add cache warming for album covers to album iterators

backend/albumiterator.go

@@ -14,6 +14,8 @@ type AlbumIterator interface {
 }
 
 type LibraryManager struct {
+	PreCacheCoverFn func(string)
+
 	s                *ServerManager
 	albumDetailCache gcache.Cache
 }
@@ -153,6 +155,11 @@ func (r *baseIter) Next() *subsonic.AlbumID3 {
 	}
 	r.prefetched = albums
 	r.prefetchedPos = 1
+	if r.l.PreCacheCoverFn != nil {
+		for _, album := range albums {
+			go r.l.PreCacheCoverFn(album.ID)
+		}
+	}
 
 	return r.prefetched[0]
 }
@@ -277,6 +284,9 @@ func (s *searchIter) addNewAlbums(al []*subsonic.AlbumID3) {
 			continue
 		}
 		s.prefetched = append(s.prefetched, album)
+		if s.l.PreCacheCoverFn != nil {
+			go s.l.PreCacheCoverFn(album.ID)
+		}
 		s.albumIDset[album.ID] = true
 	}
 }
@@ -328,6 +338,9 @@ func (r *randomIter) Next() *subsonic.AlbumID3 {
 				for _, album := range albums {
 					if _, ok := r.albumIDSet[album.ID]; !ok {
 						r.prefetched = append(r.prefetched, album)
+						if r.l.PreCacheCoverFn != nil {
+							go r.l.PreCacheCoverFn(album.ID)
+						}
 						r.albumIDSet[album.ID] = true
 					}
 				}
@@ -346,6 +359,9 @@ func (r *randomIter) Next() *subsonic.AlbumID3 {
 				if _, ok := r.albumIDSet[album.ID]; !ok {
 					hitCount++
 					r.prefetched = append(r.prefetched, album)
+					if r.l.PreCacheCoverFn != nil {
+						go r.l.PreCacheCoverFn(album.ID)
+					}
 					r.albumIDSet[album.ID] = true
 				}
 			}