"""Thin runner: probe the source duration, then execute the frame -> loop ->
transcode stages with tools.pipeline.ffmpeg_ops. The pure arg builders are
unit-tested; this glue is covered by the opt-in integration test."""

from __future__ import annotations

import shutil
import subprocess
from pathlib import Path

from .ffmpeg_ops import crossfade_loop_args, frame_args, transcode_args

MASTER_MAX_W = 3840


def resolve_ffmpeg() -> str:
    """ffmpeg from PATH, else the bundled imageio-ffmpeg binary (matches
    simulator/setup_scales_media.py). The Pi/dev box may lack a system ffmpeg."""
    if shutil.which("ffmpeg"):
        return "ffmpeg"
    import imageio_ffmpeg
    return imageio_ffmpeg.get_ffmpeg_exe()


def probe_duration(src) -> float:
    """Clip duration in seconds via cv2 (frame_count / fps) — avoids a system
    ffprobe dependency (imageio-ffmpeg ships ffmpeg only; the Pi has no ffprobe)."""
    import cv2
    cap = cv2.VideoCapture(str(src))
    fps = cap.get(cv2.CAP_PROP_FPS) or 0.0
    frames = cap.get(cv2.CAP_PROP_FRAME_COUNT) or 0.0
    cap.release()
    if fps <= 0:
        raise ValueError(f"could not read fps from {src}")
    return frames / fps


def _run(args: list[str]) -> None:
    subprocess.run(args, check=True, capture_output=True)


def process_clip(src, out_dir, *, start: float = 0.0, duration: float | None = None,
                 overlap: float = 1.0, master_w: int = MASTER_MAX_W, master_h: int = 2160,
                 ff: str | None = None) -> dict:
    """Run stages 2–4 for one clip; return {'master','proxy','loop','mezzanine'} paths.
    `duration` defaults to the full source length (minus the trim start).
    Note: `crossfade_loop_args` uses a fixed fps only to satisfy xfade's
    constant-frame-rate requirement; the final output fps is set by `transcode_args`
    (both default 30 — keep in sync if overridden)."""
    ff = ff or resolve_ffmpeg()
    src = Path(src)
    out_dir = Path(out_dir)
    out_dir.mkdir(parents=True, exist_ok=True)
    if duration is None:
        duration = probe_duration(src) - start

    mezz = out_dir / "mezzanine.mp4"
    loop = out_dir / "loop.mp4"
    master = out_dir / "master.mp4"
    proxy = out_dir / "base.mp4"          # the proxy is what the manifest's base_file points at

    _run(frame_args(src, mezz, start=start, duration=duration,
                    width=master_w, height=master_h, ff=ff))
    _run(crossfade_loop_args(mezz, loop, duration=duration, overlap=overlap, ff=ff))
    _run(transcode_args(loop, master, width=master_w, height=master_h, crf=18, ff=ff))
    _run(transcode_args(loop, proxy, width=1920, height=1080, crf=20, ff=ff))
    return {"mezzanine": mezz, "loop": loop, "master": master, "proxy": proxy}