properly decode ASCII payload from the lambda

Author: kylehoehns

src/bot/acceptReviewRequest.ts

@@ -48,7 +48,6 @@ export const acceptReviewRequest = {
           const review = await activeReviewRepo.getReviewByThreadIdOrFail(threadId);
           if (review.pdfIdentifier) {
             const url = await generateHackParserPresignedURL(review.pdfIdentifier);
-            log.e(url);
             blocks.push(textBlock(`HackerRank PDF: <${url}|${review.pdfIdentifier}>`));
 
             const codeKeys = await listHackParserCodeKeys(review.pdfIdentifier);

src/services/HackParserService.ts

@@ -24,10 +24,47 @@ async function invokeS3PresignedURLGeneratorLambda(
     expiration,
     requests,
   });
-  log.e('status code: ' + result.StatusCode);
-  log.e('payload: ' + result.Payload!.toString());
-  const response = JSON.parse(result.Payload!.toString());
-  return response;
+
+  if (!result.Payload) {
+    log.e('Error: No payload on lambda response');
+    return {};
+  }
+
+  let payload: unknown = result.Payload;
+
+  if (payload instanceof Uint8Array) {
+    payload = new TextDecoder().decode(payload);
+  }
+
+  if (typeof payload === 'string') {
+    try {
+      payload = JSON.parse(payload);
+    } catch (error) {
+      log.e('Error parsing payload as JSON:', error);
+      throw new Error('Invalid JSON response from Lambda');
+    }
+  }
+
+  if (Array.isArray(payload) && payload.every(num => typeof num === 'number')) {
+    const asciiArray = payload as number[];
+    const decoded = String.fromCharCode(...asciiArray);
+
+    log.e('Decoded Payload: ' + decoded);
+
+    try {
+      return JSON.parse(decoded);
+    } catch (error) {
+      log.e('Error parsing decoded payload:', error);
+      throw new Error('Invalid JSON structure after decoding');
+    }
+  }
+
+  if (typeof payload === 'object' && payload !== null) {
+    return payload as Record<string, string>;
+  }
+
+  log.e('Error: Unexpected payload format');
+  throw new Error('Unexpected payload format');
 }
 
 /**

src/services/__tests__/HackParserService.test.ts

@@ -30,9 +30,50 @@ describe('generateHackParserPresignedURL', () => {
     expect(result).toBeUndefined();
   });
 
-  it('should throw an error if the Lambda response is invalid', async () => {
+  it('should throw an error if the Lambda response is invalid JSON', async () => {
     (invokeLambda as jest.Mock).mockResolvedValue({ Payload: 'invalid_json' });
 
     await expect(generateHackParserPresignedURL('file3.txt')).rejects.toThrow();
   });
+
+  it('should decode ASCII-encoded payload and return a valid presigned URL', async () => {
+    const key = 'file4.txt';
+    const asciiPayload = JSON.stringify([
+      123, 34, 102, 105, 108, 101, 52, 46, 116, 120, 116, 34, 58, 32, 34, 104, 116, 116, 112, 115,
+      58, 47, 47, 109, 111, 99, 107, 45, 117, 114, 108, 45, 52, 34, 125,
+    ]);
+
+    (invokeLambda as jest.Mock).mockResolvedValue({ Payload: asciiPayload });
+
+    const result = await generateHackParserPresignedURL(key);
+
+    expect(result).toEqual('https://mock-url-4');
+  });
+
+  it('should handle Uint8ArrayBlobAdapter payload correctly', async () => {
+    const key = 'file5.txt';
+    const mockResponse = { 'file5.txt': 'https://mock-url-5' };
+    const uint8ArrayPayload = new TextEncoder().encode(JSON.stringify(mockResponse));
+
+    (invokeLambda as jest.Mock).mockResolvedValue({ Payload: uint8ArrayPayload });
+
+    const result = await generateHackParserPresignedURL(key);
+    expect(result).toEqual('https://mock-url-5');
+  });
+
+  it('should return undefined if Payload is undefined', async () => {
+    const key = 'file6.txt';
+    (invokeLambda as jest.Mock).mockResolvedValue({ Payload: undefined });
+
+    const result = await generateHackParserPresignedURL(key);
+    expect(result).toBeUndefined();
+  });
+
+  it('should handle empty Lambda response gracefully', async () => {
+    const key = 'file8.txt';
+    (invokeLambda as jest.Mock).mockResolvedValue({});
+
+    const result = await generateHackParserPresignedURL(key);
+    expect(result).toBeUndefined();
+  });
 });