"""AZ-398 — :class:`FrameSource` Protocol conformance + concrete strategy ACs."""

from __future__ import annotations

from pathlib import Path

import cv2
import numpy as np
import pytest

from gps_denied_onboard.clock.wall_clock import WallClock
from gps_denied_onboard.frame_source import (
    FrameSource,
    FrameSourceConfigError,
)
from gps_denied_onboard.frame_source.live_camera import LiveCameraFrameSource
from gps_denied_onboard.frame_source.video_file import VideoFileFrameSource


# ---------------------------------------------------------------------------
# Helpers.


def _make_synthetic_video(path: Path, n_frames: int, fps: int = 30) -> None:
    """Write an ``n_frames``-frame 64×48 BGR MP4V at ``path``."""
    fourcc = cv2.VideoWriter_fourcc(*"mp4v")
    writer = cv2.VideoWriter(str(path), fourcc, fps, (64, 48))
    if not writer.isOpened():
        raise RuntimeError(f"OpenCV could not open writer at {path!s}")
    try:
        for i in range(n_frames):
            frame = np.full((48, 64, 3), i % 256, dtype=np.uint8)
            writer.write(frame)
    finally:
        writer.release()


@pytest.fixture
def video_path_60(tmp_path: Path) -> Path:
    """A synthetic 60-frame .mp4 file for AC-2."""
    path = tmp_path / "az398_synthetic.mp4"
    _make_synthetic_video(path, n_frames=60)
    return path


@pytest.fixture
def enable_video_flag(monkeypatch: pytest.MonkeyPatch) -> None:
    monkeypatch.setenv("BUILD_VIDEO_FILE_FRAME_SOURCE", "ON")


@pytest.fixture
def disable_video_flag(monkeypatch: pytest.MonkeyPatch) -> None:
    monkeypatch.setenv("BUILD_VIDEO_FILE_FRAME_SOURCE", "OFF")


@pytest.fixture
def disable_live_flag(monkeypatch: pytest.MonkeyPatch) -> None:
    monkeypatch.setenv("BUILD_LIVE_CAMERA_FRAME_SOURCE", "OFF")


# ---------------------------------------------------------------------------
# AC-1 — Protocol conformance.


def test_video_file_frame_source_satisfies_frame_source_protocol(
    enable_video_flag: None, video_path_60: Path
) -> None:
    # Arrange + Act
    source = VideoFileFrameSource(
        path=video_path_60,
        camera_calibration_id="az398-synth",
        clock=WallClock(),
    )
    try:
        # Assert
        assert isinstance(source, FrameSource)
    finally:
        source.close()


# ---------------------------------------------------------------------------
# AC-2 — VideoFileFrameSource produces 60 ordered frames + idempotent EOS.


def test_video_file_frame_source_emits_60_frames_then_none(
    enable_video_flag: None, video_path_60: Path
) -> None:
    # Arrange
    source = VideoFileFrameSource(
        path=video_path_60,
        camera_calibration_id="az398-synth",
        clock=WallClock(),
    )
    monotonics: list[int] = []
    try:
        # Act
        for _ in range(60):
            frame = source.next_frame()
            assert frame is not None
            monotonics.append(frame.metadata["monotonic_ns"])
        # AC-2: 61st call → None; subsequent calls also None
        eos_first = source.next_frame()
        eos_second = source.next_frame()
    finally:
        source.close()
    # Assert
    assert eos_first is None
    assert eos_second is None
    assert len(monotonics) == 60
    # Non-decreasing monotonic_ns ordering (Invariant 3 / AC-2)
    assert all(b >= a for a, b in zip(monotonics, monotonics[1:], strict=False))


def test_video_file_frame_source_emits_frame_id_counter_and_metadata(
    enable_video_flag: None, video_path_60: Path
) -> None:
    # Arrange
    source = VideoFileFrameSource(
        path=video_path_60,
        camera_calibration_id="az398-synth",
        clock=WallClock(),
    )
    try:
        # Act
        first = source.next_frame()
        second = source.next_frame()
    finally:
        source.close()
    # Assert
    assert first is not None and second is not None
    assert first.frame_id == 0
    assert second.frame_id == 1
    assert first.camera_calibration_id == "az398-synth"
    assert first.metadata["source"] == "video_file"
    assert "monotonic_ns" in first.metadata
    assert "source_pts_ns" in first.metadata


# ---------------------------------------------------------------------------
# AC-7 — corrupt video file raises FrameSourceConfigError on construction.


def test_video_file_frame_source_rejects_corrupt_file(
    enable_video_flag: None, tmp_path: Path
) -> None:
    # Arrange
    corrupt = tmp_path / "garbage.mp4"
    corrupt.write_bytes(b"not actually mp4 content" * 256)
    # Act + Assert
    with pytest.raises(FrameSourceConfigError):
        VideoFileFrameSource(
            path=corrupt,
            camera_calibration_id="az398-corrupt",
            clock=WallClock(),
        )


def test_video_file_frame_source_rejects_missing_path(
    enable_video_flag: None, tmp_path: Path
) -> None:
    # Act + Assert
    with pytest.raises(FrameSourceConfigError, match="does not exist"):
        VideoFileFrameSource(
            path=tmp_path / "missing.mp4",
            camera_calibration_id="az398-missing",
            clock=WallClock(),
        )


# ---------------------------------------------------------------------------
# AC-8 — Build-flag gating.


def test_video_file_frame_source_refuses_when_build_flag_off(
    disable_video_flag: None, tmp_path: Path
) -> None:
    # Arrange — create a real file so the gate is exercised before path checks
    valid = tmp_path / "any.mp4"
    valid.write_bytes(b"")
    # Act + Assert
    with pytest.raises(
        FrameSourceConfigError, match="BUILD_VIDEO_FILE_FRAME_SOURCE is OFF"
    ):
        VideoFileFrameSource(
            path=valid,
            camera_calibration_id="az398-gate",
            clock=WallClock(),
        )


def test_live_camera_frame_source_refuses_when_build_flag_off(
    disable_live_flag: None,
) -> None:
    # Act + Assert
    with pytest.raises(
        FrameSourceConfigError, match="BUILD_LIVE_CAMERA_FRAME_SOURCE is OFF"
    ):
        LiveCameraFrameSource(
            device_index=0,
            camera_calibration_id="az398-live-gate",
            clock=WallClock(),
        )


# ---------------------------------------------------------------------------
# AC-9 — Public API re-exports.


def test_frame_source_public_module_only_exposes_protocol_and_errors() -> None:
    # Arrange
    from gps_denied_onboard import frame_source as module

    # Assert — concrete strategies MUST NOT appear in __all__ per AC-9
    assert "FrameSource" in module.__all__
    assert "FrameSourceError" in module.__all__
    assert "FrameSourceConfigError" in module.__all__
    assert "LiveCameraFrameSource" not in module.__all__
    assert "VideoFileFrameSource" not in module.__all__


# ---------------------------------------------------------------------------
# AC-10 — close is idempotent.


def test_video_file_frame_source_close_is_idempotent(
    enable_video_flag: None, video_path_60: Path
) -> None:
    # Arrange
    source = VideoFileFrameSource(
        path=video_path_60,
        camera_calibration_id="az398-synth",
        clock=WallClock(),
    )
    # Act — closing twice must not raise (AC-10)
    source.close()
    source.close()
    # Assert — next_frame after close returns None, not an exception
    assert source.next_frame() is None


# ---------------------------------------------------------------------------
# Factory.


def test_build_frame_source_video_file_returns_video_file_source(
    enable_video_flag: None, video_path_60: Path
) -> None:
    from gps_denied_onboard.runtime_root.frame_source_factory import (
        build_frame_source,
    )

    source = build_frame_source(
        kind="video_file",
        camera_calibration_id="az398-factory",
        clock=WallClock(),
        video_path=video_path_60,
    )
    try:
        # Assert
        assert isinstance(source, VideoFileFrameSource)
    finally:
        source.close()


def test_build_frame_source_rejects_unknown_kind() -> None:
    from gps_denied_onboard.runtime_root.frame_source_factory import (
        build_frame_source,
    )

    with pytest.raises(FrameSourceConfigError, match="unknown kind"):
        build_frame_source(
            kind="invalid",  # type: ignore[arg-type]
            camera_calibration_id="x",
            clock=WallClock(),
        )


def test_build_frame_source_live_rejects_video_path(enable_video_flag: None) -> None:
    from gps_denied_onboard.runtime_root.frame_source_factory import (
        build_frame_source,
    )

    with pytest.raises(FrameSourceConfigError, match="video_path must be None"):
        build_frame_source(
            kind="live",
            camera_calibration_id="x",
            clock=WallClock(),
            device_index=0,
            video_path="/tmp/whatever.mp4",
        )


def test_build_frame_source_video_file_requires_video_path() -> None:
    from gps_denied_onboard.runtime_root.frame_source_factory import (
        build_frame_source,
    )

    with pytest.raises(FrameSourceConfigError, match="video_path is required"):
        build_frame_source(
            kind="video_file",
            camera_calibration_id="x",
            clock=WallClock(),
        )