#!/usr/bin/python
import difflib, struct, mmap
from mercurial.mpatch import *

def unidiff(a, ad, b, bd, fn):
    if not a and not b: return ""
    a = a.splitlines(1)
    b = b.splitlines(1)
    l = list(difflib.unified_diff(a, b, "a/" + fn, "b/" + fn, ad, bd))

    for ln in xrange(len(l)):
        if l[ln][-1] != '\n':
            l[ln] += "\n\ No newline at end of file\n"

    return "".join(l)

def textdiff(a, b):
    return diff(a.splitlines(1), b.splitlines(1))

def sortdiff(a, b):
    la = lb = 0
    lena = len(a)
    lenb = len(b)
    while 1:
        am, bm, = la, lb
        while lb < lenb and la < len and a[la] == b[lb] :
            la += 1
            lb += 1
        if la>am: yield (am, bm, la-am)
        while lb < lenb and b[lb] < a[la]: lb += 1
        if lb>=lenb: break
        while la < lena and b[lb] > a[la]: la += 1
        if la>=lena: break
    yield (lena, lenb, 0)

def diff(a, b, sorted=0):
    if not a:
        s = "".join(b)
        return s and (struct.pack(">lll", 0, 0, len(s)) + s)

    bin = []
    p = [0]
    for i in a: p.append(p[-1] + len(i))

    if sorted:
        d = sortdiff(a, b)
    else:
        d = difflib.SequenceMatcher(None, a, b).get_matching_blocks()
    la = 0
    lb = 0
    for am, bm, size in d:
        s = "".join(b[lb:bm])
        if am > la or s:
            bin.append(struct.pack(">lll", p[la], p[am], len(s)) + s)
        la = am + size
        lb = bm + size
    
    return "".join(bin)

def patchtext(bin):
    pos = 0
    t = []
    while pos < len(bin):
        p1, p2, l = struct.unpack(">lll", bin[pos:pos + 12])
        pos += 12
        t.append(bin[pos:pos + l])
        pos += l
    return "".join(t)

def patch(a, bin):
    return patches(a, [bin])