优化客户端封面获取逻辑

修改emby客户端获取封面逻辑，修复没有设置封面导致封面为空的问题

internal/handler/emby_views_handlers.go

@@ -47,6 +47,13 @@ func embyVirtualFoldersHandler(svc *service.Container) gin.HandlerFunc {
 			case "music":
 				collectionType = "music"
 			}
+			// 库封面广告:能解析出封面时才填 ImageTags.Primary,让客户端去请求
+			// /Items/{libID}/Images/Primary(MediaFolders 是老式端点,客户端主要
+			// 靠 ImageTags 判断有无主图)。
+			imageTags := map[string]string{}
+			if svc.Emby.LibraryHasCover(c.Request.Context(), lib.ID) {
+				imageTags["Primary"] = lib.ID
+			}
 			out = append(out, gin.H{
 				"Name":               lib.Name,
 				"Locations":          []string{lib.Path},
@@ -54,6 +61,7 @@ func embyVirtualFoldersHandler(svc *service.Container) gin.HandlerFunc {
 				"ItemId":             lib.ID,
 				"Id":                 lib.ID,
 				"PrimaryImageItemId": lib.ID,
+				"ImageTags":          imageTags,
 				"RefreshStatus":      "Idle",
 				"LibraryOptions":     gin.H{},
 			})

internal/service/emby_artwork.go

@@ -3,8 +3,10 @@ package service
 import (
 	"context"
 	"strings"
+	"time"
 
 	"github.com/ShukeBta/MediaStationGo/internal/model"
+	"github.com/ShukeBta/MediaStationGo/internal/repository"
 )
 
 // ImageURL returns artwork for a media/series/season item id.
@@ -51,9 +53,97 @@ func (e *EmbyService) ImageURL(ctx context.Context, id, imageType string) (strin
 	} else if ok {
 		return pick(series.PosterURL, series.BackdropURL), nil
 	}
+	// id 既不是媒体也不是剧集组时,还可能是一个媒体库(Emby 客户端通过
+	// /Items/{libraryID}/Images/Primary 请求库封面)。复用网页的封面来源:
+	// cover_url 优先,否则挑库内评分最高的一张成员海报。
+	if raw := e.libraryCoverArtwork(ctx, id); raw != "" {
+		return raw, nil
+	}
 	return "", nil
 }
 
+// cachedLibraryCover returns a previously resolved library cover URL within TTL.
+func (e *EmbyService) cachedLibraryCover(id string) (string, bool) {
+	if e == nil || strings.TrimSpace(id) == "" {
+		return "", false
+	}
+	now := time.Now()
+	e.libraryCoverMu.Lock()
+	defer e.libraryCoverMu.Unlock()
+	entry, ok := e.libraryCoverCache[id]
+	if !ok || now.After(entry.expiresAt) {
+		if ok {
+			delete(e.libraryCoverCache, id)
+		}
+		return "", false
+	}
+	return entry.primary, true
+}
+
+func (e *EmbyService) rememberLibraryCover(id, cover string) {
+	if e == nil || strings.TrimSpace(id) == "" || strings.TrimSpace(cover) == "" {
+		return
+	}
+	e.libraryCoverMu.Lock()
+	defer e.libraryCoverMu.Unlock()
+	if e.libraryCoverCache == nil {
+		e.libraryCoverCache = make(map[string]embyArtworkCacheEntry)
+	}
+	if len(e.libraryCoverCache) > 4000 {
+		e.libraryCoverCache = make(map[string]embyArtworkCacheEntry)
+	}
+	e.libraryCoverCache[id] = embyArtworkCacheEntry{
+		primary:   cover,
+		expiresAt: time.Now().Add(embyVirtualCacheTTL),
+	}
+}
+
+// libraryCoverArtwork 解析媒体库封面,与网页媒体库封面逻辑一致:
+//  1. 用户手动设置的 cover_url 优先;
+//  2. 否则取库内最近的一批成员,按 seriesArtworkScore(同网页 artworkScore)
+//     挑出评分最高的那张海报作为封面。
+//
+// Emby 主图只能显示单张,因此返回的正是网页拼图里最靠前的那张。
+func (e *EmbyService) libraryCoverArtwork(ctx context.Context, id string) string {
+	if cached, ok := e.cachedLibraryCover(id); ok {
+		return cached
+	}
+	lib, err := e.repo.Library.FindByID(ctx, id)
+	if err != nil || lib == nil {
+		return ""
+	}
+	if strings.TrimSpace(lib.CoverURL) != "" {
+		cover := lib.CoverURL
+		e.rememberLibraryCover(id, cover)
+		return cover
+	}
+	var cover string
+	if rows, _, err := e.repo.Media.ListByLibraryFiltered(ctx, id, 0, 12, repository.MediaQueryFilter{IncludeNSFW: true}); err == nil {
+		var bestScore = -1
+		for i := range rows {
+			score := seriesArtworkScore(rows[i])
+			if score <= bestScore {
+				continue
+			}
+			bestScore = score
+			cover = rows[i].PosterURL
+			if cover == "" {
+				cover = rows[i].BackdropURL
+			}
+		}
+	}
+	if cover != "" {
+		e.rememberLibraryCover(id, cover)
+	}
+	return cover
+}
+
+// LibraryHasCover reports whether a library has an Emby-servable cover, so the
+// Views / virtual-folders payloads can advertise ImageTags.Primary to clients.
+func (e *EmbyService) LibraryHasCover(ctx context.Context, id string) bool {
+	return e.libraryCoverArtwork(ctx, id) != ""
+}
+
 func (e *EmbyService) mediaPrimaryArtwork(ctx context.Context, m *model.Media) string {
 	if m == nil {
 		return ""

internal/service/emby_artwork_test.go

@@ -0,0 +1,108 @@
+package service
+
+import (
+	"testing"
+
+	"github.com/ShukeBta/MediaStationGo/internal/model"
+)
+
+func TestImageURLFallsBackToLibraryCoverURL(t *testing.T) {
+	svc := newTestEmbyService(t)
+	lib := model.Library{Name: "电影", Path: "/media/movies", Type: "movie", Enabled: true, CoverURL: "https://example.com/lib-cover.jpg"}
+	if err := svc.repo.Library.Create(t.Context(), &lib); err != nil {
+		t.Fatalf("create library: %v", err)
+	}
+
+	raw, err := svc.ImageURL(t.Context(), lib.ID, "Primary")
+	if err != nil {
+		t.Fatalf("ImageURL: %v", err)
+	}
+	if raw != lib.CoverURL {
+		t.Fatalf("ImageURL for library = %q, want cover_url %q", raw, lib.CoverURL)
+	}
+}
+
+func TestImageURLFallsBackToBestMemberPoster(t *testing.T) {
+	svc := newTestEmbyService(t)
+	lib := model.Library{Name: "电影", Path: "/media/movies", Type: "movie", Enabled: true} // no cover_url
+	if err := svc.repo.Library.Create(t.Context(), &lib); err != nil {
+		t.Fatalf("create library: %v", err)
+	}
+	members := []model.Media{
+		{LibraryID: lib.ID, Title: "A", Path: "/media/movies/a.mkv", PosterURL: "https://example.com/a/backdrop.jpg"},
+		{LibraryID: lib.ID, Title: "B", Path: "/media/movies/b.mkv", PosterURL: "https://example.com/b/poster.jpg"},
+		{LibraryID: lib.ID, Title: "C", Path: "/media/movies/c.mkv", PosterURL: "https://example.com/c/actor.jpg"},
+	}
+	for i := range members {
+		if err := svc.repo.DB.Create(&members[i]).Error; err != nil {
+			t.Fatalf("create media: %v", err)
+		}
+	}
+
+	raw, err := svc.ImageURL(t.Context(), lib.ID, "Primary")
+	if err != nil {
+		t.Fatalf("ImageURL: %v", err)
+	}
+	// 最高分是 poster.jpg(score 40),其次是默认海报(30),actor(10)。
+	if raw != "https://example.com/b/poster.jpg" {
+		t.Fatalf("ImageURL for library = %q, want best member poster", raw)
+	}
+}
+
+func TestImageURLReturnsEmptyForUnknownID(t *testing.T) {
+	svc := newTestEmbyService(t)
+	raw, err := svc.ImageURL(t.Context(), "not-a-library-or-media", "Primary")
+	if err != nil {
+		t.Fatalf("ImageURL: %v", err)
+	}
+	if raw != "" {
+		t.Fatalf("ImageURL for unknown id = %q, want empty", raw)
+	}
+}
+
+func TestViewsAdvertisesPrimaryImageWhenLibraryHasCover(t *testing.T) {
+	svc := newTestEmbyService(t)
+	withCover := model.Library{Name: "封库", Path: "/media/set", Type: "movie", Enabled: true}
+	if err := svc.repo.Library.Create(t.Context(), &withCover); err != nil {
+		t.Fatalf("create library: %v", err)
+	}
+	if err := svc.repo.DB.Create(&model.Media{
+		Base:      model.Base{ID: "m1"},
+		LibraryID: withCover.ID,
+		Title:     "M1",
+		Path:      "/media/set/m1.mkv",
+		PosterURL: "https://example.com/m1/poster.jpg",
+	}).Error; err != nil {
+		t.Fatalf("create media: %v", err)
+	}
+	noCover := model.Library{Name: "空库", Path: "/media/empty", Type: "movie", Enabled: true}
+	if err := svc.repo.Library.Create(t.Context(), &noCover); err != nil {
+		t.Fatalf("create library: %v", err)
+	}
+
+	views, err := svc.Views(t.Context(), "user-1")
+	if err != nil {
+		t.Fatalf("Views: %v", err)
+	}
+	items := views["Items"].([]map[string]any)
+	found := map[string]map[string]any{}
+	for _, it := range items {
+		found[it["Id"].(string)] = it
+	}
+
+	withImageTags, ok := found[withCover.ID]["ImageTags"].(map[string]string)
+	if !ok {
+		t.Fatalf("library with cover should have ImageTags, got %#v", found[withCover.ID]["ImageTags"])
+	}
+	if withImageTags["Primary"] != withCover.ID {
+		t.Fatalf("library with cover should advertise ImageTags.Primary, got %#v", withImageTags)
+	}
+
+	emptyTags, ok := found[noCover.ID]["ImageTags"].(map[string]string)
+	if !ok {
+		t.Fatalf("library without cover should have empty ImageTags, got %#v", found[noCover.ID]["ImageTags"])
+	}
+	if _, has := emptyTags["Primary"]; has {
+		t.Fatalf("library without cover should NOT advertise Primary, got %#v", emptyTags)
+	}
+}

internal/service/emby_compat.go

@@ -62,6 +62,9 @@ type EmbyService struct {
 
 	cloudProbeMu       sync.Mutex
 	cloudProbeInFlight map[string]struct{}
+
+	libraryCoverMu    sync.Mutex
+	libraryCoverCache map[string]embyArtworkCacheEntry
 }
 
 type cloudPlaybackResolver interface {

internal/service/emby_items_detail.go

@@ -22,7 +22,7 @@ func (e *EmbyService) Item(ctx context.Context, mediaID, userID string) (map[str
 		if !e.libraryVisibleFromCachedVisibility(libs[0], visibility) {
 			return nil, nil
 		}
-		return e.libraryAsView(&libs[0]), nil
+		return e.libraryAsView(ctx, &libs[0]), nil
 	}
 	if strings.HasPrefix(mediaID, embyVirtualSeasonPrefix) {
 		if season, ok, err := e.findSeasonGroup(ctx, mediaID, userID); err != nil {

internal/service/emby_system.go

@@ -137,12 +137,12 @@ func (e *EmbyService) Views(ctx context.Context, userID string) (map[string]any,
 		if !e.libraryVisibleFromCachedVisibility(l, visibility) {
 			continue
 		}
-		items = append(items, e.libraryAsView(&l))
+		items = append(items, e.libraryAsView(ctx, &l))
 	}
 	return map[string]any{"Items": items, "TotalRecordCount": len(items), "StartIndex": 0}, nil
 }
 
-func (e *EmbyService) libraryAsView(l *model.Library) map[string]any {
+func (e *EmbyService) libraryAsView(ctx context.Context, l *model.Library) map[string]any {
 	collectionType := "movies"
 	switch l.Type {
 	case "tv":
@@ -154,6 +154,12 @@ func (e *EmbyService) libraryAsView(l *model.Library) map[string]any {
 	case "music":
 		collectionType = "music"
 	}
+	// 库封面:与剧集/电影一样,只有在能解析出封面时才广告 ImageTags.Primary,
+	// 否则客户端会认为该库无主图而不去请求 /Images/Primary。
+	imageTags := map[string]string{}
+	if e.LibraryHasCover(ctx, l.ID) {
+		imageTags["Primary"] = l.ID
+	}
 	return map[string]any{
 		"Id":                       l.ID,
 		"Name":                     l.Name,
@@ -178,7 +184,7 @@ func (e *EmbyService) libraryAsView(l *model.Library) map[string]any {
 		"ProviderIds":              map[string]string{},
 		"Genres":                   []string{},
 		"Tags":                     []string{},
-		"ImageTags":                map[string]string{},
+		"ImageTags":                imageTags,
 		"BackdropImageTags":        []string{},
 		"UserData": map[string]any{
 			"PlaybackPositionTicks": 0,