import sys
import unittest
from pathlib import Path

sys.path.insert(0, str(Path(__file__).resolve().parent.parent))
from sync_logic import compute_offset


class TestComputeOffset(unittest.TestCase):
    def test_audio_ahead_needs_delay(self):
        # Flash seen at 5.000s, beep heard at 4.500s -> audio is running
        # ahead of video, so audio needs to be delayed to catch up.
        offset = compute_offset(video_mark_sec=5.000, audio_mark_sec=4.500)
        self.assertAlmostEqual(offset.delay_ms, 500.0)
        self.assertEqual(offset.target, "audio")

    def test_audio_behind_needs_video_delay(self):
        # This is our synthetic test fixture: audio was shifted +350ms
        # later than video, so the fix is to delay video to catch up to
        # the already-late audio -- NOT to delay audio further.
        offset = compute_offset(video_mark_sec=5.000, audio_mark_sec=5.350)
        self.assertAlmostEqual(offset.delay_ms, -350.0)
        self.assertEqual(offset.target, "video")

    def test_already_in_sync(self):
        offset = compute_offset(video_mark_sec=5.000, audio_mark_sec=5.000)
        self.assertEqual(offset.delay_ms, 0.0)
        self.assertEqual(offset.target, "none")

    def test_describe_formatting(self):
        self.assertIn("audio will be delayed", compute_offset(5.5, 5.0).describe())
        self.assertIn("video will be delayed", compute_offset(5.0, 5.5).describe())
        self.assertIn("+500", compute_offset(5.5, 5.0).describe())
        self.assertIn("-500", compute_offset(5.0, 5.5).describe())


if __name__ == "__main__":
    unittest.main()