import cv2
import numpy as np
import pytest

from paperpod.capture.video import iter_frames, probe_video


@pytest.fixture(scope="module")
def tiny_video(tmp_path_factory):
    """3s, 24fps, 320x240 video with a moving square."""
    path = tmp_path_factory.mktemp("video") / "tiny.mp4"
    writer = cv2.VideoWriter(str(path), cv2.VideoWriter_fourcc(*"mp4v"), 24, (320, 240))
    for i in range(72):
        frame = np.full((240, 320, 3), 100, dtype=np.uint8)
        x = 10 + i * 3
        cv2.rectangle(frame, (x, 100), (x + 40, 140), (255, 255, 255), -1)
        writer.write(frame)
    writer.release()
    return path


def test_probe(tiny_video):
    meta = probe_video(tiny_video)
    assert meta.fps == pytest.approx(24, abs=0.5)
    assert meta.frame_count == 72
    assert meta.width == 320 and meta.height == 240
    assert meta.duration_s == pytest.approx(3.0, abs=0.1)


def test_iter_frames_sample_rate(tiny_video):
    frames = list(iter_frames(tiny_video, sample_fps=8))
    # 24fps sampled at 8fps -> every 3rd frame -> 24 frames
    assert len(frames) == 24
    ts = [f.t for f in frames]
    assert ts == sorted(ts)
    assert ts[0] == 0.0


def test_iter_frames_resize(tiny_video):
    frame = next(iter_frames(tiny_video, sample_fps=8, resize_width=160))
    assert frame.image.shape[1] == 160
    assert frame.image.shape[0] == 120


def test_probe_missing_file():
    with pytest.raises(FileNotFoundError):
        probe_video("does_not_exist.mp4")