playlist: Give Playlists a track-requested signal

We need to do some bookkeeping inside the Playlist before notifying the
Factory that a track has been requested.

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

emmental/playlist/playlist.py

@@ -139,6 +139,13 @@ class Playlist(model.TrackidModel):
         if self.__playlist is not None:
             self.__playlist.remove_track(track)
 
+    def request_track(self, track: db.tracks.Track) -> None:
+        """Request a track for playback directly."""
+        if self.index(track) is not None:
+            if not self.can_go_next:
+                self.__picked.trackids = set()
+            self.emit("track-requested", track)
+
     @GObject.Property(type=db.tracks.Track)
     def current_track(self) -> db.tracks.Track | None:
         """Get the current Track of the Playlist."""
@@ -217,3 +224,8 @@ class Playlist(model.TrackidModel):
     def sort_order(self, new_order: str) -> None:
         if self.__playlist is not None:
             self.__playlist.sort_order = new_order
+
+    @GObject.Signal(arg_types=(db.tracks.Track,))
+    def track_requested(self, track: db.tracks.Track) -> None:
+        """Signal that a track has been requested for playback."""
+        self.current_track = track

tests/playlist/test_playlist.py

@@ -210,6 +210,32 @@ class TestPlaylist(tests.util.TestCase):
         self.assertEqual(self.db_plist.current_trackid, self.track1.trackid)
         notify.assert_called()
 
+    def test_request_track(self):
+        """Test the Playlist request_track() function."""
+        requested = unittest.mock.Mock()
+        self.playlist.connect("track-requested", requested)
+
+        self.playlist.request_track(self.track1)
+        requested.assert_not_called()
+
+        self.playlist.playlist = self.db_plist
+        self.playlist.request_track(self.track1)
+        requested.assert_not_called()
+
+        self.db_plist.add_track(self.track1)
+        self.playlist.request_track(self.track1)
+        requested.assert_called_with(self.playlist, self.track1)
+        self.assertEqual(self.playlist.current_track, self.track1)
+
+        self.db_plist.add_track(self.track2)
+        self.playlist.request_track(self.track2)
+        self.assertFalse(self.playlist.can_go_next)
+
+        self.playlist.request_track(self.track1)
+        self.assertSetEqual(self.playlist._Playlist__picked.trackids,
+                            {self.track1.trackid})
+        self.assertTrue(self.playlist.can_go_next)
+
     def test_current_track(self):
         """Test the Playlist current-track property."""
         self.assertIsNone(self.playlist.current_track)