feat: add playback seeking

tests/fakes.py

@@ -59,9 +59,11 @@ def build_player(default_plays: int = 5) -> tuple[MusicPlayer, FakeVoiceClient]:
     bot.loop = asyncio.get_event_loop()
     voice_client = FakeVoiceClient()
 
-    async def recreate(track, loop=None):
+    async def recreate(track, loop=None, start_at=0.0):
         fresh = FakeTrack(track.id)
         fresh.plays_left = track.plays_left
+        fresh.duration = track.duration
+        fresh.elapsed = start_at
         return fresh
 
     tracks = MagicMock()

tests/test_api_surface.py

@@ -15,6 +15,7 @@ EXPECTED_ENDPOINTS = {
     ("post", "/api/play_file"),
     ("post", "/api/pause"),
     ("post", "/api/resume"),
+    ("post", "/api/seek"),
     ("post", "/api/skip"),
     ("post", "/api/stop"),
     ("post", "/api/volume"),

tests/test_music_player.py

@@ -103,6 +103,16 @@ class MusicPlayerQueueTest(unittest.IsolatedAsyncioTestCase):
         self.assertEqual(state.current.id, "b")
         self.assertEqual(state.queue[0].plays_left, 4)
 
+    async def test_seek_restarts_current_track_at_requested_position(self):
+        player, voice_client, state = await self._queue_abc()
+
+        position = await player.seek(GUILD, 4.5)
+
+        self.assertEqual(position, 4.5)
+        self.assertEqual(state.current.id, "a")
+        self.assertEqual(state.current.elapsed, 4.5)
+        self.assertIs(voice_client.playing, state.current)
+
     async def test_loop_track_replays_same_index(self):
         player, _, state = await self._queue_abc()
         await player.play_next(GUILD, advance=True)