AWSTemplateFormatVersion: '2010-09-09'
Transform: AWS::Serverless-2016-10-31
Description: Failover example
Globals:
  Function:
    Timeout: 3
    Tracing: Active
    Runtime: python3.9
    Handler: app.lambda_handler
    Architectures:
      - arm64
  Api:
    TracingEnabled: True

Parameters:
  DomainName:
    Type: String
    Description: Domian name for api
    MinLength: 5
  ZoneId:
    Type: String
    Description: Zone ID.
    MinLength: 5
  CertArn:
    Type: String
    Description: Certificate ARN
    MinLength: 5
  Priority:
    Type: String
    Description: PRIMARY or SECONDARY
    AllowedValues: ["PRIMARY", "SECONDARY"]

Resources:
  CustomDomain: # Creates the domain name
    Type: AWS::ApiGatewayV2::DomainName
    Properties: 
      DomainName: !Ref DomainName
      DomainNameConfigurations: 
        - EndpointType: REGIONAL
          CertificateArn: !Ref CertArn

  RestApiMapping: #Create a maooing to a REST API
    Type: AWS::ApiGatewayV2::ApiMapping
    Properties: 
      ApiId: !Ref RestApiGateway
      DomainName: !Ref DomainName
      Stage: Prod

  RestApiGateway: # Creates a REST API endpoint
    Type: AWS::Serverless::Api
    Properties:
      StageName: Prod
      EndpointConfiguration:
        Type: REGIONAL
  
  HelloWorldFunction:
    Type: AWS::Serverless::Function
    Properties:
      CodeUri: src/
      Events:
        Fetch:
          Type: Api
          Properties:
            RestApiId: !Ref RestApiGateway
            Path: /
            Method: get

  HealthCheck:
    Type: AWS::Route53::HealthCheck
    Properties: 
      HealthCheckConfig:
        EnableSNI: true
        FullyQualifiedDomainName: !Sub ${RestApiGateway}.execute-api.${AWS::Region}.amazonaws.com
        Type: HTTPS
        FailureThreshold: 5 ## Default is 3
        MeasureLatency: true ## Cannot be changed after creation
        ResourcePath: /Prod

  FailoverRecord:
    Type: AWS::Route53::RecordSet
    Properties:
      Failover: !Ref Priority
      Name: !Ref DomainName
      HostedZoneId: !Ref ZoneId
      SetIdentifier: !Sub ${AWS::Region}-failover
      HealthCheckId: !Ref HealthCheck
      TTL: 60
      AliasTarget:
        DNSName: !GetAtt CustomDomain.RegionalDomainName
        HostedZoneId: !GetAtt CustomDomain.RegionalHostedZoneId
      Type: A

Outputs:
  HelloWorldApi:
    Description: "API Gateway endpoint URL for Prod stage for Hello World function"
    Value: !Sub "https://${RestApiGateway}.execute-api.${AWS::Region}.amazonaws.com/Prod/"