#!/usr/bin/env python3
"""Apply a generated variant to a Minecraft instance (game closed!).

    python3 apply_variant.py <ID> <path/to/.minecraft>     # e.g. C1, dh-r64, T-deck

Copies every config file of out/<ID>/ over the instance. options.txt is
*merged* key by key, so GUI scale, resolution, keybinds etc. survive variant
switches. Prints what changed. Stdlib only; works on Windows too.
"""
import shutil
import sys
from pathlib import Path

HERE = Path(__file__).resolve().parent


def merge_options(src, dst):
    new = dict(l.split(":", 1) for l in src.read_text().splitlines() if ":" in l)
    lines = dst.read_text().splitlines() if dst.exists() else []
    seen, out, changed = set(), [], []
    for l in lines:
        k = l.split(":", 1)[0]
        if k in new:
            seen.add(k)
            if l != f"{k}:{new[k]}":
                changed.append(f"{k}:{new[k]}")
            l = f"{k}:{new[k]}"
        out.append(l)
    for k, v in new.items():
        if k not in seen:
            out.append(f"{k}:{v}")
            changed.append(f"{k}:{v} (added)")
    dst.write_text("\n".join(out) + "\n")
    return changed


def main():
    if len(sys.argv) != 3:
        sys.exit(__doc__)
    vid, game = sys.argv[1], Path(sys.argv[2])
    src = HERE / "out" / vid
    if not src.is_dir():
        sys.exit(f"{src} missing - run build.py first")
    if not (game / "mods").is_dir():
        sys.exit(f"{game} doesn't look like a .minecraft dir (no mods/)")
    for f in sorted(p for p in src.rglob("*") if p.is_file()):
        rel = f.relative_to(src)
        dst = game / rel
        if rel.as_posix() == "options.txt":
            for c in merge_options(f, dst):
                print(f"options.txt  {c}")
            continue
        dst.parent.mkdir(parents=True, exist_ok=True)
        shutil.copyfile(f, dst)
        print(f"copied       {rel.as_posix()}")
    (game / "BENCH_VARIANT.txt").write_text(vid + "\n")
    print(f"applied {vid}; recorded in BENCH_VARIANT.txt")


main()