# Copyright 2013 OpenStack Foundation
#
#    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 contextlib
import cPickle as pickle
import errno
import socket
import time
import xmlrpclib

from eventlet import queue
from eventlet import timeout
from oslo_config import cfg
from oslo_log import log as logging
from oslo_utils import versionutils
from six.moves import range

from nova import context
from nova import exception
from nova.i18n import _, _LE, _LW
from nova import objects
from nova import utils
from nova import version
from nova.virt.xenapi.client import objects as cli_objects
from nova.virt.xenapi import pool
from nova.virt.xenapi import pool_states

LOG = logging.getLogger(__name__)

xenapi_session_opts = [
    cfg.IntOpt('login_timeout',
               default=10,
               help='Timeout in seconds for XenAPI login.'),
    cfg.IntOpt('connection_concurrent',
               default=5,
               help='Maximum number of concurrent XenAPI connections. '
                    'Used only if compute_driver=xenapi.XenAPIDriver'),
    ]

CONF = cfg.CONF
CONF.register_opts(xenapi_session_opts, 'xenserver')
CONF.import_opt('host', 'nova.netconf')


def apply_session_helpers(session):
    session.VM = cli_objects.VM(session)
    session.SR = cli_objects.SR(session)
    session.VDI = cli_objects.VDI(session)
    session.VBD = cli_objects.VBD(session)
    session.PBD = cli_objects.PBD(session)
    session.PIF = cli_objects.PIF(session)
    session.VLAN = cli_objects.VLAN(session)
    session.host = cli_objects.Host(session)
    session.network = cli_objects.Network(session)
    session.pool = cli_objects.Pool(session)


class XenAPISession(object):
    """The session to invoke XenAPI SDK calls."""

    # This is not a config option as it should only ever be
    # changed in development environments.
    # MAJOR VERSION: Incompatible changes with the plugins
    # MINOR VERSION: Compatible changes, new plguins, etc
    PLUGIN_REQUIRED_VERSION = '1.2'

    def __init__(self, url, user, pw):
        version_string = version.version_string_with_package()
        self.nova_version = _('%(vendor)s %(product)s %(version)s') % \
                              {'vendor': version.vendor_string(),
                               'product': version.product_string(),
                               'version': version_string}
        import XenAPI
        self.XenAPI = XenAPI
        self._sessions = queue.Queue()
        self.is_slave = False
        exception = self.XenAPI.Failure(_("Unable to log in to XenAPI "
                                          "(is the Dom0 disk full?)"))
        url = self._create_first_session(url, user, pw, exception)
        self._populate_session_pool(url, user, pw, exception)
        self.host_uuid = self._get_host_uuid()
        self.host_ref = self._get_host_ref()
        self.product_version, self.product_brand = \
            self._get_product_version_and_brand()

        self._verify_plugin_version()

        apply_session_helpers(self)

    def _verify_plugin_version(self):
        requested_version = self.PLUGIN_REQUIRED_VERSION
        current_version = self.call_plugin_serialized(
            'nova_plugin_version', 'get_version')

        if not versionutils.is_compatible(requested_version, current_version):
            raise self.XenAPI.Failure(
                _("Plugin version mismatch (Expected %(exp)s, got %(got)s)") %
                {'exp': requested_version, 'got': current_version})

    def _create_first_session(self, url, user, pw, exception):
        try:
            session = self._create_session(url)
            with timeout.Timeout(CONF.xenserver.login_timeout, exception):
                session.login_with_password(user, pw,
                                            self.nova_version, 'OpenStack')
        except self.XenAPI.Failure as e:
            # if user and pw of the master are different, we're doomed!
            if e.details[0] == 'HOST_IS_SLAVE':
                master = e.details[1]
                url = pool.swap_xapi_host(url, master)
                session = self.XenAPI.Session(url)
                session.login_with_password(user, pw,
                                            self.nova_version, 'OpenStack')
                self.is_slave = True
            else:
                raise
        self._sessions.put(session)
        return url

    def _populate_session_pool(self, url, user, pw, exception):
        for i in range(CONF.xenserver.connection_concurrent - 1):
            session = self._create_session(url)
            with timeout.Timeout(CONF.xenserver.login_timeout, exception):
                session.login_with_password(user, pw,
                                            self.nova_version, 'OpenStack')
            self._sessions.put(session)

    def _get_host_uuid(self):
        if self.is_slave:
            aggr = objects.AggregateList.get_by_host(
                context.get_admin_context(),
                CONF.host, key=pool_states.POOL_FLAG)[0]
            if not aggr:
                LOG.error(_LE('Host is member of a pool, but DB '
                              'says otherwise'))
                raise exception.AggregateHostNotFound()
            return aggr.metadetails[CONF.host]
        else:
            with self._get_session() as session:
                host_ref = session.xenapi.session.get_this_host(session.handle)
                return session.xenapi.host.get_uuid(host_ref)

    def _get_product_version_and_brand(self):
        """Return a tuple of (major, minor, rev) for the host version and
        a string of the product brand.
        """
        software_version = self._get_software_version()

        product_version_str = software_version.get('product_version')
        # Product version is only set in some cases (e.g. XCP, XenServer) and
        # not in others (e.g. xenserver-core, XAPI-XCP).
        # In these cases, the platform version is the best number to use.
        if product_version_str is None:
            product_version_str = software_version.get('platform_version',
                                                       '0.0.0')
        product_brand = software_version.get('product_brand')
        product_version = utils.convert_version_to_tuple(product_version_str)

        return product_version, product_brand

    def _get_software_version(self):
        return self.call_xenapi('host.get_software_version', self.host_ref)

    def get_session_id(self):
        """Return a string session_id.  Used for vnc consoles."""
        with self._get_session() as session:
            return str(session._session)

    @contextlib.contextmanager
    def _get_session(self):
        """Return exclusive session for scope of with statement."""
        session = self._sessions.get()
        try:
            yield session
        finally:
            self._sessions.put(session)

    def _get_host_ref(self):
        """Return the xenapi host on which nova-compute runs on."""
        with self._get_session() as session:
            return session.xenapi.host.get_by_uuid(self.host_uuid)

    def call_xenapi(self, method, *args):
        """Call the specified XenAPI method on a background thread."""
        with self._get_session() as session:
            return session.xenapi_request(method, args)

    def call_plugin(self, plugin, fn, args):
        """Call host.call_plugin on a background thread."""
        # NOTE(armando): pass the host uuid along with the args so that
        # the plugin gets executed on the right host when using XS pools
        args['host_uuid'] = self.host_uuid

        with self._get_session() as session:
            return self._unwrap_plugin_exceptions(
                                 session.xenapi.host.call_plugin,
                                 self.host_ref, plugin, fn, args)

    def call_plugin_serialized(self, plugin, fn, *args, **kwargs):
        params = {'params': pickle.dumps(dict(args=args, kwargs=kwargs))}
        rv = self.call_plugin(plugin, fn, params)
        return pickle.loads(rv)

    def call_plugin_serialized_with_retry(self, plugin, fn, num_retries,
                                          callback, retry_cb=None, *args,
                                          **kwargs):
        """Allows a plugin to raise RetryableError so we can try again."""
        attempts = num_retries + 1
        sleep_time = 0.5
        for attempt in range(1, attempts + 1):
            try:
                if attempt > 1:
                    time.sleep(sleep_time)
                    sleep_time = min(2 * sleep_time, 15)

                callback_result = None
                if callback:
                    callback_result = callback(kwargs)

                msg = ('%(plugin)s.%(fn)s attempt %(attempt)d/%(attempts)d, '
                       'callback_result: %(callback_result)s')
                LOG.debug(msg,
                          {'plugin': plugin, 'fn': fn, 'attempt': attempt,
                           'attempts': attempts,
                           'callback_result': callback_result})
                return self.call_plugin_serialized(plugin, fn, *args, **kwargs)
            except self.XenAPI.Failure as exc:
                if self._is_retryable_exception(exc, fn):
                    LOG.warning(_LW('%(plugin)s.%(fn)s failed. '
                                    'Retrying call.'),
                                {'plugin': plugin, 'fn': fn})
                    if retry_cb:
                        retry_cb(exc=exc)
                else:
                    raise
            except socket.error as exc:
                if exc.errno == errno.ECONNRESET:
                    LOG.warning(_LW('Lost connection to XenAPI during call to '
                                    '%(plugin)s.%(fn)s.  Retrying call.'),
                                {'plugin': plugin, 'fn': fn})
                    if retry_cb:
                        retry_cb(exc=exc)
                else:
                    raise

        raise exception.PluginRetriesExceeded(num_retries=num_retries)

    def _is_retryable_exception(self, exc, fn):
        _type, method, error = exc.details[:3]
        if error == 'RetryableError':
            LOG.debug("RetryableError, so retrying %(fn)s", {'fn': fn},
                      exc_info=True)
            return True
        elif "signal" in method:
            LOG.debug("Error due to a signal, retrying %(fn)s", {'fn': fn},
                      exc_info=True)
            return True
        else:
            return False

    def _create_session(self, url):
        """Stubout point. This can be replaced with a mock session."""
        self.is_local_connection = url == "unix://local"
        if self.is_local_connection:
            return self.XenAPI.xapi_local()
        return self.XenAPI.Session(url)

    def _unwrap_plugin_exceptions(self, func, *args, **kwargs):
        """Parse exception details."""
        try:
            return func(*args, **kwargs)
        except self.XenAPI.Failure as exc:
            LOG.debug("Got exception: %s", exc)
            if (len(exc.details) == 4 and
                exc.details[0] == 'XENAPI_PLUGIN_EXCEPTION' and
                    exc.details[2] == 'Failure'):
                params = None
                try:
                    # FIXME(comstud): eval is evil.
                    params = eval(exc.details[3])
                except Exception:
                    raise exc
                raise self.XenAPI.Failure(params)
            else:
                raise
        except xmlrpclib.ProtocolError as exc:
            LOG.debug("Got exception: %s", exc)
            raise

    def get_rec(self, record_type, ref):
        try:
            return self.call_xenapi('%s.get_record' % record_type, ref)
        except self.XenAPI.Failure as e:
            if e.details[0] != 'HANDLE_INVALID':
                raise

        return None

    def get_all_refs_and_recs(self, record_type):
        """Retrieve all refs and recs for a Xen record type.

        Handles race-conditions where the record may be deleted between
        the `get_all` call and the `get_record` call.
        """

        return self.call_xenapi('%s.get_all_records' % record_type).items()
