trackdb: Implement saving through an idle task

And register with the various subscribers that modify anything in the
trackdb.

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

test_trackdb.py

@@ -1,6 +1,9 @@
 # Copyright 2020 (c) Anna Schumaker.
+from lib import data
+from lib import idle
 from lib import publisher
 import pathlib
+import threading
 import trackdb
 import unittest
 
@@ -14,6 +17,7 @@ class TestTrackDB(unittest.TestCase):
         self.count_removed = 0
 
     def tearDown(self):
+        idle.reset()
         trackdb.reset()
 
     def on_library_added(self, lib):
@@ -24,8 +28,18 @@ class TestTrackDB(unittest.TestCase):
 
     def test_trackdb_init(self):
         self.assertEqual(trackdb.library_paths, [ ])
+        self.assertFalse(trackdb.need_save)
+        self.assertIsNone(trackdb.idle_id)
         self.assertIsInstance(trackdb.LibraryAdded, publisher.Publisher)
         self.assertIsInstance(trackdb.LibraryRemoved, publisher.Publisher)
+        self.assertIsInstance(trackdb.save_lock, type(threading.Lock()))
+        self.assertEqual(trackdb.db_file, "trackdb.pickle")
+
+        self.assertIn(trackdb.save, trackdb.LibraryAdded.subscribers)
+        self.assertIn(trackdb.save, trackdb.LibraryRemoved.subscribers)
+        self.assertIn(trackdb.save, trackdb.library.TrackAdded.subscribers)
+        self.assertIn(trackdb.save, trackdb.library.TrackRemoved.subscribers)
+        self.assertIn(trackdb.save, trackdb.track.TrackUpdated.subscribers)
 
     def test_trackdb_add_path(self):
         lib = trackdb.add_path(test_tracks)
@@ -55,6 +69,26 @@ class TestTrackDB(unittest.TestCase):
         self.assertEqual(trackdb.get_track(3), lib[3])
         self.assertIsNone(trackdb.get_track(200))
 
+    def test_trackdb_save(self):
+        db_file = data.DataFile(trackdb.db_file, data.READ)
+        lib = trackdb.add_path(test_tracks)
+        lib.scan()
+
+        trackdb.save()
+        self.assertTrue(trackdb.need_save)
+        self.assertEqual(idle.Funcs, [ trackdb._do_save ])
+        self.assertFalse(db_file.exists())
+
+        idle.complete(delay=0.1)
+        self.assertIsNone(lib.thread)
+        self.assertEqual(idle.Funcs, [ ])
+        self.assertTrue(db_file.exists())
+
+    def test_trackdb_stress(self):
+        lib = trackdb.add_path("./trier/Test Library/")
+        lib.scan()
+        idle.complete(0.1)
+
     def test_trackdb_reset(self):
         trackdb.library.TrackAdded.register(1)
         trackdb.library.TrackRemoved.register(1)
@@ -62,11 +96,16 @@ class TestTrackDB(unittest.TestCase):
         trackdb.LibraryAdded.register(1)
         trackdb.LibraryRemoved.register(1)
         trackdb.library_paths = [ 1, 2, 3 ]
+        trackdb.need_save = True
+        with data.DataFile(trackdb.db_file, data.WRITE) as f:
+            f.pickle([ 0, [] ])
 
         trackdb.reset()
         self.assertEqual(trackdb.library_paths, [ ])
-        self.assertEqual(trackdb.library.TrackAdded.subscribers, set())
-        self.assertEqual(trackdb.library.TrackRemoved.subscribers, set())
-        self.assertEqual(trackdb.track.TrackUpdated.subscribers, set())
-        self.assertEqual(trackdb.LibraryAdded.subscribers, set())
-        self.assertEqual(trackdb.LibraryRemoved.subscribers, set())
+        self.assertIn(trackdb.save, trackdb.library.TrackAdded.subscribers)
+        self.assertIn(trackdb.save, trackdb.library.TrackRemoved.subscribers)
+        self.assertIn(trackdb.save, trackdb.track.TrackUpdated.subscribers)
+        self.assertIn(trackdb.save, trackdb.LibraryAdded.subscribers)
+        self.assertIn(trackdb.save, trackdb.LibraryRemoved.subscribers)
+        self.assertFalse(trackdb.need_save)
+        self.assertFalse(data.DataFile(trackdb.db_file, data.READ).exists())

trackdb/__init__.py

@@ -1,8 +1,16 @@
 # Copyright 2020 (c) Anna Schumaker.
+from lib import data
+from lib import idle
 from lib import publisher
 from . import library
+from . import track
 import pathlib
+import threading
 
+db_file = "trackdb.pickle"
+need_save = False
+idle_id = None
+save_lock = threading.Lock()
 library_paths = [ ]
 LibraryAdded = publisher.Publisher()
 LibraryRemoved = publisher.Publisher()
@@ -31,9 +39,47 @@ def remove_path(path):
     library_paths.remove(lib)
     LibraryRemoved.publish(lib)
 
+def _do_save():
+    global need_save
+    global idle_id
+    with save_lock:
+        if need_save == False:
+            idle_id = None
+            return idle.REMOVE
+
+        with data.DataFile(db_file, data.WRITE) as f:
+            with library.IDLock:
+                f.pickle([ library.NextID, library_paths ])
+        need_save = False
+        return idle.CONTINUE
+
+def save(*args):
+    global need_save
+    global idle_id
+    with save_lock:
+        if need_save == False:
+            need_save = True
+            if idle_id == None:
+                idle_id = idle.add(_do_save)
+
+def __register_callbacks():
+    LibraryAdded.register(save)
+    LibraryRemoved.register(save)
+    library.TrackAdded.register(save)
+    library.TrackRemoved.register(save)
+    track.TrackUpdated.register(save)
+__register_callbacks()
+
 def reset():
+    global need_save
+    global idle_id
     library_paths.clear()
     LibraryAdded.reset()
     LibraryRemoved.reset()
     library.reset()
     track.reset()
+
+    data.DataFile(db_file, data.READ).remove()
+    __register_callbacks()
+    need_save = False
+    idle_id = None