ymd(new Date(e.at)));
      if (r !== undefined && c !== undefined) counts[r][c]++;
    }

    const W = 320;
    const ML = 70, MR = 8, MT = 6, MB = 18;
    const rowH = 16, rowGap = 4;
    const H = MT + exercises.length * (rowH + rowGap) - rowGap + MB;
    svg.setAttribute("viewBox", `0 0 ${W} ${H}`);
    const innerW = W - ML - MR;
    const cellW = innerW / N;

    const parts = [];
    const selCol = dayIndex.get(ymd(selectedDay()));
    if (selCol !== undefined) {
      parts.push(
        `<rect class="day-highlight" x="${(ML + selCol * cellW - 0.75).toFixed(1)}" y="${MT - 2}" ` +
        `width="${cellW.toFixed(1)}" height="${(H - MT - MB + 4).toFixed(1)}" rx="3"/>`
      );
    }
    exercises.forEach((x, r) => {
      const y = MT + r * (rowH + rowGap);
      const max = Math.max(1, ...counts[r]);
      for (let c = 0; c < N; c++) {
        const n = counts[r][c];
        const d = dayList[c];
        const dateText = d.toLocaleDateString(undefined, { weekday: "short", month: "short", day: "numeric" });
        // A day that doesn't count would otherwise show as the palest cell —
        // indistinguishable from "trained nothing that day", which is the one
        // reading the mark is there to rule out.
        if (isExcluded(d)) {
          parts.push(
            `<rect class="bar bar-excluded" data-day="${ymd(d)}" ` +
            `x="${(ML + c * cellW).toFixed(1)}" y="${y.toFixed(1)}" ` +
            `width="${(cellW - 1.5).toFixed(1)}" height="${rowH}" rx="2">` +
            `<title>${escapeText(`${x.name} · ${dateText}: not counted`)}</title></rect>`
          );
          continue;
        }
        const op = n === 0 ? 0.06 : 0.35 + 0.65 * (n / max);
        parts.push(
          `<rect class="bar hm-cell hm-training" data-day="${ymd(d)}" ` +
          `x="${(ML + c * cellW).toFixed(1)}" y="${y.toFixed(1)}" ` +
          `width="${(cellW - 1.5).toFixed(1)}" height="${rowH}" rx="2" fill-opacity="${op.toFixed(2)}">` +
          `<title>${escapeText(`${x.name} · ${dateText}: ${n}`)}</title></rect>`
        );
      }
      const name = x.name.length > 12 ? x.name.slice(0, 11) + "…" : x.name;
      parts.push(`<text x="${ML - 6}" y="${(y + rowH / 2 + 3).toFixed(1)}" text-anchor="end">${escapeText(name)}</text>`);
    });

    const yAxis = H - MB + 12;
    parts.push(`<text x="${ML}" y="${yAxis}" text-anchor="start">${escapeText(dayList[0].toLocaleDateString(undefined, { month: "short", day: "numeric" }))}</text>`);
    parts.push(`<text x="${ML + innerW}" y="${yAxis}" text-anchor="end">Today</text>`);

    setChartSVG(svg, parts);
  }

  function renderTraining(events) {
    const list  = document.getElementById("training-list");
    const empty = document.getElementById("training-empty");
    const exercises = liveExercises();
    list.innerHTML = "";
    empty.hidden = exercises.length > 0;
    // Adding to the library is the owner's, like editing it.
    document.getElementById("exercise-add").hidden = isGuest();

    for (const ex of exercises) {
      const times = events
        .filter(e => e.type === "training" && e.exerciseId === ex.id)
        .map(e => e.at);

      const li = document.createElement("li");
      li.className = "exercise" + (expandedExercises.has(ex.id) ? " expanded" : "");

      const row  = document.createElement("div");
      row.className = "ex-row";
      const main = document.createElement("div");
      main.className = "ex-main";
      const nameEl = document.createElement("span");
      nameEl.className = "ex-name";
      nameEl.textContent = ex.name;
      const metaEl = document.createElement("span");
      metaEl.className = "ex-meta";
      metaEl.textContent = exerciseMeta(times);
      main.appendChild(nameEl);
      main.appendChild(metaEl);

      const logBtn = document.createElement("button");
      logBtn.type = "button";
      logBtn.className = "ex-log";
      logBtn.textContent = "Log";
      logBtn.addEventListener("click", (e) => {
        e.stopPropagation();
        // Log onto the selected day (at the current time of day), so a session
        // that was forgotten yesterday can be back-filled from that day's view.
        const day = selectedDay();
        const onToday = ymd(day) === ymd(new Date());
        let at = Date.now();
        if (!onToday) {
          const now = new Date();
          at = new Date(day.getFullYear(), day.getMonth(), day.getDate(),
                        now.getHours(), now.getMinutes(), now.getSeconds()).getTime();
        }
        const ev = addEvent("training", "", at, { exerciseId: ex.id });
        const dayStr = day.toLocaleDateString(undefined, { month: "short", day: "numeric" });
        showSnackbar(onToday ? `${ex.name} logged` : `${ex.name} logged for ${dayStr}`, ev);
      });

      row.appendChild(main);
      row.appendChild(logBtn);
      row.addEventListener("click", () => {
        if (expandedExercises.has(ex.id)) expandedExercises.delete(ex.id);
        else expandedExercises.add(ex.id);
        li.classList.toggle("expanded");
      });

      const detail = document.createElement("div");
      detail.className = "ex-detail";
      const noteEl = document.createElement("p");
      noteEl.className = "ex-note";
      noteEl.textContent = ex.note
        || (isGuest() ? "No instructions for this one yet."
                      : "No instructions yet — tap Edit to add how to train this.");
      detail.appendChild(noteEl);
      // The exercise library is the owner's, not a log: a guest trains against
      // it and reads the instructions, but doesn't get to rename or delete
      // anything in it. The server drops guest-sent exercises to match.
      if (!isGuest()) {
        const editBtn = document.createElement("button");
        editBtn.type = "button";
        editBtn.className = "ghost ex-edit";
        editBtn.textContent = "Edit";
        editBtn.addEventListener("click", (e) => {
          e.stopPropagation();
          openExerciseDialog(ex);
        });
        detail.appendChild(editBtn);
      }

      li.appendChild(row);
      li.appendChild(detail);
      list.appendChild(li);
    }

    renderTrainingHeatmap(exercises, events);
  }

  function renderDayBar() {
    const day = selectedDay();
    const isToday = ymd(day) === ymd(new Date());
    document.getElementById("day-next").disabled  = isToday;
    document.getElementById("day-today").disabled = isToday;
    // Year-less date on the picker's face — the year is implicit and the
    // saved width keeps the bar on one row on small phones.
    document.getElementById("day-date-face").textContent =
      day.toLocaleDateString(undefined, { month: "short", day: "numeric" });
    const title = document.getElementById("overview-title");
    if (title) {
      title.textContent = isToday
        ? "Today's overview"
        : day.toLocaleDateString(undefined, { weekday: "long", month: "short", day: "numeric" });
    }
    renderExcludeToggle(day);
  }

  // The "not counted" switch, and the overview's own dimmed state while it is
  // on, so the mark is legible from the day itself and not only from the charts.
  function renderExcludeToggle(day) {
    const btn = document.getElementById("exclude-day");
    const note = document.getElementById("excluded-note");
    const panel = document.querySelector('[data-panel="overview"]');
    // Deciding a day doesn't count is a judgment about the owner's own record,
    // so it sits with the rest of what a guest cannot do.
    btn.hidden = isGuest();
    const off = isExcluded(day);
    btn.setAttribute("aria-pressed", String(off));
    btn.classList.toggle("active", off);
    note.hidden = !off;
    panel.classList.toggle("day-excluded", off);
  }

  // Marking is adding an event; un-marking is deleting it — so both ride the
  // ordinary sync, offline included, with no special casing anywhere.
  function toggleExcludedDay(day) {
    const key = ymd(day);
    const existing = live().filter(
      e => e.type === EXCLUDED_TYPE && ymd(new Date(e.at)) === key);
    if (existing.length > 0) {
      // Plural in principle: two devices could each mark the same day offline.
      for (const e of existing) deleteEvent(e.id);
    } else {
      // Noon, so the day it lands on survives any clock or timezone wobble.
      const at = startOfDay(day);
      at.setHours(12, 0, 0, 0);
      addEvent(EXCLUDED_TYPE, "", at.getTime());
    }
  }

  function renderHeader() {
    const cfg   = loadConfig();
    const title = document.getElementById("app-title");
    const ageEl = document.getElementById("puppy-age");
    title.textContent = cfg.name ? `🐶 ${cfg.name}` : "🐶 Puppy Tracker";
    document.title = cfg.name ? `${cfg.name} · Puppy Tracker` : "Puppy Tracker";
    const ageText = formatAgeShort(cfg.birthday);
    ageEl.textContent = ageText;
    ageEl.hidden = !ageText;
    // Use the puppy's name in the sleep-timeline heading rather than assuming a
    // gender; fall back to a neutral phrase when no name is configured.
    const sleepTitle = document.getElementById("sleep-timeline-title");
    if (sleepTitle) sleepTitle.textContent = cfg.name ? `When ${cfg.name} sleeps` : "When sleeping";
    const walkTitle = document.getElementById("walk-timeline-title");
    if (walkTitle) walkTitle.textContent = cfg.name ? `When ${cfg.name} walks` : "When walking";
    // The guest banner names the dog too, so it follows the profile in.
    renderGuestBanner();
  }

  // Dim the quick actions that don't fit the current state — a nudge
  // toward the likely next tap. A boundary that would just repeat the latest
  // one of its pair (a second "sleep start" while already asleep, a "walk end"
  // with no walk running) is disabled outright, since it can only produce a
  // zero-length window. Everything else stays clickable so
  // corrections (a mid-nap pee) are never blocked, and a genuinely missed
  // boundary is still fixable from the event log, which accepts any time.
  function renderActionHints(events) {
    const { state } = currentSleepState(events);
    const { walking } = currentWalkState(events);
    document.querySelectorAll("button.action").forEach(btn => {
      const type = btn.dataset.type;
      const isWalk = type === "walk-start" || type === "walk-end";
      // Walks are a start→end pair of their own, so they answer to the walk
      // state rather than the sleep one: only the boundary that flips it can
      // produce a window. Mid-walk, ending it is the obvious next tap.
      const repeat = isWalk
        ? (walking ? type === "walk-start" : type === "walk-end")
        : state === "asleep" ? type === "sleep-start"
        : state === "awake" ? type === "sleep-end"
        : false; // no sleep history yet — either boundary is a fine first event
      const unlikely = !repeat && (
        isWalk ? (!walking && state === "asleep")
        : state === "asleep" ? type !== "sleep-end"
        : state === "awake" ? type === "sleep-end"
        : false // no sleep history yet — no hints to give
      );
      btn.classList.toggle("unlikely", unlikely);
      btn.disabled = repeat;
      btn.title = !repeat ? ""
        : isWalk ? (walking ? "Already on a walk" : "No walk in progress")
        : type === "sleep-start" ? "Already asleep" : "Already awake";
    });
  }

  function render() {
    const events = live();
    // Which days don't count is read straight off the event list, and settles
    // before anything draws — the chart drawers consult excludedSet directly.
    excludedSet = excludedDays(events);
    const counted = countedEvents(events);
    renderHeader();
    renderDayBar();
    renderChartWindow();
    // Day-scoped panels get the full list: you navigated to this day, so you
    // should see what is actually on it, marked or not.
    renderBigClock(events);
    renderActionHints(events);
    renderStats(events);
    renderLasts(events);
    renderSleepWake(events);
    renderWalks(events);
    renderHistory(events);
    // Weight and notes are records of fact rather than behaviour a sparse
    // logger distorts, so they count everywhere regardless.
    renderWeight(events);
    renderNotes(events);
    // Everything that aggregates across days works from the counted list.
    renderTiming(counted);
    renderWeekly(counted);
    renderSleepTimeline(counted);
    renderWalkPatterns(counted);
    renderSleepTrend(counted);
    renderHourHeatmap(counted);
    renderTraining(counted);
  }

  // ---------- sync ----------
  let syncTimer  = null;
  let syncing    = false;
  let lastError  = null;
  let lastSynced = 0;

  function setStatus(state) {
    statusEl.classList.remove("offline", "syncing", "error", "pending");
    if (!navigator.onLine) {
      statusEl.textContent = "offline";
      statusEl.classList.add("offline");
      return;
    }
    switch (state) {
      case "syncing":
        statusEl.textContent = "syncing…";
        statusEl.classList.add("syncing");
        break;
      case "error":
        statusEl.textContent = "sync error";
        statusEl.classList.add("error");
        statusEl.title = lastError || "";
        break;
      case "pending":
        statusEl.textContent = "pending";
        statusEl.classList.add("pending");
        break;
      default:
        statusEl.textContent = lastSynced
          ? `synced ${formatRelative(lastSynced)}`
          : "synced";
        statusEl.title = "";
    }
  }

  function scheduleSync() {
    if (!navigator.onLine) { setStatus("pending"); return; }
    setStatus("pending");
    clearTimeout(syncTimer);
    syncTimer = setTimeout(sync, SYNC_DEBOUNCE_MS);
  }

  // Merge a server response back into local storage. Anything local with a
  // newer updatedAt than the server's copy wins — that covers items the user
  // added/edited during the in-flight sync request. Shared by the events and
  // exercises collections, which follow the same LWW contract.
  //
  // serverWins overrides that for items we are not allowed to change: the
  // server will have refused the write, so keeping our newer local copy would
  // leave the screen showing an edit that never happened and re-posting it
  // forever. Taking the server's version instead makes the client heal itself.
  function mergeSynced(serverItems, load, save, serverWins = () => false) {
    const localById = new Map(load().map(e => [e.id, e]));
    const merged = new Map();
    for (const se of serverItems) {
      if (se && se.id) merged.set(se.id, se);
    }
    for (const [id, le] of localById) {
      const se = merged.get(id);
      if (se && serverWins(se)) continue;
      if (!se || (le.updatedAt || 0) > (se.updatedAt || 0)) {
        merged.set(id, le);
      }
    }
    save([...merged.values()]);
  }

  async function sync() {
    if (!currentUser) return;
    if (syncing) return;
    if (!navigator.onLine) { setStatus("pending"); return; }
    syncing = true;
    setStatus("syncing");
    try {
      // Push queued photos first so events that reference them won't return
      // 404s when other clients try to fetch.
      await syncPhotos();

      const res = await fetch(SYNC_URL, {
        method: "POST",
        headers: { "Content-Type": "application/json" },
        body: JSON.stringify({ events: loadAll() }),
      });
      if (res.status === 401) { handleLoggedOut(); return; }
      if (!res.ok) throw new Error(`HTTP ${res.status}`);
      const body = await res.json();

      const exRes = await fetch("api/exercises/sync", {
        method: "POST",
        headers: { "Content-Type": "application/json" },
        // A guest receives the exercise library but never writes to it, so it
        // sends nothing rather than posting a list the server would discard.
        body: JSON.stringify({ exercises: isGuest() ? [] : loadExercises() }),
      });
      if (exRes.status === 401) { handleLoggedOut(); return; }
      if (!exRes.ok) throw new Error(`HTTP ${exRes.status}`);
      const exBody = await exRes.json();

      if (Array.isArray(exBody.exercises)) {
        // Same reasoning as the events below: a guest's local exercise edits
        // can never land, so the server's copy is always the truth.
        mergeSynced(exBody.exercises, loadExercises, saveExercises, isGuest);
      }
      if (Array.isArray(body.events)) {
        mergeSynced(body.events, loadAll, saveAll, (ev) => !canEditEvent(ev));
      }
      lastSynced = Date.now();
      lastError = null;
      render();
      setStatus("synced");
    } catch (err) {
      lastError = err.message || String(err);
      console.warn("sync failed:", lastError);
      setStatus("error");
    } finally {
      syncing = false;
    }
  }

  // ---------- config sync ----------
  // Reconcile the local config cache with the host. Whichever side has the
  // newer updatedAt wins: adopt the server's copy, or push ours if it's ahead
  // (e.g. edited on this device while another client hadn't changed it). This
  // self-heals a failed push — the local copy stays newer and re-pushes next tick.
  async function syncConfig() {
    if (!currentUser) return;
    if (!navigator.onLine) return;
    const local = loadConfig();
    try {
      const res = await fetch("api/config");
      if (res.status === 401) { handleLoggedOut(); return; }
      if (!res.ok) throw new Error(`HTTP ${res.status}`);
      const body = await res.json();
      const server = {
        name: body.name || "",
        birthday: body.birthday || "",
        pedigreeId: body.pedigreeId || "",
        updatedAt: Number.isFinite(body.updatedAt) ? body.updatedAt : 0,
      };
      const merged = reconcileConfig(local, server);
      if (!sameConfig(merged, local)) {
        saveConfig(merged);
        renderHeader();
        refreshPedigreeButton();
      }
      if (!sameConfig(merged, server)) {
        await pushConfig(merged);
      }
    } catch (err) {
      console.warn("config sync failed:", err);
    }
  }

  async function pushConfig(cfg) {
    if (!navigator.onLine) return;
    const res = await fetch("api/config", {
      method: "PUT",
      headers: { "Content-Type": "application/json" },
      body: JSON.stringify(cfg),
    });
    if (!res.ok) throw new Error(`HTTP ${res.status}`);
    const body = await res.json();
    // Adopt the server's answer if it turned out to be newer (another client won).
    if (Number.isFinite(body.updatedAt) && body.updatedAt > cfg.updatedAt) {
      saveConfig({ name: body.name || "", birthday: body.birthday || "", pedigreeId: body.pedigreeId || "", updatedAt: body.updatedAt });
      renderHeader();
    }
  }

  // ---------- dialogs ----------
  const noteDialog       = document.getElementById("note-dialog");
  const noteForm         = document.getElementById("note-form");
  const noteInput        = document.getElementById("note-input");
  const noteDate         = document.getElementById("note-date");
  const noteTime         = document.getElementById("note-time");
  const noteTitle        = document.getElementById("note-title");
  const notePhotoInput   = document.getElementById("note-photo-input");
  const notePhotoBtn     = document.getElementById("note-photo-btn");
  const notePhotoPreview = document.getElementById("note-photo-preview");
  const noteWeightField  = document.getElementById("note-weight-field");
  const noteWeight       = document.getElementById("note-weight");
  const noteGramsField   = document.getElementById("note-grams-field");
  const noteGrams        = document.getElementById("note-grams");
  let pendingType        = null;
  let notePhotos         = []; // pending photos for this dialog: [{ blob, url }]
  // Whether the user has manually touched the date/time fields. While false the
  // dialog logs at the exact current millisecond rather than the minute-floored
  // input, so a just-logged event doesn't look up to ~59s old.
  let noteTimeEdited     = false;

  // An event can carry several photos: photoId holds their UUIDs
  // comma-separated. A legacy single id is just a one-element list, and the
  // server passes the string through untouched (photos themselves are
  // uploaded and fetched individually by UUID).
  function photoIdsOf(ev) {
    return (ev.photoId || "").split(",").filter(Boolean);
  }

  // A preview thumbnail with a remove button; shared by both dialogs.
  function photoThumb(url, onRemove) {
    const wrap = document.createElement("div");
    wrap.className = "photo-thumb";
    const img = document.createElement("img");
    img.alt = "";
    if (url) img.src = url;
    const rm = document.createElement("button");
    rm.type = "button";
    rm.className = "photo-thumb-remove";
    rm.setAttribute("aria-label", "Remove photo");
    rm.textContent = "×";
    rm.addEventListener("click", onRemove);
    wrap.appendChild(img);
    wrap.appendChild(rm);
    return wrap;
  }

  function renderNotePhotos() {
    notePhotoPreview.innerHTML = "";
    notePhotoPreview.hidden = notePhotos.length === 0;
    notePhotos.forEach((p, i) => {
      notePhotoPreview.appendChild(photoThumb(p.url, () => {
        URL.revokeObjectURL(p.url);
        notePhotos.splice(i, 1);
        renderNotePhotos();
      }));
    });
  }

  function clearNotePhotos() {
    for (const p of notePhotos) URL.revokeObjectURL(p.url);
    notePhotos = [];
    renderNotePhotos();
    notePhotoInput.value = "";
  }

  function openNoteDialog(type) {
    pendingType = type;
    noteInput.value = "";
    const isNote = type === "note";
    // A note is about a day, so default it to the day you're viewing (at the
    // current clock time). The logging types default to "now"; leaving
    // noteTimeEdited false lets noteDialogAt() stamp the exact instant.
    let base = Date.now();
    if (isNote) {
      const day = selectedDay();
      const now = new Date();
      day.setHours(now.getHours(), now.getMinutes(), 0, 0);
      base = day.getTime();
    }
    noteTimeEdited = isNote;
    noteDate.value = toDateInput(base);
    noteTime.value = toTimeInput(base);
    noteTitle.textContent = isNote ? "Add note" : `Log ${EVENT_LABELS[type]}`;
    const isWeight = type === "weight";
    const isEat    = type === "eat";
    noteWeightField.hidden = !isWeight;
    noteWeight.value = "";
    noteGramsField.hidden = !isEat;
    noteGrams.value = "";
    clearNotePhotos();
    noteDialog.showModal();
    setTimeout(() => (isWeight ? noteWeight : isEat ? noteGrams : noteInput).focus(), 50);
  }

  function noteDialogAt() {
    // Untouched time → stamp the exact current instant (sub-minute accurate).
    // Once the user picks a time, honor the input (minute precision is fine).
    if (!noteTimeEdited) return Date.now();
    const parsed = fromDateTimeInputs(noteDate.value, noteTime.value);
    return Number.isFinite(parsed) ? parsed : Date.now();
  }

  document.getElementById("note-time-now").addEventListener("click", () => {
    const now = Date.now();
    noteDate.value = toDateInput(now);
    noteTime.value = toTimeInput(now);
    noteTimeEdited = false; // "Now" means log at the current instant again
  });

  [noteDate, noteTime].forEach(el => {
    const markEdited = () => { noteTimeEdited = true; };
    el.addEventListener("change", markEdited);
    el.addEventListener("input", markEdited);
  });

  notePhotoBtn.addEventListener("click", () => notePhotoInput.click());
  notePhotoInput.addEventListener("change", async (e) => {
    for (const file of Array.from(e.target.files || [])) {
      try {
        const blob = await resizeImage(file);
        notePhotos.push({ blob, url: URL.createObjectURL(blob) });
      } catch (err) {
        alert("Couldn't process that photo: " + err.message);
      }
    }
    notePhotoInput.value = "";
    renderNotePhotos();
  });

  document.getElementById("note-save").addEventListener("click", async (e) => {
    e.preventDefault();
    if (!pendingType) { noteDialog.close(); return; }
    if (pendingType === "note" && noteInput.value.trim() === "" && notePhotos.length === 0) {
      alert("Write something for the note, or add a photo.");
      return;
    }
    let weight;
    if (pendingType === "weight") {
      weight = parseFloat(noteWeight.value);
      if (!(weight > 0)) { alert("Enter a weight in kilograms."); return; }
      weight = Math.round(weight * 100) / 100;
    }
    let grams;
    if (pendingType === "eat" && noteGrams.value.trim() !== "") {
      const g = parseFloat(noteGrams.value);
      if (!(g > 0)) { alert("Enter the amount in grams, or leave it empty."); return; }
      grams = Math.round(g);
    }
    const photoIds = [];
    for (const p of notePhotos) {
      const id = uuid();
      try { await putPhoto(id, p.blob, false); }
      catch (err) {
        alert("Couldn't store photo locally: " + err.message);
        return;
      }
      photoIds.push(id);
    }
    addEvent(pendingType, noteInput.value.trim(), noteDialogAt(), { photoId: photoIds.join(","), weight, grams });
    pendingType = null;
    clearNotePhotos();
    noteDialog.close();
  });
  noteForm.querySelector('button[value="cancel"]').addEventListener("click", (e) => {
    e.preventDefault();
    pendingType = null;
    clearNotePhotos();
    noteDialog.close();
  });

  // Edit dialog
  const editDialog       = document.getElementById("edit-dialog");
  const editForm         = document.getElementById("edit-form");
  const editDate         = document.getElementById("edit-date");
  const editTime         = document.getElementById("edit-time");
  const editNote         = document.getElementById("edit-note");
  const editLoggedBy     = document.getElementById("edit-logged-by");
  const editReadOnly     = document.getElementById("edit-readonly");
  const editTitle        = document.getElementById("edit-title");
  const editDelete       = document.getElementById("edit-delete");
  const editSave         = document.querySelector('#edit-form button[value="save"]');
  const editCancel       = document.querySelector('#edit-form button[value="cancel"]');
  const editPhotoInput   = document.getElementById("edit-photo-input");
  const editPhotoBtn     = document.getElementById("edit-photo-btn");
  const editPhotoPreview = document.getElementById("edit-photo-preview");
  const editWeightField  = document.getElementById("edit-weight-field");
  const editWeight       = document.getElementById("edit-weight");
  const editGramsField   = document.getElementById("edit-grams-field");
  const editGrams        = document.getElementById("edit-grams");
  let editingId          = null;
  // The dialog's working set of photos, in display order. Existing photos are
  // { id, url } (url from photoSrc's page-lifetime cache — never revoked here);
  // newly picked ones are { blob, url } with a fresh object URL we own.
  let editPhotos         = [];

  function renderEditPhotos() {
    editPhotoPreview.innerHTML = "";
    editPhotoPreview.hidden = editPhotos.length === 0;
    editPhotos.forEach((p, i) => {
      editPhotoPreview.appendChild(photoThumb(p.url, () => {
        if (p.blob) URL.revokeObjectURL(p.url);
        editPhotos.splice(i, 1);
        renderEditPhotos();
      }));
    });
  }

  function resetEditPhotos() {
    for (const p of editPhotos) if (p.blob) URL.revokeObjectURL(p.url);
    editPhotos = [];
    editPhotoInput.value = "";
  }

  // Turns the edit dialog into a viewer: every field disabled, Save and Delete
  // gone, only Cancel left. Used when a guest opens an entry that isn't theirs
  // — the server would refuse the change anyway (Store.sync), and a form that
  // silently discards what you typed is worse than one that says it is closed.
  function setEditReadOnly(on) {
    editReadOnly.hidden = !on;
    editTitle.textContent = on ? "Event" : "Edit event";
    for (const el of [editDate, editTime, editNote, editWeight, editGrams, editPhotoBtn]) {
      el.disabled = on;
    }
    editDelete.hidden = on;
    editSave.hidden = on;
    editCancel.textContent = on ? "Close" : "Cancel";
  }

  async function openEditDialog(ev) {
    editingId = ev.id;
    editLoggedBy.hidden = !ev.loggedBy;
    if (ev.loggedBy) editLoggedBy.textContent = `Logged by ${ev.loggedBy} on a guest link.`;
    setEditReadOnly(!canEditEvent(ev));
    editDate.value = toDateInput(ev.at);
    editTime.value = toTimeInput(ev.at);
    editNote.value = ev.note || "";
    editWeightField.hidden = ev.type !== "weight";
    editWeight.value = (ev.type === "weight" && Number.isFinite(ev.weight)) ? ev.weight : "";
    editGramsField.hidden = ev.type !== "eat";
    editGrams.value = (ev.type === "eat" && Number.isFinite(ev.grams) && ev.grams > 0) ? ev.grams : "";
    resetEditPhotos();
    for (const id of photoIdsOf(ev)) {
      editPhotos.push({ id, url: await photoSrc(id) });
    }
    renderEditPhotos();
    editDialog.showModal();
    // Without an explicit focus the browser autofocuses the first control —
    // the date input — and iOS immediately pops the calendar over the form.
    // Land on the first relevant text field instead (same trick and delay as
    // openNoteDialog: synchronous focus can be lost while the dialog settles).
    const focusTarget = !editWeightField.hidden ? editWeight
                      : !editGramsField.hidden  ? editGrams
                      : editNote;
    setTimeout(() => focusTarget.focus(), 50);
  }

  editPhotoBtn.addEventListener("click", () => editPhotoInput.click());
  editPhotoInput.addEventListener("change", async (e) => {
    for (const file of Array.from(e.target.files || [])) {
      try {
        const blob = await resizeImage(file);
        editPhotos.push({ blob, url: URL.createObjectURL(blob) });
      } catch (err) {
        alert("Couldn't process that photo: " + err.message);
      }
    }
    editPhotoInput.value = "";
    renderEditPhotos();
  });

  editForm.querySelector('button[value="save"]').addEventListener("click", async (e) => {
    e.preventDefault();
    if (!editingId) { editDialog.close(); return; }
    const newAt = fromDateTimeInputs(editDate.value, editTime.value);
    const patch = {
      at: Number.isFinite(newAt) ? newAt : undefined,
      note: editNote.value.trim(),
    };
    if (!editWeightField.hidden) {
      const kg = parseFloat(editWeight.value);
      if (!(kg > 0)) { alert("Enter a weight in kilograms."); return; }
      patch.weight = Math.round(kg * 100) / 100;
    }
    if (!editGramsField.hidden) {
      if (editGrams.value.trim() === "") {
        patch.grams = undefined; // cleared → drop the amount
      } else {
        const g = parseFloat(editGrams.value);
        if (!(g > 0)) { alert("Enter the amount in grams, or leave it empty."); return; }
        patch.grams = Math.round(g);
      }
    }
    const photoIds = [];
    for (const p of editPhotos) {
      if (p.id) { photoIds.push(p.id); continue; }
      const id = uuid();
      try { await putPhoto(id, p.blob, false); }
      catch (err) { alert("Couldn't store photo locally: " + err.message); return; }
      photoIds.push(id);
    }
    patch.photoId = photoIds.join(",");
    updateEvent(editingId, patch);
    editingId = null;
    resetEditPhotos();
    editDialog.close();
  });

  editForm.querySelector('button[value="cancel"]').addEventListener("click", (e) => {
    e.preventDefault();
    editingId = null;
    resetEditPhotos();
    editDialog.close();
  });

  editDelete.addEventListener("click", (e) => {
    e.preventDefault();
    if (editingId && confirm("Delete this event?")) {
      deleteEvent(editingId);
    }
    editingId = null;
    resetEditPhotos();
    editDialog.close();
  });

  // Settings dialog (puppy name + birthday)
  // ---------- theme ----------
  // Preference is device-global (not per user). No stored choice → follow the
  // OS via the prefers-color-scheme media query; a choice sets data-theme on
  // <html>, which the CSS treats as an override. The <head> applies any saved
  // choice before first paint; this just resolves state and reacts to the toggle.
  const THEME_KEY = "puppy-tracker:theme";
  const prefersDark = () =>
    window.matchMedia && window.matchMedia("(prefers-color-scheme: dark)").matches;
  function effectiveTheme() {
    const s = localStorage.getItem(THEME_KEY);
    return s === "light" || s === "dark" ? s : (prefersDark() ? "dark" : "light");
  }
  function setTheme(theme) {
    document.documentElement.dataset.theme = theme;
    try { localStorage.setItem(THEME_KEY, theme); } catch { /* ignore */ }
  }

  const settingsDialog   = document.getElementById("settings-dialog");
  const settingsForm     = document.getElementById("settings-form");
  const settingsName     = document.getElementById("settings-name");
  const settingsBirthday = document.getElementById("settings-birthday");
  const settingsPedigree = document.getElementById("settings-pedigree");
  const settingsTheme    = document.getElementById("settings-theme");
  const settingsConfetti = document.getElementById("settings-confetti");
  const settingsProfile  = document.getElementById("settings-profile");
  const settingsDanger   = document.getElementById("settings-danger");

  // Apply live so the toggle previews immediately (independent of Save/Cancel).
  settingsTheme.addEventListener("change", () => {
    setTheme(settingsTheme.checked ? "dark" : "light");
  });

  function openSettingsDialog() {
    const cfg = loadConfig();
    settingsName.value     = cfg.name;
    settingsBirthday.value = cfg.birthday;
    settingsPedigree.value = cfg.pedigreeId;
    settingsTheme.checked  = effectiveTheme() === "dark";
    settingsConfetti.checked = confettiEnabled();
    // A guest keeps the two device-local preferences and loses everything that
    // belongs to the account — profile, reminders, guest links, deletion.
    const guest = isGuest();
    settingsProfile.hidden = guest;
    settingsDanger.hidden  = guest;
    guestAccess.hidden     = guest;
    settingsDialog.showModal();
    refreshRemindersUI();
    if (!guest) {
      // Re-defaulted per open: the app can sit on screen for days, and a date
      // that was "tomorrow" when it launched may be in the past by now.
      resetGuestExpiry();
      refreshGuestLinks();
    }
    setTimeout(() => (guest ? settingsTheme : settingsName).focus(), 50);
  }

  document.getElementById("settings-btn").addEventListener("click", openSettingsDialog);

  settingsForm.querySelector('button[value="save"]').addEventListener("click", async (e) => {
    e.preventDefault();
    // A guest only ever had the two device-local toggles on screen. Saving the
    // profile from here would push the blanked-out fields over the owner's.
    if (isGuest()) {
      setConfettiEnabled(settingsConfetti.checked);
      settingsDialog.close();
      return;
    }
    const cfg = {
      name: settingsName.value.trim(),
      birthday: settingsBirthday.value,
      pedigreeId: settingsPedigree.value.trim(),
      updatedAt: Date.now(),
    };
    saveConfig(cfg);       // cache locally for instant + offline paint
    setConfettiEnabled(settingsConfetti.checked); // device-local, not synced
    renderHeader();
    refreshPedigreeButton();
    settingsDialog.close();
    // Rules are saved with the rest of Settings; the notification toggle itself
    // already acted when it was flipped, since permission needs a user gesture.
    if (!remindersSection.hidden && !remindersRules.hidden) {
      try {
        await saveReminderRules(collectReminderRules());
      } catch (err) {
        console.warn("saving reminders failed:", err);
      }
    }
    try {
      await pushConfig(cfg);
    } catch (err) {
      console.warn("config save failed:", err);
      // Kept locally; syncConfig retries automatically once the host is reachable.
    }
  });
  settingsForm.querySelector('button[value="cancel"]').addEventListener("click", (e) => {
    e.preventDefault();
    settingsDialog.close();
  });

  // ---------- guest links ----------
  // Hand someone a URL that logs events on this account without giving them the
  // password. The server holds only a hash of the token (server/auth.go), so the
  // URL is shown once, right after it is minted, and never again.

  const guestAccess   = document.getElementById("guest-access");
  const guestLabelIn  = document.getElementById("guest-label");
  const guestCreate   = document.getElementById("guest-create");
  const guestError    = document.getElementById("guest-error");
  const guestListEl   = document.getElementById("guest-list");
  const guestEmpty    = document.getElementById("guest-empty");
  const guestExpires  = document.getElementById("guest-expires");
  const guestExpHint  = document.getElementById("guest-expires-hint");

  // The owner picks a date; the link dies at the end of it. Working in whole
  // days is what people actually mean ("she has him until Sunday"), and doing
  // the conversion here is the only place the guest's timezone is known — the
  // server just stores the instant it is handed.
  function guestExpiryMs() {
    const [y, m, d] = (guestExpires.value || "").split("-").map(Number);
    if (!y || !m || !d) return 0;
    return endOfDay(new Date(y, m - 1, d)).getTime();
  }

  function renderGuestExpiryHint() {
    const ms = guestExpiryMs();
    if (!ms) { guestExpHint.textContent = "Pick the last day the link should work."; return; }
    if (ms <= Date.now()) { guestExpHint.textContent = "That date has already passed."; return; }
    guestExpHint.textContent = `Stops working ${formatWhen(ms)}.`;
  }

  // Default to tomorrow: the common case is a sitter for the day, and a link
  // that dies at midnight tonight is rarely what anyone wants.
  function resetGuestExpiry() {
    guestExpires.min = toDateInput(Date.now());
    guestExpires.value = toDateInput(Date.now() + 86_400_000);
    renderGuestExpiryHint();
  }
  guestExpires.addEventListener("change", renderGuestExpiryHint);
  resetGuestExpiry();

  // The server never sees its own public origin (it may sit behind any proxy),
  // so the URL is composed here, against wherever this page is actually served.
  function guestURL(token) {
    return new URL(`guest/${token}`, location.href).href;
  }

  // Day and month as well as the weekday: a 7-day link expires on the same
  // weekday it was made, which "Sun 09:00" alone wouldn't tell apart.
  function formatWhen(ms) {
    return new Date(ms).toLocaleString(undefined, {
      weekday: "short", day: "numeric", month: "short",
      hour: "2-digit", minute: "2-digit",
    });
  }

  function renderGuestLinks(links) {
    guestListEl.innerHTML = "";
    guestEmpty.textContent = "No active links."; // may hold a stale error
    guestEmpty.hidden = links.length > 0;
    for (const l of links) {
      const li = document.createElement("li");
      li.className = "guest-item";
      const used = l.lastUsed
        ? `last used ${formatRelative(l.lastUsed)}`
        : "never used";
      li.innerHTML = `
        <div class="guest-item-row">
          <span class="guest-item-main">
            <span class="guest-item-label"></span>
            <span class="guest-item-sub"></span>
          </span>
        </div>
      `;
      li.querySelector(".guest-item-label").textContent = l.label;
      li.querySelector(".guest-item-sub").textContent = `expires ${formatWhen(l.expires)} · ${used}`;
      const revoke = document.createElement("button");
      revoke.type = "button";
      revoke.className = "linklike guest-revoke";
      revoke.textContent = "Revoke";
      revoke.addEventListener("click", () => revokeGuestLink(l.id, l.label));
      li.querySelector(".guest-item-row").appendChild(revoke);

      // The URL stays available for as long as the link does, so it can be
      // re-sent without minting a new one and stranding whoever holds the old.
      if (l.token) {
        const url = guestURL(l.token);
        const box = document.createElement("div");
        box.className = "guest-item-url";
        const code = document.createElement("code");
        code.className = "guest-url";
        code.textContent = url;
        code.title = url; // the line is truncated; the tooltip isn't
        // Tapping the URL selects the whole of it, so it can be copied by hand
        // where the clipboard API isn't available (it needs a secure context).
        code.addEventListener("click", () => selectContents(code));
        const copy = document.createElement("button");
        copy.type = "button";
        copy.className = "ghost guest-copy";
        copy.textContent = "Copy";
        copy.addEventListener("click", () => copyGuestURL(copy, code));
        box.appendChild(code);
        box.appendChild(copy);
        li.appendChild(box);
      } else {
        // Links minted before the URL was kept: only their hash was stored, so
        // there is nothing to show. Revoking and making a new one is the fix.
        const note = document.createElement("p");
        note.className = "settings-hint guest-item-url";
        note.textContent = "Made before links could be re-shown — revoke it and create a new one to get a copyable URL.";
        li.appendChild(note);
      }
      guestListEl.appendChild(li);
    }
  }

  async function refreshGuestLinks() {
    guestError.hidden = true;
    try {
      const res = await fetch("api/shares");
      if (!res.ok) throw new Error(`HTTP ${res.status}`);
      const body = await res.json();
      renderGuestLinks(Array.isArray(body.links) ? body.links : []);
    } catch (err) {
      // Offline is the common case here and not worth an error: the list is
      // server state, so it simply isn't knowable right now.
      guestListEl.innerHTML = "";
      guestEmpty.hidden = false;
      guestEmpty.textContent = navigator.onLine
        ? "Couldn't load your links."
        : "Offline — guest links need a connection.";
    }
  }

  guestCreate.addEventListener("click", async () => {
    guestError.hidden = true;
    const expires = guestExpiryMs();
    if (!expires || expires <= Date.now()) {
      guestError.textContent = "Pick a date in the future for the link to stop working.";
      guestError.hidden = false;
      return;
    }
    guestCreate.disabled = true;
    try {
      const res = await fetch("api/shares", {
        method: "POST",
        headers: { "Content-Type": "application/json" },
        body: JSON.stringify({ label: guestLabelIn.value.trim(), expires }),
      });
      if (!res.ok) throw new Error((await res.text()).trim() || `HTTP ${res.status}`);
      await res.json();
      guestLabelIn.value = "";
      resetGuestExpiry();
      // Nothing special to do with the new link: the list shows every link's
      // URL, so it simply appears there like the rest.
      await refreshGuestLinks();
    } catch (err) {
      guestError.textContent = err.message || "Couldn't create a link";
      guestError.hidden = false;
    } finally {
      guestCreate.disabled = false;
    }
  });

  function selectContents(el) {
    const range = document.createRange();
    range.selectNodeContents(el);
    const sel = getSelection();
    sel.removeAllRanges();
    sel.addRange(range);
  }

  async function copyGuestURL(btn, code) {
    try {
      await navigator.clipboard.writeText(code.textContent);
      btn.textContent = "Copied";
      setTimeout(() => { btn.textContent = "Copy"; }, 1500);
    } catch {
      // The clipboard API needs a secure context and can be refused outright.
      // The URL is on screen either way, so select it and let them copy by hand.
      selectContents(code);
    }
  }

  async function revokeGuestLink(id, label) {
    if (!confirm(`Turn off the link for “${label}”? Whoever has it loses access straight away.`)) return;
    try {
      const res = await fetch(`api/shares/${encodeURIComponent(id)}`, { method: "DELETE" });
      if (!res.ok && res.status !== 404) throw new Error(`HTTP ${res.status}`);
      await refreshGuestLinks();
    } catch (err) {
      guestError.textContent = err.message || "Couldn't revoke that link";
      guestError.hidden = false;
    }
  }

  // ---------- reminders ----------
  // The server decides when a reminder is due and pushes it (server/reminders.go);
  // this side only manages the browser's push subscription and the rule settings.
  // Nothing here can fire a notification on its own — a closed PWA has no timers,
  // which is the whole reason the evaluation lives on the host.

  const REMINDER_LABELS = {
    sleep: "Time to sleep, awake for",
    pee:   "Time for pee, none for",
    poo:   "Time for poo, none for",
    eat:   "Time for a meal, none for",
  };

  const remindersSection = document.getElementById("reminders-section");
  const remindersToggle  = document.getElementById("reminders-enabled");
  const remindersHint    = document.getElementById("reminders-hint");
  const remindersRules   = document.getElementById("reminders-rules");
  const remindersTest    = document.getElementById("reminders-test");

  let pushKey = null;      // VAPID public key, once the server has given us one
  let reminderRules = [];  // last-known rule set, re-rendered into the dialog

  // iOS only exposes push to a PWA that was added to the Home Screen; in a plain
  // Safari tab PushManager doesn't exist at all, so the toggle would be dead.
  const isStandalone = () =>
    window.matchMedia("(display-mode: standalone)").matches || navigator.standalone === true;
  const isIOS = () =>
    /iP(hone|ad|od)/.test(navigator.userAgent) ||
    (navigator.platform === "MacIntel" && navigator.maxTouchPoints > 1);

  const pushSupported = () =>
    "serviceWorker" in navigator && "PushManager" in window && "Notification" in window;

  // applicationServerKey wants raw bytes, not the base64url the server sends.
  function b64UrlToBytes(s) {
    const pad = "=".repeat((4 - (s.length % 4)) % 4);
    const bin = atob((s + pad).replace(/-/g, "+").replace(/_/g, "/"));
    const out = new Uint8Array(bin.length);
    for (let i = 0; i < bin.length; i++) out[i] = bin.charCodeAt(i);
    return out;
  }

  function bytesToB64Url(bytes) {
    let bin = "";
    for (const b of bytes) bin += String.fromCharCode(b);
    return btoa(bin).replace(/\+/g, "-").replace(/\//g, "_").replace(/=+$/, "");
  }

  // subscribeForPush returns a live subscription, registering it with the host.
  // It runs on every launch, not just when the toggle is flipped: iOS silently
  // drops subscriptions, and a stale endpoint fails invisibly until re-posted.
  async function subscribeForPush() {
    const reg = await navigator.serviceWorker.ready;
    let sub = await reg.pushManager.getSubscription();

    // A subscription made under a different VAPID key can't be reused — the
    // browser rejects re-subscribing with a new key — so drop it first. Only
    // when we can positively see a mismatch, though: if a browser doesn't
    // expose options, re-subscribing blindly would mint a fresh endpoint on
    // every launch and strand the old row on the server.
    if (sub) {
      const existing = sub.options && sub.options.applicationServerKey;
      if (existing && bytesToB64Url(new Uint8Array(existing)) !== pushKey) {
        try { await sub.unsubscribe(); } catch { /* ignore */ }
        sub = null;
      }
    }
    if (!sub) {
      sub = await reg.pushManager.subscribe({
        userVisibleOnly: true,
        applicationServerKey: b64UrlToBytes(pushKey),
      });
    }
    const res = await fetch("api/push/subscribe", {
      method: "POST",
      headers: { "Content-Type": "application/json" },
      body: JSON.stringify(sub),
    });
    if (!res.ok) throw new Error(`subscribe failed: ${res.status}`);
    return sub;
  }

  async function unsubscribeFromPush() {
    const reg = await navigator.serviceWorker.ready;
    const sub = await reg.pushManager.getSubscription();
    if (!sub) return;
    // Tell the host first: if the local unsubscribe succeeds but the POST never
    // lands, the server would keep pushing to an endpoint nobody listens on.
    try {
      await fetch("api/push/unsubscribe", {
        method: "POST",
        headers: { "Content-Type": "application/json" },
        body: JSON.stringify({ endpoint: sub.endpoint }),
      });
    } catch { /* the endpoint dies on its own once the browser drops it */ }
    try { await sub.unsubscribe(); } catch { /* ignore */ }
  }

  async function loadReminderRules() {
    const res = await fetch("api/reminders");
    if (!res.ok) throw new Error(`reminders: ${res.status}`);
    const body = await res.json();
    reminderRules = body.reminders || [];
    return reminderRules;
  }

  async function saveReminderRules(rules) {
    const res = await fetch("api/reminders", {
      method: "PUT",
      headers: { "Content-Type": "application/json" },
      body: JSON.stringify({ reminders: rules }),
    });
    if (!res.ok) throw new Error(`reminders: ${res.status}`);
    // The server clamps intervals, so adopt what it actually stored.
    reminderRules = (await res.json()).reminders || rules;
  }

  function renderReminderRules() {
    remindersRules.replaceChildren();
    for (const rule of reminderRules) {
      const row = document.createElement("div");
      row.className = "reminder-row";
      row.dataset.kind = rule.kind;

      const name = document.createElement("label");
      name.className = "reminder-name";
      const on = document.createElement("input");
      on.type = "checkbox";
      on.className = "switch reminder-on";
      on.setAttribute("role", "switch");
      on.checked = rule.enabled;
      const text = document.createElement("span");
      text.textContent = REMINDER_LABELS[rule.kind] || rule.kind;
      name.append(on, text);

      const after = document.createElement("span");
      after.className = "reminder-after";
      const mins = document.createElement("input");
      mins.type = "number";
      mins.className = "reminder-mins";
      mins.min = "5";
      mins.max = "1440";
      mins.step = "5";
      mins.value = String(rule.intervalMin);
      const unit = document.createElement("span");
      unit.textContent = "min";
      after.append(mins, unit);

      row.append(name, after);
      remindersRules.append(row);
    }
  }

  // collectReminderRules reads the dialog back into the rule shape the API takes.
  function collectReminderRules() {
    return [...remindersRules.querySelectorAll(".reminder-row")].map((row) => ({
      kind: row.dataset.kind,
      enabled: row.querySelector(".reminder-on").checked,
      intervalMin: Number(row.querySelector(".reminder-mins").value) || 60,
    }));
  }

  function setReminderHint(text) {
    remindersHint.textContent = text || "";
    remindersHint.hidden = !text;
  }

  // Reflects permission + subscription state: the rules only matter once there
  // is somewhere to deliver them.
  function showReminderControls(subscribed) {
    remindersToggle.checked = subscribed;
    remindersRules.hidden = !subscribed;
    remindersTest.hidden = !subscribed;
  }

  // initReminders runs once at startup. It establishes whether reminders are
  // available at all (the server may have no VAPID key, the browser may have no
  // push support) and refreshes an existing subscription.
  async function initReminders() {
    // Reminders belong to the account, not the device: a guest subscribing here
    // would route the owner's reminders to the sitter's lock screen. The server
    // refuses these routes for a guest anyway; bailing early keeps the section
    // from flashing up on iOS, where it appears before any request is made.
    if (isGuest()) return;
    if (!pushSupported()) {
      // On iOS this is the Home Screen requirement rather than a missing feature,
      // and it's worth saying so — the toggle is otherwise just absent.
      if (isIOS() && !isStandalone()) {
        remindersSection.hidden = false;
        remindersToggle.disabled = true;
        setReminderHint("Add Puppy Tracker to your Home Screen to enable reminders.");
      }
      return;
    }
    try {
      const res = await fetch("api/push/key");
      if (!res.ok) return; // host has push disabled; leave the section hidden
      pushKey = (await res.json()).key;
    } catch {
      return; // offline at boot: try again next launch
    }
    if (!pushKey) return;
    remindersSection.hidden = false;

    if (Notification.permission !== "granted") {
      showReminderControls(false);
      return;
    }
    try {
      await subscribeForPush();
      showReminderControls(true);
    } catch (err) {
      console.warn("push re-subscribe failed:", err);
      showReminderControls(false);
    }
  }

  // The toggle acts immediately rather than on Save: requesting notification
  // permission has to happen inside a user gesture, and on iOS a deferred
  // request is simply ignored.
  remindersToggle.addEventListener("change", async () => {
    if (!remindersToggle.checked) {
      setReminderHint("");
      showReminderControls(false);
      await unsubscribeFromPush();
      return;
    }
    remindersToggle.disabled = true;
    try {
      const permission = await Notification.requestPermission();
      if (permission !== "granted") {
        showReminderControls(false);
        setReminderHint(
          permission === "denied"
            ? "Notifications are blocked for this app in your browser settings."
            : "Notifications need permission to work."
        );
        return;
      }
      await subscribeForPush();
      await loadReminderRules();
      renderReminderRules();
      showReminderControls(true);
      setReminderHint("");
    } catch (err) {
      console.warn("enabling reminders failed:", err);
      showReminderControls(false);
      setReminderHint("Couldn't enable reminders. Try again once you're online.");
    } finally {
      remindersToggle.disabled = false;
    }
  });

  remindersTest.addEventListener("click", async () => {
    remindersTest.disabled = true;
    try {
      const res = await fetch("api/push/test", { method: "POST" });
      setReminderHint(res.ok ? "Test sent." : "Couldn't send a test notification.");
    } catch {
      setReminderHint("Couldn't send a test notification.");
    } finally {
      remindersTest.disabled = false;
    }
  });

  // Called when the settings dialog opens, so the rows show what the host has.
  async function refreshRemindersUI() {
    if (remindersSection.hidden || !pushKey) return;
    try {
      await loadReminderRules();
      renderReminderRules();
    } catch (err) {
      console.warn("loading reminders failed:", err);
    }
  }

  // ---------- pedigree lookup ----------
  // A separate full-screen view that resolves a dog against SKK Hunddata by
  // chip / registration number / name and renders its ancestry as a tree. The
  // server returns the first generations immediately and crawls deeper in the
  // background; we poll for that and re-render as ancestors arrive. Online-only.
  const pedScreen  = document.getElementById("pedigree-screen");
  const pedStatus  = document.getElementById("pedigree-status");
  const pedChoose  = document.getElementById("pedigree-choose");
  const pedSubject = document.getElementById("pedigree-subject");
  const pedTree    = document.getElementById("pedigree-tree");
  const pedBtn     = document.getElementById("pedigree-btn");
  const pedRefresh = document.getElementById("pedigree-refresh");
  const pedRepeatNote = document.getElementById("pedigree-repeat-note");

  const PED_OPEN_DEPTH = 3; // show 3 generations expanded by default; deeper collapses
  let pedPollTimer = null;
  let pedNodes = {};        // latest ancestry map, for the progress count

  // ---- zoom ----
  // The tree gets very wide when expanded, so it's zoomable: buttons, ctrl/⌘ +
  // wheel, and pinch. We scale via the CSS `zoom` property (not transform) so the
  // scroll container reflows and every part stays reachable. The level persists.
  const pedZoomOut   = document.getElementById("ped-zoom-out");
  const pedZoomIn    = document.getElementById("ped-zoom-in");
  const pedZoomReset = document.getElementById("ped-zoom-reset");
  const PED_ZOOM_MIN = 0.4, PED_ZOOM_MAX = 1.6;
  const pedZoomKey = () => `puppy-tracker:${currentUser.id}:pedigree-zoom:v1`;
  let pedZoom = 1;

  function applyPedZoom() {
    pedZoom = Math.min(PED_ZOOM_MAX, Math.max(PED_ZOOM_MIN, Math.round(pedZoom * 100) / 100));
    pedTree.style.zoom = pedZoom;
    pedZoomReset.textContent = Math.round(pedZoom * 100) + "%";
    try { localStorage.setItem(pedZoomKey(), String(pedZoom)); } catch { /* ignore */ }
  }
  function pedZoomBy(delta) { pedZoom += delta; applyPedZoom(); }

  pedZoomIn.addEventListener("click", () => pedZoomBy(0.2));
  pedZoomOut.addEventListener("click", () => pedZoomBy(-0.2));
  pedZoomReset.addEventListener("click", () => { pedZoom = 1; applyPedZoom(); });

  // ---- collapse / expand all ----
  const pedFoldAll = document.getElementById("ped-foldall");
  function pedSetAll(collapsed) {
    pedTree.querySelectorAll("li").forEach((li) => {
      if (!li.querySelector(":scope > ul")) return; // no ancestors to fold
      li.classList.toggle("collapsed", collapsed);
      const t = li.querySelector(":scope > .ped-card > .ped-toggle");
      if (t) t.textContent = collapsed ? "+" : "−";
    });
    pedFoldAll.textContent = collapsed ? "Expand all" : "Collapse all";
  }
  pedFoldAll.addEventListener("click", () => pedSetAll(pedFoldAll.textContent[0] === "C"));

  // ---- view toggle: top-down tree vs radial fan ----
  const pedViewBtn = document.getElementById("ped-view");
  const pedCaption = document.getElementById("pedigree-caption");
  const pedViewKey = () => `puppy-tracker:${currentUser.id}:pedigree-view:v1`;
  let pedView = "tree";
  try { const v = localStorage.getItem(pedViewKey()); if (v === "fan" || v === "tree") pedView = v; } catch { /* ignore */ }

  // The fan has no per-branch folding, so hide that control in fan mode; the
  // toggle always offers the *other* view.
  function updatePedViewControls() {
    pedViewBtn.textContent = pedView === "fan" ? "Tree view" : "Fan view";
    pedFoldAll.hidden = pedView === "fan";
    if (pedView !== "fan" && pedCaption) { pedCaption.hidden = true; }
  }
  pedViewBtn.addEventListener("click", () => {
    pedView = pedView === "fan" ? "tree" : "fan";
    try { localStorage.setItem(pedViewKey(), pedView); } catch { /* ignore */ }
    renderPedigree(pedNodes);
  });

  // Trackpad/desktop: ctrl or ⌘ + wheel zooms instead of scrolling the page.
  pedTree.addEventListener("wheel", (e) => {
    if (!e.ctrlKey && !e.metaKey) return;
    e.preventDefault();
    pedZoomBy(e.deltaY < 0 ? 0.1 : -0.1);
  }, { passive: false });
  // Touch: two-finger pinch.
  let pinchDist = 0, pinchZoom = 1;
  const touchDist = (t) => Math.hypot(t[0].clientX - t[1].clientX, t[0].clientY - t[1].clientY);
  pedTree.addEventListener("touchstart", (e) => {
    if (e.touches.length === 2) { pinchDist = touchDist(e.touches); pinchZoom = pedZoom; }
  }, { passive: true });
  pedTree.addEventListener("touchmove", (e) => {
    if (e.touches.length === 2 && pinchDist > 0) {
      e.preventDefault();
      pedZoom = pinchZoom * (touchDist(e.touches) / pinchDist);
      applyPedZoom();
    }
  }, { passive: false });
  pedTree.addEventListener("touchend", (e) => { if (e.touches.length < 2) pinchDist = 0; });

  // The looked-up tree is cached locally per dog id, so reopening the page paints
  // instantly and still shows the last-known tree offline. The server caches it
  // too (per dog, permanently); this is just the client-side mirror.
  const pedCacheKey = (id) => `puppy-tracker:${currentUser.id}:pedigree:${id}:v1`;
  function loadPedCache(id) {
    try { return JSON.parse(localStorage.getItem(pedCacheKey(id))) || null; } catch { return null; }
  }
  function savePedCache(id, subject, nodes) {
    try { localStorage.setItem(pedCacheKey(id), JSON.stringify({ subject, nodes })); } catch { /* ignore */ }
  }

  // Show the 🌳 button only once a pedigree id is set in Settings.
  function refreshPedigreeButton() {
    pedBtn.hidden = !loadConfig().pedigreeId;
  }

  function openPedigree() {
    const id = loadConfig().pedigreeId;
    appEl.hidden = true;
    pedScreen.hidden = false;
    const saved = parseFloat(localStorage.getItem(pedZoomKey()));
    pedZoom = Number.isFinite(saved) ? saved : 1;
    applyPedZoom();
    if (!id) { setPedStatus("Set your dog's SKK id in Settings to see its pedigree.", ""); return; }
    lookupPedigree(id);
  }
  function closePedigree() {
    stopPedPoll();
    pedScreen.hidden = true;
    appEl.hidden = false;
  }
  function stopPedPoll() {
    if (pedPollTimer) { clearTimeout(pedPollTimer); pedPollTimer = null; }
  }

  pedBtn.addEventListener("click", openPedigree);
  document.getElementById("pedigree-back").addEventListener("click", closePedigree);
  pedRefresh.addEventListener("click", () => {
    const id = loadConfig().pedigreeId;
    if (id) lookupPedigree(id);
  });

  async function lookupPedigree(q) {
    stopPedPoll();
    pedChoose.hidden = true;  pedChoose.textContent = "";
    pedSubject.hidden = true; pedSubject.textContent = "";
    pedTree.textContent = "";
    pedNodes = {};

    // Paint the cached tree first so the page is instant (and works offline).
    const cached = loadPedCache(q);
    if (cached && cached.nodes) {
      renderSubject(cached.subject);
      renderPedigree(cached.nodes);
    }
    if (!navigator.onLine) {
      setPedStatus(cached ? "Offline — showing the last saved pedigree." : "Pedigree needs an internet connection.",
        cached ? "" : "error");
      return;
    }
    setPedStatus(cached ? "Refreshing…" : "Looking up…", "busy");
    let res;
    try {
      res = await fetch("api/pedigree", {
        method: "POST",
        headers: { "Content-Type": "application/json" },
        body: JSON.stringify({ q }),
      });
    } catch {
      setPedStatus(cached ? "Offline — showing the last saved pedigree." : "Couldn't reach the server. Try again.",
        cached ? "" : "error");
      return;
    }
    if (res.status === 401) { handleLoggedOut(); return; }
    if (res.status === 404) {
      setPedStatus("Couldn't find that dog in SKK — check the ID in Settings.", "error");
      return;
    }
    if (!res.ok) {
      const msg = (await res.text().catch(() => "")).trim();
      setPedStatus(msg || `Lookup failed (HTTP ${res.status}).`, "error");
      return;
    }
    const data = await res.json();
    if (data.status === "choose") { renderChoose(data.matches || []); return; }
    renderSubject(data.subject);
    renderPedigree(data.nodes || {});
    if (data.status === "done") {
      savePedCache(q, data.subject, data.nodes || {});
      setPedDone();
    } else {
      setPedStatus(`Tracing ancestry… ${pedCountText()}`, "busy");
      pollPedigree(data.jobId, q, data.subject);
    }
  }

  function pollPedigree(jobId, q, subject) {
    stopPedPoll();
    const tick = async () => {
      let res;
      try { res = await fetch(`api/pedigree/status?job=${encodeURIComponent(jobId)}`); }
      catch { pedPollTimer = setTimeout(tick, 3000); return; }
      if (res.status === 401) { handleLoggedOut(); return; }
      if (!res.ok) { setPedStatus("Lost track of the pedigree crawl.", "error"); return; }
      const data = await res.json();
      renderPedigree(data.nodes || {});
      if (data.status === "done")  { savePedCache(q, subject, data.nodes || {}); setPedDone(); return; }
      if (data.status === "error") { setPedStatus(data.error || "Pedigree crawl failed.", "error"); return; }
      setPedStatus(`Tracing ancestry… ${pedCountText()}`, "busy");
      pedPollTimer = setTimeout(tick, 1500);
    };
    pedPollTimer = setTimeout(tick, 1500);
  }

  // Counts derived from the ancestry map we already hold, so the summary is
  // right whether it came from a fresh crawl, a poll, or a cache hit. Distinct
  // ancestors are keyed by registration number (pedigree collapse means one dog
  // fills many positions); "generations back" is the depth of the deepest
  // position (floor(log2(pos)), since sire = 2·pos and dam = 2·pos+1).
  function pedCounts() {
    const counts = new Map();
    let maxPos = 1;
    for (const k in pedNodes) {
      const n = pedNodes[k];
      const key = n.reg || n.name;
      if (key) counts.set(key, (counts.get(key) || 0) + 1);
      const p = Number(k);
      if (p > maxPos) maxPos = p;
    }
    let repeated = 0;
    counts.forEach((c) => { if (c > 1) repeated++; });
    return { distinct: counts.size, repeated, gens: Math.floor(Math.log2(maxPos)) };
  }
  function pedCountText() {
    const { distinct: a, repeated: r, gens: g } = pedCounts();
    let s = `${a} ancestor${a === 1 ? "" : "s"} back ${g} generation${g === 1 ? "" : "s"}`;
    if (r > 0) s += `, ${r} appearing more than once`;
    return s;
  }
  function setPedDone() { setPedStatus(`Traced ${pedCountText()}.`, "done"); }
  function setPedStatus(text, kind) {
    pedStatus.hidden = false;
    pedStatus.textContent = text;
    pedStatus.className = "pedigree-status" + (kind ? " " + kind : "");
  }

  function renderSubject(s) {
    if (!s) { pedSubject.hidden = true; return; }
    pedSubject.hidden = false;
    pedSubject.textContent = "";
    const name = document.createElement("div");
    name.className = "ped-subject-name";
    name.textContent = s.name || "(unnamed)";
    const meta = document.createElement("div");
    meta.className = "ped-subject-meta";
    const bits = [];
    if (s.breed) bits.push(s.breed);
    if (s.reg) bits.push(s.reg);
    if (s.sex) bits.push(s.sex === "H" ? "♂" : s.sex === "T" ? "♀" : s.sex);
    meta.textContent = bits.join(" · ");
    pedSubject.append(name, meta);
  }

  function renderChoose(matches) {
    pedTree.textContent = "";
    pedSubject.hidden = true;
    setPedStatus(`${matches.length} matches — pick one:`, "");
    pedChoose.hidden = false;
    pedChoose.textContent = "";
    matches.slice(0, 50).forEach((m) => {
      const b = document.createElement("button");
      b.type = "button";
      b.className = "ped-match";
      const nm = (m.hundnamn || "").trim() || "(unnamed)";
      const nameEl = document.createElement("span");
      nameEl.className = "ped-match-name";
      nameEl.textContent = nm;
      const metaEl = document.createElement("span");
      metaEl.className = "ped-match-meta";
      metaEl.textContent = [m.Regnr, m.rastext].filter(Boolean).join(" · ");
      b.append(nameEl, metaEl);
      b.addEventListener("click", () => {
        pedChoose.hidden = true;
        lookupPedigree((m.Regnr || "").trim() || nm);
      });
      pedChoose.append(b);
    });
  }

  // The tree is ahnentafel-indexed: the dog is position 1, its sire 2n and dam
  // 2n+1. We render it top-down like a family tree — the dog on top, parents
  // branching below — as a nested <ul>/<li> so CSS can draw the connectors.
  // Built recursively (sire left, dam right) and collapsed below PED_OPEN_DEPTH.
  // A dog's identity for spotting pedigree collapse: its registration number,
  // or its name when it has none. Ancestors sharing a key are the same dog.
  function dogKey(n) { return n ? (n.reg || n.name || "") : ""; }
  // Stable hue per repeated dog so its badge/highlight colour is consistent
  // everywhere it appears.
  function hueFor(s) {
    let h = 0;
    for (let i = 0; i < s.length; i++) h = (h * 31 + s.charCodeAt(i)) >>> 0;
    return h % 360;
  }
  let pedRepeat = {}; // dogKey -> occurrence count, for the current tree

  // Render the ancestry in whichever view is active (top-down tree or radial
  // fan). Shared prep — cache the nodes and count pedigree collapse — lives here.
  function renderPedigree(nodes) {
    pedNodes = nodes;
    pedRepeat = {};
    for (const k in nodes) {
      const id = dogKey(nodes[k]);
      if (id) pedRepeat[id] = (pedRepeat[id] || 0) + 1;
    }
    if (pedRepeatNote) pedRepeatNote.hidden = !Object.values(pedRepeat).some((c) => c > 1);
    pedTree.textContent = "";
    if (pedView === "fan") renderFan(nodes); else renderTree(nodes);
    updatePedViewControls();
  }

  function renderTree(nodes) {
    const root = buildPedNode(nodes, 1, 0);
    if (!root) return;
    const ul = document.createElement("ul");
    ul.className = "ped-tree-h";
    ul.append(root);
    pedTree.append(ul);
    if (pedFoldAll) pedFoldAll.textContent = "Collapse all"; // fresh tree starts partly open
  }

  // ---- radial fan chart ----
  // The dog sits in a centre disc; each generation is a ring fanning outward.
  // A position p is at generation g = floor(log2 p); within that ring it takes
  // the wedge (idx=p-2^g) of 2^g equal slices, which nests each dog's parents
  // directly outside it. Labels only fit on the inner rings; deeper wedges are
  // colour only, with details on tap. Repeated dogs (pedigree collapse) carry
  // their stable hue so tapping one lights up every wedge of that dog.
  const FAN_MAX_GEN = 9;
  const SVGNS = "http://www.w3.org/2000/svg";
  const fanPolar = (r, deg) => {
    const a = (deg - 90) * Math.PI / 180;
    return [r * Math.cos(a), r * Math.sin(a)];
  };
  const fanNum = (n) => Math.round(n * 100) / 100;

  function renderFan(nodes) {
    let maxGen = 0;
    for (const k in nodes) { const g = Math.floor(Math.log2(Number(k))); if (g > maxGen) maxGen = g; }
    maxGen = Math.min(maxGen, FAN_MAX_GEN);

    const r0 = 46;
    const radii = [r0];
    for (let g = 1; g <= maxGen; g++) radii[g] = radii[g - 1] + Math.max(24, 50 - g * 3);
    const R = radii[maxGen] || r0;
    const pad = 4;
    const box = (R + pad) * 2;

    const svg = document.createElementNS(SVGNS, "svg");
    svg.setAttribute("class", "ped-fan");
    svg.setAttribute("viewBox", `${-R - pad} ${-R - pad} ${box} ${box}`);
    svg.setAttribute("width", box);
    svg.setAttribute("height", box);

    for (let g = 1; g <= maxGen; g++) {
      const count = 2 ** g, degPer = 360 / count, ri = radii[g - 1], ro = radii[g];
      for (let idx = 0; idx < count; idx++) {
        const n = nodes[String(count + idx)];
        if (!n) continue;
        const a0 = idx * degPer, a1 = a0 + degPer, large = (a1 - a0) > 180 ? 1 : 0;
        const [x1, y1] = fanPolar(ri, a0), [x2, y2] = fanPolar(ro, a0);
        const [x3, y3] = fanPolar(ro, a1), [x4, y4] = fanPolar(ri, a1);
        const path = document.createElementNS(SVGNS, "path");
        path.setAttribute("d",
          `M${fanNum(x2)} ${fanNum(y2)}A${fanNum(ro)} ${fanNum(ro)} 0 ${large} 1 ${fanNum(x3)} ${fanNum(y3)}` +
          `L${fanNum(x4)} ${fanNum(y4)}A${fanNum(ri)} ${fanNum(ri)} 0 ${large} 0 ${fanNum(x1)} ${fanNum(y1)}Z`);
        path.setAttribute("class", "ped-wedge");
        path.style.setProperty("--gen", g);
        const key = dogKey(n);
        if (key && pedRepeat[key] > 1) {
          path.dataset.dogkey = key;
          path.style.setProperty("--repeat-hue", hueFor(key));
          path.classList.add("ped-wedge-repeat");
        }
        const title = document.createElementNS(SVGNS, "title");
        title.textContent = fanTitle(n, key);
        path.append(title);
        path.addEventListener("click", () => selectFan(count + idx));
        svg.append(path);
        if (degPer >= 20) fanLabel(svg, n, (a0 + a1) / 2, ri, ro, degPer);
      }
    }

    // centre disc = the dog
    const c = document.createElementNS(SVGNS, "circle");
    c.setAttribute("r", r0);
    c.setAttribute("class", "ped-fan-center");
    c.addEventListener("click", () => selectFan(1));
    svg.append(c);
    fanCenterLabel(svg, nodes["1"], r0);

    pedTree.append(svg);
    if (pedCaption) {
      pedCaption.hidden = false;
      pedCaption.textContent = "Tap a wedge for its dog. Zoom to read the outer rings.";
    }
  }

  function fanTitle(n, key) {
    let t = n.name || "(unnamed)";
    if (n.reg) t += " — " + n.reg;
    if (key && pedRepeat[key] > 1) t += "  (×" + pedRepeat[key] + ")";
    return t;
  }

  function fanLabel(svg, n, midA, ri, ro, degPer) {
    let rot = midA - 90;
    if (rot > 90 && rot < 270) rot -= 180; // keep upright
    const [px, py] = fanPolar((ri + ro) / 2, midA);
    const t = document.createElementNS(SVGNS, "text");
    t.setAttribute("class", "ped-wedge-label");
    t.setAttribute("transform", `translate(${fanNum(px)} ${fanNum(py)}) rotate(${fanNum(rot)})`);
    const room = Math.floor((ro - ri) / 6.2); // chars that fit along the ring
    t.textContent = fanTrunc(n.name || (n.reg || "?"), Math.max(6, room));
    svg.append(t);
  }

  function fanCenterLabel(svg, n, r0) {
    if (!n) return;
    const words = (n.name || "Dog").split(" ");
    const lines = [];
    let line = "";
    for (const w of words) {
      if ((line + " " + w).trim().length > 12) { if (line) lines.push(line); line = w; }
      else line = (line ? line + " " : "") + w;
    }
    if (line) lines.push(line);
    const shown = lines.slice(0, 3);
    const t = document.createElementNS(SVGNS, "text");
    t.setAttribute("class", "ped-fan-center-label");
    t.setAttribute("text-anchor", "middle");
    const lh = 12, y0 = -(shown.length - 1) * lh / 2;
    shown.forEach((ln, i) => {
      const ts = document.createElementNS(SVGNS, "tspan");
      ts.setAttribute("x", "0");
      ts.setAttribute("y", fanNum(y0 + i * lh));
      ts.textContent = ln;
      t.append(ts);
    });
    svg.append(t);
  }

  function fanTrunc(s, max) { return s.length > max ? s.slice(0, max - 1) + "…" : s; }

  function selectFan(pos) {
    const n = pedNodes[String(pos)];
    if (!n || !pedCaption) return;
    const key = dogKey(n);
    const bits = [];
    if (n.reg) bits.push(n.reg);
    if (n.titles) bits.push(n.titles);
    if (key && pedRepeat[key] > 1) bits.push("appears ×" + pedRepeat[key]);
    pedCaption.hidden = false;
    pedCaption.textContent = (n.name || "(unnamed)") + (bits.length ? " — " + bits.join(" · ") : "");
    togglePedHighlight(key && pedRepeat[key] > 1 ? key : ""); // clears if not a repeat
  }

  // Highlight (or unhighlight) every element (tree card or fan wedge) that is the
  // same dog as `key`.
  function togglePedHighlight(key) {
    const els = pedTree.querySelectorAll("[data-dogkey]");
    let lit = false;
    els.forEach((c) => {
      if (c.dataset.dogkey === key && c.classList.contains("ped-lit")) lit = true;
    });
    els.forEach((c) => c.classList.remove("ped-lit"));
    if (!lit) els.forEach((c) => { if (c.dataset.dogkey === key) c.classList.add("ped-lit"); });
  }

  function buildPedNode(nodes, pos, depth) {
    const n = nodes[String(pos)];
    const hasSire = !!nodes[String(pos * 2)];
    const hasDam  = !!nodes[String(pos * 2 + 1)];
    if (!n && !hasSire && !hasDam) return null;

    const li = document.createElement("li");

    const card = document.createElement("div");
    card.className = "ped-card";
    const nameEl = document.createElement("div");
    nameEl.className = "ped-name";
    nameEl.textContent = n ? (n.name || "(unnamed)") : "Unknown";
    if (!n) nameEl.classList.add("ped-unknown");
    card.append(nameEl);
    if (n && n.titles) {
      const t = document.createElement("div");
      t.className = "ped-titles";
      t.textContent = n.titles;
      card.append(t);
    }
    if (n && n.reg) {
      const r = document.createElement("div");
      r.className = "ped-reg";
      r.textContent = n.reg;
      card.append(r);
    }

    // Mark dogs that fill more than one position (pedigree collapse). A ×N badge
    // shows how many times, a stable colour ties the copies together, and tapping
    // the card lights up every place this dog appears.
    const key = dogKey(n);
    if (key && pedRepeat[key] > 1) {
      card.classList.add("ped-repeat");
      card.dataset.dogkey = key;
      card.style.setProperty("--repeat-hue", hueFor(key));
      const badge = document.createElement("span");
      badge.className = "ped-repeat-badge";
      badge.textContent = "×" + pedRepeat[key];
      badge.title = "Appears " + pedRepeat[key] + " times in this pedigree — tap to highlight them all";
      card.append(badge);
      card.addEventListener("click", (e) => {
        if (e.target.closest(".ped-toggle")) return; // let the expander do its job
        togglePedHighlight(key);
      });
    }
    li.append(card);

    if (hasSire || hasDam) {
      const kids = document.createElement("ul");
      const s = buildPedNode(nodes, pos * 2, depth + 1);
      const d = buildPedNode(nodes, pos * 2 + 1, depth + 1);
      if (s) { s.classList.add("ped-sire"); kids.append(s); }
      if (d) { d.classList.add("ped-dam");  kids.append(d); }

      const collapsed = depth >= PED_OPEN_DEPTH;
      if (collapsed) li.classList.add("collapsed");
      const toggle = document.createElement("button");
      toggle.type = "button";
      toggle.className = "ped-toggle";
      toggle.setAttribute("aria-label", "Toggle ancestors");
      toggle.textContent = collapsed ? "+" : "−";
      toggle.addEventListener("click", () => {
        const nowCollapsed = li.classList.toggle("collapsed");
        toggle.textContent = nowCollapsed ? "+" : "−";
      });
      card.prepend(toggle);
      li.append(kids);
    }
    return li;
  }

  // ---------- changelog dialog ----------
  // Shows the *loaded* build's full changelog: the plain URL is served
  // cache-first by the controlling service worker, so the list always matches
  // the version actually running (the update banner handles what's newer).
  const changelogDialog = document.getElementById("changelog-dialog");
  const changelogList   = document.getElementById("changelog-list");
  const changelogEmpty  = document.getElementById("changelog-empty");

  function formatChangelogDate(iso) {
    const [y, m, d] = (iso || "").split("-").map(Number);
    if (!y || !m || !d) return iso || "";
    return new Date(y, m - 1, d).toLocaleDateString(undefined, {
      year: "numeric", month: "short", day: "numeric",
    });
  }

  document.getElementById("changelog-btn").addEventListener("click", async () => {
    let entries = [];
    try {
      const res = await fetch("changelog.json");
      if (res.ok) {
        const body = await res.json();
        if (Array.isArray(body)) entries = body.filter(e => e && e.text);
      }
    } catch { /* fall through to empty state */ }

    changelogList.innerHTML = "";
    changelogEmpty.hidden = entries.length > 0;
    let lastDate = null;
    for (const e of entries) {
      if (e.date !== lastDate) {
        lastDate = e.date;
        const dt = document.createElement("li");
        dt.className = "changelog-date";
        dt.textContent = formatChangelogDate(e.date);
        changelogList.appendChild(dt);
      }
      const li = document.createElement("li");
      li.className = "changelog-entry";
      li.textContent = e.text;
      changelogList.appendChild(li);
    }
    changelogDialog.showModal();
  });

  // ---------- exercise dialog (add / edit a training exercise) ----------
  const exerciseDialog = document.getElementById("exercise-dialog");
  const exerciseForm   = document.getElementById("exercise-form");
  const exerciseTitle  = document.getElementById("exercise-title");
  const exerciseName   = document.getElementById("exercise-name");
  const exerciseNote   = document.getElementById("exercise-note");
  const exerciseDelete = document.getElementById("exercise-delete");
  let editingExerciseId = null;

  function openExerciseDialog(ex) {
    editingExerciseId = ex ? ex.id : null;
    exerciseTitle.textContent = ex ? "Edit exercise" : "Add exercise";
    exerciseName.value = ex ? ex.name : "";
    exerciseNote.value = ex ? (ex.note || "") : "";
    exerciseDelete.hidden = !ex;
    exerciseDialog.showModal();
    setTimeout(() => exerciseName.focus(), 50);
  }

  document.getElementById("exercise-add").addEventListener("click", () => openExerciseDialog(null));

  exerciseForm.querySelector('button[value="save"]').addEventListener("click", (e) => {
    e.preventDefault();
    const name = exerciseName.value.trim();
    if (!name) { alert("Give the exercise a name."); return; }
    const note = exerciseNote.value.trim();
    if (editingExerciseId) updateExercise(editingExerciseId, { name, note });
    else addExercise(name, note);
    editingExerciseId = null;
    exerciseDialog.close();
  });
  exerciseForm.querySelector('button[value="cancel"]').addEventListener("click", (e) => {
    e.preventDefault();
    editingExerciseId = null;
    exerciseDialog.close();
  });
  exerciseDelete.addEventListener("click", (e) => {
    e.preventDefault();
    if (editingExerciseId && confirm("Delete this exercise? Logged sessions stay in history.")) {
      deleteExercise(editingExerciseId);
    }
    editingExerciseId = null;
    exerciseDialog.close();
  });

  // ---------- delete account ----------
  const deleteAccountDialog   = document.getElementById("delete-account-dialog");
  const deleteAccountPassword = document.getElementById("delete-account-password");
  const deleteAccountError    = document.getElementById("delete-account-error");
  const deleteAccountConfirm  = document.getElementById("delete-account-confirm");

  document.getElementById("delete-account-btn").addEventListener("click", () => {
    settingsDialog.close();
    deleteAccountPassword.value = "";
    deleteAccountError.hidden = true;
    deleteAccountDialog.showModal();
    setTimeout(() => deleteAccountPassword.focus(), 50);
  });

  deleteAccountConfirm.addEventListener("click", async () => {
    deleteAccountError.hidden = true;
    deleteAccountConfirm.disabled = true;
    try {
      const res = await fetch("api/me", {
        method: "DELETE",
        headers: { "Content-Type": "application/json" },
        body: JSON.stringify({ password: deleteAccountPassword.value }),
      });
      if (!res.ok) {
        const msg = (await res.text()).trim();
        throw new Error(res.status === 401 ? "Incorrect password" : (msg || `HTTP ${res.status}`));
      }
      // Account is gone server-side. Wipe this user's local cache before the
      // reload drops us back on the login screen.
      clearLocalCache();
      clearUser();
      deleteAccountDialog.close();
      location.reload();
    } catch (err) {
      deleteAccountError.textContent = err.message || "Something went wrong";
      deleteAccountError.hidden = false;
    } finally {
      deleteAccountConfirm.disabled = false;
    }
  });

  // ---------- quick-log snackbar ----------
  // A single tap on a quick-action logs the event at the current instant, then
  // shows a brief snackbar to undo it or add detail — so the two-tap dialog flow
  // is never required for a plain pee/poo/meal/sleep boundary. Weigh-ins still
  // open the dialog since they need a value.
  const snackbar     = document.getElementById("snackbar");
  const snackbarMsg  = document.getElementById("snackbar-msg");
  const snackbarUndo = document.getElementById("snackbar-undo");
  const snackbarNote = document.getElementById("snackbar-note");
  let snackbarEvent  = null;
  let snackbarTimer  = null;

  function hideSnackbar() {
    clearTimeout(snackbarTimer);
    snackbarTimer = null;
    snackbarEvent = null;
    snackbar.classList.remove("show");
    snackbar.hidden = true;
  }

  function showSnackbar(msg, ev) {
    snackbarEvent = ev;
    snackbarMsg.textContent = msg;
    snackbar.hidden = false;
    void snackbar.offsetWidth; // reflow so the fade-in transition runs
    snackbar.classList.add("show");
    clearTimeout(snackbarTimer);
    snackbarTimer = setTimeout(hideSnackbar, 5000);
  }

  function quickLog(type) {
    const ev = addEvent(type, "", Date.now());
    showSnackbar(`${EVENT_LABELS[type]} logged`, ev);
    if (type === "pee" || type === "poo") pottyConfetti(type);
  }

  // A little burst of 💧/💩 from the tapped button when a pee/poo is logged.
  // Pure DOM + CSS; particles remove themselves when their animation ends.
  // Skipped when disabled in Settings or the user prefers reduced motion.
  // Device-local preference (like the theme), on by default.
  const CONFETTI_KEY = "puppy-tracker:confetti:v1";
  function confettiEnabled() {
    try { return localStorage.getItem(CONFETTI_KEY) !== "off"; } catch { return true; }
  }
  function setConfettiEnabled(on) {
    try { localStorage.setItem(CONFETTI_KEY, on ? "on" : "off"); } catch { /* ignore */ }
  }
  let confettiLayerEl = null;
  function confettiLayer() {
    if (!confettiLayerEl) {
      confettiLayerEl = document.createElement("div");
      confettiLayerEl.id = "confetti-layer";
      document.body.appendChild(confettiLayerEl);
    }
    return confettiLayerEl;
  }
  function pottyConfetti(type) {
    if (!confettiEnabled()) return;
    if (window.matchMedia && matchMedia("(prefers-reduced-motion: reduce)").matches) return;
    const emoji = type === "poo" ? "💩" : "💧";
    const layer = confettiLayer();
    const W = window.innerWidth, H = window.innerHeight;
    for (let i = 0; i < 30; i++) {
      const piece = document.createElement("span");
      piece.className = "confetti-piece";
      piece.textContent = emoji;
      // Launch from a point across the bottom, shoot up to a random peak while
      // drifting sideways, slowing and fading out as it reaches the top.
      const peakY = -Math.round(H * (0.45 + Math.random() * 0.45));
      piece.style.left = `${Math.round(W * (0.1 + Math.random() * 0.8))}px`;
      piece.style.top = `${H + 20}px`;
      piece.style.setProperty("--peakY", `${peakY}px`);
      piece.style.setProperty("--dx", `${Math.round((Math.random() * 2 - 1) * W * 0.22)}px`);
      piece.style.setProperty("--rot", `${Math.round(Math.random() * 720 - 360)}deg`);
      piece.style.fontSize = `${Math.round(16 + Math.random() * 18)}px`;
      piece.style.animationDuration = `${Math.round(1100 + Math.random() * 700)}ms`;
      piece.style.animationDelay = `${Math.round(Math.random() * 280)}ms`;
      piece.addEventListener("animationend", () => piece.remove());
      layer.appendChild(piece);
    }
  }

  snackbarUndo.addEventListener("click", () => {
    if (snackbarEvent) deleteEvent(snackbarEvent.id);
    hideSnackbar();
  });
  snackbarNote.addEventListener("click", () => {
    const ev = snackbarEvent;
    hideSnackbar();
    if (ev) openEditDialog(ev);
  });

  // ---------- collapsible panels ----------
  // Anything in main carrying a data-panel key can be folded by clicking its
  // heading; collapsed keys are remembered across reloads. State is device-global
  // (like the theme), so a single non-namespaced key is fine — it's not per-user
  // data. Only collapsed panels are stored, so newly added panels default open.
  //
  // A whole section heads with an h2, a foldable block inside one with an h3.
  // The two nest without special handling: each has its own key, and a folded
  // section hides the block along with everything else it holds, which leaves
  // the block's own state to reappear as it was when the section reopens.
  const PANELS_KEY = "puppy-tracker:panels:v1";
  function loadPanelState() {
    try {
      const s = JSON.parse(localStorage.getItem(PANELS_KEY));
      return s && typeof s === "object" ? s : {};
    } catch { return {}; }
  }
  function savePanelState(state) {
    try { localStorage.setItem(PANELS_KEY, JSON.stringify(state)); } catch { /* ignore */ }
  }
  function initPanels() {
    const state = loadPanelState();
    document.querySelectorAll("main [data-panel]").forEach(panel => {
      const key = panel.dataset.panel;
      const head = panel.querySelector(":scope > h2, :scope > h3");
      if (!head) return;
      panel.classList.add("collapsible");
      const collapsed = !!state[key];
      panel.classList.toggle("collapsed", collapsed);
      head.setAttribute("role", "button");
      head.setAttribute("tabindex", "0");
      head.setAttribute("aria-expanded", String(!collapsed));
      const toggle = () => {
        const nowCollapsed = panel.classList.toggle("collapsed");
        head.setAttribute("aria-expanded", String(!nowCollapsed));
        const s = loadPanelState();
        if (nowCollapsed) s[key] = true; else delete s[key];
        savePanelState(s);
      };
      head.addEventListener("click", toggle);
      head.addEventListener("keydown", (e) => {
        if (e.key === "Enter" || e.key === " ") { e.preventDefault(); toggle(); }
      });
    });
  }
  initPanels();

  // ---------- tabs ----------
  // Fourteen panels in one column meant scrolling past sleep, timing and walks
  // to reach the weight curve. They are grouped into five tabs by subject; the
  // day bar and the log buttons stay above them, so logging is one tap from
  // wherever you are. Folding still works inside a tab — the two compose.
  //
  // The wrapper is what gets hidden, never the sections inside it: walk-timeline
  // and walk-trend carry their own `hidden` (renderWalkPatterns), and hiding
  // them directly would clobber that.
  const TAB_KEY = "puppy-tracker:tab:v1"; // device-global, like the fold state
  const DEFAULT_TAB = "today";
  const tabButtons = [...document.querySelectorAll(".tabs .tab")];
  const tabPanels  = [...document.querySelectorAll("main .tab-panel")];
  // Today is the one tab with no charts, so the window picker doesn't belong
  // over it.
  const TABS_WITHOUT_CHARTS = new Set(["today"]);
  let activeTab = DEFAULT_TAB;

  function loadTab() {
    try {
      const t = localStorage.getItem(TAB_KEY);
      return tabButtons.some(b => b.dataset.tab === t) ? t : DEFAULT_TAB;
    } catch { return DEFAULT_TAB; }
  }

  // Back returns to Today from any tab in one press, and a second press leaves
  // the app — two presses to get out from anywhere, whatever route you took.
  //
  // The alternative, a history entry per switch, is what a browser would do by
  // itself and is the reason tabbed apps get a reputation for trapping you:
  // flick between tabs fifteen times and it takes fifteen presses to escape.
  // So exactly one entry is ever live. It is armed on leaving Today and
  // consumed on returning, whether that return came from the back button or
  // from tapping the tab.
  let backArmed = false;

  function armBack() {
    if (backArmed) return;
    history.pushState({ puppyTab: true }, "");
    backArmed = true;
  }

  addEventListener("popstate", () => {
    // Not ours: some other navigation, so stay out of its way.
    if (!backArmed) return;
    backArmed = false;
    showTab(DEFAULT_TAB, { manageBack: false });
  });

  function showTab(id, { manageBack = true } = {}) {
    if (!tabButtons.some(b => b.dataset.tab === id)) id = DEFAULT_TAB;
    activeTab = id;
    for (const b of tabButtons) {
      const on = b.dataset.tab === id;
      b.classList.toggle("active", on);
      b.setAttribute("aria-selected", String(on));
      // Roving tabindex: the tablist is one stop, arrows move within it.
      b.tabIndex = on ? 0 : -1;
    }
    for (const p of tabPanels) p.hidden = p.dataset.tab !== id;
    document.querySelector(".chart-window").hidden = TABS_WITHOUT_CHARTS.has(id);
    // Deliberately no scrolling. Switching used to jump to the top, on the
    // theory that arriving halfway down a tab is disorienting — but the tab bar
    // is sticky, so you switch tabs *from* wherever you have scrolled to, and
    // being thrown back past the log buttons you had just scrolled off is worse.
    // If the new tab is shorter than the old scroll position the browser clamps
    // on its own, which needs no help from us.
    try { localStorage.setItem(TAB_KEY, id); } catch { /* ignore */ }
    if (manageBack) {
      if (id !== DEFAULT_TAB) {
        armBack();
      } else if (backArmed) {
        // Tapping Today gets to the same place the back button would, so spend
        // the entry rather than leaving a stale one that makes the next press
        // appear to do nothing. Clearing the flag first stops the popstate
        // this triggers from running the handler above a second time.
        backArmed = false;
        history.back();
      }
    }
    // The pill's visibility depends on whether the big card is on screen, and
    // the card only exists on one tab. A shorter tab can also leave the page
    // too short to stay scrolled, unsticking the bars, so re-check that too.
    updateBarClockMode();
    updateTabsMerged();
  }

  for (const [i, btn] of tabButtons.entries()) {
    btn.addEventListener("click", () => showTab(btn.dataset.tab));
    btn.addEventListener("keydown", (e) => {
      const step = e.key === "ArrowRight" ? 1 : e.key === "ArrowLeft" ? -1 : 0;
      if (!step) return;
      e.preventDefault();
      const next = tabButtons[(i + step + tabButtons.length) % tabButtons.length];
      showTab(next.dataset.tab);
      next.focus();
    });
  }

  // The tab bar sticks directly under the day bar, which means its `top` has to
  // be that bar's height — measured, because the bar's contents (and so its
  // height) differ between phones and orientations.
  //
  // A resize listener alone is not enough: the bar also grows the first time a
  // sleep is logged, when the timer pill appears inside it, and that fires no
  // resize. Watching the element covers both, and every other cause besides.
  const dayBarEl = document.querySelector(".day-bar");
  function measureDayBar() {
    if (!dayBarEl) return;
    document.documentElement.style.setProperty("--day-bar-h", `${dayBarEl.offsetHeight}px`);
  }
  const onDayBarResize = () => { measureDayBar(); updateTabsMerged(); };
  if (dayBarEl && typeof ResizeObserver === "function") {
    new ResizeObserver(onDayBarResize).observe(dayBarEl);
  } else {
    addEventListener("resize", onDayBarResize);
  }
  measureDayBar();

  // Once the log buttons have scrolled away the two frozen bars meet, and they
  // should look like one card rather than two stacked ones — see .merged in the
  // stylesheet. CSS cannot ask whether a sticky element is currently stuck, so
  // the test is simply whether they are touching.
  const tabsEl = document.querySelector(".tabs");
  function updateTabsMerged() {
    if (!dayBarEl || !tabsEl) return;
    const gap = tabsEl.getBoundingClientRect().top - dayBarEl.getBoundingClientRect().bottom;
    const merged = gap <= 1; // they overlap by a pixel by design
    dayBarEl.classList.toggle("merged", merged);
    tabsEl.classList.toggle("merged", merged);
  }
  updateTabsMerged();

  showTab(loadTab());

  // ---------- wiring ----------
  document.querySelectorAll("button.action").forEach(btn => {
    btn.addEventListener("click", () => {
      const type = btn.dataset.type;
      // Weigh-ins need a typed value, meals ask for grams, and a note is all
      // free text — so these open the full dialog instead of one-tap logging.
      if (type === "weight" || type === "eat" || type === "note") { openNoteDialog(type); return; }
      quickLog(type);
    });
  });

  // The timer pill doubles as a one-tap sleep toggle: tapping it logs the
  // boundary that ends the state it shows, exactly like the matching quick
  // action. Only reachable once the big card has scrolled away — in standby
  // the pill is visibility:hidden, so clicks can never land on it.
  document.getElementById("bar-clock").addEventListener("click", () => {
    const { state } = currentSleepState(live());
    if (!state) return; // no sleep history yet; the pill is hidden anyway
    quickLog(state === "asleep" ? "sleep-end" : "sleep-start");
  });

  document.querySelectorAll(".chart-days-picker button").forEach(b => {
    b.addEventListener("click", () => setChartDays(Number(b.dataset.days)));
  });

  document.querySelectorAll("#counts-metrics input[data-metric]").forEach(cb => {
    cb.addEventListener("change", () => {
      const on = [...document.querySelectorAll("#counts-metrics input[data-metric]:checked")]
        .map(el => el.dataset.metric);
      setCountsMetrics(on);
    });
  });

  // Swap the timer pill in/out of the frozen bar as the big card scrolls past,
  // and join the two frozen bars up once they meet. rAF-throttled: scroll
  // events fire far more often than we can paint.
  {
    let queued = false;
    const onScroll = () => {
      if (queued) return;
      queued = true;
      requestAnimationFrame(() => {
        queued = false;
        updateBarClockMode();
        updateTabsMerged();
      });
    };
    window.addEventListener("scroll", onScroll, { passive: true });
    window.addEventListener("resize", onScroll, { passive: true });
  }

  dayPicker.value = ymd(new Date());
  dayPicker.addEventListener("change", render);

  // The face opens the hidden input's native picker (iOS 16+ has showPicker;
  // focus() is the fallback and is what pops the picker on older iOS anyway).
  document.getElementById("day-date-face").addEventListener("click", () => {
    try {
      if (typeof dayPicker.showPicker === "function") dayPicker.showPicker();
      else dayPicker.focus();
    } catch {
      dayPicker.focus();
    }
  });

  function shiftSelectedDay(days) {
    const d = selectedDay();
    d.setDate(d.getDate() + days);
    dayPicker.value = ymd(d);
    render();
  }
  document.getElementById("day-prev").addEventListener("click", () => shiftSelectedDay(-1));
  document.getElementById("day-next").addEventListener("click", () => shiftSelectedDay(+1));
  document.getElementById("day-today").addEventListener("click", () => {
    dayPicker.value = ymd(new Date());
    render();
  });
  document.getElementById("exclude-day").addEventListener("click", () => {
    toggleExcludedDay(selectedDay()); // addEvent/deleteEvent re-render for us
  });

  // Clicking the status pill forces an immediate sync.
  statusEl.style.cursor = "pointer";
  statusEl.title = "Click to sync now";
  statusEl.addEventListener("click", () => { clearTimeout(syncTimer); sync(); });

  window.addEventListener("online", () => { setStatus(); sync(); syncConfig(); });
  window.addEventListener("offline", () => setStatus());

  // Service worker (independent of auth). The worker no longer auto-activates a
  // new build; instead we detect the waiting worker and let the user choose when
  // to swap onto fresh assets, so a long-open tab isn't left running stale JS.
  if ("serviceWorker" in navigator) {
    const updateBanner = document.getElementById("update-banner");
    const updateReload = document.getElementById("update-reload");
    const updateLater  = document.getElementById("update-later");
    let waitingWorker  = null;

    // Whether there was already a controlling worker when the page loaded. On a
    // brand-new install there isn't, and clients.claim() fires an initial
    // controllerchange we must NOT reload on (there's nothing to refresh to).
    const hadController = !!navigator.serviceWorker.controller;
    let reloadRequested = false; // user pressed Reload → controllerchange reloads
    let refreshing      = false; // guard against a reload loop

    navigator.serviceWorker.addEventListener("controllerchange", () => {
      if (refreshing) return;
      if (!hadController && !reloadRequested) return; // first-install claim
      refreshing = true;
      location.reload();
    });

    // What the waiting build changes compared to the running one. The plain
    // URL is answered by the *old* controlling worker cache-first, i.e. the
    // loaded build's changelog; the cache-busting query misses every SW cache
    // and hits the network, i.e. the new build's changelog. Entries in the
    // fresh copy that the cached one lacks are exactly "new since this build".
    async function changelogDiff() {
      const load = async (url) => {
        try {
          const res = await fetch(url);
          if (!res.ok) return null;
          const body = await res.json();
          return Array.isArray(body) ? body : null;
        } catch {
          return null;
        }
      };
      const current = await load("changelog.json");
      const fresh   = await load(`changelog.json?v=${Date.now()}`);
      if (!fresh) return [];
      const seen = new Set((current || []).map(e => e && e.text));
      return fresh.filter(e => e && e.text && !seen.has(e.text));
    }

    function showUpdateBanner(worker) {
      waitingWorker = worker;
      updateBanner.hidden = false;
      const list = document.getElementById("update-changelog");
      list.hidden = true;
      list.innerHTML = "";
      changelogDiff().then(entries => {
        if (entries.length === 0) return;
        for (const e of entries.slice(0, 6)) {
          const li = document.createElement("li");
          li.textContent = e.text;
          list.appendChild(li);
        }
        list.hidden = false;
      });
    }

    updateReload.addEventListener("click", () => {
      reloadRequested = true;
      updateBanner.hidden = true;
      // Tell the waiting worker to activate; controllerchange then reloads us.
      if (waitingWorker) waitingWorker.postMessage({ type: "SKIP_WAITING" });
    });
    // "Later" just dismisses; the next update (or reload) surfaces it again.
    updateLater.addEventListener("click", () => { updateBanner.hidden = true; });

    // Only prompt when a *previous* worker was already in control — that check
    // is what suppresses the banner on the very first install.
    function trackInstalling(worker) {
      worker.addEventListener("statechange", () => {
        if (worker.state === "installed" && navigator.serviceWorker.controller) {
          showUpdateBanner(worker);
        }
      });
    }

    function watchForUpdate(reg) {
      // A worker may already be waiting from a previous session's update.
      if (reg.waiting && navigator.serviceWorker.controller) showUpdateBanner(reg.waiting);
      reg.addEventListener("updatefound", () => {
        if (reg.installing) trackInstalling(reg.installing);
      });
      // Browsers only auto-check for a new worker on navigation, so also poll
      // hourly and whenever the tab becomes visible again.
      setInterval(() => reg.update().catch(() => {}), 60 * 60 * 1000);
      document.addEventListener("visibilitychange", () => {
        if (document.visibilityState === "visible") reg.update().catch(() => {});
      });
    }

    window.addEventListener("load", () => {
      navigator.serviceWorker.register("sw.js")
        .then(watchForUpdate)
        .catch(err => console.error("SW", err));
    });
  }

  // ---------- auth gate ----------
  // The tracker only boots once we know who the user is. startApp() does the
  // first paint, initial sync, and starts the periodic timers — guarded so it
  // runs at most once per page load even if login and the session check race.
  const authScreen   = document.getElementById("auth-screen");
  const appEl        = document.getElementById("app");
  const authForm     = document.getElementById("auth-form");
  const authEmail    = document.getElementById("auth-email");
  const authPassword = document.getElementById("auth-password");
  const authInvite   = document.getElementById("auth-invite");
  const authInviteFld= document.getElementById("auth-invite-field");
  const authError    = document.getElementById("auth-error");
  const authSubmit   = document.getElementById("auth-submit");
  const authSub      = document.getElementById("auth-sub");
  const authToggleBtn= document.getElementById("auth-toggle-btn");
  const authToggleTxt= document.getElementById("auth-toggle-text");
  const authCard     = document.getElementById("auth-card");
  const guestEnded   = document.getElementById("guest-ended");
  const guestBanner  = document.getElementById("guest-banner");
  let authMode = "login"; // or "register"
  let appStarted = false;

  // Remember who was last signed in so an offline reload can still open the
  // app against the cached data instead of stranding the user on a login screen
  // it can't verify. Cleared only on an explicit logout or a server 401.
  const SESSION_KEY = "puppy-tracker:session:v1";
  function setUser(u) {
    currentUser = u;
    try { localStorage.setItem(SESSION_KEY, JSON.stringify(u)); } catch { /* ignore */ }
  }
  function clearUser() {
    currentUser = null;
    try { localStorage.removeItem(SESSION_KEY); } catch { /* ignore */ }
  }
  function cachedUser() {
    try {
      const u = JSON.parse(localStorage.getItem(SESSION_KEY));
      return u && u.id ? u : null;
    } catch { return null; }
  }

  function startApp() {
    if (appStarted) return;
    appStarted = true;

    // Live-update relative times and (eventually) sync status text.
    setInterval(() => {
      const evs = live();
      renderHeader();
      renderBigClock(evs);
      renderActionHints(evs);
      renderStats(evs);
      renderLasts(evs);
      renderTiming(evs);
      renderSleepWake(evs);
      renderWalks(evs);
      renderWeekly(evs);
      renderSleepTimeline(evs);
      renderWalkPatterns(evs);
      renderSleepTrend(evs);
      renderHourHeatmap(evs);
      renderTraining(evs);
      if (navigator.onLine && !syncing) setStatus();
    }, 60_000);

    setInterval(tickBigClock, 1000);
    setInterval(sync, SYNC_POLL_MS);
    setInterval(syncConfig, SYNC_POLL_MS);

    setStatus();
    render();
    refreshPedigreeButton();
    sync();
    syncConfig();
    initReminders();
  }

  // ended: show the "guest link has run out" card instead of the sign-in form,
  // which a guest has no credentials to fill in anyway.
  function showAuth({ ended = false } = {}) {
    appEl.hidden = true;
    authCard.hidden = ended;
    guestEnded.hidden = !ended;
    authScreen.hidden = false;
  }

  function showApp() {
    authScreen.hidden = true;
    appEl.hidden = false;
    renderGuestBanner();
  }

  // Says whose account this is, under which name the guest's entries will
  // appear, and when the link runs out. Owners never see it.
  function renderGuestBanner() {
    if (!isGuest()) { guestBanner.hidden = true; return; }
    const name = loadConfig().name;
    const until = currentUser.expires
      ? ` · access ends ${formatWhen(currentUser.expires)}`
      : "";
    guestBanner.textContent =
      `Guest access${name ? ` to ${name}` : ""} as ${currentUser.label}` +
      `${until} — anything you log is tagged with your name.`;
    guestBanner.hidden = false;
  }

  // Called when the server reports we're no longer authenticated (expired or
  // revoked session). An owner just drops back to the login screen with their
  // cache intact — signing back in picks it straight back up. A guest's link
  // has ended for good, so their copy of someone else's history should not stay
  // sitting in their browser: wipe it, and say what happened.
  function handleLoggedOut() {
    const wasGuest = isGuest();
    if (wasGuest) clearLocalCache();
    clearUser();
    setStatus("offline");
    showAuth({ ended: wasGuest });
  }

  // Drops this account's cached data from localStorage. currentUser must still
  // be set, since the keys are namespaced by its id.
  function clearLocalCache() {
    try {
      localStorage.removeItem(eventsKey());
      localStorage.removeItem(configKey());
      localStorage.removeItem(exercisesKey());
    } catch { /* ignore */ }
  }

  function renderAuthMode() {
    const reg = authMode === "register";
    authInviteFld.hidden = !reg;
    authInvite.required = reg;
    authSubmit.textContent = reg ? "Create account" : "Sign in";
    authSub.textContent = reg ? "Create your account" : "Sign in to continue";
    authToggleTxt.textContent = reg ? "Already have an account?" : "No account yet?";
    authToggleBtn.textContent = reg ? "Sign in" : "Create one";
    authPassword.autocomplete = reg ? "new-password" : "current-password";
    authError.hidden = true;
  }

  authToggleBtn.addEventListener("click", () => {
    authMode = authMode === "login" ? "register" : "login";
    renderAuthMode();
  });

  authForm.addEventListener("submit", async (e) => {
    e.preventDefault();
    authError.hidden = true;
    authSubmit.disabled = true;
    const body = { email: authEmail.value.trim(), password: authPassword.value };
    if (authMode === "register") body.invite = authInvite.value.trim();
    try {
      const res = await fetch(authMode === "register" ? "api/register" : "api/login", {
        method: "POST",
        headers: { "Content-Type": "application/json" },
        body: JSON.stringify(body),
      });
      if (!res.ok) {
        const msg = (await res.text()).trim();
        throw new Error(msg || `HTTP ${res.status}`);
      }
      setUser(await res.json());
      authForm.reset();
      showApp();
      startApp();
    } catch (err) {
      authError.textContent = err.message || "Something went wrong";
      authError.hidden = false;
    } finally {
      authSubmit.disabled = false;
    }
  });

  document.getElementById("logout-btn").addEventListener("click", async () => {
    // Leaving as a guest ends this session but not the link — they can tap it
    // again. Their cache goes either way; it is someone else's record.
    if (isGuest()) clearLocalCache();
    try { await fetch("api/logout", { method: "POST" }); } catch { /* ignore */ }
    clearUser();
    // Full reload is the simplest way to clear in-memory app state and timers.
    location.reload();
  });

  // On load, ask the server who we are. A valid session boots straight into the
  // app. A 401 means log in. A network failure (offline PWA) falls back to the
  // last cached session so offline data stays reachable — a later sync will
  // 401 and bounce to login if that session has actually gone stale.
  (async function bootstrap() {
    // /guest/<token> bounces here with this marker when the link was already
    // expired or revoked, so we can say so rather than show a sign-in form.
    const params = new URLSearchParams(location.search);
    const deadLink = params.get("guest") === "expired";
    if (params.has("guest")) {
      history.replaceState(null, "", location.pathname);
    }

    try {
      const res = await fetch("api/me");
      if (res.ok) {
        setUser(await res.json());
        applyRole();
        showApp();
        startApp();
        return;
      }
      clearUser(); // explicit 401/403: session is gone
    } catch {
      const cached = cachedUser();
      if (cached) {
        currentUser = cached;
        applyRole();
        showApp();
        startApp();
        return;
      }
    }
    renderAuthMode();
    showAuth({ ended: deadLink });
  })();

  // One-time, role-dependent chrome. Everything else a guest sees or doesn't is
  // decided when the relevant dialog opens.
  function applyRole() {
    if (!isGuest()) return;
    const leave = document.getElementById("logout-btn");
    leave.setAttribute("aria-label", "Leave");
    leave.title = "Leave";
  }
})();