DiaryGarden Backend API

Backend API for DiaryGarden application built with NestJS, PostgreSQL, and Prisma, featuring AI-powered emotion analysis for diary entries.

🚀 Technologies

• Framework: NestJS 10
• Database: PostgreSQL with Prisma ORM 4.16.2
• Authentication: JWT (Access + Refresh tokens)
• Password Hashing: bcrypt
• AI Integration: FastAPI emotion analysis server
• Validation: class-validator, class-transformer

📋 Prerequisites

• Node.js (v20.16.0 or higher)
• PostgreSQL database
• FastAPI AI server running at localhost:8000/emotions

🛠️ Installation

1. Clone the repository

cd DiaryGarden_BE

2. Install dependencies

npm install

3. Configure environment variables

• Copy .env.example to .env
• Update DATABASE_URL with your PostgreSQL connection string
• Update JWT_SECRET with a secure random string

4. Generate Prisma client

npx prisma generate

5. Run database migrations

npx prisma migrate dev --name init

🏃 Running the App

# Development mode with hot-reload
npm run start:dev

# Production mode
npm run build
npm run start:prod

The API will be available at http://localhost:3000

📚 API Endpoints

Authentication

• POST /api/auth/register - Register new user (username, password, displayName)
• POST /api/auth/login - Login user (username, password)
• POST /api/auth/verify - Verify JWT token
• GET /api/auth/user - Get current user info (requires auth)
• POST /api/auth/refresh - Refresh access token

Diaries

• POST /api/diaries - Create diary entry (requires auth)

  • Body: { treeId, content }
  • Automatically analyzes emotions via AI and stores results

• GET /api/diaries/:id - Get single diary entry

  • Optional authentication

• GET /api/diaries - Get user's diary entries (requires auth)

  • Query params: limit (optional), lastDocId (optional for pagination)

🗄️ Database Schema

User

• id, uid, username, password (hashed), displayName, nickname
• Relations: RefreshTokens, Trees, Diaries

RefreshToken

• id, userId, token, expiresAt
• Relation: User

Tree

• id, userId, name
• Relations: User, Diaries
• Default tree created on user registration

Diary

• id, userId, treeId, content, emotionScores (JSON), dominantEmotion, writtenDate
• Relations: User, Tree

🤖 AI Integration

The API integrates with an external FastAPI server for emotion analysis:

• Endpoint: POST localhost:8000/emotions
• Request: { text: string, title?: string }
• Response: { emotionScores: Record<string, number>, dominantEmotion: string }
• Fallback: Returns neutral emotion if AI service is unavailable

🔐 Authentication Flow

1. User registers or logs in
2. Server returns AuthSession with token (access token) and refreshToken
3. Client stores both tokens
4. Client includes access token in Authorization: Bearer <token> header for protected routes
5. When access token expires, client uses refresh token to get a new access token

📝 Response Format

All API responses follow this format:

Success:

{
  "success": true,
  "data": { ... }
}

Error:

{
  "success": false,
  "message": "Error description"
}

Environment Variables

DATABASE_URL=postgresql://user:password@localhost:5432/diarygarden?schema=public
JWT_SECRET=your-super-secret-jwt-key-change-this-in-production
JWT_ACCESS_EXPIRATION=15m
JWT_REFRESH_EXPIRATION=7d
AI_SERVICE_URL=http://localhost:8000/emotions
PORT=3000
NODE_ENV=development
CORS_ORIGIN=http://localhost:3000,http://localhost:5000

next Steps

1. Set up your PostgreSQL database
2. Update .env file with your database connection string
3. Run migrations: npx prisma migrate dev
4. Ensure your FastAPI AI server is running
5. Start the development server: npm run start:dev
6. Test endpoints using your Flutter app or API client

📦 Project Structure

src/
├── auth/           # Authentication module (JWT, guards, strategies)
├── diary/          # Diary CRUD operations
├── ai/             # FastAPI integration for emotion analysis  
├── prisma/         # Prisma service (global database access)
├── common/         # Shared filters, interceptors, decorators
├── app.module.ts   # Root module
└── main.ts         # Application entry point

🔧 Development Notes

• Swagger documentation was removed for stability
• Uses classic NestJS module structure (all files in module directory)
• Prisma 4.16.2 used for better stability with NestJS 10
• Tree model implemented in backend with default tree creation on registration
• Cursor-based pagination implemented for diary listing

⚠️ Important

• Change JWT_SECRET in production
• Set up proper CORS origins
• Configure PostgreSQL connection string
• Ensure AI service is running before creating diaries