AWSTemplateFormatVersion: '2010-09-09'
Transform: AWS::Serverless-2016-10-31
Description: Amazon API Gateway header based versioning

Metadata: 
  AWS::CloudFormation::Interface: 
    ParameterGroups: 
      - 
        Label: 
          default: "HTTP Header Configuration"
        Parameters: 
          - ApiVersionHeaderName
      - 
        Label: 
          default: "Sample APIs Configuration"
        Parameters: 
          - SampleApiVersionMappingV1
          - SampleApiVersionMappingV2
    ParameterLabels: 
      ApiVersionHeaderName: 
        default: "API version HTTP header name"
      SampleApiVersionMappingV1: 
        default: "Sample API v.1 HTTP header value"
      SampleApiVersionMappingV2: 
        default: "Sample API v.2 HTTP header value"

Parameters:
  ApiVersionHeaderName:
    Description: The name of the HTTP header contains desired API Version.
    Type: String
    Default: Accept
  SampleApiVersionMappingV1:
    Description: The value of the HTTP header to specify API v.1.
    Type: String
    Default: application/vnd.example.v1+json
  SampleApiVersionMappingV2:
    Description: The value of the HTTP header to specify API v.2.
    Type: String
    Default: application/vnd.example.v2+json

Globals:
  Function:
    Timeout: 10

Resources:
  HelloWorldFunctionV1:
    Type: AWS::Serverless::Function
    Properties:
      CodeUri: hello-world/
      Handler: app.lambdaHandler
      Runtime: nodejs14.x
      Environment:
        Variables:
          API_VER: v.1
      Events:
        HelloWorld:
          Type: Api
          Properties:
            Path: /v1/hello
            Method: get 
  
  HelloWorldFunctionV2:
    Type: AWS::Serverless::Function
    Properties:
      CodeUri: hello-world/
      Handler: app.lambdaHandler
      Runtime: nodejs14.x
      Environment:
        Variables:
          API_VER: v.2
      Events:
        HelloWorld:
          Type: Api
          Properties:
            Path: /v2/hello
            Method: get

  CFDistribution:
    Type: AWS::CloudFront::Distribution
    Properties:
      DistributionConfig:
        Enabled: 'true'
        Origins:
          -
            Id: MyOrigin
            DomainName: aws.amazon.com
            CustomOriginConfig:
              HTTPPort: 80
              HTTPSPort: 443
              OriginProtocolPolicy: https-only
            OriginCustomHeaders:
              - 
                HeaderName: custom-apigw-header-name
                HeaderValue: !Ref ApiVersionHeaderName
              - 
                HeaderName: custom-apigw-table-name
                HeaderValue: !Ref ApiVersionsMappingDynamoDBTable
        DefaultCacheBehavior:
          AllowedMethods:
            - GET
            - HEAD
            - OPTIONS
            - PUT
            - PATCH
            - POST
            - DELETE
          DefaultTTL: 0
          ForwardedValues:
            Cookies:
              Forward: none
            QueryString: true
            Headers:
              - '*'
          TargetOriginId: MyOrigin
          LambdaFunctionAssociations:
            - 
              EventType: origin-request
              LambdaFunctionARN: !Ref LambdaEdgeFunctionRouteApi.Version
          ViewerProtocolPolicy: redirect-to-https

  LambdaEdgeFunctionRouteApi:
    Type: AWS::Serverless::Function
    DeletionPolicy: Retain
    Properties:
      CodeUri: edge-origin-request/
      Handler: app.lambdaHandler
      Runtime: nodejs14.x
      AutoPublishAlias: live
      Role: !GetAtt LambdaEdgeFunctionRouteApiRole.Arn
  
  LambdaEdgeFunctionRouteApiRole:
    Type: "AWS::IAM::Role"
    Properties:
        Path: "/"
        ManagedPolicyArns:
            - "arn:aws:iam::aws:policy/service-role/AWSLambdaBasicExecutionRole"
        Policies:
          - PolicyName: dyanmodb_access_policy
            PolicyDocument:
              Version: 2012-10-17
              Statement: 
                - Effect: Allow
                  Action: 
                    - dynamodb:BatchGet*
                    - dynamodb:DescribeTable
                    - dynamodb:Get*
                    - dynamodb:Query
                    - dynamodb:Scan
                  Resource: !Sub
                    - arn:aws:dynamodb:*:*:table/${DynamoDBTableName}
                    - { DynamoDBTableName: !Ref ApiVersionsMappingDynamoDBTable }
        AssumeRolePolicyDocument:
          Version: "2012-10-17"
          Statement:
            -
              Sid: "AllowLambdaServiceToAssumeRole"
              Effect: "Allow"
              Action: 
                - "sts:AssumeRole"
              Principal:
                Service: 
                  - "lambda.amazonaws.com"
                  - "edgelambda.amazonaws.com"

  # Global Table to store API Gateway version mappings 
  ApiVersionsMappingDynamoDBTable:
    Type: AWS::DynamoDB::GlobalTable
    Properties:
      BillingMode: PAY_PER_REQUEST
      Replicas:
        - Region: !Ref AWS::Region
      AttributeDefinitions: 
        - 
          AttributeName: "hk"
          AttributeType: "S"
      KeySchema: 
        - 
          AttributeName: "hk"
          KeyType: "HASH"

  # Lambda function for adding API version mappings to DDB table
  InitApiMappingsTableFunction:
    Type: AWS::Serverless::Function
    Properties:
      CodeUri: init-db/
      Handler: app.lambdaHandler
      Runtime: nodejs14.x
      Timeout: 60
      MemorySize: 128
      Environment:
        Variables:
          DynamoDBTableName: !Ref ApiVersionsMappingDynamoDBTable
          ApiHeaderV1: !Ref SampleApiVersionMappingV1
          ApiDomainV1: !Sub "${ServerlessRestApi}.execute-api.${AWS::Region}.amazonaws.com"
          ApiPathV1: /Prod/v1
          ApiHeaderV2: !Ref SampleApiVersionMappingV2
          ApiDomainV2: !Sub "${ServerlessRestApi}.execute-api.${AWS::Region}.amazonaws.com"
          ApiPathV2: /Prod/v2
      Policies:
        - DynamoDBCrudPolicy:
            TableName: !Ref ApiVersionsMappingDynamoDBTable                 

  # Triggers Lambda function after stack creation to add API version mappings to DDB table
  InitApiMappingsTableCustom:
    Type: Custom::InitApiMappingsTable
    Properties:
      ServiceToken: !GetAtt InitApiMappingsTableFunction.Arn
    DependsOn:
    - HelloWorldFunctionV1
    - HelloWorldFunctionV2
    - ApiVersionsMappingDynamoDBTable
  
Outputs:
  HelloWorldApiV1:
    Description: "API Gateway endpoint URL for Prod stage for Hello World function version 1"
    Value: !Sub "https://${ServerlessRestApi}.execute-api.${AWS::Region}.amazonaws.com/Prod/v1/hello/"
  
  HelloWorldApiV2:
    Description: "API Gateway endpoint URL for Prod stage for Hello World function version 2"
    Value: !Sub "https://${ServerlessRestApi}.execute-api.${AWS::Region}.amazonaws.com/Prod/v2/hello/"
  
  LambdaEdgeFunctionRouteApiVersion: 
    Description: Lambda@Edge Route API Function ARN with Version
    Value: !Ref LambdaEdgeFunctionRouteApi.Version

  CFDistribution: 
    Description: Cloudfront Distribution Domain Name
    Value: !GetAtt CFDistribution.DomainName

  DynamoDBTableName: 
    Description: Api Versions Mapping DynamoDB Table Name
    Value: !Ref ApiVersionsMappingDynamoDBTable