Updated Step Function definition that uses JSONata variables and functions to perform data validations rather than lambdas

README.md

Based on the following blog post:

https://aws.amazon.com/blogs/compute/simplifying-developer-experience-with-variables-and-jsonata-in-aws-step-functions/

https://github.com/aws-samples/serverless-account-signup-service/tree/jsonata-variables

check_spot_availability_lambda.py

import json


def lambda_handler(event, context):
    print(event)
    registration_info = event['registration_info']

    # Placeholder for actual availability check logic
    spots_available = 20  # This should be dynamically determined, not hardcoded

    if spots_available <= 0:
        return {
            'statusCode': 400,
            'body': json.dumps('No spots available in the daycare.')
        }

    # If spots are available, return the registration_info without changes
    return {
        'statusCode': 200,
        'body': json.dumps(registration_info)
    }

sample_input.json

{
  "registration_info": {
    "child": {
      "firstName": "Mohamed",
      "lastName": "Diallo",
      "dateOfBirth": "2022-07-01"
    },
    "parents": {
      "mother": {
        "firstName": "Aicha",
        "lastName": "Cisse",
        "email": "aicha.cisse@example.com",
        "phone": "123-456-7890"
      },
      "father": {
        "firstName": "Ibrahim",
        "lastName": "Diallo",
        "email": "ibrahim.diallo@example.com",
        "phone": "098-765-4321"
      }
    },
    "daysOfWeek": [
      "Monday",
      "Tuesday",
      "Wednesday",
      "Thursday",
      "Friday"
    ],
    "specialInstructions": "Mohamed has a peanut allergy."
  }
}

state_language.json

{
  "Comment": "A simple AWS Step Functions state machine that automates a daycare registration workflow that uses JSONata to replace lambda validation functions",
  "StartAt": "Check Information",
  "States": {
    "Check Information": {
      "Type": "Parallel",
      "Branches": [
        {
          "StartAt": "Check Identity",
          "States": {
            "Check Identity": {
              "Type": "Pass",
              "End": true,
              "Output": {
                "isInformationValid": "{% ($count($states.input.registration_info.daysOfWeek) > 0 and $not($states.input.registration_info.daysOfWeek = null)) and $not($states.input.registration_info.child = null) and $not($states.input.registration_info.parents = null) %}"
              }
            }
          }
        },
        {
          "StartAt": "Check Age Range",
          "States": {
            "Check Age Range": {
              "Type": "Pass",
              "End": true,
              "Output": {
                "Age": "{% $number($now('[Y0001]')) - $number($fromMillis($toMillis($states.input.registration_info.child.dateOfBirth), '[Y0001]')) %}"
              }
            }
          }
        }
      ],
      "Assign": {
        "inputPayload": "{% $states.context.Execution.Input %}",
        "Age": "{% $states.result.Age %}",
        "isPayloadValid": "{% $states.result.isInformationValid %}",
        "isValidAge": "{% $number($states.result.Age) >= 2 and $number($states.result.Age) < 5 %}"
      },
      "Next": "Information Check Result"
    },
    "Information Check Result": {
      "Type": "Choice",
      "Choices": [
        {
          "Condition": "{% $isPayloadValid and $isValidAge %}",
          "Next": "Check Spots Availability"
        },
        {
          "Condition": "{% $isValidAge = false %}",
          "Next": "Age Invalid"
        }
      ],
      "Default": "Notify Missing Info"
    },
    "Age Invalid": {
      "Type": "Fail",
      "Error": "InvalidAge",
      "Cause": "The age must be greater than 2 but less than 5."
    },
    "Notify Missing Info": {
      "Type": "Fail",
      "Error": "InformationIncomplete",
      "Cause": "The parent did not provide complete information."
    },
    "Check Spots Availability": {
      "Type": "Task",
      "Resource": "arn:aws:states:::lambda:invoke",
      "Output": "{% $states.result.Payload %}",
      "Arguments": {
        "FunctionName": "arn:aws:lambda:eu-west-2:XXXX:function:CheckSpotAvailable:$LATEST",
        "Payload": "{% $inputPayload %}"
      },
      "Assign": {
        "checkStatusCode": "{% $states.result.Payload.statusCode %}"
      },
      "Next": "Spot Availability Result"
    },
    "Spot Availability Result": {
      "Type": "Choice",
      "Choices": [
        {
          "Condition": "{% $checkStatusCode = 200 %}",
          "Next": "Add Registration"
        },
        {
          "Condition": "{% $checkStatusCode = 400 %}",
          "Next": "Notify No Spots"
        }
      ]
    },
    "Notify No Spots": {
      "Type": "Fail",
      "Error": "NoSpots",
      "Cause": "There are no spots available."
    },
    "Add Registration": {
      "Type": "Task",
      "Resource": "arn:aws:states:::dynamodb:putItem",
      "Arguments": {
        "TableName": "arn:aws:dynamodb:eu-west-2:XXXX:table/TestRegistration",
        "Item": {
          "PK": {
            "S": "{% $uuid() %}"
          },
          "SK": {
            "S": "name"
          },
          "email": {
            "S": "{% $inputPayload.registration_info.parents.mother.email %}"
          },
          "name": {
            "S": "{% $inputPayload.registration_info.child.firstName & ' ' & $inputPayload.registration_info.child.lastName  %}"
          },
          "dateOfBirth": {
            "S": "{% $inputPayload.registration_info.child.dateOfBirth %}"
          },
          "age": {
            "N": "{% $string($Age) %}"
          },
          "specialInstructions": {
            "S": "{% $inputPayload.registration_info.specialInstructions %}"
          },
          "timestamp": {
            "S": "{% $now() %}"
          }
        }
      },
      "Next": "Confirm Registration"
    },
    "Confirm Registration": {
      "Type": "Succeed",
      "Comment": "Registration succeeded!"
    }
  },
  "QueryLanguage": "JSONata"
}