# Copyright (C) 2004, 2005 Canonical Ltd

#

# This program is free software; you can redistribute it and/or modify

# it under the terms of the GNU General Public License as published by

# the Free Software Foundation; either version 2 of the License, or

# (at your option) any later version.

#

# This program is distributed in the hope that it will be useful,

# but WITHOUT ANY WARRANTY; without even the implied warranty of

# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

# GNU General Public License for more details.

#

# You should have received a copy of the GNU General Public License

# along with this program; if not, write to the Free Software

# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

# mbp: "you know that thing where cvs gives you conflict markers?"

# s: "i hate that."

def intersect(ra, rb):

    """Given two ranges return the range where they intersect or None.

    >>> intersect((0, 10), (0, 6))

    (0, 6)

    >>> intersect((0, 10), (5, 15))

    (5, 10)

    >>> intersect((0, 10), (10, 15))

    >>> intersect((0, 9), (10, 15))

    >>> intersect((0, 9), (7, 15))

    (7, 9)

    """

    assert ra[0] <= ra[1]

    assert rb[0] <= rb[1]

    sa = max(ra[0], rb[0])

    sb = min(ra[1], rb[1])

    if sa < sb:

        return sa, sb

    else:

        return None

def compare_range(a, astart, aend, b, bstart, bend):

    """Compare a[astart:aend] == b[bstart:bend], without slicing.

    """

    if (aend-astart) != (bend-bstart):

        return False

    for ia, ib in zip(xrange(astart, aend), xrange(bstart, bend)):

        if a[ia] != b[ib]:

            return False

    else:

        return True

    """3-way merge of texts.

        self.base = base

        self.a = a

        self.b = b

    def merge_lines(self,

                    name_a=None,

                    name_b=None,

                    name_base=None,

                    start_marker='<<<<<<<',

                    mid_marker='=======',

                    end_marker='>>>>>>>',

                    base_marker=None,

                    reprocess=False):

        """Return merge in cvs-like form.

        """

        newline = '\n'

        if len(self.a) > 0:

            if self.a[0].endswith('\r\n'):

                newline = '\r\n'

            elif self.a[0].endswith('\r'):

                newline = '\r'

        if base_marker and reprocess:

            raise CantReprocessAndShowBase()

        if name_a:

            start_marker = start_marker + ' ' + name_a

        if name_b:

            end_marker = end_marker + ' ' + name_b

        if name_base and base_marker:

            base_marker = base_marker + ' ' + name_base

        merge_regions = self.merge_regions()

        if reprocess is True:

            merge_regions = self.reprocess_merge_regions(merge_regions)

        for t in merge_regions:

            what = t[0]

            if what == 'unchanged':

                for i in range(t[1], t[2]):

                    yield self.base[i]

            elif what == 'a' or what == 'same':

                for i in range(t[1], t[2]):

                    yield self.a[i]

            elif what == 'b':

                for i in range(t[1], t[2]):

                    yield self.b[i]

            elif what == 'conflict':

                yield start_marker + newline

                for i in range(t[3], t[4]):

                    yield self.a[i]

                if base_marker is not None:

                    yield base_marker + newline

                    for i in range(t[1], t[2]):

                        yield self.base[i]

                yield mid_marker + newline

                for i in range(t[5], t[6]):

                    yield self.b[i]

                yield end_marker + newline

            else:

                raise ValueError(what)

    def merge_annotated(self):

        """Return merge with conflicts, showing origin of lines.

        Most useful for debugging merge.        

        """

        for t in self.merge_regions():

            what = t[0]

            if what == 'unchanged':

                for i in range(t[1], t[2]):

                    yield 'u | ' + self.base[i]

            elif what == 'a' or what == 'same':

                for i in range(t[1], t[2]):

                    yield what[0] + ' | ' + self.a[i]

            elif what == 'b':

                for i in range(t[1], t[2]):

                    yield 'b | ' + self.b[i]

            elif what == 'conflict':

                yield '<<<<\n'

                for i in range(t[3], t[4]):

                    yield 'A | ' + self.a[i]

                yield '----\n'

                for i in range(t[5], t[6]):

                    yield 'B | ' + self.b[i]

                yield '>>>>\n'

            else:

                raise ValueError(what)

    def merge_groups(self):

        """Yield sequence of line groups.  Each one is a tuple:

        'unchanged', lines

             Lines unchanged from base

        'a', lines

             Lines taken from a

        'same', lines

             Lines taken from a (and equal to b)

        'b', lines

             Lines taken from b

        'conflict', base_lines, a_lines, b_lines

             Lines from base were changed to either a or b and conflict.

        """

        for t in self.merge_regions():

            what = t[0]

            if what == 'unchanged':

                yield what, self.base[t[1]:t[2]]

            elif what == 'a' or what == 'same':

                yield what, self.a[t[1]:t[2]]

            elif what == 'b':

                yield what, self.b[t[1]:t[2]]

            elif what == 'conflict':

                yield (what,

                       self.base[t[1]:t[2]],

                       self.a[t[3]:t[4]],

                       self.b[t[5]:t[6]])

            else:

                raise ValueError(what)

    def merge_regions(self):

        """Return sequences of matching and conflicting regions.

        This returns tuples, where the first value says what kind we

        have:

        'unchanged', start, end

             Take a region of base[start:end]

        'same', astart, aend

             b and a are different from base but give the same result

        'a', start, end

             Non-clashing insertion from a[start:end]

        Method is as follows:

        The two sequences align only on regions which match the base

        and both descendents.  These are found by doing a two-way diff

        of each one against the base, and then finding the

        intersections between those regions.  These "sync regions"

        are by definition unchanged in both and easily dealt with.

        The regions in between can be in any of three cases:

        conflicted, or changed on only one side.

        """

        # section a[0:ia] has been disposed of, etc

        iz = ia = ib = 0

        for zmatch, zend, amatch, aend, bmatch, bend in self.find_sync_regions():

            #print 'match base [%d:%d]' % (zmatch, zend)

            matchlen = zend - zmatch

            assert matchlen >= 0

            assert matchlen == (aend - amatch)

            assert matchlen == (bend - bmatch)

            len_a = amatch - ia

            len_b = bmatch - ib

            len_base = zmatch - iz

            assert len_a >= 0

            assert len_b >= 0

            assert len_base >= 0

            #print 'unmatched a=%d, b=%d' % (len_a, len_b)

            if len_a or len_b:

                # try to avoid actually slicing the lists

                equal_a = compare_range(self.a, ia, amatch,

                                        self.base, iz, zmatch)

                equal_b = compare_range(self.b, ib, bmatch,

                                        self.base, iz, zmatch)

                same = compare_range(self.a, ia, amatch,

                                     self.b, ib, bmatch)

                if same:

                    yield 'same', ia, amatch

                elif equal_a and not equal_b:

                    yield 'b', ib, bmatch

                elif equal_b and not equal_a:

                    yield 'a', ia, amatch

                elif not equal_a and not equal_b:

                    yield 'conflict', iz, zmatch, ia, amatch, ib, bmatch

                else:

                    raise AssertionError("can't handle a=b=base but unmatched")

                ia = amatch

                ib = bmatch

            iz = zmatch

            # if the same part of the base was deleted on both sides

            # that's OK, we can just skip it.

            if matchlen > 0:

                assert ia == amatch

                assert ib == bmatch

                assert iz == zmatch

                yield 'unchanged', zmatch, zend

                iz = zend

                ia = aend

                ib = bend

    def reprocess_merge_regions(self, merge_regions):

        """Where there are conflict regions, remove the agreed lines.

        Lines where both A and B have made the same changes are 

        eliminated.

        """

        for region in merge_regions:

            if region[0] != "conflict":

                yield region

                continue

            type, iz, zmatch, ia, amatch, ib, bmatch = region

            a_region = self.a[ia:amatch]

            b_region = self.b[ib:bmatch]

            next_a = ia

            next_b = ib

            for region_ia, region_ib, region_len in matches[:-1]:

                region_ia += ia

                region_ib += ib

                reg = self.mismatch_region(next_a, region_ia, next_b,

                                           region_ib)

                if reg is not None:

                    yield reg

                yield 'same', region_ia, region_len+region_ia

                next_a = region_ia + region_len

                next_b = region_ib + region_len

            reg = self.mismatch_region(next_a, amatch, next_b, bmatch)

            if reg is not None:

                yield reg

    def mismatch_region(next_a, region_ia,  next_b, region_ib):

        if next_a < region_ia or next_b < region_ib:

            return 'conflict', None, None, next_a, region_ia, next_b, region_ib

    def find_sync_regions(self):

        """Return a list of sync regions, where both descendents match the base.

        Generates a list of (base1, base2, a1, a2, b1, b2).  There is

        always a zero-length sync region at the end of all the files.

        """

        ia = ib = 0

        len_a = len(amatches)

        len_b = len(bmatches)

        sl = []

        while ia < len_a and ib < len_b:

            abase, amatch, alen = amatches[ia]

            bbase, bmatch, blen = bmatches[ib]

            # there is an unconflicted block at i; how long does it

            # extend?  until whichever one ends earlier.

            i = intersect((abase, abase+alen), (bbase, bbase+blen))

            if i:

                intbase = i[0]

                intend = i[1]

                intlen = intend - intbase

                # found a match of base[i[0], i[1]]; this may be less than

                # the region that matches in either one

                assert intlen <= alen

                assert intlen <= blen

                assert abase <= intbase

                assert bbase <= intbase

                asub = amatch + (intbase - abase)

                bsub = bmatch + (intbase - bbase)

                aend = asub + intlen

                bend = bsub + intlen

                assert self.base[intbase:intend] == self.a[asub:aend], \

                       (self.base[intbase:intend], self.a[asub:aend])

                assert self.base[intbase:intend] == self.b[bsub:bend]

                sl.append((intbase, intend,

                           asub, aend,

                           bsub, bend))

            # advance whichever one ends first in the base text

            if (abase + alen) < (bbase + blen):

                ia += 1

            else:

                ib += 1

        intbase = len(self.base)

        abase = len(self.a)

        bbase = len(self.b)

        sl.append((intbase, intbase, abase, abase, bbase, bbase))

        return sl

    def find_unconflicted(self):

        """Return a list of ranges in base that are not conflicted."""

        unc = []

        while am and bm:

            # there is an unconflicted block at i; how long does it

            # extend?  until whichever one ends earlier.

            a1 = am[0][0]

            a2 = a1 + am[0][2]

            b1 = bm[0][0]

            b2 = b1 + bm[0][2]

            i = intersect((a1, a2), (b1, b2))

            if i:

                unc.append(i)

            if a2 < b2:

                del am[0]

            else:

                del bm[0]

        return unc

def main(argv):

    # as for diff3 and meld the syntax is "MINE BASE OTHER"

    a = file(argv[1], 'rt').readlines()

    base = file(argv[2], 'rt').readlines()

    b = file(argv[3], 'rt').readlines()

    m3 = Merge3(base, a, b)

    #for sr in m3.find_sync_regions():

    #    print sr

    # sys.stdout.writelines(m3.merge_lines(name_a=argv[1], name_b=argv[3]))

    sys.stdout.writelines(m3.merge_annotated())

if __name__ == '__main__':

    import sys

    sys.exit(main(sys.argv))