# Copyright (c) 2016 Hewlett-Packard Development Company, L.P.
#
# 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 six

import eventlet.queue
import functools

from oslo_log import log as logging
from oslo_utils import excutils

from heat.common import exception
from heat.engine import resource
from heat.engine import scheduler
from heat.engine import stack as parser
from heat.engine import sync_point
from heat.objects import resource as resource_objects
from heat.rpc import api as rpc_api
from heat.rpc import listener_client

LOG = logging.getLogger(__name__)


class CancelOperation(BaseException):
    """Exception to cancel an in-progress operation on a resource.

    This exception is raised when operations on a resource are cancelled.
    """
    def __init__(self):
        return super(CancelOperation, self).__init__('user triggered cancel')


class CheckResource(object):

    def __init__(self,
                 engine_id,
                 rpc_client,
                 thread_group_mgr,
                 msg_queue,
                 input_data):
        self.engine_id = engine_id
        self._rpc_client = rpc_client
        self.thread_group_mgr = thread_group_mgr
        self.msg_queue = msg_queue
        self.input_data = input_data

    def _try_steal_engine_lock(self, cnxt, resource_id):
        rs_obj = resource_objects.Resource.get_obj(cnxt,
                                                   resource_id,
                                                   fields=('engine_id', ))
        if rs_obj.engine_id not in (None, self.engine_id):
            if not listener_client.EngineListenerClient(
                    rs_obj.engine_id).is_alive(cnxt):
                # steal the lock.
                rs_obj.update_and_save({'engine_id': None})
                return True
        return False

    def _trigger_rollback(self, stack):
        LOG.info("Triggering rollback of %(stack_name)s %(action)s ",
                 {'action': stack.action, 'stack_name': stack.name})
        stack.rollback()

    def _handle_failure(self, cnxt, stack, failure_reason):
        updated = stack.state_set(stack.action, stack.FAILED, failure_reason)
        if not updated:
            return False

        if (not stack.disable_rollback and
                stack.action in (stack.CREATE, stack.ADOPT, stack.UPDATE,
                                 stack.RESTORE)):
            self._trigger_rollback(stack)
        else:
            stack.purge_db()
        return True

    def _handle_resource_failure(self, cnxt, is_update, rsrc_id,
                                 stack, failure_reason):
        failure_handled = self._handle_failure(cnxt, stack, failure_reason)
        if not failure_handled:
            # Another concurrent update has taken over. But there is a
            # possibility for that update to be waiting for this rsrc to
            # complete, hence retrigger current rsrc for latest traversal.
            traversal = stack.current_traversal
            latest_stack = parser.Stack.load(cnxt, stack_id=stack.id,
                                             force_reload=True)
            if traversal != latest_stack.current_traversal:
                self.retrigger_check_resource(cnxt, is_update, rsrc_id,
                                              latest_stack)

    def _handle_stack_timeout(self, cnxt, stack):
        failure_reason = u'Timed out'
        self._handle_failure(cnxt, stack, failure_reason)

    def _do_check_resource(self, cnxt, current_traversal, tmpl, resource_data,
                           is_update, rsrc, stack, adopt_stack_data):
        try:
            if is_update:
                try:
                    check_resource_update(rsrc, tmpl.id, resource_data,
                                          self.engine_id,
                                          stack, self.msg_queue)
                except resource.UpdateReplace:
                    new_res_id = rsrc.make_replacement(tmpl.id)
                    LOG.info("Replacing resource with new id %s",
                             new_res_id)
                    rpc_data = sync_point.serialize_input_data(self.input_data)
                    self._rpc_client.check_resource(cnxt,
                                                    new_res_id,
                                                    current_traversal,
                                                    rpc_data, is_update,
                                                    adopt_stack_data)
                    return False

            else:
                check_resource_cleanup(rsrc, tmpl.id, resource_data,
                                       self.engine_id,
                                       stack.time_remaining(), self.msg_queue)

            return True
        except exception.UpdateInProgress:
            if self._try_steal_engine_lock(cnxt, rsrc.id):
                rpc_data = sync_point.serialize_input_data(self.input_data)
                # set the resource state as failed
                status_reason = ('Worker went down '
                                 'during resource %s' % rsrc.action)
                rsrc.state_set(rsrc.action,
                               rsrc.FAILED,
                               six.text_type(status_reason))
                self._rpc_client.check_resource(cnxt,
                                                rsrc.id,
                                                current_traversal,
                                                rpc_data, is_update,
                                                adopt_stack_data)
        except exception.ResourceFailure as ex:
            action = ex.action or rsrc.action
            reason = 'Resource %s failed: %s' % (action,
                                                 six.text_type(ex))
            self._handle_resource_failure(cnxt, is_update, rsrc.id,
                                          stack, reason)
        except scheduler.Timeout:
            # reload the stack to verify current traversal
            stack = parser.Stack.load(cnxt, stack_id=stack.id)
            if stack.current_traversal != current_traversal:
                return
            self._handle_stack_timeout(cnxt, stack)
        except CancelOperation:
            pass

        return False

    def retrigger_check_resource(self, cnxt, is_update, resource_id, stack):
        current_traversal = stack.current_traversal
        graph = stack.convergence_dependencies.graph()
        key = (resource_id, is_update)
        if is_update:
            # When re-trigger received for update in latest traversal, first
            # check if update key is available in graph.
            # if No, then latest traversal is waiting for delete.
            if (resource_id, is_update) not in graph:
                key = (resource_id, not is_update)
        else:
            # When re-trigger received for delete in latest traversal, first
            # check if update key is available in graph,
            # if yes, then latest traversal is waiting for update.
            if (resource_id, True) in graph:
                # not is_update evaluates to True below, which means update
                key = (resource_id, not is_update)
        LOG.info('Re-trigger resource: (%(key1)s, %(key2)s)',
                 {'key1': key[0], 'key2': key[1]})
        predecessors = set(graph[key])

        try:
            propagate_check_resource(cnxt, self._rpc_client, resource_id,
                                     current_traversal, predecessors, key,
                                     None, key[1], None)
        except exception.EntityNotFound as e:
            if e.entity != "Sync Point":
                raise

    def _initiate_propagate_resource(self, cnxt, resource_id,
                                     current_traversal, is_update, rsrc,
                                     stack):
        deps = stack.convergence_dependencies
        graph = deps.graph()
        graph_key = (resource_id, is_update)

        if graph_key not in graph and rsrc.replaces is not None:
            # If we are a replacement, impersonate the replaced resource for
            # the purposes of calculating whether subsequent resources are
            # ready, since everybody has to work from the same version of the
            # graph. Our real resource ID is sent in the input_data, so the
            # dependencies will get updated to point to this resource in time
            # for the next traversal.
            graph_key = (rsrc.replaces, is_update)

        def _get_input_data(req, fwd, input_forward_data=None):
            if fwd:
                if input_forward_data is None:
                    return rsrc.node_data().as_dict()
                else:
                    # do not re-resolve attrs
                    return input_forward_data
            else:
                # Don't send data if initiating clean-up for self i.e.
                # initiating delete of a replaced resource
                if req not in graph_key:
                    # send replaced resource as needed_by if it exists
                    return (rsrc.replaced_by
                            if rsrc.replaced_by is not None
                            else resource_id)
            return None

        try:
            input_forward_data = None
            for req, fwd in deps.required_by(graph_key):
                input_data = _get_input_data(req, fwd, input_forward_data)
                if fwd:
                    input_forward_data = input_data
                propagate_check_resource(
                    cnxt, self._rpc_client, req, current_traversal,
                    set(graph[(req, fwd)]), graph_key, input_data, fwd,
                    stack.adopt_stack_data)
            if is_update:
                if input_forward_data is None:
                    # we haven't resolved attribute data for the resource,
                    # so clear any old attributes so they may be re-resolved
                    rsrc.clear_stored_attributes()
                else:
                    rsrc.store_attributes()
            check_stack_complete(cnxt, stack, current_traversal,
                                 graph_key[0], deps, graph_key[1])
        except exception.EntityNotFound as e:
            if e.entity == "Sync Point":
                # Reload the stack to determine the current traversal, and
                # check the SyncPoint for the current node to determine if
                # it is ready. If it is, then retrigger the current node
                # with the appropriate data for the latest traversal.
                stack = parser.Stack.load(cnxt, stack_id=rsrc.stack.id,
                                          force_reload=True)
                if current_traversal == stack.current_traversal:
                    LOG.debug('[%s] Traversal sync point missing.',
                              current_traversal)
                    return

                self.retrigger_check_resource(cnxt, is_update,
                                              resource_id, stack)
            else:
                raise

    def check(self, cnxt, resource_id, current_traversal,
              resource_data, is_update, adopt_stack_data,
              rsrc, stack):
        """Process a node in the dependency graph.

        The node may be associated with either an update or a cleanup of its
        associated resource.
        """
        if stack.has_timed_out():
            self._handle_stack_timeout(cnxt, stack)
            return

        tmpl = stack.t
        stack.adopt_stack_data = adopt_stack_data
        stack.thread_group_mgr = self.thread_group_mgr

        if is_update:
            if (rsrc.replaced_by is not None and
                    rsrc.current_template_id != tmpl.id):
                return

        try:
            check_resource_done = self._do_check_resource(cnxt,
                                                          current_traversal,
                                                          tmpl, resource_data,
                                                          is_update,
                                                          rsrc, stack,
                                                          adopt_stack_data)

            if check_resource_done:
                # initiate check on next set of resources from graph
                self._initiate_propagate_resource(cnxt, resource_id,
                                                  current_traversal, is_update,
                                                  rsrc, stack)
        except BaseException as exc:
            with excutils.save_and_reraise_exception():
                msg = six.text_type(exc)
                LOG.exception("Unexpected exception in resource check.")
                self._handle_resource_failure(cnxt, is_update, rsrc.id,
                                              stack, msg)


def load_resource(cnxt, resource_id, resource_data,
                  current_traversal, is_update):
    try:
        return resource.Resource.load(cnxt, resource_id, current_traversal,
                                      is_update, resource_data)
    except (exception.ResourceNotFound, exception.NotFound):
        # can be ignored
        return None, None, None


def check_stack_complete(cnxt, stack, current_traversal, sender_id, deps,
                         is_update):
    """Mark the stack complete if the update is complete.

    Complete is currently in the sense that all desired resources are in
    service, not that superfluous ones have been cleaned up.
    """
    roots = set(deps.roots())

    if (sender_id, is_update) not in roots:
        return

    def mark_complete(stack_id, data):
        stack.mark_complete()

    sender_key = (sender_id, is_update)
    sync_point.sync(cnxt, stack.id, current_traversal, True,
                    mark_complete, roots, {sender_key: None})


def propagate_check_resource(cnxt, rpc_client, next_res_id,
                             current_traversal, predecessors, sender_key,
                             sender_data, is_update, adopt_stack_data):
    """Trigger processing of node if all of its dependencies are satisfied."""
    def do_check(entity_id, data):
        rpc_client.check_resource(cnxt, entity_id, current_traversal,
                                  data, is_update, adopt_stack_data)

    sync_point.sync(cnxt, next_res_id, current_traversal,
                    is_update, do_check, predecessors,
                    {sender_key: sender_data})


def _check_for_message(msg_queue):
    if msg_queue is None:
        return
    try:
        message = msg_queue.get_nowait()
    except eventlet.queue.Empty:
        return

    if message == rpc_api.THREAD_CANCEL:
        raise CancelOperation

    LOG.error('Unknown message "%s" received', message)


def check_resource_update(rsrc, template_id, resource_data, engine_id,
                          stack, msg_queue):
    """Create or update the Resource if appropriate."""
    check_message = functools.partial(_check_for_message, msg_queue)
    if rsrc.action == resource.Resource.INIT:
        rsrc.create_convergence(template_id, resource_data, engine_id,
                                stack.time_remaining(), check_message)
    else:
        rsrc.update_convergence(template_id, resource_data, engine_id,
                                stack.time_remaining(), stack,
                                check_message)


def check_resource_cleanup(rsrc, template_id, resource_data, engine_id,
                           timeout, msg_queue):
    """Delete the Resource if appropriate."""
    check_message = functools.partial(_check_for_message, msg_queue)
    rsrc.delete_convergence(template_id, resource_data, engine_id, timeout,
                            check_message)
