curds: Add a playlist notifications system

This is mostly needed by the UI but there are a few cases where we
might need it internally, such as adding newly creating tracks to all
the required playlists.

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

curds/playlist/library.py

@@ -17,6 +17,7 @@ class LibraryPlaylist(playlist.Playlist):
     def thread_add(self, path):
         track = tags.Track.add(path)
         self.add(track)
+        self.notify("on-scan", track)
 
     def thread_scan(self):
         for dirname, subdirs, files in os.walk(self.name):

curds/playlist/playlist.py

@@ -1,12 +1,22 @@
 # Copyright 2019 (c) Anna Schumaker.
 
 class Playlist(list):
+    notifications = dict()
+
     def __init__(self, name):
         self.name = name
 
     def add(self, track):
         if track is not None:
             self.append(track)
+            self.notify("on-add", track)
+
+    def notify_me(name, func):
+        Playlist.notifications.setdefault(name, []).append(func)
+
+    def notify(self, name, *args):
+        for cb in Playlist.notifications.get(name, []):
+            cb(self, *args)
 
     def runtime(self):
         m, s = divmod(sum([ track.length for track in self ]), 60)

curds/playlist/test_library.py

@@ -14,6 +14,7 @@ class TestLibraryPlaylist(unittest.TestCase):
         library.library_thread.stop()
         library.library_thread = threadqueue.ThreadQueue()
         tags.tag_map.clear()
+        self.scan_count = 0
 
     def tearDownClass():
         library.library_thread.stop()
@@ -25,9 +26,15 @@ class TestLibraryPlaylist(unittest.TestCase):
         self.assertIsInstance(plist, playlist.Playlist)
         self.assertEqual(plist.name, test_library)
 
+    def on_scan(self, plist, track):
+        self.scan_count += 1
+
     def test_playlist_library_scan(self):
+        library.LibraryPlaylist.notify_me("on-scan", self.on_scan)
+
         plist = library.LibraryPlaylist(test_library)
         self.assertGreater(library.library_thread.qsize(), 0)
         library.library_thread.join()
         self.assertEqual(len(plist), 1250)
+        self.assertEqual(self.scan_count, 1250)
         self.assertEqual(plist.runtime(), "1 hour, 54 minutes, 35 seconds")

curds/playlist/test_playlist.py

@@ -9,6 +9,8 @@ test_library = os.path.abspath("./trier/Test Library")
 class TestPlaylist(unittest.TestCase):
     def setUp(self):
         tags.tag_map.clear()
+        self.cb_plist = None
+        self.cb_track = None
 
     def test_playlist_init(self):
         plist = playlist.Playlist("Test Playlist")
@@ -55,3 +57,26 @@ class TestPlaylist(unittest.TestCase):
         self.assertEqual(plist.runtime(), "1 day")
         track.length = 172800
         self.assertEqual(plist.runtime(), "2 days")
+
+    def on_add1(self, plist, track):
+        self.cb_plist = plist
+    def on_add2(self, plist, track):
+        self.cb_track = track
+
+    def test_playlist_notifications(self):
+        path  = os.path.join(test_library, "Test Artist 01", "Test Album 1")
+        track = tags.Track.add(os.path.join(path, "01 - Test Track 01.ogg"))
+        plist = playlist.Playlist("Test Playlist")
+        self.assertIsInstance(plist.notifications, dict)
+
+        playlist.Playlist.notify_me("on-add", self.on_add1)
+        playlist.Playlist.notify_me("on-add", self.on_add2)
+        self.assertIsInstance(playlist.Playlist.notifications["on-add"], list)
+        self.assertEqual(len(playlist.Playlist.notifications["on-add"]), 2)
+
+        plist.add(track)
+        self.assertEqual(self.cb_plist, plist)
+        self.assertEqual(self.cb_track, track)
+        plist.add(None)
+        self.assertEqual(self.cb_plist, plist)
+        self.assertEqual(self.cb_track, track)