Add album art search, auto-match and a whole-album tag editor

Search iTunes, Deezer, MusicBrainz, DuckDuckGo and Google for square covers,
embed them and/or save cover.jpg, auto-match covers for albums, and edit an
album's shared tags and track list in one place.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/api/art.go

@@ -0,0 +1,154 @@
+package api
+
+import (
+	"errors"
+	"net/http"
+	"strings"
+	"time"
+
+	"github.com/go-chi/chi/v5"
+
+	"github.com/cdnutter/playlink/internal/art"
+	"github.com/cdnutter/playlink/internal/engine"
+)
+
+func (s *Server) handleArtSettings(w http.ResponseWriter, r *http.Request) {
+	cfg := s.eng.ArtSettings(r.Context())
+	writeJSON(w, 200, map[string]any{"settings": cfg, "all_sources": art.AllSources})
+}
+
+func (s *Server) handlePutArtSettings(w http.ResponseWriter, r *http.Request) {
+	var cfg engine.ArtSettings
+	if !readJSON(w, r, &cfg) {
+		return
+	}
+	if err := s.eng.SetArtSettings(r.Context(), cfg); err != nil {
+		writeErr(w, 400, err)
+		return
+	}
+	s.handleArtSettings(w, r)
+}
+
+func (s *Server) handleArtSearch(w http.ResponseWriter, r *http.Request) {
+	q := r.URL.Query()
+	query := art.Query{Artist: q.Get("artist"), Album: q.Get("album"), Text: q.Get("q")}
+	if strings.TrimSpace(query.Artist+query.Album+query.Text) == "" {
+		writeErr(w, 400, errors.New("enter an artist, album or search text"))
+		return
+	}
+	var sources []string
+	if src := q.Get("sources"); src != "" {
+		sources = strings.Split(src, ",")
+	}
+	res, errs, err := s.eng.SearchArt(r.Context(), query, sources)
+	if err != nil {
+		writeErr(w, 500, err)
+		return
+	}
+	writeJSON(w, 200, map[string]any{"results": res, "errors": errs})
+}
+
+func (s *Server) handleArtPrepare(w http.ResponseWriter, r *http.Request) {
+	var body struct {
+		URL string `json:"url"`
+	}
+	if !readJSON(w, r, &body) {
+		return
+	}
+	p, err := s.eng.PrepareArtURL(r.Context(), body.URL)
+	if err != nil {
+		writeErr(w, 400, err)
+		return
+	}
+	writeJSON(w, 200, p)
+}
+
+func (s *Server) handleArtUpload(w http.ResponseWriter, r *http.Request) {
+	f, _, err := r.FormFile("image")
+	if err != nil {
+		writeErr(w, 400, errors.New("choose an image file"))
+		return
+	}
+	defer f.Close()
+	p, err := s.eng.PrepareArtUpload(r.Context(), f)
+	if err != nil {
+		writeErr(w, 400, err)
+		return
+	}
+	writeJSON(w, 200, p)
+}
+
+func (s *Server) handleArtPrepared(w http.ResponseWriter, r *http.Request) {
+	p, err := s.eng.PreparedArtPath(chi.URLParam(r, "token"))
+	if err != nil {
+		writeErr(w, 404, err)
+		return
+	}
+	w.Header().Set("Content-Type", "image/jpeg")
+	w.Header().Set("Cache-Control", "private, max-age=3600")
+	http.ServeFile(w, r, p)
+}
+
+func (s *Server) handleCover(w http.ResponseWriter, r *http.Request) {
+	id, _ := idParam(r)
+	q := r.URL.Query()
+	b, err := s.eng.Cover(r.Context(), id, q.Get("side"), q.Get("path"))
+	if err != nil {
+		opErr(w, err)
+		return
+	}
+	if len(b) == 0 {
+		w.WriteHeader(http.StatusNoContent)
+		return
+	}
+	w.Header().Set("Content-Type", http.DetectContentType(b))
+	w.Header().Set("Cache-Control", "no-cache")
+	http.ServeContent(w, r, "cover", time.Time{}, strings.NewReader(string(b)))
+}
+
+func (s *Server) handleAlbum(w http.ResponseWriter, r *http.Request) {
+	id, _ := idParam(r)
+	q := r.URL.Query()
+	a, err := s.eng.AlbumSongs(r.Context(), id, q.Get("side"), q.Get("path"))
+	if err != nil {
+		opErr(w, err)
+		return
+	}
+	writeJSON(w, 200, a)
+}
+
+func (s *Server) handleArtAuto(w http.ResponseWriter, r *http.Request) {
+	id, _ := idParam(r)
+	var m engine.ArtMatch
+	if !readJSON(w, r, &m) {
+		return
+	}
+	if !s.preAction(w, r, id, "auto-match album art") {
+		return
+	}
+	j, err := s.eng.StartArtAutoMatch(id, m)
+	if err != nil {
+		opErr(w, err)
+		return
+	}
+	writeJSON(w, 202, j)
+}
+
+// handleArtThumb shows a search result's thumbnail through the server, so
+// the page keeps its strict content policy and the browser never contacts
+// the image hosts directly. Fetching uses the local-network-safe client.
+func (s *Server) handleArtThumb(w http.ResponseWriter, r *http.Request) {
+	b, err := s.eng.FetchArtThumb(r.Context(), r.URL.Query().Get("u"))
+	if err != nil {
+		writeErr(w, 502, err)
+		return
+	}
+	ct := http.DetectContentType(b)
+	if !strings.HasPrefix(ct, "image/") {
+		writeErr(w, 502, errors.New("not an image"))
+		return
+	}
+	w.Header().Set("Content-Type", ct)
+	w.Header().Set("Cache-Control", "private, max-age=86400")
+	w.Write(b)
+}