---
# Copyright 2018 widdix GmbH
#
# 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.
AWSTemplateFormatVersion: '2010-09-09'
Description: 'cfn-modules: Alerting'
# cfn-modules:implements(ExposeArn)
Parameters:
  Email:
    Description: 'Optional email address that will receive alerts'
    Type: String
    Default: ''
  HttpEndpoint:
    Description: 'Optional HTTP endpoint that will receive alerts via POST requests'
    Type: String
    Default: ''
  HttpsEndpoint:
    Description: 'Optional HTTPS endpoint that will receive alerts via POST requests (e.g., marbot.io - a chatbot for AWS monitoring in Slack and Microsoft Teams)'
    Type: String
    Default: ''
  FallbackEmail:
    Description: 'Optional email address that will receive alerts if alerts can not be delivered'
    Type: String
    Default: ''
Conditions:
  HasEmail: !Not [!Equals [!Ref Email, '']]
  HasHttpEndpoint: !Not [!Equals [!Ref HttpEndpoint, '']]
  HasHttpsEndpoint: !Not [!Equals [!Ref HttpsEndpoint, '']]
  HasFallbackEmail: !Not [!Equals [!Ref FallbackEmail, '']]
Resources:
  Topic:
    Type: 'AWS::SNS::Topic'
    Properties: {}
  TopicPolicy:
    Type: 'AWS::SNS::TopicPolicy'
    Properties:
      PolicyDocument:
        Id: Id1
        Version: '2012-10-17'
        Statement:
        - Sid: Sid1
          Effect: Allow
          Principal:
            Service:
            - 'events.amazonaws.com' # Allow CloudWatch Events
            - 'budgets.amazonaws.com' # Allow Budget Notifications
            - 'rds.amazonaws.com' # Allow RDS Events
            - 's3.amazonaws.com' # Allow S3 Event Notifications
            - 'backup.amazonaws.com' # Allow Backup Events
          Action: 'sns:Publish'
          Resource: !Ref Topic
        - Sid: Sid2
          Effect: Allow
          Principal:
            AWS: '*' # Allow CloudWatch Alarms, ElastiCache Notifications, Elastic Beanstalk Notifications, Auto Scaling Notification
          Action: 'sns:Publish'
          Resource: !Ref Topic
          Condition:
            StringEquals:
              'AWS:SourceOwner': !Ref 'AWS::AccountId'
        - Sid: Sid3
          Effect: Allow
          Principal:
            Service: 'ses.amazonaws.com' # Allow SES Notifications & Events
          Action: 'sns:Publish'
          Resource: !Ref Topic
          Condition:
            StringEquals:
              'AWS:Referer': !Ref 'AWS::AccountId'
      Topics:
      - !Ref Topic
  FallbackTopic:
    Type: 'AWS::SNS::Topic'
    Properties: {}
  NumberOfNotificationsFailedTooHighAlarm:
    Type: 'AWS::CloudWatch::Alarm'
    Properties:
      AlarmDescription: 'Alerts could not be delivered'
      Namespace: 'AWS/SNS'
      MetricName: NumberOfNotificationsFailed
      Statistic: Sum
      Period: 60
      EvaluationPeriods: 1
      ComparisonOperator: GreaterThanThreshold
      Threshold: 0
      AlarmActions:
      - !Ref FallbackTopic
      Dimensions:
      - Name: TopicName
        Value: !GetAtt Topic.TopicName
      TreatMissingData: notBreaching
  EmailSubscription:
    Condition: HasEmail
    Type: 'AWS::SNS::Subscription'
    Properties:
      Endpoint: !Ref Email
      Protocol: email
      TopicArn: !Ref Topic
  HttpEndpointSubscription:
    Condition: HasHttpEndpoint
    Type: 'AWS::SNS::Subscription'
    Properties:
      DeliveryPolicy:
        healthyRetryPolicy:
          minDelayTarget: 1
          maxDelayTarget: 60
          numRetries: 100
          numNoDelayRetries: 0
          backoffFunction: exponential
        throttlePolicy:
          maxReceivesPerSecond: 1
      Endpoint: !Ref HttpEndpoint
      Protocol: http
      TopicArn: !Ref Topic
  HttpsEndpointSubscription:
    Condition: HasHttpsEndpoint
    Type: 'AWS::SNS::Subscription'
    Properties:
      DeliveryPolicy:
        healthyRetryPolicy:
          minDelayTarget: 1
          maxDelayTarget: 60
          numRetries: 100
          numNoDelayRetries: 0
          backoffFunction: exponential
        throttlePolicy:
          maxReceivesPerSecond: 1
      Endpoint: !Ref HttpsEndpoint
      Protocol: https
      TopicArn: !Ref Topic
  FallbackEmailSubscription:
    Condition: HasFallbackEmail
    Type: 'AWS::SNS::Subscription'
    Properties:
      Endpoint: !Ref FallbackEmail
      Protocol: email
      TopicArn: !Ref FallbackTopic
Outputs:
  ModuleId:
    Value: 'alerting'
  ModuleVersion:
    Value: '1.2.2'
  StackName:
    Value: !Ref 'AWS::StackName'
  Arn:
    Value: !Ref Topic
    Export:
      Name: !Sub '${AWS::StackName}-Arn'