template.yaml

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

Resources:
  ValidatePaymentFunction:
    Type: 'AWS::Serverless::Function'
    Properties:
      Handler: validate_payment.lambda_handler
      Runtime: python3.12
      CodeUri: src/
      Policies:
        - AWSLambdaBasicExecutionRole

  ProcessPaymentFunction:
    Type: 'AWS::Serverless::Function'
    Properties:
      Handler: process_payment.lambda_handler
      Runtime: python3.12
      CodeUri: src/
      Policies: AWSLambdaBasicExecutionRole

  UpdatePaymentStatusFunction:
    Type: 'AWS::Serverless::Function'
    Properties:
      Handler: update_payment_status.lambda_handler
      Runtime: python3.12
      CodeUri: src/
      Policies: 
        - AWSLambdaBasicExecutionRole
        - Version: '2012-10-17'
          Statement:
            - Effect: Allow
              Action:
                - 'dynamodb:PutItem'
                - 'dynamodb:UpdateItem'
              Resource: !GetAtt OrdersTable.Arn

  SendNotificationFunction:
    Type: 'AWS::Serverless::Function'
    Properties:
      Handler: send_notification.lambda_handler
      Runtime: python3.12
      CodeUri: src/
      Policies: 
        - AWSLambdaBasicExecutionRole
        - Version: '2012-10-17'
          Statement:
            - Effect: Allow
              Action:
                - 'sns:List*'
                - 'sns:Publish'
              Resource: !Ref OrderNotificationsTopic  
          

  HandlePaymentErrorFunction:
    Type: 'AWS::Serverless::Function'
    Properties:
      Handler: handle_payment_error.lambda_handler
      Runtime: python3.12
      CodeUri: src/
      Policies:
        - AWSLambdaBasicExecutionRole

  OrdersTable:
    Type: 'AWS::DynamoDB::Table'
    Properties:
      TableName: Orders
      AttributeDefinitions:
        - AttributeName: PaymentId
          AttributeType: S
      KeySchema:
        - AttributeName: PaymentId
          KeyType: HASH
      ProvisionedThroughput:
        ReadCapacityUnits: 5
        WriteCapacityUnits: 5

  OrderNotificationsTopic:
    Type: 'AWS::SNS::Topic'
    Properties:
      TopicName: OrderNotifications

  PaymentProcessingStateMachine:
    Type: 'AWS::StepFunctions::StateMachine'
    Properties:
      DefinitionString: !Sub |
        {
          "Comment": "Payment processing workflow triggered via API Gateway",
          "StartAt": "ValidatePayment",
          "States": {
            "ValidatePayment": {
              "Type": "Task",
              "Resource": "${ValidatePaymentFunction.Arn}",
              "Next": "ProcessPayment"
            },
            "ProcessPayment": {
              "Type": "Task",
              "Resource": "${ProcessPaymentFunction.Arn}",
              "Retry": [
                {
                  "ErrorEquals": ["TransientError"],
                  "IntervalSeconds": 5,
                  "MaxAttempts": 3,
                  "BackoffRate": 2
                }
              ],
              "Catch": [
                {
                  "ErrorEquals": ["States.ALL"],
                  "Next": "HandlePaymentError"
                }
              ],
              "Next": "UpdatePaymentStatus"
            },
            "UpdatePaymentStatus": {
              "Type": "Task",
              "Resource": "${UpdatePaymentStatusFunction.Arn}",
              "Next": "SendNotification"
            },
            "SendNotification": {
              "Type": "Task",
              "Resource": "${SendNotificationFunction.Arn}",
              "End": true
            },
            "HandlePaymentError": {
              "Type": "Task",
              "Resource": "${HandlePaymentErrorFunction.Arn}",
              "Next": "UpdatePaymentStatus"
            }
          }
        }
      RoleArn: !GetAtt StepFunctionsExecutionRole.Arn

  StepFunctionsExecutionRole:
    Type: 'AWS::IAM::Role'
    Properties:
      AssumeRolePolicyDocument:
        Version: '2012-10-17'
        Statement:
          - Effect: Allow
            Principal:
              Service: 'states.amazonaws.com'
            Action: 'sts:AssumeRole'
      Policies:
        - PolicyName: StepFunctionsExecutionPolicy
          PolicyDocument:
            Version: '2012-10-17'
            Statement:
              - Effect: Allow
                Action:
                  - 'lambda:InvokeFunction'
                Resource:
                  - !GetAtt ValidatePaymentFunction.Arn
                  - !GetAtt ProcessPaymentFunction.Arn
                  - !GetAtt UpdatePaymentStatusFunction.Arn
                  - !GetAtt SendNotificationFunction.Arn
                  - !GetAtt HandlePaymentErrorFunction.Arn

  PaymentAPI:
    Type: AWS::Serverless::Api
    Properties:
      StageName: Prod
      DefinitionBody:
        swagger: '2.0'
        info:
          title: 'PaymentAPI'
          version: '1.0'
        paths:
          /startPayment:
            post:
              summary: 'Initiate Payment Processing'
              description: 'Initiate the payment processing workflow in Step Functions.'
              consumes:
                - 'application/json'
              produces:
                - 'application/json'
              parameters:
                - in: 'body'
                  name: 'body'
                  required: true
                  schema:
                    type: 'object'
                    properties:
                      payment_details:
                        type: 'object'
                        properties:
                          card_number:
                            type: 'string'
                            description: 'The card number for payment.'
                          expiry_date:
                            type: 'string'
                            description: 'The expiry date of the card (MM/YY format).'
                          cvv:
                            type: 'string'
                            description: 'The CVV code of the card.'
                          amount:
                            type: 'number'
                            description: 'The amount to be paid.'
              responses:
                '200':
                  description: 'Successful response'
                  schema:
                    type: 'object'
                    properties:
                      statusCode:
                        type: 'integer'
                      body:
                        type: 'string'
              x-amazon-apigateway-integration:
                type: 'AWS'
                httpMethod: 'POST'
                uri: !Sub 'arn:aws:apigateway:${AWS::Region}:states:action/StartExecution'
                credentials: !GetAtt PaymentAPIGWRole.Arn
                requestTemplates:
                  application/json: !Sub |
                    {
                      "stateMachineArn": "${PaymentProcessingStateMachine}",
                      "input": "$util.escapeJavaScript($input.json('$'))"
                    }
                responses:
                  default:
                    statusCode: '200'
                    responseTemplates:
                      application/json: |
                        {
                          "statusCode": 200,
                          "body": "You Payment is being processed, you will receive a notification by mail (To get the mail notification, you must create a subscrption for the 'OrderNotifications' SNS Topic)."
                        }

  PaymentAPIGWRole:
    Type: 'AWS::IAM::Role'
    Properties:
      AssumeRolePolicyDocument:
        Version: '2012-10-17'
        Statement:
          - Effect: Allow
            Principal:
              Service: 'apigateway.amazonaws.com'
            Action: 'sts:AssumeRole'
      Policies:
        - PolicyName: ApiGatewayInvokeStepFunctionsPolicy
          PolicyDocument:
            Version: '2012-10-17'
            Statement:
              - Effect: Allow
                Action: 'states:StartExecution'
                Resource: !Ref PaymentProcessingStateMachine

Outputs:
  ApiUrl:
    Description: "API Gateway endpoint URL for Prod stage"
    Value: !Sub "https://${PaymentAPI}.execute-api.${AWS::Region}.amazonaws.com/Prod/startPayment"