Letter Generator

Powered by LetterGeneratorAI

A professional Express middleware for generating high-quality letters for various purposes using OpenAI's GPT-4o model. This package allows you to quickly create business, personal, formal, creative, and academic letters with customizable tones.

Features

• 🚀 Generate 5 types of letters (business, personal, formal, creative, academic)
• 🎭 16 different tones to choose from (professional, friendly, formal, etc.)
• 📏 Adjustable letter length (short, medium, long)
• 🔒 Built-in rate limiting for API protection
• ✅ Input validation with clear error messages
• 📚 Well-documented API for easy integration

Installation

npm install letter-generator-ai

Quick Start

const express = require('express');
const createLetterGenerator = require('letter-generator-ai');

const app = express();
const OPENAI_API_KEY = 'your-openai-api-key';

// Mount the letter generator middleware
app.use('/api/letters', createLetterGenerator(OPENAI_API_KEY, {
  maxRequestsPerHour: 20, // Optional: default is 10
  debug: false // Optional: enable debug logging
}));

app.listen(3000, () => {
  console.log('Letter generator server running on port 3000');
});

API Endpoints

GET /api/letters/options

Returns available letter types, contexts, and tones.

Example Response

{
  "letterTypes": {
    "business": {
      "description": "Professional business correspondence",
      "contexts": ["job application", "resignation", "proposal", "meeting request", "..."]
    },
    "personal": { "..." },
    "formal": { "..." },
    "creative": { "..." },
    "academic": { "..." }
  },
  "tones": ["professional", "friendly", "formal", "casual", "..."]
}

POST /api/letters/generate

Generates a letter based on the provided parameters.

Request Body

{
  "type": "business",
  "context": "job application",
  "tone": "professional",
  "sender": "John Doe",
  "recipient": "HR Department, ABC Company",
  "details": "Applying for Senior Developer position with 5 years of experience in React and Node.js",
  "length": "medium"
}

Parameters

| Parameter | Type | Required | Description | |------------|--------|----------|-----------------------------------------------| | type | string | Yes | Letter type (business, personal, etc.) | | context | string | Yes | Context for the letter (job application, etc.) | | tone | string | Yes | Tone of the letter (professional, friendly, etc.) | | sender | string | Yes | Name/details of the sender | | recipient | string | Yes | Name/details of the recipient | | details | string | No | Additional details for letter content | | length | string | No | Length of letter (short, medium, long) |

Example Response

{
  "success": true,
  "letter": "Dear HR Department, ABC Company,\n\nI am writing to express my interest in the Senior Developer position...",
  "metadata": {
    "type": "business",
    "context": "job application",
    "tone": "professional",
    "length": "medium",
    "timestamp": "2023-11-17T12:34:56.789Z"
  }
}

Error Handling

The API returns clear error messages with appropriate HTTP status codes.

{
  "success": false,
  "error": "Invalid letter type. Available types: business, personal, formal, creative, academic",
  "code": "VALIDATION_ERROR",
  "timestamp": "2023-11-17T12:34:56.789Z"
}

Configuration Options

When initializing the middleware, you can provide the following options:

| Option | Type | Default | Description | |---------------------|---------|---------|-------------------------------------------| | maxRequestsPerHour | number | 10 | Maximum requests per hour per IP address | | debug | boolean | false | Enable debug logging |

Examples

Creating a Business Proposal Letter

const axios = require('axios');

async function generateBusinessProposal() {
  try {
    const response = await axios.post('http://localhost:3000/api/letters/generate', {
      type: 'business',
      context: 'proposal',
      tone: 'professional',
      sender: 'ABC Technology Solutions',
      recipient: 'XYZ Corporation',
      details: 'Proposal for implementing a new CRM system with a budget of $50,000',
      length: 'long'
    });
    
    console.log(response.data.letter);
  } catch (error) {
    console.error('Error:', error.response?.data || error.message);
  }
}

generateBusinessProposal();

Creating a Personal Thank You Letter

const axios = require('axios');

async function generateThankYouLetter() {
  try {
    const response = await axios.post('http://localhost:3000/api/letters/generate', {
      type: 'personal',
      context: 'thank you',
      tone: 'sincere',
      sender: 'Sarah',
      recipient: 'Aunt Martha',
      details: 'Thanking for the birthday gift - a beautiful handmade quilt',
      length: 'short'
    });
    
    console.log(response.data.letter);
  } catch (error) {
    console.error('Error:', error.response?.data || error.message);
  }
}

generateThankYouLetter();

License

MIT

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

Security

This package requires a valid OpenAI API key. Make sure to keep your API key secure and never expose it in your client-side code.