"""
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",)
# Note: scene detection needs -loglevel info for showinfo filter output.
# Individual pipelines can override with .global_args()
QUIET_ARGS = ("-hide_banner", "-loglevel", "warning")


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

    MKV (Matroska) is used because:
    - Handles incomplete writes gracefully (like OBS default)
    - Proper timestamps for seeking and duration detection
    - mpv plays growing MKV files better than mpegts
    """
    stream = ffmpeg.input(stream_url, fflags="nobuffer", flags="low_delay")
    return (
        ffmpeg.output(
            stream, str(output_path),
            c="copy",
            f="matroska",
            flush_packets=1,
        )
        .global_args(*QUIET_ARGS)
    )


def receive_record_and_relay(stream_url, output_path, relay_url):
    """Receive TCP stream, write to MKV, and relay to UDP loopback for live display.

    Uses ffmpeg tee via merge_outputs: one ffmpeg process handles both outputs
    from the same decoded input, keeping them in sync with identical timestamps.
    """
    stream = ffmpeg.input(stream_url, fflags="nobuffer", flags="low_delay")
    file_out = ffmpeg.output(
        stream, str(output_path),
        c="copy", f="matroska", flush_packets=1,
    )
    relay_out = ffmpeg.output(
        stream, relay_url,
        c="copy", f="mpegts",
    )
    return ffmpeg.merge_outputs(file_out, relay_out).global_args(*QUIET_ARGS)


def extract_scene_frames(input_path, output_dir, scene_threshold=0.10,
                         start_number=1, start_time=0.0, duration=None):
    """Extract frames from a file on scene change only (no interval fallback).

    Frames are a chronological storyboard — captured whenever content changes
    meaningfully vs the previous frame. No periodic fallback so static content
    produces no spurious frames.

    start_time/duration: applied via the select filter expression (NOT as -ss/-t
    input options, which break h264 scene detection on MKV).
    Returns (stdout, stderr) as decoded strings for timestamp parsing.
    """
    scene_expr = f"gt(scene,{scene_threshold})"

    # Add time range filter if specified (incremental processing)
    time_conditions = []
    if start_time > 0:
        time_conditions.append(f"gte(t,{start_time})")
    if duration is not None:
        time_conditions.append(f"lte(t,{start_time + duration})")

    if time_conditions:
        time_filter = "*".join(time_conditions)
        select_expr = f"({scene_expr})*{time_filter}"
    else:
        select_expr = scene_expr

    stream = ffmpeg.input(str(input_path))
    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()))
    try:
        stdout, stderr = output.run(capture_stdout=True, capture_stderr=True)
    except ffmpeg.Error as e:
        # ffmpeg may exit non-zero on growing files (corrupt tail) but still
        # produce valid frames. Return the stderr for parsing anyway.
        log.debug("ffmpeg exited with error (may still have valid frames)")
        stdout = e.stdout or b""
        stderr = e.stderr or b""
    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()