# Copyright 2020 K Sai Kiran (Tata Elxsi)
#
# 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.

__author__ = "K Sai Kiran <saikiran.k@tataelxsi.co.in>"
__date__ = "$28-Apr-2020 23:59:59$"

import asyncio
import aiohttp
from http import HTTPStatus
import json
import logging
import time
from uuid import uuid4


class NotificationException(Exception):
    """
    Notification Exception
    """

    def __init__(self, message: str, http_code: int = HTTPStatus.BAD_REQUEST) -> None:
        """
        Constructor of notification exception
        :param message: String text containing exception details.
        :param http_code: HTTP status code of exception.
        """
        self.http_code = http_code
        Exception.__init__(self, message)


class NotificationBase:

    response_models = None
    # Common HTTP payload header for all notifications.
    payload_header = {
        "Content-Type": "application/json",
        "Accept": "application/json"
    }

    def __init__(self, db) -> None:
        """
        Constructor of NotificationBase class.
        :param db: Database handler.
        """
        self.db = db
        self.logger = logging.getLogger("nbi.notifications")
        self.subscriber_collection = None

    def get_models(self) -> dict:
        """
        Returns the SOL005 model of notification class
        :param None
        :return: dict of SOL005 data model
        """
        return NotificationBase.response_models

    def get_subscribers(self, **kwargs) -> NotificationException:
        """
        Method should be implemented by all notification subclasses
        :param kwargs: any keyword arguments needed for db query.
        :return: List of subscribers
        """
        raise NotificationException("Method get_subscribers() is not implemented", http_code=HTTPStatus.NOT_IMPLEMENTED)

    @staticmethod
    def _get_basic_auth(username: str, password: str) -> tuple:
        return aiohttp.BasicAuth(username, password)

    def _decrypt_password(self, hashed: str, salt: str, schema_version: str = "1.1") -> str:
        return self.db.decrypt(hashed, schema_version, salt=salt)

    def get_payload(self, meta_notification: dict) -> dict:
        """
        Generates SOL005 compliant payload structure and returns them in dictionary.
        :param meta_notification: notification meta data which needs to be formatted as SOL005 compliant
        :return: A dictionary which is SOL005 compliant.
        """
        model_name = meta_notification["notificationType"]
        response_models = self.get_models()
        if not response_models or not response_models.get(model_name):
            raise NotificationException("Response model {} is not defined.".format(model_name),
                                        HTTPStatus.NOT_IMPLEMENTED)
        model_keys = response_models[model_name]
        payload = dict.fromkeys(model_keys, "N/A")
        notification_keys = set(meta_notification.keys())
        for model_key in model_keys.intersection(notification_keys):
            payload[model_key] = meta_notification[model_key]
        self.logger.debug("Payload generated for subscriber: {} for {}".format(payload["subscriptionId"],
                                                                               payload["notificationType"]))
        return payload

    async def send_notifications(self, subscribers: list, loop: asyncio.AbstractEventLoop = None):
        """
        Generate tasks for all notification for an event.
        :param subscribers: A list of subscribers who want to be notified for event.
        :param loop: Event loop object.
        """
        notifications = []
        for subscriber in subscribers:
            # TODO add support for AuthType OAuth and TLS after support is added in subscription.
            if subscriber["authentication"]["authType"] != "basic":
                self.logger.debug("Subscriber {} can not be notified {} notification auth type is not implemented"
                                  .format(subscriber["subscriptionId"],
                                          subscriber["authentication"]["authType"]))
                continue
            salt = subscriber["subscriptionId"]
            hashed_password = subscriber["authentication"]["paramsBasic"]["password"]
            password = self._decrypt_password(hashed_password, salt)
            auth_basic = self._get_basic_auth(subscriber["authentication"]["paramsBasic"]["userName"], password)
            notifications.append({
                "headers": self.payload_header,
                "payload": self.get_payload(subscriber),
                "auth_basic": auth_basic,
                "CallbackUri": subscriber["CallbackUri"]
            })
        tasks = []
        async with aiohttp.ClientSession(loop=loop) as session:
            for notification in notifications:
                tasks.append(asyncio.ensure_future(self.send_notification(session, notification), loop=loop))
            await asyncio.gather(*tasks, loop=loop)

    async def send_notification(self, session: aiohttp.ClientSession, notification: dict,
                                loop: asyncio.AbstractEventLoop = None, retry_count: int = 5, timeout: float = 5.0):
        """
        Performs HTTP Post request to notify subscriber. In case if for any reason notification is not sent successfully
        after maximum number of reties, then notification is dropped.
        :param session: An aiohttp client session object to maintain http session.
        :param notification: A dictionary containing all necessary data to make POST request.
        :param loop: Event loop object.
        :param retry_count: An integer specifying the maximum number of reties for a notification.
        :param timeout: A float representing client timeout of each HTTP request.
        """
        backoff_delay = 1
        while retry_count > 0:
            try:
                async with session.post(url=notification["CallbackUri"], headers=notification["headers"],
                                        auth=notification["auth_basic"], data=json.dumps(notification["payload"]),
                                        timeout=timeout) as resp:
                    # self.logger.debug("Notification response: {}".format(resp.status))
                    if resp.status == HTTPStatus.NO_CONTENT:
                        self.logger.debug("Notification sent successfully to subscriber {}"
                                          .format(notification["payload"]["subscriptionId"]))
                    else:
                        error_text = "Erroneous response code: {}, ".format(resp.status)
                        error_text += await resp.text()
                        raise NotificationException(error_text)
                return True
            except Exception as e:
                error_text = type(e).__name__ + ": " + str(e)
                self.logger.debug("Unable while sending notification to subscriber {}. Details: {}"
                                  .format(notification["payload"]["subscriptionId"], error_text))
                error_detail = {
                    "error": type(e).__name__,
                    "error_text": str(e),
                    "timestamp": time.time()
                }
                if "error_details" in notification["payload"].keys():
                    notification["payload"]["error_details"].append(error_detail)
                else:
                    notification["payload"]["error_details"] = [error_detail]
                retry_count -= 1
                backoff_delay *= 2
                self.logger.debug("Retry Notification for subscriber: {} after backoff delay: {} seconds."
                                  .format(notification["payload"]["subscriptionId"], backoff_delay))
                await asyncio.sleep(backoff_delay, loop=loop)
        # Dropping notification
        self.logger.debug("Notification {} sent failed to subscriber:{}."
                          .format(notification["payload"]["notificationType"],
                                  notification["payload"]["subscriptionId"]))
        return False


class NsLcmNotification(NotificationBase):

    # SOL005 response model for nslcm notifications
    response_models = {
        "NsLcmOperationOccurrenceNotification": {"id", "nsInstanceId", "nsLcmOpOccId", "operation",
                                                 "notificationType", "subscriptionId", "timestamp",
                                                 "notificationStatus", "operationState", "isAutomaticInvocation",
                                                 "affectedVnf", "affectedVl", "affectedVnffg", "affectedNs",
                                                 "affectedSap", "error", "_links"},

        "NsIdentifierCreationNotification": {"notificationType", "subscriptionId", "timestamp",
                                             "nsInstanceId", "_links"},

        "NsIdentifierDeletionNotification": {"notificationType", "subscriptionId", "timestamp",
                                             "nsInstanceId", "_links"},

        "NsChangeNotification": {"nsInstanceId", "nsComponentType", "nsComponentId",
                                 "lcmOpOccIdImpactngNsComponent", "lcmOpNameImpactingNsComponent",
                                 "lcmOpOccStatusImpactingNsComponent", "notificationType", "subscriptionId",
                                 "timeStamp", "error", "_links"}
    }

    def __init__(self, db) -> None:
        """
        Constructor of NotificationBase class.
        :param db: Database handler.
        """
        super().__init__(db)
        self.subscriber_collection = "mapped_subscriptions"

    def get_models(self) -> dict:
        """
        Returns the SOL005 model of notification class
        :param None
        :return: dict of SOL005 data model
        """
        return NsLcmNotification.response_models

    @staticmethod
    def _format_nslcm_subscribers(subscribers: list, event_details: dict) -> list:
        """
        Formats the raw event details from kakfa message and subscriber details.
        :param subscribers: A list of subscribers whom the event needs to be notified.
        :param event_details: A dict containing all meta data of event.
        :return:
        """
        notification_id = str(uuid4())
        event_timestamp = event_details["params"]["startTime"]
        resource_links = event_details["params"]["links"]
        event_operation = event_details["command"]
        for key in ["_admin", "_id", "id", "links"]:
            event_details["params"].pop(key, None)
        for subscriber in subscribers:
            subscriber["id"] = notification_id
            subscriber["timestamp"] = event_timestamp
            subscriber["_links"] = resource_links
            subscriber["subscriptionId"] = subscriber["reference"]
            subscriber["operation"] = event_operation
            del subscriber["reference"]
            del subscriber["_id"]
            subscriber.update(event_details["params"])
        return subscribers

    def get_subscribers(self, nsd_id: str, ns_instance_id: str, command: str, op_state: str,
                        event_details: dict) -> list:
        """
        Queries database and returns list of subscribers.
        :param nsd_id: NSD id of an NS whose lifecycle has changed. (scaled, terminated. etc)
        :param ns_instance_id: NS instance id an NS whose lifecycle has changed.
        :param command: the command for event.
        :param op_state: the operation state of NS.
        :param event_details: dict containing raw data of event occured.
        :return: List of interested subscribers for occurred event.
        """
        filter_q = {"identifier": [nsd_id, ns_instance_id], "operationStates": ["ANY"], "operationTypes": ["ANY"]}
        if op_state:
            filter_q["operationStates"].append(op_state)
        if command:
            filter_q["operationTypes"].append(command)
        # self.logger.debug("Db query is: {}".format(filter_q))
        subscribers = []
        try:
            subscribers = self.db.get_list(self.subscriber_collection, filter_q)
            subscribers = self._format_nslcm_subscribers(subscribers, event_details)
        except Exception as e:
            error_text = type(e).__name__ + ": " + str(e)
            self.logger.debug("Error getting nslcm subscribers: {}".format(error_text))
        finally:
            return subscribers


class NsdNotification(NotificationBase):

    def __init__(self, db):
        """
        Constructor of the class
        """
        super().__init__(db)
        # TODO will update this once support is there from subscription
        self.response_models = {}
        self.subscriber_collection = None


class VnfdNotification(NotificationBase):

    def __init__(self, db):
        """
        Constructor of the class
        """
        super().__init__(db)
        # TODO will update this once support is there from subscription
        self.response_models = {}
        self.subscriber_collection = None