# Copyright 2012 IBM Corp.
#
# 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 oslo.config import cfg

from nova import conductor
from nova import context
from nova.openstack.common.gettextutils import _
from nova.openstack.common import log as logging
from nova.openstack.common import timeutils
from nova.servicegroup import api
from nova import utils


CONF = cfg.CONF
CONF.import_opt('service_down_time', 'nova.service')

LOG = logging.getLogger(__name__)


class DbDriver(api.ServiceGroupDriver):

    def __init__(self, *args, **kwargs):
        self.db_allowed = kwargs.get('db_allowed', True)
        self.conductor_api = conductor.API(use_local=self.db_allowed)

    def join(self, member_id, group_id, service=None):
        """Join the given service with it's group."""

        msg = _('DB_Driver: join new ServiceGroup member %(member_id)s to '
                    'the %(group_id)s group, service = %(service)s')
        LOG.debug(msg, {'member_id': member_id, 'group_id': group_id,
                        'service': service})
        if service is None:
            raise RuntimeError(_('service is a mandatory argument for DB based'
                                 ' ServiceGroup driver'))
        report_interval = service.report_interval
        if report_interval:
            service.tg.add_timer(report_interval, self._report_state,
                                 report_interval, service)

    def is_up(self, service_ref):
        """Moved from nova.utils
        Check whether a service is up based on last heartbeat.
        """
        last_heartbeat = service_ref['updated_at'] or service_ref['created_at']
        if isinstance(last_heartbeat, basestring):
            # NOTE(russellb) If this service_ref came in over rpc via
            # conductor, then the timestamp will be a string and needs to be
            # converted back to a datetime.
            last_heartbeat = timeutils.parse_strtime(last_heartbeat)
        else:
            # Objects have proper UTC timezones, but the timeutils comparison
            # below does not (and will fail)
            last_heartbeat = last_heartbeat.replace(tzinfo=None)
        # Timestamps in DB are UTC.
        elapsed = utils.total_seconds(timeutils.utcnow() - last_heartbeat)
        LOG.debug('DB_Driver.is_up last_heartbeat = %(lhb)s elapsed = %(el)s',
                  {'lhb': str(last_heartbeat), 'el': str(elapsed)})
        return abs(elapsed) <= CONF.service_down_time

    def get_all(self, group_id):
        """
        Returns ALL members of the given group
        """
        LOG.debug(_('DB_Driver: get_all members of the %s group') % group_id)
        rs = []
        ctxt = context.get_admin_context()
        services = self.conductor_api.service_get_all_by_topic(ctxt, group_id)
        for service in services:
            if self.is_up(service):
                rs.append(service['host'])
        return rs

    def _report_state(self, service):
        """Update the state of this service in the datastore."""
        ctxt = context.get_admin_context()
        state_catalog = {}
        try:
            report_count = service.service_ref['report_count'] + 1
            state_catalog['report_count'] = report_count

            service.service_ref = self.conductor_api.service_update(ctxt,
                    service.service_ref, state_catalog)

            # TODO(termie): make this pattern be more elegant.
            if getattr(service, 'model_disconnected', False):
                service.model_disconnected = False
                LOG.error(_('Recovered model server connection!'))

        # TODO(vish): this should probably only catch connection errors
        except Exception:  # pylint: disable=W0702
            if not getattr(service, 'model_disconnected', False):
                service.model_disconnected = True
                LOG.exception(_('model server went away'))
