#!/usr/bin/env python3
"""
Build static/js/mountain.js with all ASCII frames from a build/<name>/ dir
embedded as a JS array.

Usage: build_mountain_js.py <src_dir> <dst_js_path>

Frames are read in sorted order, escaped for JS template literals, and
concatenated into a window.TP_MOUNTAIN_FRAMES array.
"""
import os
import sys


def js_escape(s: str) -> str:
    return s.replace("\\", "\\\\").replace("`", "\\`").replace("${", "\\${")


def main() -> int:
    if len(sys.argv) != 3:
        print(__doc__, file=sys.stderr)
        return 2

    src = sys.argv[1]
    dst = sys.argv[2]

    txts = sorted(p for p in os.listdir(src) if p.startswith("frame-") and p.endswith(".txt"))
    if not txts:
        print(f"no frame-*.txt files in {src}", file=sys.stderr)
        return 1

    frames = []
    for name in txts:
        with open(os.path.join(src, name)) as f:
            frames.append(f.read().rstrip("\n"))

    header = """/* Autogenerated by tools/build_mountain_js.py
   ASCII frames from a video, chafa-rendered, concatenated into a JS array.
   Cycled at 12 fps by static/js/mountain-bg.js. */

window.TP_MOUNTAIN_FRAMES = [
"""
    footer = f"""];

window.TP_MOUNTAIN_N_FRAMES = {len(frames)};
window.TP_MOUNTAIN_FPS = 12;
"""
    body = ",\n".join(f"  `{js_escape(fr)}`" for fr in frames)

    os.makedirs(os.path.dirname(dst), exist_ok=True)
    with open(dst, "w") as f:
        f.write(header)
        f.write(body)
        f.write("\n")
        f.write(footer)

    print(f"  {os.path.getsize(dst):>7d} bytes  {dst}  ({len(frames)} frames)")
    return 0


if __name__ == "__main__":
    sys.exit(main())