"""
Thin wrapper around ffmpeg-python for building and running ffmpeg pipelines.

All ffmpeg command construction goes through this module.
Uses ffmpeg-python's own run/run_async for subprocess management.
"""

import logging
import signal
import subprocess

import ffmpeg

log = logging.getLogger(__name__)

GLOBAL_ARGS = ("-hide_banner", "-loglevel", "warning")


def receive_and_record(stream_url, output_path):
    """Receive mpegts stream and write to a single growing file.

    mpv reads this file for DVR-style playback.
    ffmpeg scene detection runs on this file for frame extraction.
    Audio is preserved in the recording (muxed mpegts).
    """
    stream = ffmpeg.input(stream_url, fflags="nobuffer", flags="low_delay")
    return (
        ffmpeg.output(stream, str(output_path), c="copy", f="mpegts")
        .global_args(*GLOBAL_ARGS)
    )


def extract_scene_frames(input_path, output_dir, scene_threshold=0.3,
                         max_interval=30, start_number=1, start_time=0.0):
    """Extract frames from a file on scene change.

    Uses ffmpeg select filter with scene detection and a max-interval fallback.
    start_time: skip to this position before processing (avoids re-scanning).
    Returns (stdout, stderr) as decoded strings for timestamp parsing.
    """
    select_expr = (
        f"gt(scene,{scene_threshold})"
        f"+gte(t-prev_selected_t,{max_interval})"
    )
    input_opts = {}
    if start_time > 0:
        input_opts["ss"] = str(start_time)

    stream = ffmpeg.input(str(input_path), **input_opts)
    stream = stream.filter("select", select_expr).filter("showinfo")

    output = (
        ffmpeg.output(
            stream,
            str(output_dir / "F%04d.jpg"),
            vsync="vfr",
            **{"q:v": "2"},
            start_number=start_number,
        )
        .global_args(*GLOBAL_ARGS)
    )

    log.info("extract_scene_frames: %s", " ".join(output.compile()))
    stdout, stderr = output.run(capture_stdout=True, capture_stderr=True)
    return stdout.decode("utf-8", errors="replace"), stderr.decode("utf-8", errors="replace")


def run_async(output_node, pipe_stdout=False, pipe_stderr=False):
    """Start an ffmpeg pipeline asynchronously via ffmpeg-python's run_async."""
    log.info("run_async: %s", " ".join(output_node.compile()))
    return output_node.run_async(
        pipe_stdout=pipe_stdout,
        pipe_stderr=pipe_stderr,
    )


def stop_proc(proc, timeout=5):
    """Gracefully stop an ffmpeg subprocess."""
    if proc and proc.poll() is None:
        proc.send_signal(signal.SIGINT)
        try:
            proc.wait(timeout=timeout)
        except subprocess.TimeoutExpired:
            proc.kill()