---
AWSTemplateFormatVersion: '2010-09-09'
Transform: 'AWS::Serverless-2016-10-31'


Parameters:
  S3BucketLambda:
    Type: String
    Description: The S3 bucket location where the lambda deployment package is
  KDAAppName:
    Type: String
    Description: KDA App Name
  KinesisStreamName:
    Type: String
    Description: Kinesis Stream Name
  MaxKPUs:
    Type: String
    Description: Max KPUs
    Default: 32
  KDAParallelism:
    Type: String
    Description: Initial parallelism
    Default: 1


Resources:

  CustomApplicationAutoScalingServiceRole:
    DependsOn: ScalerApi
    Type: 'AWS::IAM::Role'
    Properties: 
      AssumeRolePolicyDocument: 
        Version: '2012-10-17'
        Statement: 
          - 
            Effect: 'Allow'
            Principal: 
              Service: 
                - 'custom-resource.application-autoscaling.amazonaws.com'
            Action: 
              - 'sts:AssumeRole'
      Path: "/"
      Policies: 
        - 
          PolicyName: 'root'
          PolicyDocument: 
            Version: "2012-10-17"
            Statement: 
              - 
                Effect: 'Allow'
                Action:
                  - 'execute-api:Invoke*'
                  - 'cloudwatch:PutMetricAlarm'
                  - 'cloudwatch:DescribeAlarms'
                  - 'cloudwatch:DeleteAlarms'
                Resource: '*'

  LambdaScaler:
    Type: 'AWS::Serverless::Function'
    Properties:
      Handler: index.lambda_handler
      Runtime: python3.6
      Timeout: 10
      CodeUri: 
        Bucket: !Ref S3BucketLambda
        Key: kdattscalinglambda/index.zip        
      Policies:
        - AWSCloudFormationReadOnlyAccess
        - Statement:
          - Sid: MySSMPolicy
            Effect: Allow
            Action:
            - 'ssm:PutParameter'
            - 'ssm:GetParameters'
            - 'ssm:GetParameter'
            Resource: '*'
        - Statement:
          - Sid: MyCWMetricPolicy
            Effect: Allow
            Action:
            - 'cloudwatch:PutMetricAlarm'
            Resource: '*'
        - Statement:
          - Sid: AmazonKinesisAnalyticsPolicyForAppAutoScaling
            Effect: Allow
            Action:
            - 'kinesisanalytics:UpdateApplication'
            - 'kinesisanalytics:DescribeApplication'
            Resource: '*'
        - Statement:
          - Sid: AppAutoscalingFullPolicy
            Effect: Allow
            Action:
            - 'application-autoscaling:*'
            Resource: '*'
      Environment:
        Variables:
          ParameterStore: !Ref KDADesiredCapacityParameter
          KDAAppName: !Ref KDAAppName
          KinesisStreamName: !Ref KinesisStreamName
          MaxKPUs: !Ref MaxKPUs
      Events:
        KinesisAPI:
          Type: Api
          Properties:
            Path: /scalableTargetDimensions/{scalableTargetDimensionId}
            Method: GET
            RestApiId: !Ref ScalerApi
        KinesisAPIPatch:
          Type: Api
          Properties:              
            Path: /scalableTargetDimensions/{scalableTargetDimensionId}
            Method: PATCH                      
            RestApiId: !Ref ScalerApi

  ScalerApi:
    #DeletionPolicy: Retain
    Type: AWS::Serverless::Api
    Properties:
        StageName: prod
        DefinitionBody:
          swagger: 2.0
          info:
            title:
              Ref: AWS::StackName
          securityDefinitions:
            sigv4:
              type: apiKey
              name: Authorization
              in: header
              x-amazon-apigateway-authtype: awsSigv4
          paths:
            "/scalableTargetDimensions/{scalableTargetDimensionId}":
              get:
                security:
                  - sigv4: []                
                x-amazon-apigateway-any-method:
                  produces:
                    - application/json
                  consumes:
                    - application/json
                x-amazon-apigateway-integration:
                  httpMethod: POST
                  type: aws_proxy
                  uri:
                    Fn::Sub: arn:aws:apigateway:${AWS::Region}:lambda:path/2015-03-31/functions/${LambdaScaler.Arn}/invocations
                responses: {} 

              patch:              
                security:
                  - sigv4: []                                
                x-amazon-apigateway-any-method:
                  security:
                    - sigv4: []
                  produces:
                    - application/json
                  consumes:
                    - application/json
                x-amazon-apigateway-integration:
                  httpMethod: POST
                  type: aws_proxy
                  uri:
                    Fn::Sub: arn:aws:apigateway:${AWS::Region}:lambda:path/2015-03-31/functions/${LambdaScaler.Arn}/invocations
                responses: {} 

  KDADesiredCapacityParameter:
    Type: "AWS::SSM::Parameter"
    Properties:
      Type: "String"
      Value: !Ref KDAParallelism
      Description: "Store DesiredCapacity in Parameter Store"
      AllowedPattern: "[0-9]+"

  KDAScalableTarget:
    Type: AWS::ApplicationAutoScaling::ScalableTarget
    DependsOn: LambdaScaler
    DependsOn: ScalerApi
    DependsOn: CustomApplicationAutoScalingServiceRole
    Properties:
      MaxCapacity: !Ref MaxKPUs
      MinCapacity: 1
      ResourceId: !Sub https://${ScalerApi}.execute-api.${AWS::Region}.amazonaws.com/prod/scalableTargetDimensions/${KDAAppName}
      RoleARN: !Sub ${CustomApplicationAutoScalingServiceRole.Arn}
      ScalableDimension: 'custom-resource:ResourceType:Property'
      ServiceNamespace: custom-resource

  # For the target tracking policy below, we need a utilization metric
  # as described in https://github.com/aws/aws-auto-scaling-custom-resource
  # "The value of the metric must increase or decrease in inverse proportion to
  # the number of capacity units. That is, the value of the metric should decrease
  # when capacity increases and increase when capacity decreases."
  # For KDA, we need a custom metric that satisfies this criterion
  KDATrackingTrackingPolicy:
    Type : AWS::ApplicationAutoScaling::ScalingPolicy
    DependsOn: KDAScalableTarget
    Properties:
      PolicyName: KDATargetTracking
      PolicyType: TargetTrackingScaling
      ResourceId: !Sub https://${ScalerApi}.execute-api.${AWS::Region}.amazonaws.com/prod/scalableTargetDimensions/${KDAAppName}      
      ScalableDimension: "custom-resource:ResourceType:Property"
      ServiceNamespace: custom-resource
      TargetTrackingScalingPolicyConfiguration:
        TargetValue: 60000
        ScaleInCooldown: 60
        ScaleOutCooldown: 60
        CustomizedMetricSpecification:
          MetricName: millisBehindLatest
          Namespace: AWS/KinesisAnalytics
          Dimensions:
          - Name: Id
            Value: !Ref KinesisStreamName
          - Name: Application
            Value: !Ref KDAAppName
          - Name: Flow
            Value: Input
          Statistic: Average

Outputs:
  URL:
    Description: the URL
    Value: !Sub https://${ScalerApi}.execute-api.${AWS::Region}.amazonaws.com/prod/scalableTargetDimensions/${KDAAppName}
  CustomAASServiceRoleArn:
    Description: Custom AASService Role Arn
    Value: !Sub ${CustomApplicationAutoScalingServiceRole.Arn}