# mpatch.py - CFFI implementation of mpatch.c

#

# Copyright 2016 Maciej Fijalkowski <fijall@gmail.com>

#

# This software may be used and distributed according to the terms of the

# GNU General Public License version 2 or any later version.

from typing import List

from ..pure.mpatch import *

from ..pure.mpatch import mpatchError  # silence pyflakes

from . import _mpatch  # pytype: disable=import-error

ffi = _mpatch.ffi

lib = _mpatch.lib

@ffi.def_extern()

def cffi_get_next_item(arg, pos):

    all, bins = ffi.from_handle(arg)

    container = ffi.new(b"struct mpatch_flist*[1]")

    to_pass = ffi.new(b"char[]", str(bins[pos]))

    all.append(to_pass)

    r = lib.mpatch_decode(to_pass, len(to_pass) - 1, container)

    if r < 0:

        return ffi.NULL

    return container[0]

def patches(text: bytes, bins: List[bytes]) -> bytes:

    lgt = len(bins)

    all = []

    if not lgt:

        return text

    arg = (all, bins)

    patch = lib.mpatch_fold(ffi.new_handle(arg), lib.cffi_get_next_item, 0, lgt)

    if not patch:

        raise mpatchError(b"cannot decode chunk")

    outlen = lib.mpatch_calcsize(len(text), patch)

    if outlen < 0:

        lib.mpatch_lfree(patch)

        raise mpatchError(b"inconsistency detected")

    buf = ffi.new(b"char[]", outlen)

    if lib.mpatch_apply(buf, text, len(text), patch) < 0:

        lib.mpatch_lfree(patch)

        raise mpatchError(b"error applying patches")

    res = ffi.buffer(buf, outlen)[:]

    lib.mpatch_lfree(patch)

    return res