db: Create a function to find playlists based on state id

So we can write the current playlist stateid to the settings file and
look it up later.

Implements: #36 (Find playlists based on playlist state id)
Signed-off-by: Anna Schumaker <Anna@NoWheyCreamery.com>

db/__init__.py

@@ -21,6 +21,31 @@ from . import track
 from . import state
 from . import user
 
+from . import sql
+def _search_table(table, key, search):
+    if row := sql.execute(f"SELECT {key} FROM {table} "
+                          f"WHERE plstateid=?", [ search ]).fetchone():
+        return row[0]
+
+def find_playlist(plstateid):
+    if playlistid := _search_table("playlists", "playlistid", plstateid):
+        return user.Table.get(playlistid)
+    if artistid := _search_table("artists", "artistid", plstateid):
+        return artist.Table.get(artistid)
+    if albumid := _search_table("albums", "albumid", plstateid):
+        return album.Table.get(albumid)
+    if discid := _search_table("discs", "discid", plstateid):
+        return disc.Table.get(discid)
+    if genreid := _search_table("genres", "genreid", plstateid):
+        return genre.Table.get(genreid)
+    if decadeid := _search_table("decades", "decadeid", plstateid):
+        return decade.Table.get(decadeid)
+    if yearid := _search_table("years", "yearid", plstateid):
+        return year.Table.get(yearid)
+    if libraryid := _search_table("libraries", "libraryid", plstateid):
+        return library.Table.get(libraryid)
+    return None
+
 def make_fake_track(trackno, length, title, path, lib="/a/b/c", art="Test Artist",
                     alb="Test Album", disk=1, subtitle=None, yeer=2021):
     lib = library.Table.find(pathlib.Path(lib))

db/test_db.py

@@ -4,6 +4,17 @@ import unittest
 
 class TestDB(unittest.TestCase):
     def test_new_db(self):
+        db.reset()
         self.assertTrue(db.new_db())
         db.make_fake_track(1, 1, "Test Track", "/a/b/c/1.ogg")
         self.assertFalse(db.new_db())
+
+    def test_find_playlist(self):
+        track = db.make_fake_track(1, 1, "Test Track", "/a/b/c/1.ogg")
+        collection = db.user.Table.find("Collection")
+        genre = db.genre.Table.find("Test Genre")
+
+        self.assertIsNone(db.find_playlist(123456))
+        for plist in [ collection, track.artist, track.album, track.disc,
+                       genre, track.decade, track.year, track.library ]:
+            self.assertEqual(db.find_playlist(plist.plist_state.rowid), plist)