extract some sharable utils out of tracklist in prep for playqueuelist

ui/util/tracklistutil.go

@@ -0,0 +1,64 @@
+package util
+
+import "github.com/dweymouth/supersonic/backend/mediaprovider"
+
+type TrackListModel struct {
+	Track    *mediaprovider.Track
+	Selected bool
+}
+
+func SelectTrack(tracks []*TrackListModel, idx int) {
+	if tracks[idx].Selected {
+		return
+	}
+	UnselectAllTracks(tracks)
+	tracks[idx].Selected = true
+}
+
+func SelectAllTracks(tracks []*TrackListModel) {
+	for _, tm := range tracks {
+		tm.Selected = true
+	}
+}
+
+func UnselectAllTracks(tracks []*TrackListModel) {
+	for _, tm := range tracks {
+		tm.Selected = false
+	}
+}
+
+func SelectTrackRange(tracks []*TrackListModel, idx int) {
+	if tracks[idx].Selected {
+		return
+	}
+	lastSelected := -1
+	for i := len(tracks) - 1; i >= 0; i-- {
+		if tracks[i].Selected {
+			lastSelected = i
+			break
+		}
+	}
+	if lastSelected < 0 {
+		tracks[idx].Selected = true
+		return
+	}
+	from := minInt(idx, lastSelected)
+	to := maxInt(idx, lastSelected)
+	for i := from; i <= to; i++ {
+		tracks[i].Selected = true
+	}
+}
+
+func minInt(a, b int) int {
+	if a < b {
+		return a
+	}
+	return b
+}
+
+func maxInt(a, b int) int {
+	if a > b {
+		return a
+	}
+	return b
+}