extract additional iterator helper to share with Jellyfin

backend/mediaprovider/helpers/albumiterator.go

@@ -5,10 +5,67 @@ import (
 	"strings"
 
 	"github.com/dweymouth/supersonic/backend/mediaprovider"
+	"github.com/dweymouth/supersonic/sharedutil"
 )
 
 type AlbumFetchFn func(offset, limit int) ([]*mediaprovider.Album, error)
 
+type baseIter struct {
+	filter        mediaprovider.AlbumFilter
+	prefetchCB    func(string)
+	serverPos     int
+	fetchFn       AlbumFetchFn
+	prefetched    []*mediaprovider.Album
+	prefetchedPos int
+	done          bool
+}
+
+func NewBaseIter(fetchFn AlbumFetchFn, filter mediaprovider.AlbumFilter, cb func(string)) *baseIter {
+	return &baseIter{
+		prefetchCB: cb,
+		filter:     filter,
+		fetchFn:    fetchFn,
+	}
+}
+
+func (r *baseIter) Next() *mediaprovider.Album {
+	if r.done {
+		return nil
+	}
+	if r.prefetched != nil && r.prefetchedPos < len(r.prefetched) {
+		a := r.prefetched[r.prefetchedPos]
+		r.prefetchedPos++
+		return a
+	}
+	r.prefetched = nil
+	for { // keep fetching until we are done or have mathcing results
+		albums, err := r.fetchFn(r.serverPos, 20)
+		if err != nil {
+			log.Printf("error fetching albums: %s", err.Error())
+			albums = nil
+		}
+		if len(albums) == 0 {
+			r.done = true
+			return nil
+		}
+		r.serverPos += len(albums)
+		albums = sharedutil.FilterSlice(albums, func(al *mediaprovider.Album) bool {
+			return filterMatches(r.filter, al)
+		})
+		r.prefetched = albums
+		if len(albums) > 0 {
+			break
+		}
+	}
+	r.prefetchedPos = 1
+	if r.prefetchCB != nil {
+		for _, album := range r.prefetched {
+			go r.prefetchCB(album.CoverArtID)
+		}
+	}
+	return r.prefetched[0]
+}
+
 type randomIter struct {
 	filter        mediaprovider.AlbumFilter
 	prefetchCB    func(coverArtID string)
@@ -60,7 +117,7 @@ func (r *randomIter) Next() *mediaprovider.Album {
 			}
 			r.offset += len(albums)
 			for _, album := range albums {
-				if _, ok := r.albumIDSet[album.ID]; !ok && filterMatches(r.filter, album, false) {
+				if _, ok := r.albumIDSet[album.ID]; !ok && filterMatches(r.filter, album) {
 					r.prefetched = append(r.prefetched, album)
 					if r.prefetchCB != nil {
 						go r.prefetchCB(album.CoverArtID)
@@ -83,7 +140,7 @@ func (r *randomIter) Next() *mediaprovider.Album {
 					// by the filter because we need to know when to move to phase two
 					hitCount++
 					r.albumIDSet[album.ID] = true
-					if filterMatches(r.filter, album, false) {
+					if filterMatches(r.filter, album) {
 						r.prefetched = append(r.prefetched, album)
 						if r.prefetchCB != nil {
 							go r.prefetchCB(album.CoverArtID)
@@ -112,7 +169,7 @@ func (r *randomIter) Next() *mediaprovider.Album {
 	return nil
 }
 
-func filterMatches(f mediaprovider.AlbumFilter, album *mediaprovider.Album, ignoreGenre bool) bool {
+func filterMatches(f mediaprovider.AlbumFilter, album *mediaprovider.Album) bool {
 	if album == nil {
 		return false
 	}
@@ -125,7 +182,7 @@ func filterMatches(f mediaprovider.AlbumFilter, album *mediaprovider.Album, igno
 	if y := album.Year; y < f.MinYear || (f.MaxYear > 0 && y > f.MaxYear) {
 		return false
 	}
-	if ignoreGenre || len(f.Genres) == 0 {
+	if len(f.Genres) == 0 {
 		return true
 	}
 	return genresMatch(f.Genres, album.Genres)