#    Copyright (c) 2013 Mirantis, Inc.
#
#    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.
from collections import namedtuple

from amqplib.client_0_8 import Message
import anyjson
import eventlet
from muranoapi.common import config
from muranoapi.db.models import Session, Environment
from muranoapi.db.session import get_session


amqp = eventlet.patcher.import_patched('amqplib.client_0_8')
rabbitmq = config.CONF.rabbitmq

SessionState = namedtuple('SessionState', ['open', 'deploying', 'deployed'])(
    open='open', deploying='deploying', deployed='deployed'
)


class SessionServices(object):
    @staticmethod
    def get_sessions(environment_id, state=None):
        """
        Get list of sessions for specified environment

        :param environment_id: Environment Id
        :param state: glazierapi.db.services.environments.EnvironmentStatus
        :return: Sessions for specified Environment, if SessionState is
        not defined all sessions for specified environment is returned.
        """

        unit = get_session()
        # Here we duplicate logic for reducing calls to database
        # Checks for validation is same as in validate.
        environment = unit.query(Environment).get(environment_id)

        return unit.query(Session).filter(
            #Get all session for this environment
            Session.environment_id == environment_id,
            #in this state, if state is not specified return in all states
            Session.state.in_(SessionState if state is None else [state]),
            #Only sessions with same version as current env version are valid
            Session.version == environment.version
        ).all()

    @staticmethod
    def create(environment_id, user_id):
        """
        Creates session object for specific environment for specified user.

        :param environment_id: Environment Id
        :param user_id: User Id
        :return: Created session
        """
        unit = get_session()
        environment = unit.query(Environment).get(environment_id)

        session = Session()
        session.environment_id = environment.id
        session.user_id = user_id
        session.state = SessionState.open
        # used for checking if other sessions was deployed before this one
        session.version = environment.version
        # all changes to environment is stored here, and translated to
        # environment only after deployment completed
        session.description = environment.description

        with unit.begin():
            unit.add(session)

        return session

    @staticmethod
    def validate(session):
        """
        Session is valid only if no other session for same
        environment was already deployed on in deploying state,

        :param session: Session for validation
        """

        #if other session is deploying now current session is invalid
        unit = get_session()
        other_is_deploying = unit.query(Session).filter_by(
            environment_id=session.environment_id, state=SessionState.deploying
        ).count() > 0
        if session.state == SessionState.open and other_is_deploying:
            return False

        #if environment version is higher then version on which current session
        #is created then other session was already deployed
        current_env = unit.query(Environment).get(session.environment_id)
        if current_env.version > session.version:
            return False

        return True

    @staticmethod
    def deploy(session, token):
        """
        Prepares environment for deployment and send deployment command to
        orchestration engine

        :param session: session that is going to be deployed
        :param token: auth token that is going to be used by orchestration
        """
        unit = get_session()

        #Set X-Auth-Token for conductor
        environment = session.description
        environment['token'] = token

        session.state = SessionState.deploying
        session.save(unit)

        connection = amqp.Connection('{0}:{1}'.
                                     format(rabbitmq.host, rabbitmq.port),
                                     virtual_host=rabbitmq.virtual_host,
                                     userid=rabbitmq.login,
                                     password=rabbitmq.password,
                                     ssl=rabbitmq.use_ssl, insist=True)
        channel = connection.channel()
        channel.exchange_declare('tasks', 'direct', durable=True,
                                 auto_delete=False)

        channel.basic_publish(
            Message(body=anyjson.serialize(environment)), 'tasks', 'tasks'
        )