Performance fix by adham667 · Pull Request #17 · acmASCIS/cf-cheating-detector

adham667 · 2025-10-27T23:58:41Z

Key Changes Summary

Authentication & Session Management

Use puppeteer-real-browser for interactive login and capture session data (cookies, localStorage, sessionStorage).
Restore saved session into regular puppeteer instances so we can spawn multiple pages/tabs for concurrent fetching.
Persist sessions to disk for reliability across restarts.
Note: this improves throughput and reliability, but we'll keep monitoring for edge cases.

Caching & Performance

Added file-based caching of submissions to avoid re-fetching on subsequent runs
Implemented retry logic for failed submission fetches

UI/UX Improvements

Added validation for matching percentage threshold input
Implemented Excel export functionality for results
Updated links with target="_blank" for better user experience

Code Quality & Edge Cases

Added edge case handling for empty string comparisons in code comparison
Commented out request timeout for better debugging

Dependencies & Configuration

Added dependencies for Excel generation and advanced Puppeteer capabilities
Updated axios and react-scripts to newer versions
Updated default API port from 3000 to 3030
Updated ESLint auto-fix setting to explicit mode in VS Code configuration
Expanded environment configuration with updated port and default values

Documentation

Expanded README from minimal to comprehensive setup and troubleshooting guide

File-by-File Changes

`src/schedule-jobs.ts`

Added typed error handling with failure callback support and result filtering

`src/index.ts`

Added EventEmitter configuration
Added Excel export capability
Commented out request timeout

`src/compare-code/compare-code.ts`

Added edge case handling for empty string comparisons

`src/cheating-detector.ts`

Major refactor: Switched to persistent browser sessions
Added file-based submission caching
Implemented retry logic and session management

`package.json`

Added dependencies for Excel generation and advanced Puppeteer capabilities

`client/src/InputForm.js`

Added validation for matching percentage threshold input

`client/src/CheatersTable.js`

Added target="_blank" to links for better UX

`client/src/App.js`

Updated default API port from 3000 to 3030

`client/package.json`

Updated axios and react-scripts to newer versions

`README.md`

Expanded from minimal to comprehensive setup and troubleshooting guide

`.vscode/settings.json`

Updated ESLint auto-fix setting to explicit mode

`.env.example`

Updated port and added default values for configuration parameters

… backend port to 3030 and added verifying feature on matching percentage in frontend

Copilot

Pull Request Overview

This PR implements a comprehensive performance optimization and robustness improvement for the Codeforces cheating detector, transitioning from cookie-based authentication to a persistent browser session approach with file-based submission caching.

Key changes:

Replaced cookie-based authentication with puppeteer-real-browser for better session management and anti-bot detection bypass
Implemented file-based caching of submissions to avoid re-fetching on subsequent runs
Added error handling and retry logic for failed submission fetches
Enhanced the UI with validation, Excel export functionality, and improved accessibility

Reviewed Changes

Copilot reviewed 12 out of 15 changed files in this pull request and generated 14 comments.

Show a summary per file

File	Description
src/schedule-jobs.ts	Added typed error handling with failure callback support and result filtering
src/index.ts	Added EventEmitter configuration, Excel export capability, and commented out request timeout
src/compare-code/compare-code.ts	Added edge case handling for empty string comparisons
src/cheating-detector.ts	Major refactor: switched to persistent browser sessions, added file-based submission caching, implemented retry logic, and session management
package.json	Added dependencies for Excel generation and advanced Puppeteer capabilities
client/src/InputForm.js	Added validation for matching percentage threshold input
client/src/CheatersTable.js	Added target="_blank" to links for better UX
client/src/App.js	Updated default API port from 3000 to 3030
client/package.json	Updated axios and react-scripts to newer versions
README.md	Expanded from minimal to comprehensive setup and troubleshooting guide
.vscode/settings.json	Updated ESLint auto-fix setting to explicit mode
.env.example	Updated port and added default values for configuration parameters

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Copilot · 2025-10-28T12:26:26Z

+        // Ensure result is of type T
+        return { status: 'fulfilled', value: result as T }; 


The type assertion as T is unnecessary since result is already inferred as type T from the job's return type. The comment on line 25 also mentions ensuring the type, but this is redundant. Remove both the comment and the type assertion.

Suggested change

// Ensure result is of type T

return { status: 'fulfilled', value: result as T };

return { status: 'fulfilled', value: result };

Copilot · 2025-10-28T12:26:26Z

+
+    batchResults.forEach((result, idx) => {
+      if (result.status === 'fulfilled' && result.value !== undefined) {
+        results.push(result.value); // Make sure value is not undefined


The comment 'Make sure value is not undefined' describes what the code is doing rather than why. Since the condition already checks for undefined, this comment is redundant and should be removed.

Suggested change

results.push(result.value); // Make sure value is not undefined

results.push(result.value);

Copilot · 2025-10-28T12:26:26Z


 app.post('/api/cheating-detection', async (req, res) => {
-  req.setTimeout(1000 * 60 * 5); // 5 Minutes
+  // req.setTimeout(1000 * 60 * 5); // 5 Minutes


This commented-out timeout configuration should either be removed entirely or replaced with a proper solution. Commented code creates confusion about whether this was intentionally disabled or forgotten.

Suggested change

// req.setTimeout(1000 * 60 * 5); // 5 Minutes

// Set a timeout for this request (default: 5 minutes, configurable via CHEATING_DETECTION_TIMEOUT_MS)

req.setTimeout(Number(process.env.CHEATING_DETECTION_TIMEOUT_MS) || 1000 * 60 * 5);

Copilot · 2025-10-28T12:26:27Z

+      XLSX.writeFile(workbook, 'possibleCheaters.xlsx');
+
      res.json(result);


The Excel file is being written to disk on the server but never sent to the client. This creates a file in the server's working directory without delivering it to the user who made the request. Either remove this line or implement proper file download by using XLSX.write() with type 'buffer' and sending it in the response.

Suggested change

XLSX.writeFile(workbook, 'possibleCheaters.xlsx');

res.json(result);

const excelBuffer = XLSX.write(workbook, { bookType: 'xlsx', type: 'buffer' });

res.setHeader('Content-Type', 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet');

res.setHeader('Content-Disposition', 'attachment; filename="possibleCheaters.xlsx"');

res.send(excelBuffer);

Copilot · 2025-10-28T12:26:27Z

 import check from 'string-similarity';

 export default function compareCode(a: string, b: string) {
+  if(a===''&&b===''){


Missing spaces around operators. Should be if (a === '' && b === '') { to follow standard JavaScript/TypeScript formatting conventions.

Suggested change

if(a===''&&b===''){

if (a === '' && b === '') {

Copilot · 2025-10-28T12:26:28Z

      )
      .map(submission => ({
-        id: submission.id,
+        id: submission.id.toString(), 


Trailing whitespace should be removed from this line.

Suggested change

id: submission.id.toString(),

id: submission.id.toString(),

Copilot · 2025-10-28T12:26:29Z

    matchingPercentageThreshold,
    setMatchingPercentageThreshold,
  ] = useState('');
+  const[error, setError] = useState('');


Missing space after const. Should be const [error, setError] = useState(''); to follow standard JavaScript formatting.

Suggested change

const[error, setError] = useState('');

const [error, setError] = useState('');

Copilot · 2025-10-28T12:26:29Z

+          <td><a href={cheatingCase.first.url} target="_blank">Code</a></td>
+          <td><a href={cheatingCase.second.url} target="_blank">Code</a></td>


Links with target=\"_blank\" should include rel=\"noopener noreferrer\" to prevent security vulnerabilities where the opened page can access the window.opener object.

Suggested change

<td><a href={cheatingCase.first.url} target="_blank">Code</a></td>

<td><a href={cheatingCase.second.url} target="_blank">Code</a></td>

<td><a href={cheatingCase.first.url} target="_blank" rel="noopener noreferrer">Code</a></td>

<td><a href={cheatingCase.second.url} target="_blank" rel="noopener noreferrer">Code</a></td>

Copilot · 2025-10-28T12:26:29Z

+### Starting Fresh on a New Contest
+**Important**: If this is not your first time running the detector and you're analyzing a new contest:
+
+1. Navigate to the `submissions.json` file in the cd-cheating-detector directoy


Corrected spelling of 'directoy' to 'directory'.

Suggested change

1. Navigate to the `submissions.json` file in the cd-cheating-detector directoy

1. Navigate to the `submissions.json` file in the cd-cheating-detector directory

Copilot · 2025-10-28T12:26:30Z

+### Starting Fresh on a New Contest
+**Important**: If this is not your first time running the detector and you're analyzing a new contest:
+
+1. Navigate to the `submissions.json` file in the cd-cheating-detector directoy


The repository name 'cd-cheating-detector' appears to be a typo. Based on the clone command on line 21, it should be 'cf-cheating-detector'.

Suggested change

1. Navigate to the `submissions.json` file in the cd-cheating-detector directoy

1. Navigate to the `submissions.json` file in the cf-cheating-detector directory

adham667 added 7 commits November 29, 2024 01:02

fixed verification issue using puppeteer real browser and changed the…

05a8492

… backend port to 3030 and added verifying feature on matching percentage in frontend

fix:forbidden error work around & making excel sheet as output

6648f8f

change delay times to make it more optimal and fixed empty code case

e623759

retry login approach

38d915e

files approach completed

5298a07

added guide to operate cheating detector

75c12d9

speed up detector by using puppeteer-real-browser only for login

3630ec3

bolesawny7 requested a review from Copilot October 28, 2025 12:23

Copilot AI reviewed Oct 28, 2025

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Performance fix#17

Performance fix#17
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adham667 commented Oct 27, 2025 •

edited

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		// Ensure result is of type T
		return { status: 'fulfilled', value: result as T };

	results.push(result.value); // Make sure value is not undefined
	results.push(result.value);

	// req.setTimeout(1000 * 60 * 5); // 5 Minutes
	// Set a timeout for this request (default: 5 minutes, configurable via CHEATING_DETECTION_TIMEOUT_MS)
	req.setTimeout(Number(process.env.CHEATING_DETECTION_TIMEOUT_MS) \|\| 1000 * 60 * 5);

		XLSX.writeFile(workbook, 'possibleCheaters.xlsx');

		res.json(result);

-      XLSX.writeFile(workbook, 'possibleCheaters.xlsx');
-      res.json(result);
+      const excelBuffer = XLSX.write(workbook, { bookType: 'xlsx', type: 'buffer' });
+      res.setHeader('Content-Type', 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet');
+      res.setHeader('Content-Disposition', 'attachment; filename="possibleCheaters.xlsx"');
+      res.send(excelBuffer);

	const[error, setError] = useState('');
	const [error, setError] = useState('');

		<td><a href={cheatingCase.first.url} target="_blank">Code</a></td>
		<td><a href={cheatingCase.second.url} target="_blank">Code</a></td>

	1. Navigate to the `submissions.json` file in the cd-cheating-detector directoy
	1. Navigate to the `submissions.json` file in the cd-cheating-detector directory

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adham667 commented Oct 27, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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Key Changes Summary

Authentication & Session Management

Caching & Performance

UI/UX Improvements

Code Quality & Edge Cases

Dependencies & Configuration

Documentation

File-by-File Changes

src/schedule-jobs.ts

src/index.ts

src/compare-code/compare-code.ts

src/cheating-detector.ts

package.json

client/src/InputForm.js

client/src/CheatersTable.js

client/src/App.js

client/package.json

README.md

.vscode/settings.json

.env.example

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adham667 commented Oct 27, 2025 •

edited

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`src/schedule-jobs.ts`

`src/index.ts`

`src/compare-code/compare-code.ts`

`src/cheating-detector.ts`

`package.json`

`client/src/InputForm.js`

`client/src/CheatersTable.js`

`client/src/App.js`

`client/package.json`

`README.md`

`.vscode/settings.json`

`.env.example`