#!/usr/bin/env python
import sys, os
from struct import pack as pk, unpack as up

def align_up(val, algn):
    val += algn - 1
    return val - (val % algn)


def main(argc, argv):
    if argc != 1:
        print('Usage: %s' % argv[0])
        return 1
    with open('kernel_ldr/kernel_ldr.bin', 'rb') as f:
        kernel_ldr = f.read()
    with open('kernel/kernel.bin', 'rb') as f:
        kernel = f.read()
    kernel_metadata_offset = up('<I', kernel[4:8])[0]
    assert (kernel_metadata_offset <= len(kernel) - 0x40)
    assert (kernel[kernel_metadata_offset:kernel_metadata_offset + 4] == b'MSS0')
    kernel_end = up('<I', kernel[kernel_metadata_offset + 0x30:kernel_metadata_offset + 0x34])[0]
    assert (kernel_end >= len(kernel))

    embedded_ini = b''
    embedded_ini_offset = align_up(kernel_end, 0x1000) + 0x1000
    embedded_ini_end = embedded_ini_offset + 0 # TODO: Create and embed an INI, eventually.

    kernel_ldr_offset = align_up(embedded_ini_end, 0x1000) + 0x1000
    kernel_ldr_end    = kernel_ldr_offset + len(kernel_ldr)

    with open('mesosphere.bin', 'wb') as f:
        f.write(kernel[:kernel_metadata_offset + 8])
        f.write(pk('<II', embedded_ini_offset, kernel_ldr_offset))
        f.write(kernel[kernel_metadata_offset + 0x10:])
        f.seek(embedded_ini_offset)
        f.write(embedded_ini)
        f.seek(embedded_ini_end)
        f.seek(kernel_ldr_offset)
        f.write(kernel_ldr)
        f.seek(kernel_ldr_end)
    return 0


if __name__ == '__main__':
    sys.exit(main(len(sys.argv), sys.argv))