#!/usr/bin/env python3
"""Unpacks Argonaut .cor images (Ein Königreich für ein Lama) to PNG.

Layout: 8-byte signature 17 98 AF 89 FE 42 D1 12, u32 version (1),
u32 unpacked size, u32 packed size, then LZ data:
  n < 0x80          -> n bytes of raw data follow
  1LLL oooo oooooooo -> copy L+3 bytes from o bytes back
The result is 640x480 pixels at 3 bytes (RGB) or 1 byte (greyscale, e.g. 151.cor).
Usage: cor2png.py input.cor output.png   (requires Pillow)
"""
import struct
import sys

MAGIC = bytes.fromhex('1798af89fe42d112')


def unpack(data):
    if data[:8] != MAGIC:
        raise ValueError('not a COR file')
    _, size, packed = struct.unpack_from('<III', data, 8)
    src = data[20:20 + packed]
    out = bytearray()
    i = 0
    while i < len(src) and len(out) < size:
        b = src[i]
        if b < 0x80:
            out += src[i + 1:i + 1 + b]
            i += 1 + b
        else:
            length = ((b >> 4) & 7) + 3
            off = ((b & 0x0F) << 8) | src[i + 1]
            i += 2
            for _ in range(length):
                out.append(out[-off])
    return bytes(out), size


if __name__ == '__main__':
    raw, size = unpack(open(sys.argv[1], 'rb').read())
    print(f'{sys.argv[1]}: {len(raw)} of {size} bytes')
    if len(sys.argv) > 2:
        from PIL import Image
        mode = {640 * 480 * 3: 'RGB', 640 * 480: 'L'}[size]
        Image.frombytes(mode, (640, 480), raw).save(sys.argv[2])