curds: Move the ThreadPoolExecutor into the track code

I think it makes sense to do this transparently through the Track code
so higher layers don't have to do as much work.  We'll just return a
Future-object corresponding to the track that will be added.

It makes sense to only have one thread in this case, since __add() needs
exclusive access to the track_list for its entire execution.  Anything
more would just create conflicts and actually increase execution time.

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

curds/test_track.py

@@ -1,15 +1,17 @@
 # Copyright 2019 (c) Anna Schumaker.
-import asyncio
 import concurrent.futures
 import mutagen
-import unittest
 import os
 import track
+import unittest
 
 test_tracks  = os.path.abspath("./trier/Test Album")
 test_library = os.path.abspath("./trier/Test Library")
 
 class TestTrackClass(unittest.TestCase):
+    def setUp(self):
+        track.track_list.clear()
+
     def test_init_basic(self):
         p = [ test_tracks, "01 - Test Track.ogg" ]
         t = track.Track(os.path.join(*p))
@@ -23,7 +25,7 @@ class TestTrackClass(unittest.TestCase):
         self.assertEqual(t.album.date,   2019)
         self.assertEqual(t.album.genre, "Test")
         self.assertEqual(t.album.albumartist, "Test Artist")
-        self.assertEqual(len(track.tracklist), 0)
+        self.assertEqual(len(track.track_list), 0)
 
     def test_init_empty(self):
         p = [ test_tracks, "00 - Empty Track.ogg" ]
@@ -38,7 +40,7 @@ class TestTrackClass(unittest.TestCase):
         self.assertEqual(t.album.date,   0)
         self.assertEqual(t.album.genre, "Unknown")
         self.assertEqual(t.album.albumartist, "Unknown Artist")
-        self.assertEqual(len(track.tracklist), 0)
+        self.assertEqual(len(track.track_list), 0)
 
     def test_init_discno_detect(self):
         join = os.path.join
@@ -53,35 +55,40 @@ class TestTrackClass(unittest.TestCase):
         self.assertEqual(track.Track(join(test_tracks, "10 - Test {Disc 20}.ogg")).discnumber,   20)
 
     def test_track_add(self):
-        track.tracklist.clear()
-        t = track.add(os.path.join(test_tracks, "01 - Test Track.ogg"))
+        fs = track.add(os.path.join(test_tracks, "01 - Test Track.ogg"))
+        self.assertEqual(len(track.track_list), 0)
+        t = fs.result()
         self.assertIsNotNone(t)
-        self.assertEqual(len(track.tracklist), 1)
-        self.assertIn(t, track.tracklist)
+        self.assertEqual(len(track.track_list), 1)
+        self.assertIn(t, track.track_list)
 
-        self.assertIsNone(track.add(os.path.join(test_tracks, "01 - Test Track.ogg")))
-        self.assertEqual(len(track.tracklist), 1)
-        self.assertIsNone(track.add("99 - No Such Track.ogg"))
-        self.assertEqual(len(track.tracklist), 1)
+        self.assertIsNone(track.add(os.path.join(test_tracks, "01 - Test Track.ogg")).result())
+        self.assertEqual(len(track.track_list), 1)
+        self.assertIsNone(track.add("99 - No Such Track.ogg").result())
+        self.assertEqual(len(track.track_list), 1)
 
-        u = track.add(os.path.join(test_tracks, "02 - Test {Disc 2}.ogg"))
+        fs = track.add(os.path.join(test_tracks, "02 - Test {Disc 2}.ogg"))
+        u  = fs.result()
         self.assertIsNotNone(u)
-        self.assertEqual(len(track.tracklist), 2)
-        self.assertIn(u, track.tracklist)
+        self.assertEqual(len(track.track_list), 2)
+        self.assertIn(u, track.track_list)
 
     def test_parallel_add(self):
-        track.tracklist.clear()
-        count  = 0
-        tracks = [ ]
-        with concurrent.futures.ThreadPoolExecutor(max_workers=5) as pool:
-            for dirname, subdirs, files in os.walk(test_library):
-                for f in files:
-                    tracks.append(pool.submit(track.add, os.path.join(dirname, f)))
-                    count += 1
-        self.assertEqual(len(track.tracklist), count)
-        self.assertEqual(len(tracks), count)
-        for t in tracks:
-            self.assertIsNotNone(t)
-
-if __name__ == '__main--':
-        unittest.main()
+        count   = 0
+        futures = [ ]
+        done = [ ]
+        none = [ ]
+        for dirname, subdirs, files in os.walk(test_library):
+            for f in files:
+                futures.append(track.add(os.path.join(dirname, f)))
+                futures.append(track.add(os.path.join(dirname, f)))
+                count += 1
+        self.assertLess(len(track.track_list), count)
+        for fs in concurrent.futures.as_completed(futures):
+            if fs.result() is not None:
+                done.append(fs.result())
+            else:
+                none.append(fs.result())
+        self.assertEqual(len(done), count)
+        self.assertEqual(len(none), count)
+        self.assertEqual(len(track.track_list), count)

curds/track.py

@@ -1,11 +1,13 @@
 # Copyright 2019 (c) Anna Schumaker.
 import album
+import concurrent.futures
 import mutagen
 import os
 import re
 
 discno_map = { "one" : "1", "two" : "2", "three" : "3", "four" : "4", "five" : "5" }
-tracklist  = [ ]
+track_list = [ ]
+track_pool = concurrent.futures.ThreadPoolExecutor(max_workers = 1)
 
 class Track:
     def __init__(self, path):
@@ -26,11 +28,14 @@ class Track:
             self.discnumber = int(discno_map.get(match.group(), match.group()))
 
 
-def add(path):
+def __add(path):
     try:
-        if not any(t.path == path for t in tracklist):
+        if not any(t.path == path for t in track_list):
             track = Track(path)
-            tracklist.append(track)
+            track_list.append(track)
             return track
     except mutagen.MutagenError:
         return None
+
+def add(path):
+    return track_pool.submit(__add, path)