AWSTemplateFormatVersion: "2010-09-09"
Parameters:
    SNSTopicName:
        Type: String
        Description: Please enter your SNS Topic Name. (SNS Topic must exist in the same region where this stack is launched).
Resources: 
  LambdaFunctionRole: 
    Type: "AWS::IAM::Role"
    Properties: 
      AssumeRolePolicyDocument: 
        Version: "2012-10-17"
        Statement: 
          - 
            Effect: "Allow"
            Principal: 
              Service: 
                - "lambda.amazonaws.com"
            Action: 
              - "sts:AssumeRole"
      Path: "/"
  LambdaRolePolicies: 
    Type: "AWS::IAM::Policy"
    Properties: 
      PolicyName: "LambdaPolicy"
      PolicyDocument: 
        Version: "2012-10-17"
        Statement: 
          - 
            Sid: Stmt1477516473539
            Action:
              - logs:CreateLogGroup
              - logs:CreateLogStream
              - logs:PutLogEvents
            Effect: Allow
            Resource: arn:aws:logs:*:*:*
          - 
            Sid: Stmt1484080345748
            Action:
              - sns:Publish
            Effect: Allow
            Resource: 
              Fn::Join:
                - "" 
                - - "arn:aws:sns:"
                  - !Ref "AWS::Region"
                  - ":"
                  - !Ref "AWS::AccountId"
                  - ":"
                  - !Ref "SNSTopicName"
      Roles: 
        - 
          Ref: "LambdaFunctionRole"
  SNSPublishFunction: 
    Type: "AWS::Lambda::Function"
    Properties: 
      Handler: "index.handler"
      Role: 
        Fn::GetAtt: 
          - "LambdaFunctionRole"
          - "Arn"
      Environment: 
          Variables: 
            SNSARN: 
              Fn::Join:
                - "" 
                - - "arn:aws:sns:"
                  - !Ref "AWS::Region"
                  - ":"
                  - !Ref "AWS::AccountId"
                  - ":"
                  - !Ref "SNSTopicName"
      Code: 
        ZipFile: !Sub |
            // Sample Lambda Function to send notifications to a SNS topic when an AWS Health event happens
            var AWS = require('aws-sdk');
            var sns = new AWS.SNS();

            // define configuration
            const snsTopic =process.env.SNSARN; //use ARN

            //main function which gets AWS Health data from Cloudwatch event
            exports.handler = (event, context, callback) => {
                //extract details from Cloudwatch event
                healthMessage = event.detail.eventDescription[0].latestDescription + ' For more details, please see https://phd.aws.amazon.com/phd/home?region=us-east-1#/dashboard/open-issues';
                eventName = event.detail.eventTypeCode
                //prepare message for SNS to publish
                var snsPublishParams = {
                    Message: healthMessage, 
                    Subject: eventName,
                    TopicArn: snsTopic
                };
                sns.publish(snsPublishParams, function(err, data) {
                if (err) {
                    const snsPublishErrorMessage = `Error publishing AWS Health event to SNS`;
                    console.log(snsPublishErrorMessage, err);
                    callback(snsPublishErrorMessage);
                    } 
                else {
                    const snsPublishSuccessMessage = `Successfully got details from AWS Health event, ${!eventName} and published to SNS topic.`;
                    console.log(snsPublishSuccessMessage, data);
                    callback(null, snsPublishSuccessMessage); //return success
                    }
                });
            };
      Runtime: "nodejs14.x"
      Timeout: "25"
  LambdaInvokePermission: 
    Type: "AWS::Lambda::Permission"
    Properties: 
      FunctionName: 
        Fn::GetAtt: 
          - "SNSPublishFunction"
          - "Arn"
      Action: "lambda:InvokeFunction"
      Principal: "events.amazonaws.com"
      SourceArn: 
        !GetAtt CloudWatchEventRule.Arn
  CloudWatchEventRule: 
    Type: "AWS::Events::Rule"
    Properties: 
      Description: "EventRule"
      EventPattern: 
        source: 
          - "aws.health"
      State: "ENABLED"
      Targets: 
        - 
          Arn: 
            Fn::GetAtt: 
              - "SNSPublishFunction"
              - "Arn"
          Id: "SNSPublishFunction"