#!/usr/bin/python3

import argparse
import pathlib
import shutil
import struct
import sys


module_magic = b'~Module signature appended~\n'
# Only relevant fields are id_type and sig_len
module_signature = struct.Struct('!2xB2x3xL')
module_signature_PKEY_ID_PKCS7 = 2


def sign_file_attach(sig_base: pathlib.Path, module_base: pathlib.Path, output_base: pathlib.Path) -> None:
    for line in sys.stdin:
        path, _, file = line.strip().rpartition('/')
        name, _, _ = file.partition('.')

        sig = sig_base / path / f'{name}.ko.sig'
        module = module_base / path / f'{name}.ko'
        output = output_base / path / f'{name}.ko'
        output.parent.mkdir(parents=True, exist_ok=True)

        with sig.open('rb') as f_sig, module.open('rb') as f_module, output.open('wb') as f_output:
            shutil.copyfileobj(f_module, f_output)
            shutil.copyfileobj(f_sig, f_output)
            len_sig = f_sig.tell()
            f_output.write(module_signature.pack(
                module_signature_PKEY_ID_PKCS7,
                len_sig,
            ))
            f_output.write(module_magic)


if __name__ == '__main__':
    parser = argparse.ArgumentParser()
    parser.add_argument(
        'sig_base',
        metavar='SIGNATURE',
        type=pathlib.Path,
    )
    parser.add_argument(
        'module_base',
        metavar='MODULE',
        type=pathlib.Path,
    )
    parser.add_argument(
        'output_base',
        metavar='OUTPUT',
        type=pathlib.Path,
    )
    args = parser.parse_args()

    sign_file_attach(**vars(args))