#!/usr/bin/env python3
"""Converte os BMP de 24 bits do Nikwi Deluxe no formato .ut do jogo, igual ao
src/tools/bmp2ut do autor com --halfbits (RGB565, sem alfa), mas sem depender do SDL.
Uso: bmp2ut.py <pasta-de-bmp> <pasta-de-saida>
Le o BMP direto (24 bits, sem compressao), sem biblioteca nenhuma."""
import os, struct, sys


def convert(src, dst):
    with open(src, "rb") as f:
        d = f.read()
    assert d[:2] == b"BM", src
    off = struct.unpack_from("<I", d, 10)[0]
    w, h, planes, bpp, comp = struct.unpack_from("<iiHHI", d, 18)
    assert bpp == 24 and comp == 0, (src, bpp, comp)
    flip = h > 0
    h = abs(h)
    stride = (w * 3 + 3) & ~3
    out = bytearray(b"UT\0\x01" + struct.pack("<HH", w, h))
    # O bmp2ut do autor le o buffer do SDL em sequencia, sem olhar o pitch: o SDL alinha as linhas
    # a 4 bytes, entao so e igual a ler pixel a pixel quando w*3 ja e multiplo de 4.
    rows = range(h - 1, -1, -1) if flip else range(h)
    buf = bytearray()
    for y in rows:
        buf += d[off + y * stride: off + y * stride + stride]
    px = 0
    for i in range(w * h):
        b, g, r = buf[px], buf[px + 1], buf[px + 2]
        px += 3
        v = (b >> 3) | ((g >> 2) << 5) | ((r >> 3) << 11)
        out += struct.pack("<H", v)
    with open(dst, "wb") as f:
        f.write(out)


if __name__ == "__main__":
    src, dst = sys.argv[1:3]
    os.makedirs(dst, exist_ok=True)
    for n in sorted(os.listdir(src)):
        if n.endswith(".bmp"):
            convert(os.path.join(src, n), os.path.join(dst, n[:-4] + ".ut"))