AWSTemplateFormatVersion: '2010-09-09'
Transform: AWS::Serverless-2016-10-31
Description: >
  Blue service app for for single bus, multi-account-pattern


Globals:
  Function:
    Timeout: 3
    Handler: app.lambda_handler
    Runtime: python3.9


Parameters:
  EventBusName:
    Description: Name of the blue service app event bus
    Type: String
    Default: blue-service-event-bus
    
  DevOpsEventBusArn:
    Description: The ARN of the devops event bus # e.g. arn:aws:events:us-east-1:[DEVOPS-ACCOUNT]:event-bus/devops-event-bus
    Type: String


Resources:
  BlueServicePublisherE1:
    Type: AWS::Serverless::Function
    Properties:
      CodeUri: blue_p_e1/
      Policies:
        - Version: '2012-10-17' 
          Statement:
            - Effect: Allow
              Action:
                - events:PutEvents
              Resource: "*" 
      Environment:
        Variables:
          DEVOPS_EVENT_BUS_ARN: !Ref DevOpsEventBusArn


  # Event bus for blue service. In single bus topology 
  # this is the target for the devops event bus rule 
  BlueServiceEventBus: 
    Type: AWS::Events::EventBus
    Properties: 
        Name: !Ref EventBusName

  BlueServiceSubscriberE2:
    Type: AWS::Serverless::Function 
    Properties:
      CodeUri: blue_s_e2/
      Events:
        BlueE2Rule:
          Type: EventBridgeRule
          Properties:
            EventBusName: !Ref BlueServiceEventBus
            Pattern:
              source:
                - com.exampleCorp.PurpleService
              detail-type:
                - Event2

  # Rule that is placed on the DevOps event bus for Event 2
  BlueServiceEvent2SubscriptionRule:
    Type: AWS::Events::Rule
    Properties:
      Name: BlueE2Subscription
      Description: Cross account rule created by Blue service for event 2
      EventBusName: !Ref DevOpsEventBusArn # ARN of the devops event bus
      EventPattern:
        source:
          - com.exampleCorp.PurpleService
        detail-type:
          - Event2
      State: ENABLED
      Targets: 
        - Id: SendEvent2ToBlueServiceEventBus
          Arn: !GetAtt BlueServiceEventBus.Arn
          RoleArn: !GetAtt DevOpsEventBusToBlueServiceEventBusRole.Arn
          DeadLetterConfig:
            Arn: !GetAtt BlueServiceEventBusDlq.Arn

  # This IAM role allows EventBridge to assume the permissions necessary to send events 
  # from the DevOps event bus to the Blue service event bus. No resource policy is required
  # on the Blue service event bus.
  DevOpsEventBusToBlueServiceEventBusRole:
    Type: 'AWS::IAM::Role'
    Properties:
      AssumeRolePolicyDocument:
        Version: 2012-10-17
        Statement:
          - Effect: Allow
            Principal:
              Service:
              - events.amazonaws.com
            Action:
              - 'sts:AssumeRole'
      Path: /
      Policies:   
        - PolicyName: PutEventsOnBlueServiceEventBus
          PolicyDocument:
            Version: 2012-10-17
            Statement:
              - Effect: Allow
                Action: 'events:PutEvents'
                Resource: !GetAtt BlueServiceEventBus.Arn

  # Blue service event bus targe DLQ 
  BlueServiceEventBusDlq:
    Type: AWS::SQS::Queue

  # SQS resource policy required to allow target on devops bus to send failed messages to target DLQ
  BlueServiceEventBusDlqPolicy: 
    Type: AWS::SQS::QueuePolicy
    Properties: 
      Queues: 
        - !Ref BlueServiceEventBusDlq
      PolicyDocument: 
        Statement: 
          - Action: 
              - "SQS:SendMessage" 
            Effect: "Allow"
            Resource: !GetAtt BlueServiceEventBusDlq.Arn
            Principal:  
              Service: "events.amazonaws.com"
            Condition:
              ArnEquals:
                "aws:SourceArn": !GetAtt BlueServiceEvent2SubscriptionRule.Arn

Outputs:
  BlueServicePublisherE1:
    Description: Lambda function name for blue service publishing event 1
    Value: !Ref BlueServicePublisherE1
  BlueServiceSubscriberE2:
    Description: Lambda function name for purple service subscriber to event 2
    Value: !Ref BlueServiceSubscriberE2
  BlueServiceEventBusDlqUrl:
    Description: URL of the SQS Queue for rules DeadLetterConfig
    Value: !Ref BlueServiceEventBusDlq
  BlueServiceEventBusDlqArn:
    Description: ARN of the SQS Queue for rules DeadLetterConfig
    Value: !GetAtt BlueServiceEventBusDlq.Arn