#!/usr/bin/env python3
"""macOS: Dock / Cmd-Tab / menu bar show the game as "wine" (the loader's file name). This makes a copy of Wine's
loader lib/wine/x86_64-unix/wine named "OldEraMT2" whose embedded __TEXT,__info_plist names the app "OldEraMT2"
(bundle id com.olderamt2.client.game). oldera-wine.sh starts the game through this copy when it exists; Wine's
helper processes keep using "wine". Only the embedded plist text changes (same byte length, padded with XML
whitespace); the copy is re-signed by build-macos.sh. Modification of an LGPL binary: noted in THIRD-PARTY-NOTICES.
usage: make-game-loader.py WINE_DIR"""
import struct, sys, pathlib

MH_MAGIC_64, LC_SEGMENT_64 = 0xfeedfacf, 0x19


def info_plist_range(b):
    magic, _, _, _, ncmds, _, _, _ = struct.unpack_from('<IiiIIIII', b, 0)
    assert magic == MH_MAGIC_64, 'thin 64-bit Mach-O expected'
    off = 32
    for _ in range(ncmds):
        cmd, size = struct.unpack_from('<II', b, off)
        if cmd == LC_SEGMENT_64:
            nsects = struct.unpack_from('<I', b, off + 64)[0]
            for i in range(nsects):
                s = off + 72 + 80 * i
                sect = b[s:s + 16].rstrip(b'\0'); seg = b[s + 16:s + 32].rstrip(b'\0')
                if sect == b'__info_plist' and seg == b'__TEXT':
                    size64, offset = struct.unpack_from('<QI', b, s + 40)
                    return offset, size64
        off += size
    raise SystemExit('no __info_plist section')


def main(wine_dir):
    src = pathlib.Path(wine_dir) / 'lib/wine/x86_64-unix/wine'
    dst = src.with_name('OldEraMT2')
    b = bytearray(src.read_bytes())
    off, size = info_plist_range(b)
    old = bytes(b[off:off + size]).rstrip(b'\0')
    new = (old.replace(b'<string>wine</string>', b'<string>OldEraMT2</string>')
              .replace(b'<string>org.winehq.wine</string>', b'<string>com.olderamt2.client.game</string>')
              .replace(b'<string>Wine</string>', b'<string>OldEraMT2</string>'))
    assert new.count(b'OldEraMT2') == 2 and b'olderamt2.client.game' in new, 'unexpected plist'
    new = b'\n'.join(line.strip() for line in new.split(b'\n'))          # drop indentation to keep the size
    assert len(new) <= size, (len(new), size)
    b[off:off + size] = new + b'\n' * (size - len(new) - 1) + b'\0' if len(new) < size else new
    dst.write_bytes(bytes(b)); dst.chmod(0o755)
    print('%s: plist %d/%d bytes' % (dst, len(new), size))


if __name__ == '__main__':
    main(sys.argv[1])