#!/usr/bin/python

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))

    return "".join(l)

def textdiff(a, b):

    return diff(a.splitlines(1), b.splitlines(1))

def sortdiff(a, b):

    la = lb = 0

    while 1:

        if la >= len(a) or lb >= len(b): break

        if b[lb] < a[la]:

            si = lb

            while lb < len(b) and b[lb] < a[la] : lb += 1

            yield "insert", la, la, si, lb

        elif a[la] < b[lb]:

            si = la

            while la < len(a) and a[la] < b[lb]: la += 1

            yield "delete", si, la, lb, lb

        else:

            la += 1

            lb += 1

    if lb < len(b):

        yield "insert", la, la, lb, len(b)

    if la < len(a):

        yield "delete", la, len(a), lb, lb

def diff(a, b, sorted=0):

    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_opcodes()

    for o, m, n, s, t in d:

        if o == 'equal': continue

        s = "".join(b[s:t])

        bin.append(struct.pack(">lll", p[m], p[n], len(s)) + s)

    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])