# -*- coding: utf-8 -*-
"""
Trac Plugin for Monotone

Copyright 2006-2008 Thomas Moschny (thomas.moschny@gmx.de)

{{{
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
}}}

"""

backends = {}

def add_backend(name, factory):
    backends[name] = factory

def get_cache(realm, cachespec):
    cachespec = cachespec.split(':')
    backend = cachespec[0]
    args = cachespec[1:]
    return backends[backend](realm, *args)

# ----------------------------------------------------------------------

class LocalMem(object):
    """A handle to a simple dictionary."""

    caches = {}

    def __init__(self, realm, prefix=''):
        name = prefix + realm
        self.cache = self.caches.setdefault(name, {})

    def __getitem__(self, key):
        return self.cache[key]

    def __setitem__(self, key, value):
        self.cache[key] = value

    def close(self):
        pass

add_backend('localmem', LocalMem)

# ----------------------------------------------------------------------

try:
    import shelve
    import dbm
except ImportError:
    dbm = None

class DBMShelve(object):
    """Using Python's shelve on a DBM database."""

    def __init__(self, realm, prefix):
        self.dbname = prefix + realm
        self.cache = shelve.Shelf(dbm.open(self.dbname, 'c'))

    def __getitem__(self, key):
        return self.cache[key]

    def __setitem__(self, key, value):
        self.cache[key] = value

    def close(self):
        self.cache.close()

if dbm:
    add_backend('dbmshelve', DBMShelve)

# ----------------------------------------------------------------------

try:
    from bsddb3 import dbshelve, db
except ImportError:
    try:
        from bsddb import dbshelve, db
    except ImportError:
        dbshelve, db = None, None


class BSDDBShelve(object):
    """Using the bsddb3 interface to db."""

    # fixme: using reference counting, and passing the DB_THREAD flag
    # to bsddb, we could probably do with only one env and db handle
    # for all threads.

    def __init__(self, realm, dir, prefix=''):
        name = prefix + realm
        self.dbenv = db.DBEnv()
        self.dbenv.open(
            dir, db.DB_INIT_CDB|db.DB_INIT_MPOOL| db.DB_CREATE)
        self.cache = dbshelve.open(
            name, flags=db.DB_CREATE, dbenv=self.dbenv)
        
    def __getitem__(self, key):
        return self.cache[key]

    def __setitem__(self, key, value):
        self.cache[key] = value

    def close(self):
        self.cache.close()
        self.dbenv.close()

if db:
    add_backend('bsddb', BSDDBShelve)