Refactor & add comments

integration-endpoint/incoming-message-processor/src/eventSettings.ts

@@ -12,7 +12,8 @@ interface EventSettings {
 }
 
 /**
- * A static object with keys corresponding to event types and values holding corresponding SQS Queues and JSON Schemas
+ * A static singleton object with keys corresponding to event types and values holding corresponding SQS Queues
+ * and JSON Schemas
  */
 const eventSettings: EventSettings = {
   PRODUCT_UPDATED: {

integration-endpoint/incoming-message-processor/src/lambda-handlers/receive-incoming-message.ts

@@ -6,16 +6,14 @@ import eventSettings from "../eventSettings";
 
 /**
  * A lambda handler for receiving any type of message.
- * If a message is successfully received, returns an empty 202 responce.
- * If while processing a message a known type of error was encountered, returns
+ * If a message is successfully received, returns an empty 202 response.
+ * If while processing a message a known type of error was encountered, returns 400 response with error description.
+ * If an unknown error was encountered, the Error is propagated and lambda function fallbacks on default AWS behaviour.
  */
 export const lambdaHandler = async (event: lambda.APIGatewayEvent): Promise<APIGatewayProxyResult> => {
   try {
     const { eventType, payload } = validateMessage(event.body);
-
-    if (eventSettings[eventType].runBeforeSendingToQueue) {
-      await eventSettings[eventType].runBeforeSendingToQueue!(payload);
-    }
+    eventSettings[eventType].runBeforeSendingToQueue?.call(null, payload);
     await sendMessageToQueue(eventType, payload);
 
     return {

integration-endpoint/incoming-message-processor/src/sendToQueue.ts

@@ -1,6 +1,10 @@
 import { SendMessageCommand, SQSClient } from "@aws-sdk/client-sqs";
 import eventSettings from "./eventSettings";
 
+/**
+ * Pushes a payload to a corresponding queue. The queue URL is depends on the EventType and is extracted from the
+ * eventSettings object.
+ */
 const sendMessageToQueue = async (eventType: string, payload: any) => {
   const sqs = new SQSClient({
     region: process.env.AWS_REGION,

integration-endpoint/incoming-message-processor/src/validateMessage.ts

@@ -8,6 +8,10 @@ interface Message {
   payload: any;
 }
 
+/**
+ * Checks that an incoming message is valid: it is of a known type and conforms to a corresponding JSON-schema.
+ * If there is a validation error, an error that is a subclass of ErrorWithPredefinedResponse is raised.
+ */
 export const validateMessage = (incomingMessage: string | null) => {
   let message: Message;
 
@@ -17,7 +21,7 @@ export const validateMessage = (incomingMessage: string | null) => {
     throw new ErrorBodyIsNotAJSON();
   }
 
-  if (!message || message == null) {
+  if (!message) {
     throw new ErrorBodyIsNotAJSON();
   }