curds: Add a Previous playlist

This playlist is designed to hold all the tracks that have been selected
for playback, and iterate through them backwards if needed.

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

curds/playlist/previous.py

@@ -0,0 +1,19 @@
+# Copyright 2019 (c) Anna Schumaker.
+from . import playlist
+from .. import notify
+
+class PreviousPlaylist(playlist.Playlist):
+    def __init__(self):
+        playlist.Playlist.__init__(self, "Previous", "edit-undo")
+
+    def add(self, track):
+        if track is not None and track not in self:
+            self.list.insert(0, track)
+            self.current = 0
+            notify.Notify.notify("add-track", self, track)
+
+    def set_loop(self, loop):
+        return playlist.Playlist.set_loop(self, False)
+
+    def set_random(self, random):
+        return playlist.Playlist.set_random(self, False)

curds/playlist/test_previous.py

@@ -0,0 +1,67 @@
+# Copyright 2019 (c) Anna Schumaker.
+from . import playlist
+from . import previous
+from .. import notify
+from .. import tags
+import os
+import unittest
+
+test_album = os.path.abspath("./trier/Test Library/Test Artist 01/Test Album 1")
+
+class TestPreviousPlaylist(unittest.TestCase):
+    def setUp(self):
+        self.cb_plist = None
+        self.cb_track = None
+
+    def tearDown(self):
+        notify.Notify.notifications.clear()
+
+    def on_add_track(self, plist, track):
+        if isinstance(plist, previous.PreviousPlaylist):
+            self.cb_plist = plist
+            self.cb_track = track
+
+    def test_previous_playlist(self):
+        plist = previous.PreviousPlaylist()
+        notify.Notify.notify_me("add-track", self.on_add_track)
+
+        self.assertIsInstance(plist, previous.PreviousPlaylist)
+        self.assertIsInstance(plist, playlist.Playlist)
+        self.assertEqual(plist.name, "Previous")
+        self.assertEqual(plist.icon, "edit-undo")
+
+        self.assertFalse(plist.loop)
+        self.assertFalse(plist.set_loop(True))
+        self.assertFalse(plist.loop)
+
+        self.assertFalse(plist.random)
+        self.assertFalse(plist.set_random(True))
+        self.assertFalse(plist.random)
+
+        track1 = tags.Track.lookup(os.path.join(test_album, "01 - Test Track 01.ogg"))
+        track2 = tags.Track.lookup(os.path.join(test_album, "02 - Test Track 02.ogg"))
+        track3 = tags.Track.lookup(os.path.join(test_album, "03 - Test Track 03.ogg"))
+
+        self.assertEqual(plist.current, -1)
+        self.assertEqual(plist.next(),  None)
+
+        plist.add(track1)
+        self.assertEqual(self.cb_plist, plist)
+        self.assertEqual(self.cb_track, track1)
+        self.assertEqual(plist.current, 0)
+        self.assertEqual(plist.next(),  None)
+
+        plist.add(track2)
+        self.assertEqual(self.cb_plist, plist)
+        self.assertEqual(self.cb_track, track2)
+        self.assertEqual(plist.current, 0)
+
+        self.assertEqual(len(plist), 2)
+        self.assertEqual(plist[0], track2)
+        self.assertEqual(plist[1], track1)
+
+        self.assertEqual(plist.next(),  track1)
+        self.assertEqual(plist.current, 1)
+
+        plist.add(track3)
+        self.assertEqual(plist.current, 0)