feat: add support for Step Functions (#668)

README.md

@@ -281,6 +281,8 @@ serverlessExpress({
     'AWS_SQS': '/sqs'
     'AWS_EVENTBRIDGE': '/eventbridge',
     'AWS_KINESIS_DATA_STREAM': '/kinesis',
+    'AWS_S3': '/s3',
+    'AWS_STEP_FUNCTIONS': '/step-functions',
   }
 })
 ```

src/configure.d.ts

@@ -3,7 +3,7 @@ import { Handler } from 'aws-lambda';
 import { Logger } from './logger';
 import Framework from './frameworks';
 
-type EventSources = 'AWS_SNS' | 'AWS_DYNAMODB' | 'AWS_EVENTBRIDGE' | 'AWS_SQS' | 'AWS_KINESIS_DATA_STREAM' | 'AWS_S3';
+type EventSources = 'AWS_SNS' | 'AWS_DYNAMODB' | 'AWS_EVENTBRIDGE' | 'AWS_SQS' | 'AWS_KINESIS_DATA_STREAM' | 'AWS_S3' | 'AWS_STEP_FUNCTIONS';
 
 interface EventSource {
   getRequest?: any; // TODO:

src/event-sources/aws/step-functions.js

@@ -0,0 +1,27 @@
+const getRequestValuesFromStepFunctions = ({ event }) => {
+  const method = 'POST'
+  const headers = { host: 'stepfunctions.amazonaws.com' }
+  const body = event
+
+  return {
+    method,
+    headers,
+    body
+  }
+}
+
+const getResponseToStepFunctions = ({
+  body,
+  isBase64Encoded = false
+}) => {
+  if (isBase64Encoded) {
+    throw new Error('base64 encoding is not supported')
+  }
+
+  return JSON.parse(body)
+}
+
+module.exports = {
+  getRequest: getRequestValuesFromStepFunctions,
+  getResponse: getResponseToStepFunctions
+}

src/event-sources/azure/http-function-runtime-v4.js

@@ -1,6 +1,6 @@
 const { getRequest, getResponse } = require('./http-function-runtime-v3')
 
 module.exports = {
-  getRequest: getRequest,
-  getResponse: getResponse
+  getRequest,
+  getResponse
 }

src/event-sources/index.js

@@ -10,6 +10,7 @@ const azureHttpFunctionV4EventSource = require('./azure/http-function-runtime-v4
 const awsEventBridgeEventSource = require('./aws/eventbridge')
 const awsKinesisEventSource = require('./aws/kinesis')
 const awsS3 = require('./aws/s3')
+const awsStepFunctionsEventSource = require('./aws/step-functions')
 
 function getEventSource ({ eventSourceName }) {
   switch (eventSourceName) {
@@ -37,6 +38,8 @@ function getEventSource ({ eventSourceName }) {
       return awsKinesisEventSource
     case 'AWS_S3':
       return awsS3
+    case 'AWS_STEP_FUNCTIONS':
+      return awsStepFunctionsEventSource
     default:
       throw new Error('Couldn\'t detect valid event source.')
   }

src/event-sources/utils.js

@@ -127,6 +127,10 @@ function getEventSourceNameBasedOnEvent ({
     return 'AWS_EVENTBRIDGE'
   }
 
+  if (event.context && event.context.Execution && event.context.State && event.context.StateMachine) {
+    return 'AWS_STEP_FUNCTIONS'
+  }
+
   throw new Error('Unable to determine event source based on event.')
 }