#!/usr/bin/env python3
"""
Builds GameCube / Wii disc images (NTSC-J, NTSC-U, PAL) using xorrisofs /
mkisofs + Swiss-GC system-area headers.

The Swiss-GC headers contain a working GCN apploader that boots any DOL via
the El Torito catalog — no custom PPC assembly needed.

Headers are cached in <script_dir>/../buildtools/iso/ and downloaded from the
Swiss-GC repository on first use.

Disc layout (produced by xorrisofs):
  sectors 0-15   system area  (boot.bin + bi2 + apploader, from Swiss header)
  sector  16     ISO 9660 PVD
  sector  17     El Torito Boot Record
  ...            directory records, file data
                 Dusk.dol  (El Torito boot image — loaded by apploader)
                 dusk.dsk  (asset archive — found at runtime via ISO 9660)
"""

import argparse
import os
import shutil
import struct
import subprocess
import sys
import urllib.request

SWISS_BASE = (
    "https://raw.githubusercontent.com/emukidid/swiss-gc/"
    "6f78e41940d2699b69ec62636d57411ae2857f1e/buildtools/iso/"
)

REGIONS = [
    ('j', 'J', 'NTSC-J', 0),
    ('u', 'E', 'NTSC-U', 1),
    ('e', 'P', 'PAL',    2),
]


def _buildtools_iso_dir():
    here = os.path.dirname(os.path.abspath(__file__))
    return os.path.join(here, '..', 'buildtools', 'iso')


def _get_hdr(region_suffix):
    """Return the raw bytes of the Swiss system-area header for *region_suffix*
    ('j', 'u', or 'e'), downloading it if necessary."""
    cache_dir = _buildtools_iso_dir()
    os.makedirs(cache_dir, exist_ok=True)
    path = os.path.join(cache_dir, f'eltorito-{region_suffix}.hdr')
    if not os.path.exists(path):
        url = SWISS_BASE + f'eltorito-{region_suffix}.hdr'
        print(f'Downloading {url} ...', flush=True)
        with urllib.request.urlopen(url) as resp:
            data = resp.read()
        with open(path, 'wb') as f:
            f.write(data)
    with open(path, 'rb') as f:
        return f.read()


def _patch_hdr(hdr_data, game_id, title):
    """Patch game ID (bytes 0-5) and title (bytes 0x20-0x3FF) into the
    system-area header.  Everything else (magic, bi2, apploader) is unchanged."""
    hdr = bytearray(hdr_data)
    hdr[0:6] = game_id.encode('ascii')
    tb = title.encode('ascii')[:0x3E0]
    hdr[0x20:0x20 + len(tb)] = tb
    # zero remaining title bytes so stale Swiss title doesn't bleed through
    hdr[0x20 + len(tb):0x400] = bytes(0x3E0 - len(tb))
    return bytes(hdr)


def _find_mkisofs():
    for tool in ('xorrisofs', 'mkisofs'):
        if shutil.which(tool):
            return tool
    sys.exit('Error: neither xorrisofs nor mkisofs found. '
             'Install xorriso (apt install xorriso) or mkisofs.')


def _build_iso(platform, game_id, title, region_suffix, dol_path, dsk_path,
               out_path):
    hdr_data = _patch_hdr(_get_hdr(region_suffix), game_id, title)

    # Write patched header to a temp file alongside the output so we have a
    # stable path (avoids tempfile cleanup races on some systems).
    hdr_tmp = out_path + '.hdr.tmp'
    try:
        with open(hdr_tmp, 'wb') as f:
            f.write(hdr_data)

        mkisofs = _find_mkisofs()
        dol_name = os.path.basename(dol_path)

        cmd = [
            mkisofs,
            '-R', '-J',
            '-G', hdr_tmp,
            '-no-emul-boot',
            '-eltorito-platform', 'PPC',
            '-b', dol_name,
            '-o', out_path,
            dol_path,
            dsk_path,
        ]
        subprocess.run(cmd, check=True)
    finally:
        if os.path.exists(hdr_tmp):
            os.remove(hdr_tmp)

    size = os.path.getsize(out_path)
    print(f'Created {out_path}  ({size:,} bytes)')


def main():
    ap = argparse.ArgumentParser(
        description='Build GCN/Wii disc images from a DOL and asset file.')
    ap.add_argument('platform',  choices=['GCN', 'WII'])
    ap.add_argument('dol',       help='Path to Dusk.dol')
    ap.add_argument('dsk',       help='Path to dusk.dsk asset archive')
    ap.add_argument('title',     help='Game title string')
    ap.add_argument('build_dir', help='Output directory')
    args = ap.parse_args()

    id_prefix = 'G' if args.platform == 'GCN' else 'R'

    for region_suffix, region_char, region_name, _ in REGIONS:
        game_id  = f'{id_prefix}DK{region_char}01'
        out_path = os.path.join(args.build_dir, f'Dusk-{region_name}.iso')
        _build_iso(args.platform, game_id, args.title,
                   region_suffix, args.dol, args.dsk, out_path)


if __name__ == '__main__':
    main()