"""Replay images / video to the SUT's V4L2 file frame source.

Two replay modes:
    1. Image-set replay (FT-P-01, FT-P-05) — emit a sequence of JPEG / PNG
       still images at a configurable rate to the file frame source path the
       SUT polls.
    2. Video replay (FT-P-02, FT-P-04, FT-N-01..04, NFT-PERF-*) — decode an
       MP4 with OpenCV and emit frames at the encoded FPS (or a user-supplied
       rate for fast-forward). ``replay_video`` also accepts a directory of
       extracted frames (`AD000001.jpg`-style) so the AZ-408 injectors that
       emit frame directories rather than MP4s can use the same surface.

The actual frame-source path inside the SUT container is configured via the
``ONBOARD_FRAME_SOURCE_PATH`` environment variable on the SUT — the runner
writes to a shared tmpfs volume mounted at the same path inside both
containers.
"""

from __future__ import annotations

import time
from dataclasses import dataclass
from pathlib import Path
from typing import Callable, Protocol

import cv2

# Image extensions handled by ``replay_image_directory`` / ``replay_video``
# when given a directory rather than a file. Sorted-by-name ordering implies
# zero-padded filenames (``AD000001.jpg``) which the AZ-407 / AZ-408
# fixture builders already produce.
_IMAGE_EXTENSIONS = (".jpg", ".jpeg", ".png", ".bmp")


@dataclass(frozen=True)
class ReplayCadence:
    """Frame-rate / pace configuration for a replay session."""

    fps: float = 10.0
    realtime: bool = True


class FrameSink(Protocol):
    """Abstract destination for replayed frames (file path or memory queue)."""

    def write_frame(self, jpeg_bytes: bytes, timestamp_ms: int) -> None:
        ...


class FrameSourceReplayer:
    """Public surface for replaying frames into the SUT's frame-source path."""

    def __init__(
        self,
        sink: FrameSink,
        cadence: ReplayCadence | None = None,
        *,
        sleep_fn: Callable[[float], None] = time.sleep,
    ) -> None:
        self._sink = sink
        self._cadence = cadence or ReplayCadence()
        # Injected so unit tests can drop wall-clock pacing entirely.
        self._sleep = sleep_fn

    def replay_image_directory(self, directory: Path) -> int:
        """Replay every image in ``directory`` (sorted by name) at the configured
        cadence. Returns the number of frames emitted to the sink.

        Raises ``FileNotFoundError`` if ``directory`` does not exist or is not
        a directory. The sink is invoked with raw JPEG-encoded bytes and a
        monotonic-ms timestamp that starts at 0 and advances by the period
        derived from ``self._cadence.fps``.
        """
        if not directory.exists() or not directory.is_dir():
            raise FileNotFoundError(
                f"frame directory not found: {directory}"
            )
        files = sorted(
            p for p in directory.iterdir()
            if p.is_file() and p.suffix.lower() in _IMAGE_EXTENSIONS
        )
        return self._emit_files(files)

    def replay_video(self, video_path: Path) -> int:
        """Replay frames from ``video_path``. Returns count emitted.

        Auto-detects:
        * a regular file (``.mp4`` / ``.avi`` / ``.h264``) — decoded with
          OpenCV ``VideoCapture`` and re-encoded as JPEG before emission.
        * a directory — delegates to ``replay_image_directory`` so the
          AZ-408 injectors that emit frame directories can use this entry
          point without the caller knowing the difference.

        Raises ``FileNotFoundError`` on a missing path.
        """
        if not video_path.exists():
            raise FileNotFoundError(f"video path not found: {video_path}")
        if video_path.is_dir():
            return self.replay_image_directory(video_path)
        return self._decode_and_emit_video(video_path)

    def _decode_and_emit_video(self, video_path: Path) -> int:
        cap = cv2.VideoCapture(str(video_path))
        if not cap.isOpened():
            raise ValueError(f"OpenCV failed to open video: {video_path}")
        try:
            encoded_fps = cap.get(cv2.CAP_PROP_FPS) or 0.0
            fps = encoded_fps if (self._cadence.realtime and encoded_fps > 0) else self._cadence.fps
            period_ms = self._period_ms(fps)
            emitted = 0
            t_ms = 0
            while True:
                ok, frame = cap.read()
                if not ok:
                    break
                success, encoded = cv2.imencode(".jpg", frame)
                if not success:
                    raise ValueError(
                        f"OpenCV failed to JPEG-encode frame {emitted} of {video_path}"
                    )
                self._sink.write_frame(encoded.tobytes(), t_ms)
                emitted += 1
                t_ms += period_ms
                if self._cadence.realtime and period_ms > 0:
                    self._sleep(period_ms / 1000.0)
            return emitted
        finally:
            cap.release()

    def _emit_files(self, files: list[Path]) -> int:
        period_ms = self._period_ms(self._cadence.fps)
        emitted = 0
        t_ms = 0
        for path in files:
            jpeg_bytes = path.read_bytes()
            if path.suffix.lower() != ".jpg" and path.suffix.lower() != ".jpeg":
                # Re-encode non-JPEG sources so the sink always gets JPEG bytes.
                img = cv2.imread(str(path), cv2.IMREAD_UNCHANGED)
                if img is None:
                    raise ValueError(f"OpenCV failed to read image: {path}")
                success, encoded = cv2.imencode(".jpg", img)
                if not success:
                    raise ValueError(f"OpenCV failed to JPEG-encode image: {path}")
                jpeg_bytes = encoded.tobytes()
            self._sink.write_frame(jpeg_bytes, t_ms)
            emitted += 1
            t_ms += period_ms
            if self._cadence.realtime and period_ms > 0:
                self._sleep(period_ms / 1000.0)
        return emitted

    @staticmethod
    def _period_ms(fps: float) -> int:
        if fps <= 0:
            return 0
        return int(round(1000.0 / fps))