DiagramAI Server

A powerful AI-driven API service that converts natural language descriptions into beautiful Mermaid.js diagrams using Google's Gemini AI.

🚀 Features

• Natural Language Processing: Convert plain text descriptions into professional diagrams
• Multiple Diagram Types: Support for flowcharts, sequence diagrams, class diagrams, state diagrams, Gantt charts, and ER diagrams
• AI-Powered: Leverages Google Gemini 2.5 Flash for intelligent diagram generation
• RESTful API: Simple and intuitive API endpoints
• TypeScript: Full TypeScript support for better development experience
• Production Ready: Built with security, logging, and CORS support

📋 Supported Diagram Types

• Flowcharts - Process flows and workflows
• Sequence Diagrams - System interactions and communications
• Class Diagrams - Object-oriented models and structures
• State Diagrams - State transitions and workflows
• Gantt Charts - Project timelines and schedules
• ER Diagrams - Database relationships and entities

🛠️ Tech Stack

• Runtime: Node.js
• Framework: Express.js
• Language: TypeScript
• AI Provider: Google Gemini (via LangChain)
• Package Manager: pnpm
• Security: Helmet.js, CORS
• Logging: Morgan
• Environment: dotenv

📦 Installation

Prerequisites

• Node.js (v16 or higher)
• pnpm (recommended) or npm
• Google Gemini API key

Setup

1. Clone the repository

   git clone https://github.com/brijeshdevio/DiagramAIAPI.git
   cd DiagramAIAPI

2. Install dependencies

   pnpm install

3. Environment Configuration

   cp .env.example .env

   Update .env with your configuration:

   PORT=3000
   NODE_ENV=development
   GEMINI_API_KEY=your_gemini_api_key_here

4. Start the development server

   pnpm dev

5. Build for production

   pnpm build
   pnpm start

🌐 API Endpoints

Generate Diagram

POST /api/diagram

Generate a Mermaid.js diagram from natural language description.

Request Body

{
  "prompt": "Show a user login flow with authentication and error handling"
}

Response

{
  "response": "flowchart TD\n    User([User]) --> Login[Enter Credentials]\n    Login --> Validate{Valid Credentials?}\n    Validate -->|Yes| Dashboard[Access Dashboard]\n    Validate -->|No| Error[Show Error Message]\n    Error --> Login",
  "prompt": "Show a user login flow with authentication and error handling"
}

Health Check

GET /

Returns API status and welcome message.

Response

{
  "message": "Welcome to the DiagramAI API"
}

💡 Usage Examples

Simple Process Flow

curl -X POST http://localhost:3000/api/diagram \
  -H "Content-Type: application/json" \
  -d '{
    "prompt": "Create a diagram showing how a user orders food online"
  }'

Database Design

curl -X POST http://localhost:3000/api/diagram \
  -H "Content-Type: application/json" \
  -d '{
    "prompt": "Design a database schema for a blog with users, posts, and comments"
  }'

System Architecture

curl -X POST http://localhost:3000/api/diagram \
  -H "Content-Type: application/json" \
  -d '{
    "prompt": "Show the interaction between frontend, API, and database in a web application"
  }'

⚙️ Configuration

Environment Variables

Variable	Description	Required	Default
PORT	Server port	No	3000
NODE_ENV	Environment mode	No	development
GEMINI_API_KEY	Google Gemini API key	Yes	-
SYSTEM_PROMPT	Custom AI system prompt	No	Built-in prompt

Custom System Prompt

You can customize the AI behavior by setting the SYSTEM_PROMPT environment variable. The default prompt is optimized for generating clean, valid Mermaid.js diagrams.

🔒 Security Features

• Helmet.js: Security headers for HTTP responses
• CORS: Cross-origin resource sharing configuration
• Environment Variables: Sensitive data protection
• Input Validation: Request body validation and sanitization

🚀 Deployment

Production Build

pnpm build
NODE_ENV=production pnpm start

Docker (Optional)

FROM node:18-alpine
WORKDIR /app
COPY package*.json ./
RUN npm install --production
COPY . .
RUN npm run build
EXPOSE 3000
CMD ["npm", "start"]

📝 Development

Available Scripts

• pnpm dev - Start development server with hot reload
• pnpm build - Build TypeScript to JavaScript
• pnpm start - Start production server
• pnpm test - Run tests (placeholder)

Code Style

The project uses TypeScript with strict type checking. Follow these guidelines:

• Use TypeScript interfaces for type definitions
• Implement proper error handling
• Follow REST API conventions
• Use meaningful variable and function names

🤝 Contributing

1. Fork the repository
2. Create your feature branch (git checkout -b feature/amazing-feature)
3. Commit your changes (git commit -m 'Add some amazing feature')
4. Push to the branch (git push origin feature/amazing-feature)
5. Open a Pull Request

📄 License

This project is licensed under the ISC License.

👨‍💻 Author

Brijesh - brijeshio@duck.com

🔗 Related Projects

• Mermaid.js - Diagram syntax and rendering
• LangChain - AI framework for LLM integration
• Google Gemini - AI model provider

---

Happy Diagramming! 🎨✨