# bdiff.py - CFFI implementation of bdiff.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 __future__ import absolute_import

import struct

from ..pure.bdiff import *

from . import _bdiff

ffi = _bdiff.ffi

lib = _bdiff.lib

def blocks(sa, sb):

    a = ffi.new("struct bdiff_line**")

    b = ffi.new("struct bdiff_line**")

    ac = ffi.new("char[]", str(sa))

    bc = ffi.new("char[]", str(sb))

    l = ffi.new("struct bdiff_hunk*")

    try:

        an = lib.bdiff_splitlines(ac, len(sa), a)

        bn = lib.bdiff_splitlines(bc, len(sb), b)

        if not a[0] or not b[0]:

            raise MemoryError

        count = lib.bdiff_diff(a[0], an, b[0], bn, l)

        if count < 0:

            raise MemoryError

        rl = [None] * count

        h = l.next

        i = 0

        while h:

            rl[i] = (h.a1, h.a2, h.b1, h.b2)

            h = h.next

            i += 1

    finally:

        lib.free(a[0])

        lib.free(b[0])

        lib.bdiff_freehunks(l.next)

    return rl

def bdiff(sa, sb):

    a = ffi.new("struct bdiff_line**")

    b = ffi.new("struct bdiff_line**")

    ac = ffi.new("char[]", str(sa))

    bc = ffi.new("char[]", str(sb))

    l = ffi.new("struct bdiff_hunk*")

    try:

        an = lib.bdiff_splitlines(ac, len(sa), a)

        bn = lib.bdiff_splitlines(bc, len(sb), b)

        if not a[0] or not b[0]:

            raise MemoryError

        count = lib.bdiff_diff(a[0], an, b[0], bn, l)

        if count < 0:

            raise MemoryError

        rl = []

        h = l.next

        la = lb = 0

        while h:

            if h.a1 != la or h.b1 != lb:

                lgt = (b[0] + h.b1).l - (b[0] + lb).l

                rl.append(struct.pack(">lll", (a[0] + la).l - a[0].l,

                                      (a[0] + h.a1).l - a[0].l, lgt))

                rl.append(str(ffi.buffer((b[0] + lb).l, lgt)))

            la = h.a2

            lb = h.b2

            h = h.next

    finally:

        lib.free(a[0])

        lib.free(b[0])

        lib.bdiff_freehunks(l.next)

    return "".join(rl)