AWSTemplateFormatVersion: '2010-09-09'
Transform: AWS::Serverless-2016-10-31
Description: Serverless patterns - AppSync to DynamoDB single-table

Resources:
  # Define a DynamoDB table
  DDBTable:
    Type: "AWS::DynamoDB::Table"
    Properties:
      BillingMode: PAY_PER_REQUEST
      AttributeDefinitions:
        - AttributeName: PK
          AttributeType: S
        - AttributeName: SK
          AttributeType: S
      KeySchema:
        - AttributeName: PK
          KeyType: HASH
        - AttributeName: SK
          KeyType: RANGE

  # AppSync Role
  DDBRole:
    Type: AWS::IAM::Role
    Properties:
      AssumeRolePolicyDocument:
        Version: 2012-10-17
        Statement:
          - Effect: Allow
            Action:
              - sts:AssumeRole
            Principal:
              Service:
                - appsync.amazonaws.com
      Policies:
        - PolicyName: DDBAccess
          PolicyDocument:
            Version: 2012-10-17
            Statement:
              - Effect: Allow
                Action:
                  - dynamodb:GetItem
                  - dynamodb:PutItem
                  - dynamodb:DeleteItem
                  - dynamodb:UpdateItem
                  - dynamodb:Query
                  - dynamodb:Scan
                Resource: !GetAtt DDBTable.Arn

  # AppSync API
  AppSyncApi:
    Type: "AWS::AppSync::GraphQLApi"
    Description: "The GraphQL API for the single table App"
    Properties:
      Name: SingleTableApi
      AuthenticationType: "AMAZON_COGNITO_USER_POOLS"
      XrayEnabled: true
      AuthenticationType: API_KEY

  # API Key for external access
  AppSyncApiKey:
    Type: AWS::AppSync::ApiKey
    Properties: 
      ApiId: !GetAtt AppSyncApi.ApiId

  # AppSync Schema
  AppSyncSchema:
    Type: "AWS::AppSync::GraphQLSchema"
    Properties:
      ApiId: !GetAtt AppSyncApi.ApiId
      Definition: |
        type Parent{
          PK: String!
          SK: String!
          children: [Child]
          data: String!
          type: String!
        }

        type Child {
          PK: String!
          SK: String!
          data: String!
          type: String!
        }

        type Mutation {
          createParentItem(
            PK: ID!,
            SK: String!,
            data: String!,
            type: String!
          ): Parent
        
          createChildItem(
            PK: ID!,
            SK: String!,
            data: String!,
            type: String!
          ): Child
        }
        
        type Query{
          getParentWithChildren(PK: ID!): Parent
        }

  # AppSync Data Source for DynamoDB
  DDBDataSource:
    Type: "AWS::AppSync::DataSource"
    Properties:
      Name: SingleTableDataSource
      ApiId: !GetAtt AppSyncApi.ApiId
      Description: "The Single Table AppSync Data Source"
      Type: AMAZON_DYNAMODB
      ServiceRoleArn: !GetAtt DDBRole.Arn
      DynamoDBConfig:
        TableName: !Ref DDBTable
        AwsRegion: !Sub ${AWS::Region}

  # Resolver: Qiery - Get parent with all child records
  GetParentAndChildResolver:
    Type: "AWS::AppSync::Resolver"
    DependsOn: AppSyncSchema
    Properties:
      ApiId: !GetAtt AppSyncApi.ApiId
      TypeName: Query
      FieldName: getParentWithChildren
      DataSourceName: !GetAtt DDBDataSource.Name
      RequestMappingTemplate: |
        {
          "version" : "2017-02-28",
          "operation" : "Query",
          "query" : {
            "expression": "PK = :pk",
            "expressionValues" : {
                ":pk" : $util.dynamodb.toDynamoDBJson($ctx.args.PK)
            }
          }
        }
      ResponseMappingTemplate: |
        #set($children = [])

        #foreach($item in $ctx.result.items)
          #if($item['type'] == "parent")
            #set($PK = $item['PK'])
            #set($SK = $item['SK'])
            #set($data = $item['data'])
            #set($type = $item['type'])
          #end
          #if($item['type'] == "child")
            $util.qr($children.add($item))
          #end
        #end
        
        {
          "PK": "${PK}",
            "SK": "${SK}",
            "children": $utils.toJson($children),
            "data": "${data}",
            "type": "${type}"
        }

  # Resolver: Mutation - Create parent
  CreateParentMutationResolver:
    Type: "AWS::AppSync::Resolver"
    DependsOn: AppSyncSchema
    Properties:
      ApiId: !GetAtt AppSyncApi.ApiId
      TypeName: Mutation
      FieldName: createParentItem
      DataSourceName: !GetAtt DDBDataSource.Name
      RequestMappingTemplate: |
        {
          "version": "2018-05-29",
          "operation": "PutItem",
          "key": {
            "PK": $util.dynamodb.toDynamoDBJson($ctx.args.PK),
            "SK": $util.dynamodb.toDynamoDBJson($ctx.args.SK)
          },
          "attributeValues": {
            "data": $util.dynamodb.toDynamoDBJson($ctx.args.data),
            "type": $util.dynamodb.toDynamoDBJson($ctx.args.type)
          }
        }
      ResponseMappingTemplate: "$util.toJson($ctx.result)"

  # Resolver: Mutation - Create child
  CreateChildMutationResolver:
    Type: "AWS::AppSync::Resolver"
    DependsOn: AppSyncSchema
    Properties:
      ApiId: !GetAtt AppSyncApi.ApiId
      TypeName: Mutation
      FieldName: createChildItem
      DataSourceName: !GetAtt DDBDataSource.Name
      RequestMappingTemplate: |
        {
          "version": "2018-05-29",
          "operation": "PutItem",
          "key": {
            "PK": $util.dynamodb.toDynamoDBJson($ctx.args.PK),
            "SK": $util.dynamodb.toDynamoDBJson($ctx.args.SK)
          },
          "attributeValues": {
            "data": $util.dynamodb.toDynamoDBJson($ctx.args.data),
            "type": $util.dynamodb.toDynamoDBJson($ctx.args.type)
          }
        }
      ResponseMappingTemplate: "$util.toJson($ctx.result)"