first commit

backend/albumiterator.go

@@ -0,0 +1,129 @@
+package backend
+
+import (
+	"log"
+	"strconv"
+
+	"github.com/bluele/gcache"
+	subsonic "github.com/dweymouth/go-subsonic"
+)
+
+type AlbumIterator interface {
+	Next() *subsonic.AlbumID3
+	NextN(int, func(*subsonic.AlbumID3))
+}
+
+type LibraryManager struct {
+	s          *subsonic.Client
+	albumCache gcache.Cache
+}
+
+func NewLibraryManager(s *subsonic.Client) *LibraryManager {
+	cache := gcache.New(250).LRU().Build()
+	return &LibraryManager{
+		s:          s,
+		albumCache: cache,
+	}
+}
+
+func (l *LibraryManager) RecentlyAddedIter() AlbumIterator {
+	return l.newBaseIter("newest")
+}
+
+func (l *LibraryManager) RecentlyPlayedIter() AlbumIterator {
+	return l.newBaseIter("recent")
+}
+
+func (l *LibraryManager) StarredIter() AlbumIterator {
+	return l.newBaseIter("starred")
+}
+
+func (l *LibraryManager) FrequentlyPlayedIter() AlbumIterator {
+	return l.newBaseIter("frequent")
+}
+
+func (l *LibraryManager) CacheAlbum(a *subsonic.AlbumID3) {
+	l.albumCache.Set(a.ID, a)
+}
+
+func (l *LibraryManager) GetAlbum(id string) (*subsonic.AlbumID3, error) {
+	if l.albumCache.Has(id) {
+		if a, err := l.albumCache.Get(id); err == nil {
+			return a.(*subsonic.AlbumID3), nil
+		}
+	}
+	a, err := l.s.GetAlbum(id)
+	if err != nil {
+		return nil, err
+	}
+	l.albumCache.Set(a.ID, a)
+	return a, nil
+}
+
+type baseIter struct {
+	listType      string
+	pos           int
+	l             *LibraryManager
+	s             *subsonic.Client
+	prefetched    []*subsonic.AlbumID3
+	prefetchedPos int
+	done          bool
+}
+
+func (l *LibraryManager) newBaseIter(listType string) *baseIter {
+	return &baseIter{
+		listType: listType,
+		l:        l,
+		s:        l.s,
+	}
+}
+
+// TODO: figure out why the iterator sometimes returns an album twice
+
+func (r *baseIter) Next() *subsonic.AlbumID3 {
+	if r.done {
+		return nil
+	}
+	if r.prefetched != nil {
+		a := r.prefetched[r.prefetchedPos]
+		r.prefetchedPos++
+		if r.prefetchedPos == len(r.prefetched) {
+			r.prefetched = nil
+			r.prefetchedPos = 0
+		}
+		r.pos++
+
+		r.l.CacheAlbum(a)
+		return a
+	}
+	albums, err := r.s.GetAlbumList2(r.listType, map[string]string{"size": "20", "offset": strconv.Itoa(r.pos)})
+	if err != nil {
+		log.Println(err)
+		albums = nil
+	}
+	if len(albums) == 0 {
+		r.done = true
+		return nil
+	} else if len(albums) == 1 {
+		r.l.CacheAlbum(albums[0])
+		r.done = true
+		return albums[0]
+	}
+	r.prefetched = albums
+	r.prefetchedPos = 1
+
+	r.l.CacheAlbum(r.prefetched[0])
+	return r.prefetched[0]
+}
+
+func (r *baseIter) NextN(n int, cb func(*subsonic.AlbumID3)) {
+	go func() {
+		for i := 0; i < n; i++ {
+			a := r.Next()
+			cb(a)
+			if a == nil {
+				break
+			}
+		}
+	}()
+}