puppy-tracker/server/main.go

package main

import (
	"database/sql"
	"encoding/json"
	"errors"
	"flag"
	"io"
	"io/fs"
	"log"
	"net/http"
	"os"
	"path/filepath"
	"regexp"
	"strings"
	"time"

	_ "modernc.org/sqlite"
)

type Event struct {
	ID        string  `json:"id"`
	Type      string  `json:"type"`
	At        int64   `json:"at"`
	Note      string  `json:"note"`
	PhotoID   string  `json:"photoId,omitempty"`
	Weight    float64 `json:"weight,omitempty"` // kilograms, for "weight" events
	UpdatedAt int64   `json:"updatedAt"`
	Deleted   bool    `json:"deleted,omitempty"`
}

var uuidRE = regexp.MustCompile(`^[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}$`)

func validUUID(s string) bool { return uuidRE.MatchString(s) }

var birthdayRE = regexp.MustCompile(`^\d{4}-\d{2}-\d{2}$`)

func validBirthday(s string) bool { return s == "" || birthdayRE.MatchString(s) }

// Config is the shared puppy profile (name + birthday). It lives on the host so
// every client sees the same values without configuring each device. UpdatedAt
// drives last-write-wins, mirroring how events sync.
type Config struct {
	Name      string `json:"name"`
	Birthday  string `json:"birthday"`
	UpdatedAt int64  `json:"updatedAt"`
}

type ConfigStore struct {
	db *sql.DB
}

func newConfigStore(db *sql.DB) *ConfigStore {
	return &ConfigStore{db: db}
}

func (cs *ConfigStore) get() Config {
	var c Config
	// The profile lives in a single row (id = 1). A missing row is the
	// pre-configuration state, so a zero-value Config is the right answer.
	err := cs.db.QueryRow(
		`SELECT name, birthday, updated FROM config WHERE id = 1`,
	).Scan(&c.Name, &c.Birthday, &c.UpdatedAt)
	if err != nil && !errors.Is(err, sql.ErrNoRows) {
		log.Printf("config get: %v", err)
	}
	return c
}

// merge applies an incoming config with last-write-wins by UpdatedAt and
// returns the resulting stored config (which the caller sends back).
func (cs *ConfigStore) merge(in Config) (Config, error) {
	// The upsert's WHERE clause enforces last-write-wins: the incoming row only
	// replaces the stored one when it is strictly newer.
	_, err := cs.db.Exec(`
		INSERT INTO config (id, name, birthday, updated)
		VALUES (1, ?, ?, ?)
		ON CONFLICT(id) DO UPDATE SET
			name = excluded.name, birthday = excluded.birthday, updated = excluded.updated
		WHERE excluded.updated > config.updated`,
		in.Name, in.Birthday, in.UpdatedAt)
	if err != nil {
		return Config{}, err
	}
	return cs.get(), nil
}

type Store struct {
	db *sql.DB
}

func newStore(db *sql.DB) *Store {
	return &Store{db: db}
}

// sync merges client events into the store using last-write-wins by UpdatedAt,
// then returns the full merged set (including tombstones, which must propagate).
func (s *Store) sync(client []Event) ([]Event, error) {
	tx, err := s.db.Begin()
	if err != nil {
		return nil, err
	}
	defer tx.Rollback()

	// The WHERE clause on the upsert is the last-write-wins rule: an incoming
	// event only overwrites the stored one when its updatedAt is strictly newer.
	stmt, err := tx.Prepare(`
		INSERT INTO events (id, type, at, note, photo_id, weight, updated, deleted)
		VALUES (?, ?, ?, ?, ?, ?, ?, ?)
		ON CONFLICT(id) DO UPDATE SET
			type = excluded.type, at = excluded.at, note = excluded.note,
			photo_id = excluded.photo_id, weight = excluded.weight,
			updated = excluded.updated, deleted = excluded.deleted
		WHERE excluded.updated > events.updated`)
	if err != nil {
		return nil, err
	}
	defer stmt.Close()

	for _, ce := range client {
		if ce.ID == "" {
			continue
		}
		if _, err := stmt.Exec(
			ce.ID, ce.Type, ce.At, ce.Note, ce.PhotoID, ce.Weight, ce.UpdatedAt, ce.Deleted,
		); err != nil {
			return nil, err
		}
	}
	if err := tx.Commit(); err != nil {
		return nil, err
	}
	return s.all()
}

// all returns every stored event, tombstones included.
func (s *Store) all() ([]Event, error) {
	rows, err := s.db.Query(
		`SELECT id, type, at, note, photo_id, weight, updated, deleted FROM events`)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	out := make([]Event, 0)
	for rows.Next() {
		var e Event
		if err := rows.Scan(
			&e.ID, &e.Type, &e.At, &e.Note, &e.PhotoID, &e.Weight, &e.UpdatedAt, &e.Deleted,
		); err != nil {
			return nil, err
		}
		out = append(out, e)
	}
	return out, rows.Err()
}

// openDB opens (creating if needed) the SQLite database and ensures the schema
// exists. WAL mode plays nicely with concurrent readers during a sync write;
// busy_timeout avoids spurious "database is locked" errors under contention.
func openDB(path string) (*sql.DB, error) {
	if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
		return nil, err
	}
	db, err := sql.Open("sqlite", path)
	if err != nil {
		return nil, err
	}
	for _, pragma := range []string{
		`PRAGMA journal_mode = WAL`,
		`PRAGMA busy_timeout = 5000`,
		`PRAGMA synchronous = NORMAL`,
	} {
		if _, err := db.Exec(pragma); err != nil {
			db.Close()
			return nil, err
		}
	}
	schema := `
		CREATE TABLE IF NOT EXISTS events (
			id       TEXT PRIMARY KEY,
			type     TEXT NOT NULL DEFAULT '',
			at       INTEGER NOT NULL DEFAULT 0,
			note     TEXT NOT NULL DEFAULT '',
			photo_id TEXT NOT NULL DEFAULT '',
			weight   REAL NOT NULL DEFAULT 0,
			updated  INTEGER NOT NULL DEFAULT 0,
			deleted  INTEGER NOT NULL DEFAULT 0
		);
		CREATE TABLE IF NOT EXISTS config (
			id       INTEGER PRIMARY KEY CHECK (id = 1),
			name     TEXT NOT NULL DEFAULT '',
			birthday TEXT NOT NULL DEFAULT '',
			updated  INTEGER NOT NULL DEFAULT 0
		);`
	if _, err := db.Exec(schema); err != nil {
		db.Close()
		return nil, err
	}
	return db, nil
}

// migrateJSON imports a pre-SQLite events.json / config.json sitting in dataDir
// into an otherwise-empty database, then renames each file to *.imported so the
// import runs exactly once. It is a no-op when the DB already holds data or the
// legacy files are absent.
func migrateJSON(db *sql.DB, dataDir string) error {
	if err := importEvents(db, filepath.Join(dataDir, "events.json")); err != nil {
		return err
	}
	return importConfig(db, filepath.Join(dataDir, "config.json"))
}

func importEvents(db *sql.DB, path string) error {
	var n int
	if err := db.QueryRow(`SELECT COUNT(*) FROM events`).Scan(&n); err != nil {
		return err
	}
	if n > 0 {
		return nil // DB already has data; never clobber it
	}
	f, err := os.Open(path)
	if err != nil {
		if errors.Is(err, fs.ErrNotExist) {
			return nil
		}
		return err
	}
	var evs []Event
	dec := json.NewDecoder(f)
	err = dec.Decode(&evs)
	f.Close()
	if err != nil && !errors.Is(err, io.EOF) {
		return err
	}
	store := newStore(db)
	if _, err := store.sync(evs); err != nil {
		return err
	}
	log.Printf("migrated %d events from %s", len(evs), path)
	return os.Rename(path, path+".imported")
}

func importConfig(db *sql.DB, path string) error {
	var n int
	if err := db.QueryRow(`SELECT COUNT(*) FROM config`).Scan(&n); err != nil {
		return err
	}
	if n > 0 {
		return nil
	}
	f, err := os.Open(path)
	if err != nil {
		if errors.Is(err, fs.ErrNotExist) {
			return nil
		}
		return err
	}
	var c Config
	dec := json.NewDecoder(f)
	err = dec.Decode(&c)
	f.Close()
	if err != nil && !errors.Is(err, io.EOF) {
		return err
	}
	if c.UpdatedAt == 0 {
		// Nothing meaningful to import; leave config empty.
		return os.Rename(path, path+".imported")
	}
	if _, err := newConfigStore(db).merge(c); err != nil {
		return err
	}
	log.Printf("migrated config from %s", path)
	return os.Rename(path, path+".imported")
}

type syncRequest struct {
	Events []Event `json:"events"`
}

type syncResponse struct {
	Events    []Event `json:"events"`
	ServerNow int64   `json:"serverNow"`
}

type cacheControlFS struct {
	root http.FileSystem
}

func (c cacheControlFS) Open(name string) (http.File, error) { return c.root.Open(name) }

func main() {
	addr := flag.String("addr", ":8080", "listen address (e.g. :8080 or 0.0.0.0:8080)")
	dataPath := flag.String("data", "puppy.db", "path to SQLite database file")
	staticDir := flag.String("static", "", "directory of static files to serve")
	flag.Parse()

	db, err := openDB(*dataPath)
	if err != nil {
		log.Fatalf("open db: %v", err)
	}
	defer db.Close()

	// One-time import of any pre-SQLite JSON data sitting next to the DB.
	if err := migrateJSON(db, filepath.Dir(*dataPath)); err != nil {
		log.Fatalf("migrate json: %v", err)
	}

	store := newStore(db)
	configStore := newConfigStore(db)

	photosDir := filepath.Join(filepath.Dir(*dataPath), "photos")
	if err := os.MkdirAll(photosDir, 0o755); err != nil {
		log.Fatalf("mkdir photos: %v", err)
	}

	mux := http.NewServeMux()

	mux.HandleFunc("/api/events/sync", func(w http.ResponseWriter, r *http.Request) {
		if r.Method != http.MethodPost {
			http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
			return
		}
		var req syncRequest
		if err := json.NewDecoder(io.LimitReader(r.Body, 8<<20)).Decode(&req); err != nil {
			http.Error(w, "bad json: "+err.Error(), http.StatusBadRequest)
			return
		}
		merged, err := store.sync(req.Events)
		if err != nil {
			log.Printf("sync: %v", err)
			http.Error(w, "server error", http.StatusInternalServerError)
			return
		}
		w.Header().Set("Content-Type", "application/json")
		w.Header().Set("Cache-Control", "no-store")
		_ = json.NewEncoder(w).Encode(syncResponse{
			Events:    merged,
			ServerNow: time.Now().UnixMilli(),
		})
	})

	// GET  /api/config — return the shared puppy profile.
	// PUT  /api/config — update it (last-write-wins by updatedAt).
	mux.HandleFunc("/api/config", func(w http.ResponseWriter, r *http.Request) {
		writeConfig := func(c Config) {
			w.Header().Set("Content-Type", "application/json")
			w.Header().Set("Cache-Control", "no-store")
			_ = json.NewEncoder(w).Encode(c)
		}
		switch r.Method {
		case http.MethodGet:
			writeConfig(configStore.get())
		case http.MethodPut, http.MethodPost:
			var in Config
			if err := json.NewDecoder(io.LimitReader(r.Body, 1<<16)).Decode(&in); err != nil {
				http.Error(w, "bad json: "+err.Error(), http.StatusBadRequest)
				return
			}
			in.Name = strings.TrimSpace(in.Name)
			if len(in.Name) > 100 {
				in.Name = in.Name[:100]
			}
			if !validBirthday(in.Birthday) {
				http.Error(w, "invalid birthday (want YYYY-MM-DD)", http.StatusBadRequest)
				return
			}
			merged, err := configStore.merge(in)
			if err != nil {
				log.Printf("config save: %v", err)
				http.Error(w, "server error", http.StatusInternalServerError)
				return
			}
			writeConfig(merged)
		default:
			http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
		}
	})

	mux.HandleFunc("/healthz", func(w http.ResponseWriter, r *http.Request) {
		w.Write([]byte("ok"))
	})

	// POST /api/photos — multipart upload with form fields `id` (UUID) and
	// `file` (JPEG). The client generates the ID so the event referencing
	// the photo can be written before the upload round-trips.
	mux.HandleFunc("/api/photos", func(w http.ResponseWriter, r *http.Request) {
		if r.Method != http.MethodPost {
			http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
			return
		}
		r.Body = http.MaxBytesReader(w, r.Body, 15<<20)
		if err := r.ParseMultipartForm(15 << 20); err != nil {
			http.Error(w, "parse: "+err.Error(), http.StatusBadRequest)
			return
		}
		id := r.FormValue("id")
		if !validUUID(id) {
			http.Error(w, "invalid id", http.StatusBadRequest)
			return
		}
		file, _, err := r.FormFile("file")
		if err != nil {
			http.Error(w, "no file: "+err.Error(), http.StatusBadRequest)
			return
		}
		defer file.Close()

		dstPath := filepath.Join(photosDir, id+".jpg")
		tmp := dstPath + ".tmp"
		dst, err := os.Create(tmp)
		if err != nil {
			http.Error(w, "create: "+err.Error(), http.StatusInternalServerError)
			return
		}
		if _, err := io.Copy(dst, file); err != nil {
			dst.Close()
			os.Remove(tmp)
			http.Error(w, "copy: "+err.Error(), http.StatusInternalServerError)
			return
		}
		if err := dst.Close(); err != nil {
			os.Remove(tmp)
			http.Error(w, "close: "+err.Error(), http.StatusInternalServerError)
			return
		}
		if err := os.Rename(tmp, dstPath); err != nil {
			os.Remove(tmp)
			http.Error(w, "rename: "+err.Error(), http.StatusInternalServerError)
			return
		}

		w.Header().Set("Content-Type", "application/json")
		w.Header().Set("Cache-Control", "no-store")
		_ = json.NewEncoder(w).Encode(map[string]string{"id": id})
	})

	// GET /api/photos/<id> — serves the JPEG. Photos are immutable per ID
	// so we mark them as long-lived; both browser and SW can cache freely.
	mux.HandleFunc("/api/photos/", func(w http.ResponseWriter, r *http.Request) {
		if r.Method != http.MethodGet && r.Method != http.MethodHead {
			http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
			return
		}
		id := strings.TrimPrefix(r.URL.Path, "/api/photos/")
		if !validUUID(id) {
			http.Error(w, "invalid id", http.StatusBadRequest)
			return
		}
		path := filepath.Join(photosDir, id+".jpg")
		f, err := os.Open(path)
		if err != nil {
			http.NotFound(w, r)
			return
		}
		defer f.Close()
		stat, err := f.Stat()
		if err != nil {
			http.Error(w, "stat: "+err.Error(), http.StatusInternalServerError)
			return
		}
		w.Header().Set("Content-Type", "image/jpeg")
		w.Header().Set("Cache-Control", "public, max-age=31536000, immutable")
		http.ServeContent(w, r, path, stat.ModTime(), f)
	})

	if *staticDir != "" {
		fileServer := http.FileServer(http.Dir(*staticDir))
		mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
			// PWA: sw.js and manifest.json must revalidate so updates propagate.
			if r.URL.Path == "/sw.js" || r.URL.Path == "/manifest.json" {
				w.Header().Set("Cache-Control", "no-cache")
			}
			// SPA fallback: unknown paths -> index.html (so deep links work).
			if !strings.HasPrefix(r.URL.Path, "/api/") {
				candidate := filepath.Join(*staticDir, filepath.FromSlash(r.URL.Path))
				if r.URL.Path != "/" {
					if info, err := os.Stat(candidate); err != nil || info.IsDir() {
						r.URL.Path = "/"
					}
				}
			}
			fileServer.ServeHTTP(w, r)
		})
	}

	srv := &http.Server{
		Addr:              *addr,
		Handler:           mux,
		ReadHeaderTimeout: 5 * time.Second,
	}
	log.Printf("puppy-tracker listening on %s (data=%s, static=%s)", *addr, *dataPath, *staticDir)
	log.Fatal(srv.ListenAndServe())
}