# Copyright (C) 2009 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

"""A manager of caches."""


from bzrlib import lru_cache


class CacheManager(object):

    def __init__(self, info, verbose=False, inventory_cache_size=10):
        """Create a manager of caches.

        :param info: a ConfigObj holding the output from
            the --info processor, or None if no hints are available
        """
        self.verbose = verbose

        # dataref -> data. datref is either :mark or the sha-1.
        # Sticky blobs aren't removed after being referenced.
        self._blobs = {}
        self._sticky_blobs = {}

        # revision-id -> Inventory cache
        # these are large and we probably don't need too many as
        # most parents are recent in history
        self.inventories = lru_cache.LRUCache(inventory_cache_size)

        # import commmit-ids -> revision-id lookup table
        # we need to keep all of these but they are small
        self.revision_ids = {}

        # path -> file-ids - as generated
        self.file_ids = {}

        # Head tracking: last ref, last id per ref & map of commit ids to ref*s*
        self.last_ref = None
        self.last_ids = {}
        self.heads = {}

        # Work out the blobs to make sticky - None means all
        self._blobs_to_keep = None
        if info is not None:
            try:
                self._blobs_to_keep = info['Blob usage tracking']['multi']
            except KeyError:
                # info not in file - possible when no blobs used
                pass

    def store_blob(self, id, data):
        """Store a blob of data."""
        if (self._blobs_to_keep is None or data == '' or
            id in self._blobs_to_keep):
            self._sticky_blobs[id] = data
        else:
            self._blobs[id] = data

    def fetch_blob(self, id):
        """Fetch a blob of data."""
        try:
            return self._sticky_blobs[id]
        except KeyError:
            return self._blobs.pop(id)

    def delete_path(self, path):
        """Remove a path from caches."""
        # we actually want to remember what file-id we gave a path,
        # even when that file is deleted, so doing nothing is correct
        pass

    def rename_path(self, old_path, new_path):
        """Rename a path in the caches."""
        # In this case, we need to forget the file-id we gave a path,
        # otherwise, we'll get duplicate file-ids in the repository.
        self.file_ids[new_path] = self.file_ids[old_path]
        del self.file_ids[old_path]

    def track_heads_for_ref(self, cmd_ref, cmd_id, parents=None):
        if parents is not None:
            for parent in parents:
                refs = self.heads.get(parent)
                if refs:
                    refs.discard(cmd_ref)
                    if not refs:
                        del self.heads[parent]
        self.heads.setdefault(cmd_id, set()).add(cmd_ref)
        self.last_ids[cmd_ref] = cmd_id
        self.last_ref = cmd_ref