# Advanced Express.js PDF Generation API

This example demonstrates how to build a comprehensive RESTful API for PDF generation using `pdf-reporter` with Express.js.

## Features

- 🚀 **RESTful API Design** - Clean, intuitive endpoints
- 📊 **Advanced PDF Generation** - Multiple templates and customization options
- ⚡ **Async Processing** - Background job processing for large datasets
- 📈 **Performance Monitoring** - Built-in metrics and estimation
- 🔒 **Rate Limiting** - Protection against abuse
- 🛡️ **Error Handling** - Comprehensive error handling and validation
- 📁 **File Operations** - PDF merging, splitting, and page extraction
- 🔍 **PDF Analysis** - Analyze PDF properties and metadata
- 📊 **Health Checks** - Service monitoring and diagnostics

## Quick Start

### Installation

```bash
cd examples/express-app
npm install
```

### Start the Server

```bash
# Development mode with auto-reload
npm run dev

# Production mode
npm start
```

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

## API Endpoints

### Core Endpoints

| Method | Endpoint | Description |
|--------|----------|-------------|
| `GET` | `/` | API information and documentation |
| `GET` | `/api/health` | Detailed health check |
| `GET` | `/api/metrics` | Service metrics and statistics |

### Data Endpoints

| Method | Endpoint | Description |
|--------|----------|-------------|
| `GET` | `/api/samples/:type` | Get sample data (customers/sales) |

### PDF Generation

| Method | Endpoint | Description |
|--------|----------|-------------|
| `POST` | `/api/generate` | Generate PDF synchronously |
| `POST` | `/api/generate/async` | Generate PDF asynchronously |
| `POST` | `/api/estimate` | Estimate generation performance |

### PDF Operations

| Method | Endpoint | Description |
|--------|----------|-------------|
| `POST` | `/api/merge` | Merge multiple PDFs |
| `POST` | `/api/split` | Split PDF into individual pages |
| `POST` | `/api/extract` | Extract specific pages from PDF |
| `POST` | `/api/analyze` | Analyze PDF properties |

### Job Management

| Method | Endpoint | Description |
|--------|----------|-------------|
| `GET` | `/api/job/:id` | Get async job status |
| `GET` | `/api/job/:id/download` | Download completed PDF |

## Usage Examples

### 1. Get Sample Data

```bash
curl -X GET "http://localhost:3000/api/samples/customers?count=50"
```

### 2. Generate PDF Synchronously

```bash
curl -X POST http://localhost:3000/api/generate \\
  -H "Content-Type: application/json" \\
  -d '{
    "title": "Customer Report",
    "data": [
      {
        "id": 1,
        "name": "John Doe",
        "email": "john@example.com",
        "amount": 1250.00,
        "status": "Active",
        "region": "North America"
      }
    ],
    "columns": [
      {"key": "id", "title": "ID", "dataIndex": "id", "flex": 1},
      {"key": "name", "title": "Name", "dataIndex": "name", "flex": 3},
      {"key": "email", "title": "Email", "dataIndex": "email", "flex": 3},
      {"key": "amount", "title": "Amount", "dataIndex": "amount", "flex": 2, "type": "currency"},
      {"key": "status", "title": "Status", "dataIndex": "status", "flex": 2},
      {"key": "region", "title": "Region", "dataIndex": "region", "flex": 2}
    ],
    "options": {
      "template": "modern-business",
      "format": "A4",
      "orientation": "portrait"
    },
    "userInfo": {
      "companyName": "Your Company",
      "name": "Your Name"
    }
  }' \\
  --output report.pdf
```

### 3. Generate PDF Asynchronously

```bash
# Start async job
curl -X POST http://localhost:3000/api/generate/async \\
  -H "Content-Type: application/json" \\
  -d '{
    "title": "Large Dataset Report",
    "data": [...], // Large dataset
    "columns": [...]
  }'

# Response: {"jobId": "abc123", "status": "accepted", "checkStatusUrl": "/api/job/abc123"}

# Check job status
curl -X GET http://localhost:3000/api/job/abc123

# Download when complete
curl -X GET http://localhost:3000/api/job/abc123/download --output large-report.pdf
```

### 4. Estimate Performance

```bash
curl -X POST http://localhost:3000/api/estimate \\
  -H "Content-Type: application/json" \\
  -d '{
    "data": [...], // Your dataset
    "columns": [...], // Your columns
    "options": {"template": "modern-business"}
  }'

# Response includes estimated time and memory usage
```

### 5. Merge PDFs

```bash
curl -X POST http://localhost:3000/api/merge \\
  -H "Content-Type: application/json" \\
  -d '{
    "pdfs": [
      "base64-encoded-pdf-1",
      "base64-encoded-pdf-2"
    ]
  }' \\
  --output merged.pdf
```

### 6. Split PDF

```bash
curl -X POST http://localhost:3000/api/split \\
  -H "Content-Type: application/json" \\
  -d '{
    "pdf": "base64-encoded-pdf-data"
  }'

# Returns array of base64-encoded pages
```

### 7. Extract Pages

```bash
curl -X POST http://localhost:3000/api/extract \\
  -H "Content-Type: application/json" \\
  -d '{
    "pdf": "base64-encoded-pdf-data",
    "pages": [1, 3, 5]
  }' \\
  --output extracted-pages.pdf
```

## Templates

The API includes a advanced `modern-business` template with:

- 🎨 Modern gradient design
- 📊 Automatic metrics calculation
- 📈 Status badges with color coding
- 💫 Animated background patterns
- 📱 Responsive layout
- 🏢 Company branding support

## Configuration

### Environment Variables

```env
PORT=3000
NODE_ENV=production
```

### Rate Limiting

- 100 requests per 15 minutes per IP
- Configurable in the server setup

### File Storage

The API creates these directories:
- `uploads/` - Temporary file uploads
- `output/` - Generated PDF storage
- `cache/` - Cached results

### Job Management

- Jobs are automatically cleaned up after 24 hours
- In production, consider using Redis for job storage

## Error Handling

The API provides comprehensive error responses:

```json
{
  "error": "Error description",
  "message": "Detailed error message",
  "code": "ERROR_CODE",
  "timestamp": "2024-01-01T00:00:00.000Z"
}
```

Common error codes:
- `VALIDATION_ERROR` - Invalid request data
- `PDF_GENERATION_ERROR` - PDF generation failed
- `JOB_NOT_FOUND` - Async job not found
- `RATE_LIMIT_EXCEEDED` - Too many requests

## Monitoring

### Health Check

```bash
curl -X GET http://localhost:3000/api/health
```

### Metrics

```bash
curl -X GET http://localhost:3000/api/metrics
```

Metrics include:
- Request counts and success rates
- Average processing times
- Memory usage
- Active/completed jobs
- Template usage statistics

## Production Deployment

### Docker

```dockerfile
FROM node:18-alpine
WORKDIR /app
COPY package*.json ./
RUN npm ci --only=production
COPY . .
EXPOSE 3000
CMD ["npm", "start"]
```

### Environment Setup

```bash
# Install dependencies
npm ci --only=production

# Set environment
export NODE_ENV=production
export PORT=3000

# Start server
npm start
```

### Scaling Considerations

- Use Redis for job storage in clustered environments
- Implement proper logging (Winston, etc.)
- Add authentication/authorization
- Set up monitoring (Prometheus, New Relic, etc.)
- Use a reverse proxy (Nginx) for SSL and load balancing

## Integration Examples

### Frontend Integration (JavaScript)

```javascript
class PDFGeneratorClient {
  constructor(baseUrl = 'http://localhost:3000') {
    this.baseUrl = baseUrl;
  }

  async generatePDF(data) {
    const response = await fetch(\`\${this.baseUrl}/api/generate\`, {
      method: 'POST',
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify(data)
    });
    
    if (!response.ok) {
      throw new Error(\`PDF generation failed: \${response.statusText}\`);
    }
    
    return response.blob();
  }

  async generateAsync(data) {
    const response = await fetch(\`\${this.baseUrl}/api/generate/async\`, {
      method: 'POST',
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify(data)
    });
    
    const job = await response.json();
    return this.pollJob(job.jobId);
  }

  async pollJob(jobId, interval = 2000) {
    while (true) {
      const response = await fetch(\`\${this.baseUrl}/api/job/\${jobId}\`);
      const job = await response.json();
      
      if (job.status === 'completed') {
        const pdfResponse = await fetch(\`\${this.baseUrl}/api/job/\${jobId}/download\`);
        return pdfResponse.blob();
      } else if (job.status === 'failed') {
        throw new Error(\`Job failed: \${job.error}\`);
      }
      
      await new Promise(resolve => setTimeout(resolve, interval));
    }
  }
}

// Usage
const client = new PDFGeneratorClient();
const pdfBlob = await client.generatePDF({
  title: "My Report",
  data: [...],
  columns: [...]
});
```

### Python Integration

```python
import requests
import time
import json

class PDFGeneratorClient:
    def __init__(self, base_url="http://localhost:3000"):
        self.base_url = base_url
    
    def generate_pdf(self, data):
        response = requests.post(
            f"{self.base_url}/api/generate",
            json=data,
            headers={"Content-Type": "application/json"}
        )
        response.raise_for_status()
        return response.content
    
    def generate_async(self, data):
        response = requests.post(
            f"{self.base_url}/api/generate/async",
            json=data
        )
        job = response.json()
        return self.poll_job(job["jobId"])
    
    def poll_job(self, job_id, interval=2):
        while True:
            response = requests.get(f"{self.base_url}/api/job/{job_id}")
            job = response.json()
            
            if job["status"] == "completed":
                pdf_response = requests.get(f"{self.base_url}/api/job/{job_id}/download")
                return pdf_response.content
            elif job["status"] == "failed":
                raise Exception(f"Job failed: {job['error']}")
            
            time.sleep(interval)

# Usage
client = PDFGeneratorClient()
pdf_data = client.generate_pdf({
    "title": "My Report",
    "data": [...],
    "columns": [...]
})

with open("report.pdf", "wb") as f:
    f.write(pdf_data)
```

## Contributing

1. Fork the repository
2. Create your feature branch
3. Make your changes
4. Add tests if applicable
5. Submit a pull request

## License

MIT License - see the [LICENSE](../../LICENSE) file for details.

## Support

- 📚 [Documentation](https://github.com/Safeersoft/pdf-reporter)
- 🐛 [Issue Tracker](https://github.com/Safeersoft/pdf-reporter/issues)
- 📧 [Email Support](mailto:support@safeersoft.com)