#!/usr/bin/env python3
"""Dump the title's Xbox 360 achievement table (XACH) out of the decrypted `.pe`.

The XEX embeds an SPA/XDBF resource holding the achievement definitions and one
string table per language. `GamePart_Debriefing` awards these (it walks the
`ACHIEVEMENTS_REQUIREMENTS` config list and sets bit *i* for entry *i*), and
`GamePart_ChallengeMission` gates each challenge mission on a bit of the same
space — so this table names the bits.

Layout, derived here and self-checked (see below):
  XDBF section header : magic[4] "XACH", version u32, size u32, count u16
  record, 36 bytes    : id u16, name_id u16, unlocked_desc_id u16,
                        locked_desc_id u16, image_id u32, gamerscore u16,
                        pad u16, flags u32, then 16 bytes of zeroes
  XSTR section header : magic[4] "XSTR", version u32, size u32, count u16
  string entry        : id u16, len u16, `len` bytes of ASCII

Self-check: the 24 records' gamerscore sums to **1000**, the retail total — a
wrong stride or field offset does not add up to a round 1000.

Usage:  xach_dump.py <path-to.pe> [--lang-index N]
"""
import struct
import sys


def find_all(buf, needle):
    out, i = [], 0
    while True:
        i = buf.find(needle, i)
        if i < 0:
            return out
        out.append(i)
        i += 1


def parse_xstr(d, off):
    count = struct.unpack_from(">H", d, off + 12)[0]
    o, table = off + 14, {}
    for _ in range(count):
        sid, ln = struct.unpack_from(">HH", d, o)
        table[sid] = d[o + 4 : o + 4 + ln].decode("ascii", "replace")
        o += 4 + ln
    return table


def main():
    if len(sys.argv) < 2:
        print(__doc__)
        return 1
    d = open(sys.argv[1], "rb").read()

    # The real XACH section is the one whose header count is small (the other
    # "XACH" hit is the XDBF entry table, which merely *names* it).
    xach = None
    for off in find_all(d, b"XACH"):
        ver, size, count = struct.unpack_from(">IIH", d, off + 4)
        if ver == 1 and 0 < count < 256 and size >= count * 36:
            xach = (off, count)
            break
    if xach is None:
        print("no XACH section found", file=sys.stderr)
        return 2
    off, count = xach

    # One XSTR per language. Default to English: the only table whose achievement
    # strings are pure 7-bit ASCII (every other localisation carries accents or
    # multi-byte text, which our ASCII decode turns into replacement chars).
    strs = [parse_xstr(d, o) for o in find_all(d, b"XSTR") if len(d) - o > 16]
    ids = [struct.unpack_from(">HHHH", d, off + 14 + i * 36)[1:] for i in range(count)]
    lang = int(sys.argv[sys.argv.index("--lang-index") + 1]) if "--lang-index" in sys.argv else None
    if lang is None:
        def ascii_score(t):
            txt = "".join(t.get(s, "") for rec in ids for s in rec)
            return (txt.count("�") == 0 and len(txt) > 0, len(txt))
        lang = max(range(len(strs)), key=lambda i: ascii_score(strs[i]))
    S = strs[lang]

    print(f"XACH @0x{off:X}  {count} achievements  (string table #{lang} of {len(strs)})\n")
    total = 0
    for i in range(count):
        b = off + 14 + i * 36
        aid, nid, did, lid = struct.unpack_from(">HHHH", d, b)
        gs = struct.unpack_from(">H", d, b + 12)[0]
        total += gs
        print(f"id {aid:2d} | bit {aid - 1:2d} | {gs:3d}G | {S.get(nid, '?')}")
        print(f"        unlocked: {S.get(did, '?')}")
        print(f"        locked  : {S.get(lid, '?')}")
    print(f"\ntotal gamerscore = {total}" + ("  [OK: retail total]" if total == 1000 else "  [!! expected 1000]"))
    return 0


if __name__ == "__main__":
    raise SystemExit(main())