"""ffmpeg helpers: representative frame; OPTIONAL dominant color. Runner injectable."""

from __future__ import annotations

import subprocess


def _run_bytes(args) -> bytes:
    return subprocess.run(args, capture_output=True, check=True).stdout


def dominant_color_from_rgb(rgb: bytes) -> str:
    r, g, b = rgb[0], rgb[1], rgb[2]
    return f"#{r:02x}{g:02x}{b:02x}"


def compute_dominant_color(path, *, midpoint_s=0.0, runner=_run_bytes) -> str:
    """ffmpeg-only single-color palette of a mid-segment frame -> #rrggbb."""
    args = [
        "ffmpeg",
        "-v",
        "quiet",
        "-ss",
        str(midpoint_s),
        "-i",
        str(path),
        "-vf",
        "thumbnail,palettegen=max_colors=1",
        "-frames:v",
        "1",
        "-f",
        "rawvideo",
        "-pix_fmt",
        "rgb24",
        "-",
    ]
    return dominant_color_from_rgb(runner(args))


def extract_frame(path, dest, *, midpoint_s=0.0, runner=None):
    """Write one representative frame to dest (PNG) for the review preview."""
    runner = runner or (lambda a: subprocess.run(a, check=True))
    runner(
        [
            "ffmpeg",
            "-v",
            "quiet",
            "-y",
            "-ss",
            str(midpoint_s),
            "-i",
            str(path),
            "-frames:v",
            "1",
            str(dest),
        ]
    )
    return dest