# org.onap.dcae
# ================================================================================
# Copyright (c) 2018 AT&T Intellectual Property. 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.
# ============LICENSE_END=========================================================
#
# ECOMP is a trademark and service mark of AT&T Intellectual Property.

"""
policy-receiver communicates with policy-engine
thru web-socket to receive push notifications
on updates and removal of policies.

on receiving the policy-notifications, the policy-receiver
filters them out by the policy scope(s) provided in policy-handler config
and passes the notifications to policy-updater
"""

import json
import logging
import re
import time
from threading import Lock, Thread

import websocket

from .config import Config
from .onap.audit import Audit
from .policy_updater import PolicyUpdater

LOADED_POLICIES = 'loadedPolicies'
REMOVED_POLICIES = 'removedPolicies'
POLICY_NAME = 'policyName'
POLICY_VER = 'versionNo'

class _PolicyReceiver(Thread):
    """web-socket to PolicyEngine"""
    _logger = logging.getLogger("policy_handler.policy_receiver")

    def __init__(self):
        """web-socket inside the thread to receive policy notifications from PolicyEngine"""
        Thread.__init__(self, name="policy_receiver")
        self.daemon = True

        self._lock = Lock()
        self._keep_running = True

        config = Config.config[Config.FIELD_POLICY_ENGINE]
        self.web_socket_url = resturl = config["url"] + config["path_pdp"]

        if resturl.startswith("https:"):
            self.web_socket_url = resturl.replace("https:", "wss:") + "notifications"
        else:
            self.web_socket_url = resturl.replace("http:", "ws:") + "notifications"

        self._web_socket = None

        scope_prefixes = [scope_prefix.replace(".", "[.]")
                          for scope_prefix in Config.config["scope_prefixes"]]
        self._policy_scopes = re.compile("(" + "|".join(scope_prefixes) + ")")
        _PolicyReceiver._logger.info("_policy_scopes %s", self._policy_scopes.pattern)
        self._policy_updater = PolicyUpdater()
        self._policy_updater.start()

    def run(self):
        """listen on web-socket and pass the policy notifications to policy-updater"""
        websocket.enableTrace(True)
        restarting = False
        while True:
            if not self._get_keep_running():
                break

            self._stop_notifications()

            if restarting:
                time.sleep(5)

            _PolicyReceiver._logger.info(
                "connecting to policy-notifications at: %s", self.web_socket_url)
            self._web_socket = websocket.WebSocketApp(
                self.web_socket_url,
                on_message=self._on_pdp_message,
                on_close=self._on_ws_close,
                on_error=self._on_ws_error
            )

            _PolicyReceiver._logger.info("waiting for policy-notifications...")
            self._web_socket.run_forever()
            restarting = True

        _PolicyReceiver._logger.info("exit policy-receiver")

    def _get_keep_running(self):
        """thread-safe check whether to continue running"""
        with self._lock:
            keep_running = self._keep_running
        return keep_running

    def _stop_notifications(self):
        """Shuts down the AutoNotification service if running."""
        with self._lock:
            if self._web_socket and self._web_socket.sock and self._web_socket.sock.connected:
                self._web_socket.close()
                _PolicyReceiver._logger.info("Stopped receiving notifications from PDP")

    def _on_pdp_message(self, _, message):
        """received the notification from PDP"""
        _PolicyReceiver._logger.info("Received notification message: %s", message)
        if not message:
            return
        message = json.loads(message)

        if not message:
            return

        policies_updated = [(policy.get(POLICY_NAME), policy.get(POLICY_VER))
                            for policy in message.get(LOADED_POLICIES, [])
                            if self._policy_scopes.match(policy.get(POLICY_NAME))]
        policies_removed = [(policy.get(POLICY_NAME), policy.get(POLICY_VER))
                            for policy in message.get(REMOVED_POLICIES, [])
                            if self._policy_scopes.match(policy.get(POLICY_NAME))]

        if not policies_updated and not policies_removed:
            _PolicyReceiver._logger.info(
                "no policy updated or removed for scopes %s", self._policy_scopes.pattern
            )
            return

        audit = Audit(req_message="policy-notification - updated[{0}], removed[{1}]" \
                        .format(len(policies_updated), len(policies_removed)))
        audit.retry_get_config = True
        self._policy_updater.enqueue(audit, policies_updated, policies_removed)

    def _on_ws_error(self, _, error):
        """report an error"""
        _PolicyReceiver._logger.error("policy-notification error: %s", error)

    def _on_ws_close(self, _):
        """restart web-socket on close"""
        _PolicyReceiver._logger.info("lost connection to PDP - restarting...")

    def shutdown(self, audit):
        """Shutdown the policy-receiver"""
        _PolicyReceiver._logger.info("shutdown policy-receiver")
        with self._lock:
            self._keep_running = False

        self._stop_notifications()

        if self.is_alive():
            self.join()

        self._policy_updater.shutdown(audit)

    def catch_up(self, audit):
        """need to bring the latest policies to DCAE-Controller"""
        self._policy_updater.catch_up(audit)

class PolicyReceiver(object):
    """policy-receiver - static singleton wrapper"""
    _policy_receiver = None

    @staticmethod
    def shutdown(audit):
        """Shutdown the notification-handler"""
        PolicyReceiver._policy_receiver.shutdown(audit)

    @staticmethod
    def catch_up(audit):
        """bring the latest policies from policy-engine"""
        PolicyReceiver._policy_receiver.catch_up(audit)

    @staticmethod
    def run(audit):
        """Using policy-engine client to talk to policy engine"""
        sub_aud = Audit(aud_parent=audit)
        sub_aud.metrics_start("start policy receiver")

        PolicyReceiver._policy_receiver = _PolicyReceiver()
        PolicyReceiver._policy_receiver.start()

        sub_aud.metrics("started policy receiver")

        PolicyReceiver.catch_up(audit)