"""Unit tests for scene change detection."""

import numpy as np

from fansifter_clipper.reframing import Reframer


class TestSceneDetection:
    """Test suite for scene change detection."""

    def test_scene_change_different_frames(self):
        """Test detection between completely different frames."""
        reframer = Reframer()

        # Create black and white frames (extreme difference)
        frame1 = np.zeros((720, 1280, 3), dtype=np.uint8)  # Black
        frame2 = np.ones((720, 1280, 3), dtype=np.uint8) * 255  # White

        is_change, confidence, reason = reframer._detect_scene_change(
            frame2, frame1, 0.9, 0.9
        )

        assert is_change is True
        assert confidence > 0.4  # Chi-square distance normalized to ~0.5 for extreme differences
        assert reason in ["histogram", "pixel_difference"]

    def test_no_scene_change_similar_frames(self):
        """Test no false positive on similar frames."""
        reframer = Reframer()

        # Create similar frames with slight variation
        frame1 = np.random.randint(100, 150, (720, 1280, 3), dtype=np.uint8)
        frame2 = np.roll(frame1, 10, axis=1)  # Camera motion simulation

        is_change, confidence, reason = reframer._detect_scene_change(
            frame2, frame1, 0.85, 0.87
        )

        assert is_change is False

    def test_scene_change_color_shift(self):
        """Test detection on major color changes."""
        reframer = Reframer()

        # Create frames with different dominant colors
        frame1 = np.zeros((720, 1280, 3), dtype=np.uint8)
        frame1[:, :, 2] = 255  # Red frame

        frame2 = np.zeros((720, 1280, 3), dtype=np.uint8)
        frame2[:, :, 0] = 255  # Blue frame

        is_change, confidence, reason = reframer._detect_scene_change(
            frame2, frame1, 0.8, 0.8
        )

        assert is_change is True
        assert reason in ["histogram", "pixel_difference"]

    def test_no_scene_change_lighting_variation(self):
        """Test that gradual lighting changes don't trigger false positives."""
        reframer = Reframer()

        # Create realistic scene with gradient
        frame1 = np.zeros((720, 1280, 3), dtype=np.uint8)
        y_gradient = np.linspace(50, 200, 720, dtype=np.uint8)
        frame1[:, :, :] = y_gradient[:, np.newaxis, np.newaxis]

        # Apply very slight brightening across entire frame
        frame2 = np.clip(frame1.astype(int) + 5, 0, 255).astype(np.uint8)

        is_change, confidence, reason = reframer._detect_scene_change(
            frame2, frame1, 0.85, 0.83
        )

        # Slight lighting change should not trigger scene detection
        assert is_change is False

    def test_scene_change_confidence_drop(self):
        """Test detection via significant confidence drop."""
        reframer = Reframer()

        # Create moderately different frames
        frame1 = np.random.randint(80, 120, (720, 1280, 3), dtype=np.uint8)
        frame2 = np.random.randint(140, 180, (720, 1280, 3), dtype=np.uint8)

        # Significant confidence drop should help trigger detection
        is_change, confidence, reason = reframer._detect_scene_change(
            frame2, frame1, 0.3, 0.9  # Large confidence drop
        )

        # Should detect scene change due to combined signals
        assert is_change is True


class TestSceneSegmentation:
    """Test suite for scene segmentation."""

    def test_segment_by_scene_changes(self):
        """Test keyframe segmentation by scene boundaries."""
        from fansifter_clipper.models import CropKeyframe

        reframer = Reframer()

        # Create keyframes with scene changes
        keyframes = [
            CropKeyframe(time=0.0, x=100, y=50, width=720, height=1280, scene_change=False),
            CropKeyframe(time=1.0, x=110, y=55, width=720, height=1280, scene_change=False),
            CropKeyframe(time=2.0, x=120, y=60, width=720, height=1280, scene_change=False),
            CropKeyframe(time=3.0, x=800, y=200, width=720, height=1280, scene_change=True),
            CropKeyframe(time=4.0, x=810, y=205, width=720, height=1280, scene_change=False),
            CropKeyframe(time=5.0, x=300, y=400, width=720, height=1280, scene_change=True),
            CropKeyframe(time=6.0, x=310, y=405, width=720, height=1280, scene_change=False),
        ]

        segments = reframer._segment_by_scene_changes(keyframes)

        # Should have 3 segments
        assert len(segments) == 3
        assert len(segments[0]) == 3  # First scene (0-2s)
        assert len(segments[1]) == 2  # Second scene (3-4s)
        assert len(segments[2]) == 2  # Third scene (5-6s)

    def test_segment_no_scene_changes(self):
        """Test segmentation with no scene changes."""
        from fansifter_clipper.models import CropKeyframe

        reframer = Reframer()

        # Create keyframes without scene changes
        keyframes = [
            CropKeyframe(time=0.0, x=100, y=50, width=720, height=1280, scene_change=False),
            CropKeyframe(time=1.0, x=110, y=55, width=720, height=1280, scene_change=False),
            CropKeyframe(time=2.0, x=120, y=60, width=720, height=1280, scene_change=False),
        ]

        segments = reframer._segment_by_scene_changes(keyframes)

        # Should have 1 segment (entire sequence)
        assert len(segments) == 1
        assert len(segments[0]) == 3

    def test_segment_empty_keyframes(self):
        """Test segmentation with empty keyframe list."""
        reframer = Reframer()

        segments = reframer._segment_by_scene_changes([])

        assert len(segments) == 0