tracklist: Add a SortField object

The SortField object is used to represent a single column in the
Tracklist that the user could sort by.

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

emmental/tracklist/sorter.py

@@ -0,0 +1,55 @@
+# Copyright 2022 (c) Anna Schumaker.
+"""A Sorter designed for sorting Playlists."""
+from gi.repository import GObject
+from gi.repository import Gio
+
+SORT_FIELDS = {"Album": ["album"], "Artist": ["artist"],
+               "Album Artist": ["albumartist"],
+               "Filepath": ["filepath"], "Length": ["length"],
+               "Last Played Date": ["lastplayed"],
+               "Last Started Date": ["laststarted"],
+               "Play Count": ["playcount"], "Release Date": ["release"],
+               "Title": ["title"], "Track Number": ["mediumno", "number"]}
+
+
+class SortField(GObject.GObject):
+    """Used to represent a single field in the sort order."""
+
+    name = GObject.Property(type=str)
+    model = GObject.Property(type=Gio.ListModel)
+
+    enabled = GObject.Property(type=bool, default=False)
+    reversed = GObject.Property(type=bool, default=False)
+
+    def __init__(self, model: Gio.ListStore, name: str):
+        """Initialize a Sort Field."""
+        if name not in SORT_FIELDS:
+            raise KeyError
+        super().__init__(model=model, name=name)
+
+    def __str__(self) -> str:
+        """Convert this Field into a string."""
+        columns = SORT_FIELDS[self.name]
+        if self.reversed:
+            columns = [f"{col} DESC" for col in columns]
+        return ", ".join(columns)
+
+    def disable(self) -> bool:
+        """Disable this Sort Field."""
+        return self.model.disable(self)
+
+    def enable(self) -> bool:
+        """Enable this Sort Field."""
+        return self.model.enable(self)
+
+    def move_down(self) -> bool:
+        """Move this Sort Field down in the list."""
+        return self.model.move_down(self)
+
+    def move_up(self) -> bool:
+        """Move this Sort Field up in the list."""
+        return self.model.move_up(self)
+
+    def reverse(self) -> None:
+        """Reverse the direction of this Sort Field."""
+        self.model.reverse(self)

tests/tracklist/test_sorter.py

@@ -0,0 +1,86 @@
+# Copyright 2022 (c) Anna Schumaker.
+"""Tests our Playlist Sorter."""
+import emmental.tracklist.sorter
+import unittest
+from gi.repository import GObject
+from gi.repository import Gio
+
+
+class TestSortConstants(unittest.TestCase):
+    """Test case for Sort Order constants."""
+
+    def test_sort_fields(self):
+        """Test the sort fields definition dictionary."""
+        self.assertDictEqual(emmental.tracklist.sorter.SORT_FIELDS,
+                             {"Album": ["album"], "Artist": ["artist"],
+                              "Album Artist": ["albumartist"],
+                              "Filepath": ["filepath"], "Length": ["length"],
+                              "Last Played Date": ["lastplayed"],
+                              "Last Started Date": ["laststarted"],
+                              "Play Count": ["playcount"],
+                              "Release Date": ["release"],
+                              "Title": ["title"],
+                              "Track Number": ["mediumno", "number"]})
+
+
+class TestSortField(unittest.TestCase):
+    """Test case for our SortField object."""
+
+    def setUp(self):
+        """Set up common variables."""
+        self.model = Gio.ListStore()
+        self.field = emmental.tracklist.sorter.SortField(self.model, "Album")
+
+    def test_init(self):
+        """Test that the Sort Field is initialized correctly."""
+        self.assertIsInstance(self.field, GObject.GObject)
+        self.assertEqual(self.field.name, "Album")
+        self.assertEqual(self.field.model, self.model)
+        self.assertFalse(self.field.enabled)
+        self.assertFalse(self.field.reversed)
+
+        with self.assertRaises(KeyError):
+            emmental.tracklist.sorter.SortField(self.model, "Invalid Field")
+
+    def test_str(self):
+        """Test converting a Sort Field to a string."""
+        for (field, cols) in emmental.tracklist.sorter.SORT_FIELDS.items():
+            expected = ", ".join(cols)
+            reversed = ", ".join([f"{c} DESC" for c in cols])
+            with self.subTest(field=field, expected=(expected, reversed)):
+                self.field.name = field
+                self.field.reversed = False
+                self.assertEqual(str(self.field), expected)
+
+                self.field.reversed = True
+                self.assertEqual(str(self.field), reversed)
+
+    def test_disable(self):
+        """Test disabling a Sort Field."""
+        self.model.disable = unittest.mock.Mock()
+        self.field.disable()
+        self.model.disable.assert_called_with(self.field)
+
+    def test_enable(self):
+        """Test enabling a Sort Field."""
+        self.model.enable = unittest.mock.Mock()
+        self.field.enable()
+        self.model.enable.assert_called_with(self.field)
+
+    def test_move_down(self):
+        """Test moving a Sort Field down."""
+        self.model.move_down = unittest.mock.Mock()
+        self.field.move_down()
+        self.model.move_down.assert_called_with(self.field)
+
+    def test_move_up(self):
+        """Test moving a Sort Field up."""
+        self.model.move_up = unittest.mock.Mock()
+        self.field.move_up()
+        self.model.move_up.assert_called_with(self.field)
+
+    def test_reverse(self):
+        """Test reversing a Sort Field."""
+        self.model.reverse = unittest.mock.Mock()
+        self.field.reverse()
+        self.model.reverse.assert_called_with(self.field)