fix: Pass complete SQS event to offline queue consumer (#1208)

Our current offline SQS event payload contains only the message body.
This is insufficient in applications where we need to inspect the
metadata of received messages, and leads to `TypeError` in the consumer
during testing.

This PR adds the missing fields to the event, trying to be relatively
accurate. For example, the source queue ARN includes the correct queue
name and AWS account ID. In terms of overall structure, an `SQSEvent`
type is helpfully provided in the `@types/aws-lambda` package, which
I've used to ensure our mocked event meets expectations.

Complete event samples can be found here for reference:
https://docs.aws.amazon.com/lambda/latest/dg/with-sqs.html

Jira: [ENG-3437]

[ENG-3437]: https://comicrelief.atlassian.net/browse/ENG-3437

Author: seb-cr

src/services/SQSService.ts

@@ -1,3 +1,5 @@
+import { createHash } from 'crypto';
+
 import {
   InvokeCommand,
   LambdaClient,
@@ -13,6 +15,7 @@ import {
 } from '@aws-sdk/client-sqs';
 import { NodeHttpHandler } from '@smithy/node-http-handler';
 import alai from 'alai';
+import { SQSEvent } from 'aws-lambda';
 import { v4 as uuid } from 'uuid';
 
 import DependencyAwareClass from '../core/DependencyAwareClass';
@@ -226,6 +229,8 @@ export default class SQSService<
 
   private $lambda?: LambdaClient;
 
+  private accountId?: string;
+
   constructor(di: DependencyInjection<TConfig>) {
     super(di);
 
@@ -241,7 +246,7 @@ export default class SQSService<
       REGION,
     } = process.env;
 
-    const accountId = (di.context.invokedFunctionArn && alai.parse(di.context))
+    this.accountId = (di.context.invokedFunctionArn && alai.parse(di.context))
       || AWS_ACCOUNT_ID;
 
     if (di.isOffline && !Object.values(SQS_OFFLINE_MODES).includes(offlineMode)) {
@@ -254,7 +259,7 @@ export default class SQSService<
       Object.entries(this.queues).map((
         ([key, queueName]) => [key, useLocalQueues
           ? `http://${offlineHost}:${offlinePort}/queue/${queueName}`
-          : `https://sqs.${REGION}.amazonaws.com/${accountId}/${queueName}`]
+          : `https://sqs.${REGION}.amazonaws.com/${this.accountId}/${queueName}`]
       )),
     ) as Record<QueueName<TConfig>, string>;
   }
@@ -487,24 +492,46 @@ export default class SQSService<
     }
 
     const prefix = this.di.getLambdaPrefix();
-    const FunctionName = shortOrLongFunctionName.startsWith(prefix)
+    const fullFunctionName = shortOrLongFunctionName.startsWith(prefix)
       ? shortOrLongFunctionName
       : `${prefix}${shortOrLongFunctionName}`;
 
-    const InvocationType = 'RequestResponse';
+    const body = messageParameters.MessageBody || '';
+    const region = process.env.AWS_REGION || 'eu-west-1';
+    const timestamp = Date.now().toString();
 
-    const Payload = JSON.stringify({
+    const event: SQSEvent = {
       Records: [
         {
-          body: messageParameters.MessageBody,
+          messageId: uuid(),
+          receiptHandle: 'test',
+          body,
+          attributes: {
+            ApproximateReceiveCount: '1',
+            SentTimestamp: timestamp,
+            SenderId: process.env.AWS_ACCESS_KEY_ID || '',
+            ApproximateFirstReceiveTimestamp: timestamp,
+          },
+          messageAttributes: {},
+          md5OfBody: createHash('md5').update(body).digest('hex'),
+          eventSource: 'aws:sqs',
+          eventSourceARN: `arn:aws:sqs:${region}:${this.accountId}:${this.queues[queue]}`,
+          awsRegion: region,
         },
       ],
-    });
+    };
+
+    if (messageParameters.MessageGroupId) {
+      const attributes = event.Records[0].attributes;
+      attributes.SequenceNumber = '0';
+      attributes.MessageGroupId = messageParameters.MessageGroupId;
+      attributes.MessageDeduplicationId = messageParameters.MessageDeduplicationId;
+    }
 
     await this.lambda.send(new InvokeCommand({
-      FunctionName,
-      InvocationType,
-      Payload,
+      FunctionName: fullFunctionName,
+      InvocationType: 'RequestResponse',
+      Payload: JSON.stringify(event),
     }));
   }