# mdiff.py - diff and patch routines for mercurial

#

# Copyright 2005 Matt Mackall <mpm@selenic.com>

#

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

# of the GNU General Public License, incorporated herein by reference.

import difflib, struct

from mercurial.mpatch import *

    if not a and not b: return ""

    if a == None:

        b = b.splitlines(1)

        l1 = "--- %s\t%s\n" % ("/dev/null", ad)

        l2 = "+++ %s\t%s\n" % ("b/" + fn, bd)

        l3 = "@@ -0,0 +1,%d @@\n" % len(b)

        l = [l1, l2, l3] + ["+" + e for e in b]

    elif b == None:

        a = a.splitlines(1)

        l1 = "--- %s\t%s\n" % ("a/" + fn, ad)

        l2 = "+++ %s\t%s\n" % ("/dev/null", bd)

        l3 = "@@ -1,%d +0,0 @@\n" % len(a)

        l = [l1, l2, l3] + ["-" + e for e in a]

    else:

        a = a.splitlines(1)

        b = b.splitlines(1)

        l = list(difflib.unified_diff(a, b, "a/" + fn, "b/" + fn))

        if not l: return ""

        # difflib uses a space, rather than a tab

        l[0] = l[0][:-2] + "\t" + ad + "\n"

        l[1] = l[1][:-2] + "\t" + bd + "\n"

    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

        # walk over matching lines

        while lb < lenb and la < lena and a[la] == b[lb] :

            la += 1

            lb += 1

        if la > am:

            yield (am, bm, la - am) # return a match

        # skip mismatched lines from b

        while la < lena and lb < lenb and b[lb] < a[la]:

            lb += 1

        if lb >= lenb:

            break

        # skip mismatched lines from a

        while la < lena and lb < lenb 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:

        try:

            d = sortdiff(a, b)

        except:

            print a, b

            raise

    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])