audio: Create a StopWatch object

The StopWatch will be used to calculate how long a track is in the
'playing' state so we can accurately determin if it has been played or
not.

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

emmental/audio/stopwatch.py

@@ -0,0 +1,42 @@
+# Copyright 2024 (c) Anna Schumaker.
+"""A custom StopWatch object for tracking play time."""
+import datetime
+from gi.repository import GObject
+
+
+class StopWatch(GObject.GObject):
+    """A StopWatch object."""
+
+    def __init__(self) -> None:
+        """Initialize the StopWatch."""
+        super().__init__()
+        self._saved = None
+        self._started = None
+
+    def elapsed_time(self) -> float:
+        """Get the elapsed time (in seconds)."""
+        total = datetime.timedelta()
+        if self._saved is not None:
+            total += self._saved
+        if self._started is not None:
+            total += datetime.datetime.now() - self._started
+        return total.total_seconds()
+
+    def reset(self) -> None:
+        """Reset the StopWatch."""
+        self._saved = None
+        self._started = None
+
+    def start(self) -> None:
+        """Start the StopWatch."""
+        self._started = datetime.datetime.now()
+
+    def stop(self) -> None:
+        """Stop the StopWatch."""
+        if self._started is not None:
+            delta = datetime.datetime.now() - self._started
+            if self._saved is None:
+                self._saved = delta
+            else:
+                self._saved += delta
+            self._started = None

tests/audio/test_stopwatch.py

@@ -0,0 +1,87 @@
+# Copyright 2024 (c) Anna Schumaker.
+"""Tests our StopWatch object."""
+import datetime
+import emmental.audio.stopwatch
+import unittest
+from gi.repository import GObject
+
+
+@unittest.mock.patch.object(emmental.audio.stopwatch, "datetime")
+class TestStopwatch(unittest.TestCase):
+    """Our stopwatch test case."""
+
+    def setUp(self):
+        """Set up common variables."""
+        self.now = datetime.datetime.now()
+        self.newdelta = datetime.timedelta
+        self.stopwatch = emmental.audio.stopwatch.StopWatch()
+
+    def test_init(self, mock_datetime: unittest.mock.Mock):
+        """Test that the StopWatch was created properly."""
+        self.assertIsInstance(self.stopwatch, GObject.GObject)
+
+    def test_elapsed_time(self, mock_datetime: unittest.mock.Mock):
+        """Test the elapsed_time() function."""
+        mock_datetime.timedelta = self.newdelta
+        self.assertEqual(self.stopwatch.elapsed_time(), 0.0)
+
+        mock_datetime.datetime.now.return_value = self.now
+        self.stopwatch.start()
+
+        soon = self.now + datetime.timedelta(seconds=12.345)
+        mock_datetime.datetime.now.return_value = soon
+        self.assertEqual(self.stopwatch.elapsed_time(), 12.345)
+
+        self.stopwatch._saved = datetime.timedelta(seconds=2)
+        self.assertEqual(self.stopwatch.elapsed_time(), 14.345)
+
+        self.stopwatch.stop()
+        self.assertEqual(self.stopwatch.elapsed_time(), 14.345)
+
+        self.stopwatch.reset()
+        self.assertEqual(self.stopwatch.elapsed_time(), 0.0)
+
+    def test_reset(self, mock_datetime: unittest.mock.Mock):
+        """Test resetting the StopWatch."""
+        mock_datetime.datetime.now.return_value = self.now
+        self.stopwatch.start()
+        soon = self.now + datetime.timedelta(seconds=12.345)
+        mock_datetime.datetime.now.return_value = soon
+        self.stopwatch.stop()
+
+        self.stopwatch.reset()
+        self.assertIsNone(self.stopwatch._saved)
+        self.assertIsNone(self.stopwatch._started)
+
+    def test_start(self, mock_datetime: unittest.mock.Mock):
+        """Test starting the StopWatch."""
+        self.assertIsNone(self.stopwatch._started)
+
+        mock_datetime.datetime.now.return_value = self.now
+        self.stopwatch.start()
+        self.assertEqual(self.stopwatch._started, self.now)
+
+    def test_stop(self, mock_datetime: unittest.mock.Mock):
+        """Test stopping the StopWatch."""
+        self.assertIsNone(self.stopwatch._saved)
+        self.stopwatch.stop()
+        self.assertIsNone(self.stopwatch._saved)
+
+        mock_datetime.datetime.now.return_value = self.now
+        self.stopwatch.start()
+        delta1 = datetime.timedelta(seconds=12.345)
+        mock_datetime.datetime.now.return_value = self.now + delta1
+        self.stopwatch.stop()
+        self.assertEqual(self.stopwatch._saved, delta1)
+        self.assertIsNone(self.stopwatch._started)
+
+        now = self.now + delta1 + datetime.timedelta(seconds=2)
+        mock_datetime.datetime.now.return_value = now
+        self.stopwatch.start()
+        delta2 = datetime.timedelta(seconds=3)
+        mock_datetime.datetime.now.return_value = now + delta2
+        self.stopwatch.stop()
+        self.assertEqual(self.stopwatch._saved, delta1 + delta2)
+
+        self.stopwatch.stop()
+        self.assertEqual(self.stopwatch._saved, delta1 + delta2)