AWSTemplateFormatVersion: '2010-09-09'
Transform: AWS::Serverless-2016-10-31
Description: Serverless Pattern - IoT rule with custom lambda authorizer forwarding events to SQS for post iot event processing
Parameters:
  VPC:
    Type: AWS::EC2::VPC::Id
  Subnets:
    Type: List<AWS::EC2::Subnet::Id>
Resources:
  IotEventQueue:
    Type: AWS::SQS::Queue
    Properties:
      QueueName: iot-events 
  ProcessorSecurityGroup:
    Type: AWS::EC2::SecurityGroup
    Properties:
      GroupDescription: iot-events-processor
      VpcId: !Ref VPC
      SecurityGroupEgress:
        - IpProtocol: tcp
          FromPort: 443
          ToPort: 443
          CidrIp: 0.0.0.0/0
  Processor:
    Type: AWS::Serverless::Function
    Properties:
      FunctionName: iot-events-processor
      Handler: app.handler
      Runtime: nodejs14.x
      Timeout: 29
      CodeUri: src/
      Events:
        IotEvent:
          Type: SQS
          Properties:
            Queue: !GetAtt IotEventQueue.Arn
            BatchSize: 10000
            MaximumBatchingWindowInSeconds: 5
      VpcConfig:
        SecurityGroupIds:
          - !Ref ProcessorSecurityGroup
        SubnetIds: !Ref Subnets
  TopicRuleRole:
    Type: AWS::IAM::Role
    Properties:
      RoleName: iot-topic-forwarder
      AssumeRolePolicyDocument:
        Version: '2012-10-17'
        Statement:
        - Effect: Allow
          Principal:
            Service:
            - iot.amazonaws.com
          Action:
          - sts:AssumeRole
      Path: /
      Policies:
      - PolicyName: iot-topic-forwarder-policy
        PolicyDocument:
          Version: '2012-10-17'
          Statement:
          - Effect: Allow
            Action:
              - sqs:SendMessage
            Resource: !GetAtt IotEventQueue.Arn 
  SQSRule:
    Type: AWS::IoT::TopicRule
    Properties:
      RuleName: device_events
      TopicRulePayload:
        Sql: SELECT * 
        Actions:
          - Sqs: 
              QueueUrl: !Ref IotEventQueue
              RoleArn: !GetAtt TopicRuleRole.Arn



  LambdaAuthorizer:
    Type: AWS::Serverless::Function
    Properties:
      FunctionName: iot-publish-authorizer
      Handler: index.handler
      Runtime: nodejs14.x
      Environment:
        Variables:
          AWS_ACCOUNTID: !Ref AWS::AccountId
      InlineCode: |
        exports.handler = function(event, context, callback) { 
          var deviceId = event.protocolData.http.headers["x-device-id"];
          callback(null, generateAuthResponse(deviceId)); 
        };

        var generateAuthResponse = function(deviceId) {
          var response = {};
          response.isAuthenticated = true;
          response.principalId = deviceId;
          var policy = {};
          policy.Version = '2012-10-17';
          policy.Statement = [];
          var publishStatement = {}; 
          var connectStatement = {};
          connectStatement.Action = ["iot:Connect"];
          connectStatement.Effect = 'Allow';
          connectStatement.Resource = ["*"];
          publishStatement.Action = ["iot:Publish"]; 
          publishStatement.Effect = 'Allow'; 
          publishStatement.Resource = [`arn:aws:iot:${process.env.AWS_REGION}:${process.env.AWS_ACCOUNTID}:topic/*`]; 
          policy.Statement[0] = connectStatement;
          policy.Statement[1] = publishStatement; 
          response.policyDocuments = [policy];
          response.disconnectAfterInSeconds = 3600;
          response.refreshAfterInSeconds = 300;
          
          return response;
        };

  CustomAuthorizer:
    Type: AWS::IoT::Authorizer
    Properties:
      AuthorizerName: anonymous-authorizer
      Status: ACTIVE
      SigningDisabled: true
      AuthorizerFunctionArn: !GetAtt LambdaAuthorizer.Arn
  IotLambdaPermission:
    Type: AWS::Lambda::Permission
    Properties:
      FunctionName: !GetAtt LambdaAuthorizer.Arn
      Principal: iot.amazonaws.com
      Action: lambda:InvokeFunction