~bzr-pqm/bzr/bzr.dev

# Copyright (C) 2006, 2009, 2010 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

#

# Author: Martin Pool <mbp@canonical.com>

#         Aaron Bentley <aaron.bentley@utoronto.ca>

from __future__ import absolute_import

from bzrlib.lazy_import import lazy_import

lazy_import(globals(), """

from bzrlib import patiencediff

""")

class TextMerge(object):

    """Base class for text-mergers

    Subclasses must implement _merge_struct.

    Many methods produce or consume structured merge information.

    This is an iterable of tuples of lists of lines.

    Each tuple may have a length of 1 - 3, depending on whether the region it

    represents is conflicted.

    Unconflicted region tuples have length 1.

    Conflicted region tuples have length 2 or 3.  Index 1 is text_a, e.g. THIS.

    Index 1 is text_b, e.g. OTHER.  Index 2 is optional.  If present, it

    represents BASE.

    """

    # TODO: Show some version information (e.g. author, date) on conflicted

    # regions.

    A_MARKER = '<<<<<<< \n'

    B_MARKER = '>>>>>>> \n'

    SPLIT_MARKER = '=======\n'

    def __init__(self, a_marker=A_MARKER, b_marker=B_MARKER,

                 split_marker=SPLIT_MARKER):

        self.a_marker = a_marker

        self.b_marker = b_marker

        self.split_marker = split_marker

    def _merge_struct(self):

        """Return structured merge info.  Must be implemented by subclasses.

        See TextMerge docstring for details on the format.

        """

        raise NotImplementedError('_merge_struct is abstract')

    def struct_to_lines(self, struct_iter):

        """Convert merge result tuples to lines"""

        for lines in struct_iter:

            if len(lines) == 1:

                for line in lines[0]:

                    yield line

            else:

                yield self.a_marker

                for line in lines[0]:

                    yield line

                yield self.split_marker

                for line in lines[1]:

                    yield line

                yield self.b_marker

    def iter_useful(self, struct_iter):

        """Iterate through input tuples, skipping empty ones."""

        for group in struct_iter:

            if len(group[0]) > 0:

                yield group

            elif len(group) > 1 and len(group[1]) > 0:

                yield group

    def merge_lines(self, reprocess=False):

        """Produce an iterable of lines, suitable for writing to a file

        Returns a tuple of (line iterable, conflict indicator)

        If reprocess is True, a two-way merge will be performed on the

        intermediate structure, to reduce conflict regions.

        """

        struct = []

        conflicts = False

        for group in self.merge_struct(reprocess):

            struct.append(group)

            if len(group) > 1:

                conflicts = True

        return self.struct_to_lines(struct), conflicts

    def merge_struct(self, reprocess=False):

        """Produce structured merge info"""

        struct_iter = self.iter_useful(self._merge_struct())

        if reprocess is True:

            return self.reprocess_struct(struct_iter)

        else:

            return struct_iter

    @staticmethod

    def reprocess_struct(struct_iter):

        """ Perform a two-way merge on structural merge info.

        This reduces the size of conflict regions, but breaks the connection

        between the BASE text and the conflict region.

        This process may split a single conflict region into several smaller

        ones, but will not introduce new conflicts.

        """

        for group in struct_iter:

            if len(group) == 1:

                yield group

            else:

                for newgroup in Merge2(group[0], group[1]).merge_struct():

                    yield newgroup

class Merge2(TextMerge):

    """ Two-way merge.

    In a two way merge, common regions are shown as unconflicting, and uncommon

    regions produce conflicts.

    """

    def __init__(self, lines_a, lines_b, a_marker=TextMerge.A_MARKER,

                 b_marker=TextMerge.B_MARKER,

                 split_marker=TextMerge.SPLIT_MARKER):

        TextMerge.__init__(self, a_marker, b_marker, split_marker)

        self.lines_a = lines_a

        self.lines_b = lines_b

    def _merge_struct(self):

        """Return structured merge info.

        See TextMerge docstring.

        """

        sm = patiencediff.PatienceSequenceMatcher(

            None, self.lines_a, self.lines_b)

        pos_a = 0

        pos_b = 0

        for ai, bi, l in sm.get_matching_blocks():

            # non-matching lines

            yield(self.lines_a[pos_a:ai], self.lines_b[pos_b:bi])

            # matching lines

            yield(self.lines_a[ai:ai+l],)

            pos_a = ai + l

            pos_b = bi + l

        # final non-matching lines

        yield(self.lines_a[pos_a:-1], self.lines_b[pos_b:-1])