Codify Backend

A backend server for code compilation and user management, supporting multiple programming languages and user CRUD operations.

Project Structure

.
├── app.js
├── bin/
│   └── www
├── install-languages.sh
├── models/
│   └── Users.js
├── package.json
├── public/
│   ├── images/
│   ├── javascripts/
│   └── stylesheets/
│       └── style.css
├── routes/
│   ├── index.js
│   └── users.js
└── views/
    ├── error.ejs
    └── index.ejs

Features

User Management: Create, read, update, and delete users (MongoDB).
Code Compilation API: Compile and execute code in Python, JavaScript, Java, C, C++, Go, Ruby, and PHP.
RESTful API: Endpoints for users and code compilation.
EJS Views: Basic web pages for home and error display.
Language Installer: Bash script to install all supported languages and configure environment.

Setup

Prerequisites

Node.js & npm
MongoDB (running at mongodb://localhost:27017/codify)
Bash (for running the install script)

Install Dependencies

npm install

Install Programming Languages

Run the provided script (Ubuntu/Debian):

chmod +x install-languages.sh
./install-languages.sh

Start the Server

npm start

The server runs on http://localhost:5000 by default.

API Endpoints

User Endpoints

GET /users
- List users with pagination and filtering.
- Query params: page, limit, name, email
- Returns: user list (without passwords), pagination info.
GET /user/:id
- Get a user by MongoDB ObjectId.
- Returns: user data (without password).
POST /user
- Create a new user.
- Body: All required user fields except createdAt.
- Returns: created user (without password).
- Handles duplicate email and validation errors.
PUT /user/:id
- Update user fields (except password).
- Body: Fields to update.
- Returns: updated user (without password).
- Handles duplicate email and validation errors.
DELETE /user/:id
- Delete a user by ID.
- Returns: deleted user ID.

Code Compilation Endpoints

POST /compile
- Compile and execute code in supported languages.
- Body: { code: "...", lang: "python|javascript|java|cpp|c|go|ruby|php", input: "..." }
- Returns: output, stderr, language, execution time, timestamp.
- Handles timeouts, compilation/runtime errors, and concurrency limits.
GET /compile/languages
- Lists supported languages with details (name, key, extensions, version, description).
GET /compile/stats
- Returns current compilation concurrency stats.

Pagination & Filtering Example

GET /users?page=2&limit=5&name=John&email=gmail

Contest Endpoints:

POST /api/contests - Create new contest
POST /api/contests/:id/register - Register participant
POST /api/contests/:id/status - Update contest status
GET /api/contests - Get all contests with pagination and filtering
GET /api/contests/:id - Get contest by ID
GET /api/contests/:id/leaderboard - Get contest leaderboard
GET /api/contests/status/:status - Get contests by status
GET /api/contests/filter/upcoming - Get upcoming contests
GET /api/contests/filter/active - Get active contests
GET /api/contests/:id/analytics - Get contest analytics
PUT /api/contests/:id - Update contest
DELETE /api/contests/:id - Delete contest (soft delete)

Problem Endpoints:

POST /api/problems - Create new problem
POST /api/problems/:id/test - Test solution against problem
GET /api/problems - Get all problems with pagination and filtering
GET /api/problems/:id - Get problem by ID
GET /api/problems/difficulty/:difficulty - Get problems by difficulty
GET /api/problems/tags/:tag - Get problems by tag
GET /api/problems/meta/tags - Get all unique tags
GET /api/problems/meta/statistics - Get problem statistics
PUT /api/problems/:id - Update problem
DELETE /api/problems/:id - Delete problem (soft delete)

Submission API Endpoints

Submit Code

POST /api/submissions/submit
- Body: { userId, problemId, contestId (optional), code, language }
- Returns: { success, message, submissionId, status, totalTestCases }
- Queues submission for evaluation and returns immediately.

Get Submission Status

GET /api/submissions/submission/:id
- Returns: Submission details, including test case results and evaluation status.

Get User Submissions

GET /api/submissions/user/:userId/submissions?page=1&limit=20&status=accepted&problemId=...&contestId=...
- Returns: Paginated list of submissions for a user (code omitted for privacy).

Get Problem Submissions

GET /api/submissions/problem/:problemId/submissions?page=1&limit=20&status=accepted
- Returns: Paginated list of public submissions for a problem.

Get Submission Statistics

GET /api/submissions/stats/submissions
- Returns:
  - total: Total submissions
  - accepted: Accepted submissions
  - acceptanceRate: Percentage accepted
  - languageDistribution: Submissions per language
  - statusDistribution: Submissions per status
  - activeEvaluations: Currently running evaluations
  - queuedEvaluations: Submissions waiting in queue

See models/Submission.js and routes/submissions.js for implementation details.

AutoSave API Endpoints

Save Code (Auto-Save)

POST /api/autosave/save
- Body: { userId, problemId, contestId (optional), code, language, metadata (optional) }
- Returns: { success, message, autoSaveId, lastSavedAt, codeLength }
- Creates or updates an auto-save for the user/problem/contest.

Get Restore Options

GET /api/autosave/restore-options/:userId/:problemId?contestId=...
- Returns:
  - hasAutoSave: Boolean
  - hasLatestSubmission: Boolean
  - autoSave: Latest auto-save info
  - latestSubmission: Latest submission info
  - recommendations: Array of suggestions (e.g., "continue from auto-save", "review last submission", "start fresh")

Load Auto-Saved Code

GET /api/autosave/load/:userId/:problemId?contestId=...
- Returns: { code, language, lastSavedAt, metadata }
- Loads the latest active auto-save for the user/problem/contest.

Load Latest Submission Code

GET /api/autosave/submission/:userId/:problemId?contestId=...
- Returns: { code, language, status, score, submittedAt, passedTestCases, totalTestCases }
- Loads the code from the user's latest submission for the problem.

Clear Auto-Saved Code

DELETE /api/autosave/clear/:userId/:problemId?contestId=...
- Returns: { success, message }
- Marks the auto-save as inactive (soft delete).

List User's Auto-Saves

GET /api/autosave/user/:userId?page=1&limit=20
- Returns: Paginated list of user's active auto-saves (without full code), with problem and contest titles.

Cleanup Old Auto-Saves

POST /api/autosave/cleanup
- Returns: { success, message, deletedCount }
- Removes old/inactive auto-saves (also runs daily via scheduled task).

Auto-Save Statistics

GET /api/autosave/stats/overview
- Returns:
  - total: Total auto-saves
  - active: Active auto-saves
  - recentlyActive: Auto-saves in last 24h
  - languageDistribution: Array of { language, count }

Scheduled Tasks

Old/inactive auto-saves are cleaned up daily at 2 AM via a scheduled cron job (utils/scheduledTasks.js).

See models/AutoSave.js and routes/autosave.js for implementation details.

Error Handling

All endpoints return success: false and an error message on failure.
Validation and duplicate errors are handled with appropriate HTTP status codes.

See routes/index.js for implementation details.

User Model

The User schema defines the structure for user documents in MongoDB:

Field	Type	Required	Unique	Description
username	String	Yes	Yes	Username for login
student_id	String	Yes	Yes	Unique student identifier
name	String	Yes	No	Full name
email	String	Yes	Yes	User email (must be unique)
password	String	Yes	No	Hashed password
department	String	Yes	No	Department name
batch	String	Yes	No	Batch/year
div	String	Yes	No	Division
createdAt	Date	No	No	Creation timestamp (auto-set)

See models/Users.js for implementation details.

Problem Model

The Problem schema defines coding problems for the platform, including metadata, test cases, and statistics.

Field	Type	Required	Description
title	String	Yes	Problem title (max 200 chars)
description	String	Yes	Detailed problem description (max 2000 chars)
difficulty	String (enum)	Yes	Difficulty level: `Easy`, `Medium`, or `Hard` (default: `Easy`)
testCases	Array of objects	Yes	List of test cases (`input`, `output` required for each)
createdBy	ObjectId (User ref)	Yes	Reference to the user who created the problem
isActive	Boolean	No	Problem visibility (default: `true`)
tags	Array of String	No	Tags for categorization (lowercase, trimmed)
totalSubmissions	Number	No	Total number of submissions (default: `0`)
successfulSubmissions	Number	No	Number of successful submissions (default: `0`)
createdAt	Date	No	Creation timestamp (auto-set)
updatedAt	Date	No	Last update timestamp (auto-set)
successRate (virtual)	String	No	Percentage of successful submissions (auto-calculated)

Submission Model

The Submission schema tracks user code submissions, their evaluation status, and test case results.

Field	Type	Required	Description
userId	ObjectId (User ref)	Yes	Reference to the submitting user
problemId	String/ObjectId	Yes	Problem ID (can be manual or DB problem)
contestId	ObjectId (Contest ref)	No	Reference to contest (null for standalone)
code	String	Yes	Submitted code (max 50KB)
language	String (enum)	Yes	Language: python, javascript, java, cpp, c, go, ruby, php
status	String (enum)	No	Submission status: pending, running, accepted, wrong_answer, etc.
score	Number	No	Score for this submission (default: 0)
totalTestCases	Number	Yes	Number of test cases
passedTestCases	Number	No	Number of passed test cases
testCaseResults	Array of objects	No	Results for each test case (see below)
compilationOutput	String	No	Compilation errors/warnings
executionTime	Number	No	Total execution time (ms)
memoryUsed	Number	No	Peak memory usage (bytes)
submittedAt	Date	No	Submission timestamp
evaluatedAt	Date	No	Evaluation timestamp
isPublic	Boolean	No	Public visibility (default: true)
successRate (virtual)	String	No	Percentage of passed test cases

TestCaseResult Structure:

Field	Type	Description
testCaseIndex	Number	Index of the test case
input	String	Input for the test case
expectedOutput	String	Expected output
actualOutput	String	Actual output from code
status	String	passed, failed, error, timeout
executionTime	Number	Execution time (ms)
memoryUsed	Number	Memory used (bytes)
errorMessage	String	Error message if any

Indexes:

{ userId, submittedAt }, { problemId, status }, { contestId, userId }, { status, submittedAt }

Virtuals & Methods:

successRate: Percentage of passed test cases
isAccepted(): Returns true if all test cases passed
calculateScore(maxScore): Calculates partial score

Test Case Structure

Each test case object contains:

input: String (required)
output: String (required)

Indexes

By difficulty and isActive
By createdBy
By createdAt (descending)

Virtuals

successRate: Returns the percentage of successful submissions.

See models/Problem.js

Contest Model

The Contest schema defines coding contests, including problems, participants, rules, analytics, and settings.

Field	Type	Required	Description
title	String	Yes	Contest title (max 200 chars)
description	String	Yes	Contest description (max 1000 chars)
startDate	Date	Yes	Contest start date/time
endDate	Date	Yes	Contest end date/time (must be after start)
duration	String	Yes	Duration (e.g., "2h")
status	String (enum)	No	`Upcoming`, `Active`, `Completed`, `Cancelled` (default: Upcoming)
rules	String	No	Contest rules (max 2000 chars, default: Standard contest rules)
maxParticipants	Number	Yes	Maximum allowed participants (default: 100)
problems	Array of ContestProblem	Yes	Problems in contest (at least one required)
participants	Array of ContestParticipant	No	Registered participants
participantSelection	String (enum)	No	Selection mode: manual/department/semester/division/batch
filterCriteria	Object	No	Criteria for participant filtering
totalPoints	Number	No	Total points for all problems
createdBy	ObjectId (User ref)	Yes	Reference to contest creator
createdAt	Date	No	Creation timestamp
updatedAt	Date	No	Last update timestamp
analytics	Object	No	Contest statistics (submissions, scores, participation rate)
settings	Object	No	Contest settings (late submission, leaderboard, freeze, etc.)
isActive	Boolean	No	Contest visibility (default: true)

AutoSave Feature

The AutoSave API allows users to automatically save, restore, and manage their in-progress code for problems and contests. This helps prevent code loss and enables smooth recovery of work.

AutoSave Model

Field	Type	Required	Description
userId	ObjectId (User ref)	Yes	Reference to the user
problemId	String/ObjectId	Yes	Problem ID (can be manual or DB problem)
contestId	ObjectId (Contest)	No	Contest ID if code is for a contest problem
code	String	Yes	Auto-saved code
language	String	Yes	Programming language (lowercase)
metadata	Object	No	Additional info (e.g., cursor position, theme)
isActive	Boolean	No	Whether this auto-save is active (default: true)
lastSavedAt	Date	No	Last save timestamp (auto-set)

Indexes:

{ userId, problemId, contestId, isActive }
{ lastSavedAt }

Virtuals & Methods:

isRecent(): Returns true if auto-save is recent (e.g., within 1 hour)
cleanupOld(): Static method to remove old/inactive auto-saves

ContestProblem Structure

problemId: ObjectId (Problem ref), required
title: String, required
difficulty: String (enum), required
category: String, required
points: Number, required
order: Number, optional
solvedCount: Number, optional
attemptCount: Number, optional

ContestParticipant Structure

userId: ObjectId (User ref), required
name, email, department, semester, division, batch: required
score, submissions: Number, default 0
problemsAttempted: Array of objects (problemId, attempts, solved, score, lastAttemptTime)
registrationTime, lastActivityTime: Date

FilterCriteria Structure

department, semester, division, batch: for filtering participants

Analytics

totalSubmissions, successfulSubmissions, averageScore, participationRate

Settings

allowLateSubmission, showLeaderboard, showLeaderboardDuringContest, freezeLeaderboard, freezeTime, allowViewProblemsBeforeStart, penaltyPerWrongSubmission

Virtuals

durationInHours: Contest duration in hours
successRate: Percentage of successful submissions
activeParticipantsCount: Number of participants with submissions

Methods

isCurrentlyActive(): Returns true if contest is active and within date range
getLeaderboard(): Returns sorted leaderboard with ranks
addParticipant(user): Adds a user as participant (with checks)
Static methods: findByStatus, findUpcoming, findActive

Indexes

By status, startDate, createdBy, participants.userId, createdAt, startDate, endDate

See models/Contest.js

File Descriptions

app.js: Main Express app, sets up middleware and routes.
bin/www: HTTP server bootstrap.
models/Users.js: Mongoose User schema.
routes/index.js: Main API routes (users, compile).
routes/users.js: Example users route.
views/: EJS templates for web pages.
public/stylesheets/style.css: Basic CSS.
install-languages.sh: Installs and configures all supported languages.

Load Test Results

A load test was performed using load_test.sh with 100 concurrent requests to the /compile endpoint.

Summary:

Total requests: 100
Target endpoint: http://localhost:5000/compile
Concurrency: 100

Status Code Distribution:

200 OK: 100 requests (all successfully processed)
429 Too Many Requests: 0 requests

Response Time Statistics:

Average: 853.2 ms
Minimum: 237 ms
Maximum: 1456 ms

Requests per second: 100

Notes:

The server successfully handled all requests without rate limiting, demonstrating improved concurrency handling.
Raw results are saved to /tmp/load_test_results.txt.

This demonstrates the backend’s ability to handle high concurrency and process all code compilation requests

Name		Name	Last commit message	Last commit date
Latest commit History 29 Commits
.vscode		.vscode
bin		bin
models		models
public/stylesheets		public/stylesheets
routes		routes
utils		utils
views		views
.gitignore		.gitignore
app.js		app.js
install-languages.sh		install-languages.sh
load_test.sh		load_test.sh
package-lock.json		package-lock.json
package.json		package.json
readme.md		readme.md
vercel.json		vercel.json

Bantipatel20/Codify-Backend

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Codify Backend

Project Structure

Features

Setup

Prerequisites

Install Dependencies

Install Programming Languages

Start the Server

API Endpoints

User Endpoints

Code Compilation Endpoints

Pagination & Filtering Example

Contest Endpoints:

Problem Endpoints:

Submission API Endpoints

Submit Code

Get Submission Status

Get User Submissions

Get Problem Submissions

Get Submission Statistics

AutoSave API Endpoints

Save Code (Auto-Save)

Get Restore Options

Load Auto-Saved Code

Load Latest Submission Code

Clear Auto-Saved Code

List User's Auto-Saves

Cleanup Old Auto-Saves

Auto-Save Statistics

Scheduled Tasks

Error Handling

User Model

Problem Model

Submission Model

Test Case Structure

Indexes

Virtuals

Contest Model

AutoSave Feature

AutoSave Model

ContestProblem Structure

ContestParticipant Structure

FilterCriteria Structure

Analytics

Settings

Virtuals

Methods

Indexes

File Descriptions

Load Test Results

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