💬 Real-Time Chat App

A real-time chat application built with Flutter (Frontend), FastAPI (Backend), and PostgreSQL (Database). Includes modern authentication, encrypted OTP/password flow, biometric login, and persistent chat rooms.

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🚀 Tech Stack

Layer	Technology
Frontend	Flutter
Backend	FastAPI (WebSocket)
Database	PostgreSQL

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📦 Dependencies

Flutter

dependencies:
  flutter:
  http:
  shared_preferences:
  web_socket_channel:
  intl:
  local_auth:

Backend (Python)

fastapi
uvicorn
sqlalchemy
psycopg2-binary
python-jose[cryptography]  # for JWT
smtplib       # for sending emails

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✅ Features

👤 Authentication

• JWT-based login + OTP verification (OTP & password hashed in DB)
• SharedPreferences for storing user ID and JWT token
• Password reset with OTP
• Biometric login with local_auth

💬 Chat System

• WebSocket-based real-time messaging
• Chat inside private or group rooms
• Create & join rooms
• Persistent messages (PostgreSQL)
• Auto-scroll to latest message
• Last message + timestamp shown on chat list screen

📂 State & Storage

• SharedPreferences to store:

  • current_user_id
  • (planned: username for better UX)

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📁 Project Structure

lib/
├── auth/
│   └── screens/
│       ├── auth_gate.dart
│       ├── forgot_password_screen.dart
│       ├── login_screen.dart
│       ├── otpscreen.dart
│       ├── register_screen.dart
│       └── reset_password_screen.dart
│
├── chat/
│   └── screens/
│       ├── chat_screen.dart
│       ├── chats.dart
│       ├── create_group_screen.dart
│       └── fetch_users.dart
│
├── services/
│   ├── api_service.dart
│   └── biometric_auth.dart
│
└── main.dart

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🛠️ Setup & Run

1. Backend (FastAPI)

cd backend
python -m venv venv
source venv/bin/activate
pip install -r requirements.txt
uvicorn main:app --reload

2. Frontend (Flutter)

flutter pub get
flutter run

Make sure your backend URL is correctly set in api_service.dart.

Example:

static const baseUrl = "http://<your-localhost-or-tunnel>";

3. PostgreSQL Setup

• Create DB & Tables (Users, Messages, Rooms, RoomMembers)
• SQLAlchemy handles schema (via Base.metadata.create_all)

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🔐 JWT Authentication

• Token is returned on successful OTP verification
• Stored in SharedPreferences
• Backend validates token on protected endpoints

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📱 Biometric Login

• Uses local_auth
• User prompted for fingerprint before accessing app if previously authenticated

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🧑‍💻 Author

Built as an individual project for internship learning.

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📃 License

MIT License - feel free to fork & customize.