# Copyright 2011 VMware, 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.

import inspect
import logging as std_logging
import os
import random

from oslo.config import cfg
from oslo.messaging import server as rpc_server
from oslo.utils import excutils
from oslo.utils import importutils

from neutron.common import config
from neutron.common import rpc as n_rpc
from neutron import context
from neutron.db import api as session
from neutron import manager
from neutron.openstack.common import log as logging
from neutron.openstack.common import loopingcall
from neutron.openstack.common import service as common_service
from neutron import wsgi


service_opts = [
    cfg.IntOpt('periodic_interval',
               default=40,
               help=_('Seconds between running periodic tasks')),
    cfg.IntOpt('api_workers',
               default=0,
               help=_('Number of separate API worker processes for service')),
    cfg.IntOpt('rpc_workers',
               default=0,
               help=_('Number of RPC worker processes for service')),
    cfg.IntOpt('periodic_fuzzy_delay',
               default=5,
               help=_('Range of seconds to randomly delay when starting the '
                      'periodic task scheduler to reduce stampeding. '
                      '(Disable by setting to 0)')),
]
CONF = cfg.CONF
CONF.register_opts(service_opts)

LOG = logging.getLogger(__name__)


class WsgiService(object):
    """Base class for WSGI based services.

    For each api you define, you must also define these flags:
    :<api>_listen: The address on which to listen
    :<api>_listen_port: The port on which to listen

    """

    def __init__(self, app_name):
        self.app_name = app_name
        self.wsgi_app = None

    def start(self):
        self.wsgi_app = _run_wsgi(self.app_name)

    def wait(self):
        self.wsgi_app.wait()


class NeutronApiService(WsgiService):
    """Class for neutron-api service."""

    @classmethod
    def create(cls, app_name='neutron'):

        # Setup logging early, supplying both the CLI options and the
        # configuration mapping from the config file
        # We only update the conf dict for the verbose and debug
        # flags. Everything else must be set up in the conf file...
        # Log the options used when starting if we're in debug mode...

        config.setup_logging()
        # Dump the initial option values
        cfg.CONF.log_opt_values(LOG, std_logging.DEBUG)
        service = cls(app_name)
        return service


def serve_wsgi(cls):

    try:
        service = cls.create()
        service.start()
    except Exception:
        with excutils.save_and_reraise_exception():
            LOG.exception(_('Unrecoverable error: please check log '
                            'for details.'))

    return service


class RpcWorker(object):
    """Wraps a worker to be handled by ProcessLauncher"""
    def __init__(self, plugin):
        self._plugin = plugin
        self._servers = []

    def start(self):
        # We may have just forked from parent process.  A quick disposal of the
        # existing sql connections avoids producing errors later when they are
        # discovered to be broken.
        session.get_engine().pool.dispose()
        self._servers = self._plugin.start_rpc_listeners()

    def wait(self):
        for server in self._servers:
            if isinstance(server, rpc_server.MessageHandlingServer):
                server.wait()

    def stop(self):
        for server in self._servers:
            if isinstance(server, rpc_server.MessageHandlingServer):
                server.stop()
            self._servers = []


def serve_rpc():
    plugin = manager.NeutronManager.get_plugin()

    # If 0 < rpc_workers then start_rpc_listeners would be called in a
    # subprocess and we cannot simply catch the NotImplementedError.  It is
    # simpler to check this up front by testing whether the plugin supports
    # multiple RPC workers.
    if not plugin.rpc_workers_supported():
        LOG.debug(_("Active plugin doesn't implement start_rpc_listeners"))
        if 0 < cfg.CONF.rpc_workers:
            msg = _("'rpc_workers = %d' ignored because start_rpc_listeners "
                    "is not implemented.")
            LOG.error(msg, cfg.CONF.rpc_workers)
        raise NotImplementedError()

    try:
        rpc = RpcWorker(plugin)

        if cfg.CONF.rpc_workers < 1:
            rpc.start()
            return rpc
        else:
            launcher = common_service.ProcessLauncher(wait_interval=1.0)
            launcher.launch_service(rpc, workers=cfg.CONF.rpc_workers)
            return launcher
    except Exception:
        with excutils.save_and_reraise_exception():
            LOG.exception(_('Unrecoverable error: please check log '
                            'for details.'))


def _run_wsgi(app_name):
    app = config.load_paste_app(app_name)
    if not app:
        LOG.error(_('No known API applications configured.'))
        return
    server = wsgi.Server("Neutron")
    server.start(app, cfg.CONF.bind_port, cfg.CONF.bind_host,
                 workers=cfg.CONF.api_workers)
    # Dump all option values here after all options are parsed
    cfg.CONF.log_opt_values(LOG, std_logging.DEBUG)
    LOG.info(_("Neutron service started, listening on %(host)s:%(port)s"),
             {'host': cfg.CONF.bind_host,
              'port': cfg.CONF.bind_port})
    return server


class Service(n_rpc.Service):
    """Service object for binaries running on hosts.

    A service takes a manager and enables rpc by listening to queues based
    on topic. It also periodically runs tasks on the manager.
    """

    def __init__(self, host, binary, topic, manager, report_interval=None,
                 periodic_interval=None, periodic_fuzzy_delay=None,
                 *args, **kwargs):

        self.binary = binary
        self.manager_class_name = manager
        manager_class = importutils.import_class(self.manager_class_name)
        self.manager = manager_class(host=host, *args, **kwargs)
        self.report_interval = report_interval
        self.periodic_interval = periodic_interval
        self.periodic_fuzzy_delay = periodic_fuzzy_delay
        self.saved_args, self.saved_kwargs = args, kwargs
        self.timers = []
        super(Service, self).__init__(host, topic, manager=self.manager)

    def start(self):
        self.manager.init_host()
        super(Service, self).start()
        if self.report_interval:
            pulse = loopingcall.FixedIntervalLoopingCall(self.report_state)
            pulse.start(interval=self.report_interval,
                        initial_delay=self.report_interval)
            self.timers.append(pulse)

        if self.periodic_interval:
            if self.periodic_fuzzy_delay:
                initial_delay = random.randint(0, self.periodic_fuzzy_delay)
            else:
                initial_delay = None

            periodic = loopingcall.FixedIntervalLoopingCall(
                self.periodic_tasks)
            periodic.start(interval=self.periodic_interval,
                           initial_delay=initial_delay)
            self.timers.append(periodic)
        self.manager.after_start()

    def __getattr__(self, key):
        manager = self.__dict__.get('manager', None)
        return getattr(manager, key)

    @classmethod
    def create(cls, host=None, binary=None, topic=None, manager=None,
               report_interval=None, periodic_interval=None,
               periodic_fuzzy_delay=None):
        """Instantiates class and passes back application object.

        :param host: defaults to CONF.host
        :param binary: defaults to basename of executable
        :param topic: defaults to bin_name - 'nova-' part
        :param manager: defaults to CONF.<topic>_manager
        :param report_interval: defaults to CONF.report_interval
        :param periodic_interval: defaults to CONF.periodic_interval
        :param periodic_fuzzy_delay: defaults to CONF.periodic_fuzzy_delay

        """
        if not host:
            host = CONF.host
        if not binary:
            binary = os.path.basename(inspect.stack()[-1][1])
        if not topic:
            topic = binary.rpartition('neutron-')[2]
            topic = topic.replace("-", "_")
        if not manager:
            manager = CONF.get('%s_manager' % topic, None)
        if report_interval is None:
            report_interval = CONF.report_interval
        if periodic_interval is None:
            periodic_interval = CONF.periodic_interval
        if periodic_fuzzy_delay is None:
            periodic_fuzzy_delay = CONF.periodic_fuzzy_delay
        service_obj = cls(host, binary, topic, manager,
                          report_interval=report_interval,
                          periodic_interval=periodic_interval,
                          periodic_fuzzy_delay=periodic_fuzzy_delay)

        return service_obj

    def kill(self):
        """Destroy the service object."""
        self.stop()

    def stop(self):
        super(Service, self).stop()
        for x in self.timers:
            try:
                x.stop()
            except Exception:
                LOG.exception(_("Exception occurs when timer stops"))
                pass
        self.timers = []

    def wait(self):
        super(Service, self).wait()
        for x in self.timers:
            try:
                x.wait()
            except Exception:
                LOG.exception(_("Exception occurs when waiting for timer"))
                pass

    def periodic_tasks(self, raise_on_error=False):
        """Tasks to be run at a periodic interval."""
        ctxt = context.get_admin_context()
        self.manager.periodic_tasks(ctxt, raise_on_error=raise_on_error)

    def report_state(self):
        """Update the state of this service."""
        # Todo(gongysh) report state to neutron server
        pass