Show age in weight graph

src/app.js

@@ -222,26 +222,27 @@
     localStorage.setItem(CONFIG_KEY, JSON.stringify(cfg));
   }
 
-  // Age in whole days / weeks / calendar months from a "YYYY-MM-DD" birthday.
-  // Returns null for a missing/invalid/future birthday.
-  function ageParts(birthday) {
+  // 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 now   = startOfDay(new Date());
-    if (birth > now) return null;
-    const days  = Math.floor((now - birth) / 86_400_000);
+    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 = (now.getFullYear() - birth.getFullYear()) * 12 +
-                 (now.getMonth() - birth.getMonth());
-    if (now.getDate() < birth.getDate()) months--;
+    let months = (ref.getFullYear() - birth.getFullYear()) * 12 +
+                 (ref.getMonth() - birth.getMonth());
+    if (ref.getDate() < birth.getDate()) months--;
     if (months < 0) months = 0;
     return { days, weeks, months };
   }
 
-  function formatAge(birthday) {
-    const a = ageParts(birthday);
+  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`;
@@ -939,14 +940,23 @@
     return { lo, hi, steps: Math.max(1, Math.round((hi - lo) / step)) };
   }
 
-  function drawWeightChart(weights) {
-    const svg = document.getElementById("chart-weight");
+  // 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 = ""; return; }
+    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));
@@ -972,11 +982,16 @@
       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 => {
-      const title = `${new Date(w.at).toLocaleDateString(undefined, { weekday: "short", month: "short", day: "numeric" })} — ${formatWeight(w.weight)}`;
+      parts.push(`<circle class="weight-dot" cx="${xOf(w.at).toFixed(1)}" cy="${yOf(w.weight).toFixed(1)}" r="3.5"/>`);
+    });
+    weights.forEach((w, i) => {
+      const detail = weightPointInfo(w, birthday);
       parts.push(
-        `<circle class="weight-dot" cx="${xOf(w.at).toFixed(1)}" cy="${yOf(w.weight).toFixed(1)}" r="3.5">` +
-        `<title>${escapeText(title)}</title></circle>`
+        `<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>`
       );
     });
 
@@ -987,6 +1002,19 @@
     }
 
     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) {
@@ -999,6 +1027,8 @@
     const changeEl = document.getElementById("weight-change");
     const list     = document.getElementById("weight-list");
 
+    const birthday = loadConfig().birthday;
+
     list.innerHTML = "";
     changeEl.classList.remove("up", "down");
 
@@ -1006,7 +1036,7 @@
       empty.hidden = false;
       latestEl.textContent = "—";
       changeEl.textContent = "—";
-      drawWeightChart([]);
+      drawWeightChart([], birthday);
       return;
     }
     empty.hidden = true;
@@ -1031,7 +1061,9 @@
       li.className = "ww weight-ww";
       const date = document.createElement("span");
       date.className = "ww-range";
-      date.textContent = new Date(w.at).toLocaleDateString(undefined, { month: "short", day: "numeric" });
+      const age = formatAge(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);
@@ -1041,7 +1073,7 @@
       list.appendChild(li);
     }
 
-    drawWeightChart(weights);
+    drawWeightChart(weights, birthday);
   }
 
   function renderDayBar() {