db: Create a GenreTable and Genre object

I'll eventually need to add a mapping between tracks and their genre
list, but I still need to build up to having Track objects first

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

db/__init__.py

@@ -14,9 +14,10 @@ executemany = Connection.executemany
 from . import artist
 from . import album
 from . import disc
+from . import genre
 
 def reset():
-    mods = [ artist, album, disc ]
+    mods = [ artist, album, disc, genre ]
 
     for mod in mods: mod.Table.drop()
     for mod in mods: mod.Table.do_create()

db/genre.py

@@ -0,0 +1,49 @@
+# Copyright 2021 (c) Anna Schumaker.
+#
+# Table: genres
+# +---------+------+------+
+# | genreid | name | sort |
+# +---------+------+------+
+#
+# Index: genre_index
+# +-----------------+
+# | name -> genreid |
+# +-----------------+
+from . import execute
+from . import objects
+
+class Genre(objects.Tag):
+    def do_get_column(self, column):
+        return execute(f"SELECT {column} FROM genres "
+                        "WHERE genreid=?", [ self.rowid ])
+
+
+class GenreTable(objects.Table):
+    def __init__(self):
+        objects.Table.__init__(self, "genres", Genre)
+
+    def do_create(self):
+        execute("CREATE TABLE IF NOT EXISTS genres "
+                    "(genreid INTEGER PRIMARY KEY, "
+                    " name TEXT UNIQUE, "
+                    " sort TEXT)")
+        execute("CREATE INDEX IF NOT EXISTS genre_index "
+                "ON genres(name)")
+
+    def do_insert(self, name):
+        return execute("INSERT INTO genres (name, sort) "
+                       "VALUES (?, ?)", (name, name.casefold()))
+
+    def do_delete(self, genre):
+        return execute("DELETE FROM genres WHERE genreid=?", [ int(genre) ])
+
+    def do_get(self, rowid):
+        return execute("SELECT genreid FROM genres "
+                       "WHERE genreid=?", [ rowid ])
+
+    def do_lookup(self, name):
+        return execute("SELECT genreid FROM genres "
+                       "WHERE name=?", [ name ])
+
+
+Table = GenreTable()

db/test_genre.py

@@ -0,0 +1,46 @@
+# Copyright 2021 (c) Anna Schumaker.
+import db
+import sqlite3
+import unittest
+from gi.repository import GObject
+
+
+class TestGenreTable(unittest.TestCase):
+    def on_row_inserted(self, table, row):
+        self.row_inserted = row
+
+    def setUp(self):
+        db.reset()
+
+    def test_genre_table_init(self):
+        self.assertIsInstance(db.genre.Table, db.genre.GenreTable)
+        db.execute("SELECT genreid,name,sort FROM genres")
+
+    def test_genre_table_insert(self):
+        db.genre.Table.connect("row-inserted", self.on_row_inserted)
+
+        genre = db.genre.Table.insert("Test Genre")
+        self.assertIsInstance(genre, db.genre.Genre)
+        self.assertIsInstance(genre, db.objects.Tag)
+        self.assertEqual(self.row_inserted, genre)
+
+        self.assertEqual(genre.name, "Test Genre")
+        self.assertEqual(genre.sort, "test genre")
+
+        with self.assertRaises(sqlite3.IntegrityError):
+            db.genre.Table.insert("Test Genre")
+
+    def test_genre_table_delete(self):
+        genre = db.genre.Table.find("Test Genre")
+        db.genre.Table.delete(genre)
+        self.assertIsNone(db.genre.Table.lookup("Test Genre"))
+
+    def test_genre_table_get(self):
+        genre = db.genre.Table.insert("Test Genre")
+        self.assertEqual(db.genre.Table.get(1), genre)
+        self.assertIsNone(db.genre.Table.get(2))
+
+    def test_genre_table_lookup(self):
+        genre = db.genre.Table.insert("Test Genre")
+        self.assertEqual(db.genre.Table.lookup("Test Genre"), genre)
+        self.assertIsNone(db.genre.Table.lookup("none"))