~bzr-pqm/bzr/bzr.dev

from difflib import SequenceMatcher

from bzrlib import patiencediff

class MultiParent(object):

    def __init__(self, hunks=None):

        if hunks is not None:

            self.hunks = hunks

        else:

            self.hunks = []

    def __repr__(self):

        return "MultiParent(%r)" % self.hunks

    def __eq__(self, other):

        if self.__class__ is not other.__class__:

            return False

        return (self.hunks == other.hunks)

    @staticmethod

    def from_lines(text, parents=()):

        """Produce a MultiParent from a list of lines and parents"""

        def compare(parent):

            matcher = patiencediff.PatienceSequenceMatcher(None, parent,

                                                           text)

            return matcher.get_matching_blocks()

        parent_comparisons = [compare(p) for p in parents]

        cur_line = 0

        new_text = NewText([])

        parent_text = []

        block_iter = [iter(i) for i in parent_comparisons]

        diff = MultiParent([])

        def next_block(p):

            try:

                return block_iter[p].next()

            except StopIteration:

                return None

        cur_block = [next_block(p) for p, i in enumerate(block_iter)]

        while cur_line < len(text):

            best_match = None

            for p, block in enumerate(cur_block):

                if block is None:

                    continue

                i, j, n = block

                while j + n < cur_line:

                    block = cur_block[p] = next_block(p)

                    if block is None:

                        break

                    i, j, n = block

                if block is None:

                    continue

                if j > cur_line:

                    continue

                offset = cur_line - j

                i += offset

                j = cur_line

                n -= offset

                if n == 0:

                    continue

                if best_match is None or n > best_match.num_lines:

                    best_match = ParentText(p, i, j, n)

            if best_match is None:

                new_text.lines.append(text[cur_line])

                cur_line += 1

            else:

                if len(new_text.lines) > 0:

                    diff.hunks.append(new_text)

                    new_text = NewText([])

                diff.hunks.append(best_match)

                cur_line += best_match.num_lines

        if len(new_text.lines) > 0:

            diff.hunks.append(new_text)

        return diff

    @classmethod

    def from_texts(cls, text, parents=()):

        """Produce a MultiParent from a text and list of parent text"""

        return cls.from_lines(text.splitlines(True),

                              [p.splitlines(True) for p in parents])

    def to_patch(self):

        """Yield text lines for a patch"""

        for hunk in self.hunks:

            for line in hunk.to_patch():

                yield line

    def range_iterator(self):

        """Iterate through the hunks, with range indicated

        kind is "new" or "parent".

        for "new", data is a list of lines.

        for "parent", data is (parent, parent_start, parent_end)

        :return: a generator of (start, end, kind, data)

        """

        start = 0

        for hunk in self.hunks:

            if isinstance(hunk, NewText):

                kind = 'new'

                end = start + len(hunk.lines)

                data = hunk.lines

            else:

                kind = 'parent'

                start = hunk.child_pos

                end = start + hunk.num_lines

                data = (hunk.parent, hunk.parent_pos, hunk.parent_pos +

                        hunk.num_lines)

            yield start, end, kind, data

            start = end

    def num_lines(self):

        extra_n = 0

        for hunk in reversed(self.hunks):

            if isinstance(hunk, ParentText):

               return hunk.child_pos + hunk.num_lines + extra_n

            extra_n += len(hunk.lines)

        return extra_n

class NewText(object):

    """The contents of text that is introduced by this text"""

    def __init__(self, lines):

        self.lines = lines

    def __eq__(self, other):

        if self.__class__ is not other.__class__:

            return False

        return (other.lines == self.lines)

    def __repr__(self):

        return 'NewText(%r)' % self.lines

    def to_patch(self):

        yield 'i %d\n' % len(self.lines)

        for line in self.lines:

            yield line

        yield '\n'

class ParentText(object):

    """A reference to text present in a parent text"""

    def __init__(self, parent, parent_pos, child_pos, num_lines):

        self.parent = parent

        self.parent_pos = parent_pos

        self.child_pos = child_pos

        self.num_lines = num_lines

    def __repr__(self):

        return 'ParentText(%(parent)r, %(parent_pos)r, %(child_pos)r,'\

            ' %(num_lines)r)' % self.__dict__

    def __eq__(self, other):

        if self.__class__ != other.__class__:

            return False

        return (self.__dict__ == other.__dict__)

    def to_patch(self):

        yield 'c %(parent)d %(parent_pos)d %(child_pos)d %(num_lines)d\n'\

            % self.__dict__

class MultiVersionedFile(object):

    """VersionedFile skeleton for MultiParent"""

    def __init__(self, snapshot_interval=25, max_snapshots=None):

        self._diffs = {}

        self._lines = {}

        self._parents = {}

        self._snapshots = set()

        self.snapshot_interval = snapshot_interval

        self.max_snapshots = max_snapshots

    def do_snapshot(self, version_id, parent_ids):

        if self.snapshot_interval is None:

            return False

        if self.max_snapshots is not None and\

            len(self._snapshots) == self.max_snapshots:

            return False

        if len(parent_ids) == 0:

            return True

        for ignored in xrange(self.snapshot_interval):

            if len(parent_ids) == 0:

                return False

            version_ids = parent_ids

            parent_ids = []

            for version_id in version_ids:

                if version_id not in self._snapshots:

                    parent_ids.extend(self._parents[version_id])

        else:

            return True

    def add_version(self, lines, version_id, parent_ids,

                    force_snapshot=None):

        if force_snapshot is None:

            do_snapshot = self.do_snapshot(version_id, parent_ids)

        else:

            do_snapshot = force_snapshot

        if do_snapshot:

            self._snapshots.add(version_id)

            diff = MultiParent([NewText(lines)])

        else:

            parent_lines = self.get_line_list(parent_ids)

            diff = MultiParent.from_lines(lines, parent_lines)

        self.add_diff(diff, version_id, parent_ids)

        self._lines[version_id] = lines

    def add_diff(self, diff, version_id, parent_ids):

        self._diffs[version_id] = diff

        self._parents[version_id] = parent_ids

    def clear_cache(self):

        self._lines.clear()

    def get_line_list(self, version_ids):

        return [self.cache_version(v) for v in version_ids]

    def cache_version(self, version_id):

        try:

            return self._lines[version_id]

        except KeyError:

            pass

        diff = self._diffs[version_id]

        lines = []

        reconstructor = _Reconstructor(self._diffs, self._lines,

                                       self._parents)

        reconstructor.reconstruct_version(lines, version_id)

        self._lines[version_id] = lines

        return lines

class _Reconstructor(object):

    """Build a text from the diffs, ancestry graph and cached lines"""

    def __init__(self, diffs, lines, parents):

        self.diffs = diffs

        self.lines = lines

        self.parents = parents

        self.cursor = {}

    def reconstruct(self, lines, parent_text, version_id):

        """Append the lines referred to by a ParentText to lines"""

        parent_id = self.parents[version_id][parent_text.parent]

        end = parent_text.parent_pos + parent_text.num_lines

        return self._reconstruct(lines, parent_id, parent_text.parent_pos,

                                 end)

    def _reconstruct(self, lines, req_version_id, req_start, req_end):

        """Append lines for the requested version_id range"""

        # stack of pending range requests

        pending_reqs = [(req_version_id, req_start, req_end)]

        while len(pending_reqs) > 0:

            req_version_id, req_start, req_end = pending_reqs.pop()

            # lazily allocate cursors for versions

            try:

                start, end, kind, data, iterator = self.cursor[req_version_id]

            except KeyError:

                iterator = self.diffs[req_version_id].range_iterator()

                start, end, kind, data = iterator.next()

            # find the first hunk relevant to the request

            while end <= req_start:

                start, end, kind, data = iterator.next()

            self.cursor[req_version_id] = start, end, kind, data, iterator

            # if the hunk can't satisfy the whole request, split it in two,

            # and leave the second half for later.

            if req_end > end:

                pending_reqs.append((req_version_id, end, req_end))

                req_end = end

            if kind == 'new':

                lines.extend(data[req_start - start: (req_end - start)])

            else:

                # If the hunk is a ParentText, rewrite it as a range request

                # for the parent, and make it the next pending request.

                parent, parent_start, parent_end = data

                new_version_id = self.parents[req_version_id][parent]

                new_start = parent_start + req_start - start

                new_end = parent_end + req_end - end

                pending_reqs.append((new_version_id, new_start, new_end))

    def reconstruct_version(self, lines, version_id):

        length = self.diffs[version_id].num_lines()

        return self._reconstruct(lines, version_id, 0, length)