# -*- coding: utf-8 -*-

#    Copyright (C) 2014 Yahoo! 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 logging
import threading

import six

from kombu import exceptions as kombu_exc

from taskflow.engines.action_engine import executor
from taskflow.engines.worker_based import cache
from taskflow.engines.worker_based import protocol as pr
from taskflow.engines.worker_based import proxy
from taskflow import exceptions as exc
from taskflow.utils import async_utils
from taskflow.utils import misc

LOG = logging.getLogger(__name__)


class WorkerTaskExecutor(executor.TaskExecutorBase):
    """Executes tasks on remote workers."""

    def __init__(self, uuid, exchange, workers_info, **kwargs):
        self._uuid = uuid
        self._proxy = proxy.Proxy(uuid, exchange, self._on_message,
                                  self._on_wait, **kwargs)
        self._proxy_thread = None
        self._requests_cache = cache.Cache()

        # TODO(skudriashev): This data should be collected from workers
        # using broadcast messages directly.
        self._workers_info = {}
        for topic, tasks in six.iteritems(workers_info):
            for task in tasks:
                self._workers_info[task] = topic

    def _get_proxy_thread(self):
        proxy_thread = threading.Thread(target=self._proxy.start)
        # NOTE(skudriashev): When the main thread is terminated unexpectedly
        # and proxy thread is still alive - it will prevent main thread from
        # exiting unless the daemon property is set to True.
        proxy_thread.daemon = True
        return proxy_thread

    def _on_message(self, data, message):
        """This method is called on incoming message."""
        LOG.debug("Got message: %s", data)
        try:
            # acknowledge message before processing
            message.ack()
        except kombu_exc.MessageStateError:
            LOG.exception("Failed to acknowledge AMQP message.")
        else:
            LOG.debug("AMQP message acknowledged.")
            try:
                msg_type = message.properties['type']
            except KeyError:
                LOG.warning("The 'type' message property is missing.")
            else:
                if msg_type == pr.RESPONSE:
                    self._process_response(data, message)
                else:
                    LOG.warning("Unexpected message type: %s", msg_type)

    def _process_response(self, response, message):
        """Process response from remote side."""
        LOG.debug("Start processing response message.")
        try:
            task_uuid = message.properties['correlation_id']
        except KeyError:
            LOG.warning("The 'correlation_id' message property is missing.")
        else:
            LOG.debug("Task uuid: '%s'", task_uuid)
            request = self._requests_cache.get(task_uuid)
            if request is not None:
                response = pr.Response.from_dict(response)
                if response.state == pr.RUNNING:
                    request.set_running()
                elif response.state == pr.PROGRESS:
                    request.on_progress(**response.data)
                elif response.state in (pr.FAILURE, pr.SUCCESS):
                    request.set_result(**response.data)
                    self._requests_cache.delete(request.uuid)
                else:
                    LOG.warning("Unexpected response status: '%s'",
                                response.state)
            else:
                LOG.debug("Request with id='%s' not found.", task_uuid)

    @staticmethod
    def _handle_expired_request(request):
        """Handle expired request.

        When request has expired it is removed from the requests cache and
        the `Timeout` exception is set as a request result.
        """
        LOG.debug("Request '%r' has expired.", request)
        request.set_result(misc.Failure.from_exception(
            exc.Timeout("Request '%r' has expired" % request)))

    def _on_wait(self):
        """This function is called cyclically between draining events."""
        self._requests_cache.cleanup(self._handle_expired_request)

    def _submit_task(self, task, task_uuid, action, arguments,
                     progress_callback, timeout=pr.REQUEST_TIMEOUT, **kwargs):
        """Submit task request to workers."""
        request = pr.Request(task, task_uuid, action, arguments,
                             progress_callback, timeout, **kwargs)
        self._requests_cache.set(request.uuid, request)
        try:
            # get task's workers topic to send request to
            try:
                topic = self._workers_info[request.task_cls]
            except KeyError:
                raise exc.NotFound("Workers topic not found for the '%s'"
                                   " task" % request.task_cls)
            else:
                # publish request
                LOG.debug("Sending request: %s", request)
                self._proxy.publish(request,
                                    routing_key=topic,
                                    reply_to=self._uuid,
                                    correlation_id=request.uuid)
        except Exception:
            with misc.capture_failure() as failure:
                LOG.exception("Failed to submit the '%s' task", request)
                self._requests_cache.delete(request.uuid)
                request.set_result(failure)
        return request.result

    def execute_task(self, task, task_uuid, arguments,
                     progress_callback=None):
        return self._submit_task(task, task_uuid, pr.EXECUTE, arguments,
                                 progress_callback)

    def revert_task(self, task, task_uuid, arguments, result, failures,
                    progress_callback=None):
        return self._submit_task(task, task_uuid, pr.REVERT, arguments,
                                 progress_callback, result=result,
                                 failures=failures)

    def wait_for_any(self, fs, timeout=None):
        """Wait for futures returned by this executor to complete."""
        return async_utils.wait_for_any(fs, timeout)

    def start(self):
        """Start proxy thread."""
        if self._proxy_thread is None:
            self._proxy_thread = self._get_proxy_thread()
            self._proxy_thread.start()
            self._proxy.wait()

    def stop(self):
        """Stop proxy, so its thread would be gracefully terminated."""
        if self._proxy_thread is not None:
            if self._proxy_thread.is_alive():
                self._proxy.stop()
                self._proxy_thread.join()
            self._proxy_thread = None