/brz/remove-bazaar

# Copyright (C) 2005 by Canonical Ltd

#   Authors: Robert Collins <robert.collins@canonical.com>

#

# 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

"""This module provides an IdentityMap."""

import bzrlib.errors as errors

class IdentityMap(object):

    """An in memory map from object id to instance.

    An IdentityMap maps from keys to single instances of objects in memory.

    We have explicit calls on the map for the root of each inheritance tree

    that is store in the map. Look for find_CLASS and add_CLASS methods.

    """

    def add_revision_history(self, revision_history):

        """Add a revision_history object to the map.

        There can only be one!

        """

        if self._revision_history is not None:

            raise errors.BzrError("A revision history (%s) is already "

                                  "identity map" % self._revision_history)

        self._revision_history = revision_history

    def add_weave(self, id, weave):

        """Add weave to the map with a given id."""

        if self._weave_key(id) in self._map:

            raise errors.BzrError('weave %s already in the identity map' % id)

        self._map[self._weave_key(id)] = weave

        self._reverse_map[weave] = self._weave_key(id)

    def find_revision_history(self):

        return self._revision_history

    def find_weave(self, id):

        """Return the weave for 'id', or None if it is not present."""

        return self._map.get(self._weave_key(id), None)

    def __init__(self):

        super(IdentityMap, self).__init__()

        self._map = {}

        self._reverse_map = {}

        self._revision_history = None

    def remove_object(self, an_object):

        """Remove object from map."""

        if isinstance(an_object, list):

            if self._revision_history is an_object:

                self._revision_history = None

            else:

                raise KeyError('%r not in identity map' % an_object)

        else:

            self._map.pop(self._reverse_map[an_object])

            self._reverse_map.pop(an_object)

    def _weave_key(self, id):

        """Return the key for a weaves id."""

        return "weave-" + id

class NullIdentityMap(object):

    """A pretend in memory map from object id to instance.

    A NullIdentityMap is an Identity map that does not store anything in it.

    """

    def add_weave(self, id, weave):

        """See IdentityMap.add_weave."""

    def add_revision_history(self, revision_history):

        """See IdentityMap.add_revision_history."""

    def find_weave(self, id):

        """See IdentityMap.find_weave."""

        return None

    def find_revision_history(self):

        """See IdentityMap.find_revision_history."""