AWSTemplateFormatVersion: '2010-09-09'
Transform: AWS::Serverless-2016-10-31
Description: Serverless patterns - AWS WAF to Amazon API Gateway REST (uksb-1tthgi812) (tag:waf-apigw-rest)

Resources:
  # AWS WAF Access Control List limits each IP to 100 requestes per second
  MyWAFACL:
    Type: AWS::WAFv2::WebACL
    Properties:
      CustomResponseBodies: # Define a response from WAF
        CountryNotValid:
          Content: Country not allowed
          ContentType: TEXT_PLAIN
      DefaultAction:
        Block: 
          CustomResponse: # Choose a defined template to respond when blocked
            ResponseCode: "403"
            CustomResponseBodyKey: CountryNotValid
      Description: Application WAF
      Scope: REGIONAL
      VisibilityConfig:
        CloudWatchMetricsEnabled: true
        MetricName: AppRules
        SampledRequestsEnabled: true
      Rules:
        - Action:
            Allow: {} # Allow if conditions are met
          Name: AllowCountryList
          Priority: 0
          Statement:
            GeoMatchStatement:
              CountryCodes: # Requests from following countries are allowed (Add your country code to test)
                - US
          VisibilityConfig:
            CloudWatchMetricsEnabled: true
            MetricName: AllowCountryList
            SampledRequestsEnabled: true
  
  # Amazon API gateway REST API
  MyApi: 
    Type: AWS::Serverless::Api 
    Properties: 
      StageName: Prod
      EndpointConfiguration: REGIONAL
      TracingEnabled: true

  # Associate the WebACL with the API gateway
  MyWAFAssociation:
    Type: AWS::WAFv2::WebACLAssociation
    Properties: 
      ResourceArn: !Sub arn:aws:apigateway:${AWS::Region}::/restapis/${MyApi}/stages/${MyApi.Stage}
      WebACLArn: !GetAtt MyWAFACL.Arn

# Lambda function as an example micro-service behind the API Gateway REST endpoint
  MyLambdaFunction:
    Type: AWS::Serverless::Function
    Properties:
      CodeUri: src/
      Handler: app.lambda_handler
      Runtime: python3.9
      Events:
        RootGet:
          Type: Api
          Properties:
            Path: /
            Method: get
            RestApiId: !Ref MyApi

Outputs:
  # API endpoint for testing
  ApiEndpoint:
    Description: "API endpoint URL"
    Value: !Sub https://${MyApi}.execute-api.${AWS::Region}.amazonaws.com/Prod