# Copyright 2011 OpenStack Foundation
# 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.


import time

from trove.common import cfg
from trove.common import context
from trove.common import instance as rd_instance
from trove.conductor import api as conductor_api
from trove.guestagent.common import timeutils
from trove.instance import models as rd_models
from trove.openstack.common import log as logging

LOG = logging.getLogger(__name__)
CONF = cfg.CONF


class BaseDbStatus(object):
    """
    Answers the question "what is the status of the DB application on
    this box?" The answer can be that the application is not installed, or
    the state of the application is determined by calling a series of
    commands.

    This class also handles saving and load the status of the DB application
    in the database.
    The status is updated whenever the update() method is called, except
    if the state is changed to building or restart mode using the
     "begin_install" and "begin_restart" methods.
    The building mode persists in the database while restarting mode does
    not (so if there is a Python Pete crash update() will set the status to
    show a failure).
    These modes are exited and functionality to update() returns when
    end_install_or_restart() is called, at which point the status again
    reflects the actual status of the DB app.

    This is a base class, subclasses must implement real logic for
    determining current status of DB in _get_actual_db_status()
    """

    _instance = None

    def __init__(self):
        if self._instance is not None:
            raise RuntimeError("Cannot instantiate twice.")
        self.status = rd_models.InstanceServiceStatus(
            instance_id=CONF.guest_id,
            status=rd_instance.ServiceStatuses.NEW)
        self.restart_mode = False

    def begin_install(self):
        """Called right before DB is prepared."""
        self.set_status(rd_instance.ServiceStatuses.BUILDING)

    def begin_restart(self):
        """Called before restarting DB server."""
        self.restart_mode = True

    def end_install_or_restart(self):
        """Called after DB is installed or restarted.

        Updates the database with the actual DB server status.
        """
        LOG.info("Ending install_if_needed or restart.")
        self.restart_mode = False
        real_status = self._get_actual_db_status()
        LOG.info("Updating status to %s" % real_status)
        self.set_status(real_status)

    def _get_actual_db_status(self):
        raise NotImplementedError()

    @property
    def is_installed(self):
        """
        True if DB app should be installed and attempts to ascertain
        its status won't result in nonsense.
        """
        return (self.status is not None and
                self.status != rd_instance.ServiceStatuses.NEW and
                self.status != rd_instance.ServiceStatuses.BUILDING and
                self.status != rd_instance.ServiceStatuses.FAILED)

    @property
    def _is_restarting(self):
        return self.restart_mode

    @property
    def is_running(self):
        """True if DB server is running."""
        return (self.status is not None and
                self.status == rd_instance.ServiceStatuses.RUNNING)

    def set_status(self, status):
        """Use conductor to update the DB app status."""
        LOG.debug("Casting set_status message to conductor.")
        ctxt = context.TroveContext(user=CONF.nova_proxy_admin_user,
                                    auth_token=CONF.nova_proxy_admin_pass)

        heartbeat = {
            'service_status': status.description,
        }
        conductor_api.API(ctxt).heartbeat(CONF.guest_id,
                                          heartbeat,
                                          sent=timeutils.float_utcnow())
        LOG.debug("Successfully cast set_status.")
        self.status = status

    def update(self):
        """Find and report status of DB on this machine.
        The database is updated and the status is also returned.
        """
        if self.is_installed and not self._is_restarting:
            LOG.info("Determining status of DB server...")
            status = self._get_actual_db_status()
            self.set_status(status)
        else:
            LOG.info("DB server is not installed or is in restart mode, so "
                     "for now we'll skip determining the status of DB on this "
                     "box.")

    def wait_for_real_status_to_change_to(self, status, max_time,
                                          update_db=False):
        """
        Waits the given time for the real status to change to the one
        specified. Does not update the publicly viewable status Unless
        "update_db" is True.
        """
        WAIT_TIME = 3
        waited_time = 0
        while waited_time < max_time:
            time.sleep(WAIT_TIME)
            waited_time += WAIT_TIME
            LOG.info("Waiting for DB status to change to %s..." % status)
            actual_status = self._get_actual_db_status()
            LOG.info("DB status was %s after %d seconds."
                     % (actual_status, waited_time))
            if actual_status == status:
                if update_db:
                    self.set_status(actual_status)
                return True
        LOG.error("Time out while waiting for DB status to change!")
        return False
