import struct
from os.path import splitext
import json
import sys


def rotate_right(val, rshift):
    return ((val >> rshift) | ((val << (8 - rshift)) & 0xFF)) & 0xFF


def encrypt_bytes(data: bytes) -> bytes:
    # Matches inverse of decrypt in unpack_softpal_text_dat.py
    CONST = 0x084DF873 ^ 0xFF987DEE
    b = bytearray(data)
    pos = 0x10
    shift = 4
    while pos + 4 <= len(b):
        val = struct.unpack('<I', b[pos:pos+4])[0]
        val ^= CONST
        packed = bytearray(struct.pack('<I', val))
        packed[0] = rotate_right(packed[0], shift)
        b[pos:pos+4] = packed
        pos += 4
        shift = (shift + 1) % 8
    return bytes(b)


def pack_table(table: dict, encoding: str = 'cp932', encrypt: bool = True) -> bytes:
    # header: 12 bytes (unused by unpack)
    header = b"\x00" * 12
    items = sorted(((int(k), v) for k, v in table.items()), key=lambda x: x[0])
    count = len(items)
    out = bytearray()
    out += header
    out += struct.pack('<I', count)
    # After this, the first u32 at offset 16 will be the first key
    # We'll write entries immediately after (so first key sits at offset 16)
    for key, s in items:
        out += struct.pack('<I', key)
        if isinstance(s, str):
            encoded = s.encode(encoding)
        else:
            encoded = bytes(s)
        out += encoded + b'\x00'
    if encrypt:
        out = encrypt_bytes(bytes(out))
    return bytes(out)


if __name__ == '__main__':
    if len(sys.argv) < 2:
        print("Usage: python pack_softpal_text_dat.py <input.json> [<output.dat>] [<encoding>] [--no-encrypt]")
        sys.exit(1)

    infile = sys.argv[1]
    outfile = sys.argv[2] if len(sys.argv) > 2 else splitext(infile)[0] + '.dat'
    encoding = sys.argv[3] if len(sys.argv) > 3 and not sys.argv[3].startswith('--') else 'cp932'
    encrypt = True
    if '--no-encrypt' in sys.argv:
        encrypt = False

    with open(infile, 'r', encoding='utf-8') as f:
        table = json.load(f)

    data = pack_table(table, encoding=encoding, encrypt=encrypt)
    with open(outfile, 'wb') as f:
        f.write(data)

    print(f'Wrote {outfile} ({len(data)} bytes)')