db: Create a new Model class

This inherits from the Table, but also implements the Gio.ListModel
interface with sorting for use in the sidebar Gtk.ListView

Implements: Issue #1 (Have SQLite sort our sidebar tables)
Signed-off-by: Anna Schumaker <Anna@NoWheyCreamery.com>

db/table.py

@@ -1,4 +1,6 @@
 # Copyright 2021 (c) Anna Schumaker.
+from gi.repository import GObject
+from gi.repository import Gio
 from . import sql
 
 class Table:
@@ -44,3 +46,44 @@ class Table:
         self.do_drop()
         self.cache.clear()
         self.do_create()
+
+
+class Model(GObject.GObject, Gio.ListModel, Table):
+    def __init__(self, table, order):
+        GObject.GObject.__init__(self)
+        Table.__init__(self, table)
+        self.order = order
+
+    def do_get_item_type(self):
+        return GObject.TYPE_PYOBJECT
+
+    def do_get_n_items(self):
+        return sql.execute(f"SELECT COUNT(*) FROM {self.table}").fetchone()[0]
+
+    def do_get_item(self, n):
+        cur = sql.execute(f"SELECT * FROM {self.table} ORDER BY {self.order} "
+                           "LIMIT 1 OFFSET ?", [ n ])
+        return self.factory(cur.fetchone())
+
+    def get_item_index(self, item):
+        cur = sql.execute("SELECT * FROM (SELECT rowid,ROW_NUMBER() "
+                                        f"OVER (ORDER BY {self.order}) "
+                                        f"FROM {self.table}) "
+                          "WHERE rowid=?", [ item.rowid ])
+        return cur.fetchone()[1] - 1
+
+    def delete(self, item):
+        pos = self.get_item_index(item)
+        super().delete(item)
+        self.emit("items-changed", pos, 1, 0)
+
+    def insert(self, *args):
+        row = super().insert(*args)
+        pos = self.get_item_index(row)
+        self.emit("items-changed", pos, 0, 1)
+        return row
+
+    def reset(self):
+        n = self.get_n_items()
+        super().reset()
+        self.emit("items-changed", 0, n, self.get_n_items())

db/test_table.py

@@ -1,10 +1,13 @@
 # Copyright 2021 (c) Anna Schumaker.
 import unittest
+from gi.repository import GObject
+from gi.repository import Gio
 from . import sql
 from . import table
 
-class FakeRow:
+class FakeRow(GObject.GObject):
     def __init__(self, data):
+        GObject.GObject.__init__(self)
         self.rowid = data["fakeid"]
         self.name = data["name"]
 
@@ -26,6 +29,13 @@ class FakeTable(table.Table):
     def do_lookup(self, name):
         return sql.execute("SELECT * FROM fake_table WHERE name=?", [ name ])
 
+class FakeModel(table.Model, FakeTable):
+    def __init__(self):
+        table.Model.__init__(self, "fake_table", "lower(name)")
+        self.reset()
+
+
+
 class TestTable(unittest.TestCase):
     def test_init(self):
         fake = FakeTable()
@@ -76,3 +86,56 @@ class TestTable(unittest.TestCase):
 
         fake.reset()
         self.assertEqual(fake.cache, { })
+
+
+class TestModel(unittest.TestCase):
+    def items_changed(self, table, pos, rm, add):
+        self.changed = (pos, rm, add)
+
+    def setUp(self):
+        self.changed = None
+
+    def test_init(self):
+        fake = FakeModel()
+        self.assertIsInstance(fake, GObject.GObject)
+        self.assertIsInstance(fake, Gio.ListModel)
+        self.assertIsInstance(fake, table.Table)
+        self.assertEqual(fake.order, "lower(name)")
+
+    def test_insert_delete(self):
+        fake = FakeModel()
+        fake.connect("items-changed", self.items_changed)
+
+        row = fake.insert("Test Row")
+        self.assertEqual(self.changed, (0, 0, 1))
+
+        fake.delete(row)
+        self.assertEqual(self.changed, (0, 1, 0))
+
+    def test_model(self):
+        fake = FakeModel()
+        self.assertEqual(fake.get_item_type(), GObject.TYPE_PYOBJECT)
+        self.assertEqual(fake.get_n_items(), 0)
+
+        c = fake.insert("C")
+        self.assertEqual(fake.get_n_items(), 1)
+        self.assertEqual(fake.get_item(0), c)
+
+        b = fake.insert("B")
+        self.assertEqual(fake.get_n_items(), 2)
+        self.assertEqual(fake.get_item(0), b)
+        self.assertEqual(fake.get_item(1), c)
+
+        a = fake.insert("A")
+        self.assertEqual(fake.get_n_items(), 3)
+        self.assertEqual(fake.get_item(0), a)
+        self.assertEqual(fake.get_item(1), b)
+        self.assertEqual(fake.get_item(2), c)
+
+    def test_reset(self):
+        fake = FakeModel()
+        fake.insert("Test Row")
+        fake.insert("Test Row 2")
+        fake.connect("items-changed", self.items_changed)
+        fake.reset()
+        self.assertEqual(self.changed, (0, 2, 0))