curds: Add a function for moving tracks in a playlist

Signed-off-by: Anna Schumaker <Anna@NoWheyCreamery.com>

curds/playlist/playlist.py

@@ -76,6 +76,24 @@ class Playlist(node.PlaylistNode):
                     return i
         return None
 
+    def move(self, track, new):
+        old = self.index(track)
+        if old == None:
+            return
+
+        self.list.remove(track)
+        self.list.insert(new, track)
+        self.sort_order.clear()
+
+        if old == self.current:
+            self.current = new
+        elif new < old and new  <= self.current:
+            self.current += 1
+        elif new > old and new == self.current:
+            self.current += 1
+        elif new > old and new > self.current:
+            self.current -= 1
+
     def next(self):
         max = len(self) - 1
         if max == -1:

curds/playlist/test_playlist.py

@@ -131,6 +131,54 @@ class TestPlaylist(unittest.TestCase):
         self.assertIsNone(self.plist.index(track))
         self.assertIsNone(self.plist.index(None))
 
+    def test_playlist_move_up(self):
+        tracks = self.add_tracks(range(1, 11))
+        self.plist.current = 5
+        self.plist.sort("tracknumber")
+
+        self.plist.move(tracks[8], 6)
+        self.assertEqual(self.plist.current, 5)
+        self.assertEqual(self.plist.list[6], tracks[8])
+        self.assertEqual(self.plist.sort_order, [ ])
+
+        self.plist.move(tracks[8], 5)
+        self.assertEqual(self.plist.current, 6)
+        self.assertEqual(self.plist.list[5], tracks[8])
+
+        self.plist.move(tracks[9], 0)
+        self.assertEqual(self.plist.current, 7)
+        self.assertEqual(self.plist.list[0], tracks[9])
+
+    def test_playlist_move_down(self):
+        tracks = self.add_tracks(range(1, 11))
+        self.plist.current = 5
+
+        self.plist.move(tracks[1], 4)
+        self.assertEqual(self.plist.current, 5)
+        self.assertEqual(self.plist.list[4], tracks[1])
+
+        self.plist.move(tracks[1], 5)
+        self.assertEqual(self.plist.current, 6)
+        self.assertEqual(self.plist.list[5], tracks[1])
+
+        self.plist.move(tracks[0], 9)
+        self.assertEqual(self.plist.current, 5)
+        self.assertEqual(self.plist.list[9], tracks[0])
+
+        self.plist.move(42, 0)
+
+    def test_playlist_move_current(self):
+        tracks = self.add_tracks(range(1, 11))
+        self.plist.current = 5
+
+        self.plist.move(tracks[5], 8)
+        self.assertEqual(self.plist.current, 8)
+        self.assertEqual(self.plist.list[8], tracks[5])
+
+        self.plist.move(tracks[5], 0)
+        self.assertEqual(self.plist.current, 0)
+        self.assertEqual(self.plist.list[0], tracks[5])
+
     def test_playlist_next_empty_one(self):
         self.assertIsNone(self.plist.next())
         self.assertEqual(self.plist.current, -1)