# 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, see <http://www.gnu.org/licenses/>.

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

# s: "i hate that."

from __future__ import absolute_import

import os

import sys

from .i18n import _

from . import (

    mdiff,

    scmutil,

    util,

)

class CantReprocessAndShowBase(Exception):

    pass

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

class Merge3Text(object):

    """3-way merge of texts.

    Given strings BASE, OTHER, THIS, tries to produce a combined text

    incorporating the changes from both BASE->OTHER and BASE->THIS."""

    def __init__(self, basetext, atext, btext, base=None, a=None, b=None):

        self.basetext = basetext

        self.atext = atext

        self.btext = btext

        if base is None:

            base = mdiff.splitnewlines(basetext)

        if a is None:

            a = mdiff.splitnewlines(atext)

        if b is None:

            b = mdiff.splitnewlines(btext)

        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):

        """Return merge in cvs-like form.

        """

        self.conflicts = False

        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'

            start_marker = start_marker + ' ' + name_a

            end_marker = end_marker + ' ' + name_b

        if name_base and base_marker:

            base_marker = base_marker + ' ' + name_base

        merge_regions = self.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':

                self.conflicts = True

                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]

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

                    yield self.b[i]

            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 descendants.  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 region in self.find_sync_regions():

            zmatch, zend, amatch, aend, bmatch, bend = region

            #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 find_sync_regions(self):

        """Return a list of sync regions, where both descendants 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

        amatches = mdiff.get_matching_blocks(self.basetext, self.atext)

        bmatches = mdiff.get_matching_blocks(self.basetext, self.btext)

        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."""

        am = mdiff.get_matching_blocks(self.basetext, self.atext)

        bm = mdiff.get_matching_blocks(self.basetext, self.btext)

        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 simplemerge(ui, local, base, other, **opts):

    def readfile(filename):

        f = open(filename, "rb")

        text = f.read()

        f.close()

        if util.binary(text):

            msg = _("%s looks like a binary file.") % filename

            if not opts.get('quiet'):

                ui.warn(_('warning: %s\n') % msg)

            if not opts.get('text'):

                raise util.Abort(msg)

        return text

    try:

        localtext = readfile(local)

        basetext = readfile(base)

        othertext = readfile(other)

    except util.Abort:

        return 1

    local = os.path.realpath(local)

    if not opts.get('print'):

        opener = scmutil.opener(os.path.dirname(local))

        out = opener(os.path.basename(local), "w", atomictemp=True)

    else:

        out = sys.stdout

    m3 = Merge3Text(basetext, localtext, othertext)

    extrakwargs = {}