#!/usr/bin/env python3
"""Materialise a 1.12 asset tree out of a hash-addressed asset store.

Minecraft 1.12.2 does not read an index plus an object store. It reads
``<assetsDir>/minecraft/<path>`` directly. A launcher such as AstralRinth keeps
assets the modern way, as ``indexes/1.12.json`` pointing at
``objects/<aa>/<sha1>``, and a launcher that wants them for an old client is
responsible for laying them out.

Passing the store root as ``--assetsDir`` does not fail loudly. Texts and
textures still appear, because those live inside the client jar, so the game
looks correct while every sound is silently absent: nothing requested is ever
found on disk.

Usage:
    materialize_assets.py <meta-assets-dir> <out-dir> [--index 1.12]

Hard links are used where the filesystem allows it, so the materialised tree
costs almost nothing and repeated runs are cheap.
"""

import argparse
import json
import os
import sys


def human(count):
    return "{:,}".format(count).replace(",", " ")


def main(argv):
    ap = argparse.ArgumentParser(description=__doc__,
                                 formatter_class=argparse.RawDescriptionHelpFormatter)
    ap.add_argument("meta_assets", help="store root holding indexes/ and objects/")
    ap.add_argument("out", help="assets dir to create for the client")
    ap.add_argument("--index", default="1.12", help="index file name (default: 1.12)")
    args = ap.parse_args(argv)

    meta = args.meta_assets
    index_path = os.path.join(meta, "indexes", args.index + ".json")
    if not os.path.isfile(index_path):
        sys.exit("no asset index at " + index_path)

    with open(index_path, "r", encoding="utf-8") as fh:
        objects = json.load(fh)["objects"]

    out = args.out
    linked = copied = reused = 0
    missing = []

    for name, info in sorted(objects.items()):
        digest = info["hash"]
        src = os.path.join(meta, "objects", digest[:2], digest)
        dst = os.path.join(out, *name.split("/"))

        if os.path.isfile(src) and os.path.getsize(src) == info["size"]:
            if os.path.exists(dst) and os.path.getsize(dst) == info["size"]:
                reused += 1
                continue
            os.makedirs(os.path.dirname(dst), exist_ok=True)
            if os.path.exists(dst):
                os.remove(dst)
            try:
                os.link(src, dst)
                linked += 1
            except OSError:
                with open(src, "rb") as r, open(dst, "wb") as w:
                    w.write(r.read())
                copied += 1
        else:
            missing.append(name)

    sounds = sum(1 for n in objects if n.endswith(".ogg"))
    print("index   : {} ({} objects, {} ogg)".format(
        os.path.join("indexes", args.index + ".json"), human(len(objects)), human(sounds)))
    print("output  : {}".format(out))
    print("hardlink: {}   copy: {}   reused: {}".format(
        human(linked), human(copied), human(reused)))
    if missing:
        print("MISSING : {} object(s) not in the store".format(human(len(missing))))
        for name in missing[:10]:
            print("          " + name)
        return 1
    print("ok      : every indexed object is present")
    return 0


if __name__ == "__main__":
    raise SystemExit(main(sys.argv[1:]))