# vim: tabstop=4 shiftwidth=4 softtabstop=4

# Copyright 2011 Nicira Networks, Inc
# All Rights Reserved.
#
#    Licensed under the Apache License, Version 2.0 (the "License"); you may
#    not use this file except in compliance with the License. You may obtain
#    a copy of the License at
#
#         http://www.apache.org/licenses/LICENSE-2.0
#
#    Unless required by applicable law or agreed to in writing, software
#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
#    License for the specific language governing permissions and limitations
#    under the License.
# @author: Somik Behera, Nicira Networks, Inc.


"""
Quantum's Manager class is responsible for parsing a config file and
instantiating the correct plugin that concretely implement quantum_plugin_base
class.

The caller should make sure that QuantumManager is a singleton.
"""
import gettext
import logging
import os
gettext.install('quantum', unicode=1)

from common import utils
from quantum_plugin_base import QuantumPluginBase

CONFIG_FILE = "plugins.ini"
LOG = logging.getLogger('quantum.manager')

def find_config(basepath):
    for root, dirs, files in os.walk(basepath):
        if CONFIG_FILE in files:
            return os.path.join(root, CONFIG_FILE)
    return None


class QuantumManager(object):
    def __init__(self, config=None):
        if config == None:
            self.configuration_file = find_config(
                os.path.abspath(os.path.dirname(__file__)))
        else:
            self.configuration_file = config
        plugin_location = utils.getPluginFromConfig(self.configuration_file)
        plugin_klass = utils.import_class(plugin_location)
        LOG.debug("Plugin location:%s", plugin_location)
        if not issubclass(plugin_klass, QuantumPluginBase):
            raise Exception("Configured Quantum plug-in " \
                            "didn't pass compatibility test")
        else:
            LOG.debug("Successfully imported Quantum plug-in." \
                      "All compatibility tests passed")
        self.plugin = plugin_klass()

    def get_manager(self):
        return self.plugin