curds: Add a function for picking the next track

If "loop" is True, then we loop back to the beginning of the playlist
when we reach the end.

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

curds/playlist/playlist.py

@@ -3,13 +3,23 @@ from .. import notify
 
 class Playlist(list):
     def __init__(self, name):
-        self.name = name
+        self.name    = name
+        self.current = -1
+        self.loop    = False
 
     def add(self, track):
         if track is not None:
             self.append(track)
             notify.Notify.notify("on-add", self, track)
 
+    def next(self):
+        if self.loop == True and self.current >= len(self) - 1:
+            self.current = -1
+        if self.current < len(self) - 1:
+            self.current += 1
+            return self[self.current]
+        return None
+
     def runtime(self):
         m, s = divmod(sum([ track.length for track in self ]), 60)
         h, m = divmod(m, 60)
@@ -20,3 +30,7 @@ class Playlist(list):
         if m > 0: res.append(f"{int(m)} minute{'s' if m  != 1 else ''}")
         if s > 0: res.append(f"{int(s)} second{'s' if s  != 1 else ''}")
         return ", ".join(res)
+
+    def set_loop(self, loop):
+        self.loop = loop
+        return self.loop

curds/playlist/test_playlist.py

@@ -20,6 +20,8 @@ class TestPlaylist(unittest.TestCase):
         self.assertEqual(plist.name, "Test Playlist")
         self.assertEqual(len(plist), 0)
         self.assertEqual(plist.runtime(), "")
+        self.assertEqual(plist.current, -1)
+        self.assertFalse(plist.loop)
 
     def test_playlist_add(self):
         path  = os.path.join(test_library, "Test Artist 01", "Test Album 1")
@@ -77,3 +79,43 @@ class TestPlaylist(unittest.TestCase):
         plist.add(None)
         self.assertEqual(self.cb_plist, plist)
         self.assertEqual(self.cb_track, track)
+
+    def test_playlist_next(self):
+        path   = os.path.join(test_library, "Test Artist 01", "Test Album 1")
+        plist  = playlist.Playlist("Test Playlist")
+        tracks = [ ]
+
+        self.assertTrue(plist.set_loop(True))
+        self.assertTrue(plist.loop)
+
+        for i in range(1, 9):
+            track = tags.Track.lookup(os.path.join(path, f"0{i} - Test Track 0{i}.ogg"))
+            tracks.append(track)
+            plist.add(track)
+
+        self.assertEqual(plist.current, -1)
+        for i in range(16):
+            track = plist.next()
+            self.assertEqual(track, tracks[i % 8])
+            self.assertEqual(plist.current, i % 8)
+
+        track = tags.Track.lookup(os.path.join(path, "09 - Test Track 09.ogg"))
+        tracks.append(track)
+        plist.add(track)
+        for i in [ 8, 0 ]:
+            self.assertEqual(plist.next(), tracks[i])
+            self.assertEqual(plist.current, i)
+
+        self.assertFalse(plist.set_loop(False))
+        for i in range(1, 9):
+            self.assertEqual(plist.next(), tracks[i])
+            self.assertEqual(plist.current, i)
+
+        self.assertEqual(plist.current, 8)
+        self.assertIsNone(plist.next())
+        self.assertEqual(plist.current, 8)
+
+        track = tags.Track.lookup(os.path.join(path, "10 - Test Track 10.ogg"))
+        plist.add(track)
+        self.assertEqual(plist.next(), track)
+        self.assertEqual(plist.current, 9)