Skip to content

README.md

Latest commit

 

History

History
139 lines (98 loc) · 3.16 KB

README.md

File metadata and controls

139 lines (98 loc) · 3.16 KB
Raw

ProblemService

ProblemService is the catalog service for the platform. It stores LeetCode-style problem statements, difficulty, optional editorial content, and the test cases used later by the evaluation pipeline.

Responsibilities

  • Expose CRUD APIs for coding problems
  • Store problem metadata and test cases in MongoDB
  • Sanitize markdown-based description and editorial fields before persistence
  • Provide problem details to SubmissionService during submission intake

Tech Stack

  • Node.js
  • TypeScript
  • Express 5
  • MongoDB with Mongoose
  • Zod for request validation
  • Winston with daily rotating log files

Default Runtime Configuration

The service loads environment variables from .env.

Variable Default Purpose
PORT 3000 HTTP port
DB_URL mongodb://localhost:27017/lc_problem_db MongoDB connection string

Local Setup

  1. Install dependencies:
npm install
  1. Create .env:
PORT=3000
DB_URL=mongodb://localhost:27017/lc_problem_db
  1. Start the service:
npm run dev

The server connects to MongoDB on startup.

API Surface

Base path: /api/v1

Health

  • GET /ping
  • GET /ping/health

Problems

  • POST /problems
  • GET /problems
  • GET /problems/:id
  • PUT /problems/:id
  • DELETE /problems/:id
  • GET /problems/difficulty/:difficulty
  • GET /problems/search/:query

Problem Payload Shape

{
  "title": "Two Sum",
  "description": "Given an array of integers...",
  "difficulty": "easy",
  "editorial": "Use a hash map.",
  "testcases": [
    {
      "input": "4\n2 7 11 15\n9",
      "output": "0 1"
    }
  ]
}

Data Model

Each problem document contains:

  • title
  • description
  • difficulty: easy | medium | hard
  • editorial
  • testcases[]
  • createdAt
  • updatedAt

Indexes defined in code:

  • Unique index on title
  • Secondary index on difficulty

Request Flow

  1. Express receives JSON requests.
  2. A correlation ID is attached with AsyncLocalStorage.
  3. Zod validates request bodies or params where middleware is applied.
  4. ProblemService sanitizes markdown content.
  5. ProblemRepository persists and fetches data through Mongoose.
  6. Errors are returned through shared error middleware.

Markdown Sanitization

Before saving a problem:

  • Markdown is converted to HTML with marked
  • HTML is sanitized with sanitize-html
  • Sanitized HTML is converted back to markdown with turndown

This reduces the chance of persisting unsafe HTML in descriptions or editorials.

Logging

Logs go to:

  • Console
  • logs/%DATE%-app.log

Each log entry includes a correlation ID where available.

Current Implementation Notes

  • GET /problems/search/:query is registered with a path parameter, but the controller currently reads req.query.q. As written, searches will not use :query unless that controller is corrected.
  • POST /problems allows testcases to be optional at validation layer, but the Mongoose schema requires them. Invalid payloads will fail at persistence time rather than validation time.
  • PUT /problems/:id is not currently protected by a request-body validator.
  • /api/v2 exists but has no routes yet.