AssessAI

This repository is a monorepo for an AI-powered interview practice platform. It contains a Next.js frontend, an Express + TypeScript backend, and a Python LiveKit-based voice agent.

Goals

• Run live voice interviews with an AI interviewer
• Capture transcripts and candidate code edits
• Generate structured evaluations after each interview

Contents

• frontend/ — Next.js app (UI, interview experience, results)
• backend/ — Express API (session management, evaluation service)
• agent/ — Python LiveKit agent (STT, LLM, TTS, evaluation delivery)

Prerequisites

• Node.js v18+ (frontend & backend)
• Python 3.10+ (agent)
• MongoDB (local or Atlas)
• Redis
• npm or yarn

Quick Setup

1. Install dependencies

# Backend
cd backend
npm install

# Frontend
cd frontend
npm install

# Agent (Python)
cd agent
pip install -r requirements.txt

2. Configure environment variables

• Backend: copy .env.example to .env and set:

  • MONGODB_URI (required)
  • REDIS_HOST, REDIS_PORT (if using Redis)
  • GROQ_API_KEY (LLM)
  • VAPI_PRIVATE_KEY, VAPI_PUBLIC_KEY, VAPI_AGENT_ID (optional)

• Frontend: copy .env.local.example to .env.local and set:

  • NEXT_PUBLIC_API_URL (default http://localhost:5000/api)

• Agent: set MONGODB_URI and optionally BACKEND_URL (default http://localhost:5000)

3. Start services

Start MongoDB and Redis as needed, then run backend and frontend in separate terminals:

# Backend
cd backend
npm run seed   # seeds sample questions
npm run dev

# Frontend
cd ../frontend
npm run dev

# Agent (in a new terminal)
cd ../agent
python -m venv .venv  # optional
.\.venv\Scripts\activate
pip install -r requirements.txt
python agent.py  dev# or use your start script

Using the included Windows batch files

This repository includes three helper batch files at the repo root for Windows users:

• install.bat — installs dependencies and creates the Python virtual environment for the agent.
• start.bat — launches the Python agent, backend, and frontend in separate command windows.
• stop.bat — kills Node and Python processes started by start.bat.

Run them from PowerShell in the repository root (D:\java_prog\Projects\Interview_platform):

# Install dependencies and create the agent venv
.\install.bat

# Start services (each service opens in its own window)
.\start.bat

# Stop services
.\stop.bat

Notes

• If you see permission errors, run PowerShell as Administrator. Most users don't need admin rights.
• install.bat will create agent\venv and install Python packages into it; if you already have a venv, it will reuse it.
• start.bat uses start to open new terminals — close those terminal windows to stop the individual service, or use stop.bat to stop all services.
• If the agent doesn't start, activate the venv manually and run the agent for debugging:

cd agent
.\venv\Scripts\activate
python agent.py

URLs

• Frontend: http://localhost:3000
• Backend API: http://localhost:5000
• Backend health: http://localhost:5000/health

Key Endpoints

• POST /api/sessions/start — create a session
• PUT /api/sessions/:sessionId/code — update candidate code snapshot
• POST /api/sessions/:sessionId/end — mark session ended (backend orchestrator)
• PUT /api/sessions/:sessionId/evaluation — agent POSTs evaluation (schema-compliant)
• GET /api/sessions/:sessionId/results — fetch results/evaluation

Agent & Evaluation Flow (High-level)

1. Frontend requests a new session and creates a LiveKit room.
2. The Python agent joins the room, processes audio (STT), uses an LLM to respond, and TTS to speak.
3. When interview ends (token [[END_INTERVIEW]] or user action), agent generates a structured evaluation and sends it to backend via /api/sessions/:sessionId/evaluation.
4. Backend persists evaluation and sets session status to evaluated.
5. Frontend polls /results and shows the evaluation once available.

Schema Notes

• Session.transcripts.role must be user or assistant (case-sensitive). Agent and backend sanitize roles before saving.
• evaluation is an object with arrays: strengths, improvements, edgeCases, nextSteps, and generatedAt (ISO datetime string).

Troubleshooting

• 500 when saving evaluation: ensure agent payload is schema-compliant (no extra types in transcripts.role) and includes evaluation.generatedAt to avoid conflicting update operators.
• MongoDB connection: verify MONGODB_URI and that MongoDB is running.
• CORS issues: set FRONTEND_URL in backend .env or configure CORS accordingly.

Testing the evaluation endpoint with curl

curl -X PUT http://localhost:5000/api/sessions/<sessionId>/evaluation \
   -H "Content-Type: application/json" \
   -d '{
      "status":"evaluated",
      "finalCode":"",
      "evaluation": {"strengths":["Good"], "improvements":[], "edgeCases":[], "nextSteps":[], "generatedAt":"2026-01-11T00:00:00Z"},
      "transcripts": [{"role":"user","content":"Hi"}]
   }'

Development Tips

• Use the browser devtools Network tab to inspect API calls.
• Check backend logs for Mongoose validation errors to see which field fails.

Contributing

• Fork, create a feature branch, run tests, and open a PR.

License

• MIT

Contact

• For questions, open an issue in this repo or message the maintainer.