1 files changed, 48 insertions, 0 deletions
diff --git a/playlist.go b/playlist.go
new file mode 100644
index 0000000..b37ab3d
--- /dev/null
+++ b/playlist.go
@@ -0,0 +1,48 @@
+package main
+
+import (
+	"container/heap"
+)
+
+type Playlist []*Song
+
+func (pl Playlist) Len() int { return len(pl) }
+
+func (pl Playlist) Less(i, j int) bool {
+	return pl[i].Weight > pl[j].Weight
+}
+
+func (pl Playlist) Swap(i, j int) {
+	pl[i], pl[j] = pl[j], pl[i]
+	pl[i].index = i
+	pl[j].index = j
+}
+
+func (pl *Playlist) Push(x any) {
+	n := len(*pl)
+	song := x.(*Song)
+	song.index = n
+	*pl = append(*pl, song)
+}
+
+func (pl *Playlist) Pop() any {
+	old := *pl
+	n := len(old)
+	s := old[n-1]
+	old[n-1] = nil // avoid memory leak
+	s.index = -1   // for safety
+	*pl = old[0 : n-1]
+	return s
+}
+
+func (pl *Playlist) PopSong() *Song {
+	return heap.Pop(pl).(*Song)
+}
+
+func (pl *Playlist) Add(s *Song) {
+	heap.Push(pl, s)
+}
+
+func (pl *Playlist) Adjust(s *Song) {
+	heap.Fix(pl, s.index)
+}