#!/usr/bin/env python3
import struct


# --------------------------------------------------------------------------- KTX2
def build_ktx2():
    ident = bytes([0xAB, 0x4B, 0x54, 0x58, 0x20, 0x32, 0x30, 0xBB, 0x0D, 0x0A, 0x1A, 0x0A])
    vk_format = 0            # 0 => block-compressed via DFD
    type_size = 1
    w, h = 0xFFFF, 0xFFFF
    depth, layers, faces, levels = 0, 0, 1, 1
    scheme = 0
    kvd_off, kvd_len = 0, 0
    sgdt_off, sgdt_len = 0, 0
    header = struct.pack("<9I", vk_format, type_size, w, h, depth, layers, faces, levels, scheme)
    header += struct.pack("<IQ", kvd_off, kvd_len)
    header += struct.pack("<IQQ", sgdt_off, sgdt_len, 0)
    # level index: one level, claiming a tiny byteOffset/byteLength
    level_index = struct.pack("<QQQ", 0, 0, 64)
    body = b"\x00" * 64
    return ident + header + level_index + body


# --------------------------------------------------------------------------- DDS BC7

if __name__ == "__main__":
    import sys
    out = sys.argv[1] if len(sys.argv) > 1 else "ktx2_bad_dims.ktx2"
    open(out, "wb").write(build_ktx2())
    print("wrote", out)