One API Call. PDF + Excel.

// invoice-pdf-service.ts - Puppeteer + Handlebars
// Full implementation for generating PDF invoices

import puppeteer, { Browser } from 'puppeteer';
import Handlebars from 'handlebars';
import * as fs from 'fs';
import * as path from 'path';

// ============================================
// Type Definitions
// ============================================
interface InvoiceItem {
  description: string;
  quantity: number;
  unitPrice: number;
  total: number;
}

interface InvoiceData {
  invoiceNumber: string;
  customerName: string;
  customerEmail: string;
  companyName: string;
  companyAddress: string;
  items: InvoiceItem[];
  subtotal: number;
  tax: number;
  total: number;
  dueDate: string;
  issueDate: string;
}

// ============================================
// Puppeteer Browser Management
// ============================================
let browser: Browser | null = null;

async function getBrowser(): Promise<Browser> {
  if (!browser) {
    browser = await puppeteer.launch({
      headless: true,
      args: [
        '--no-sandbox',
        '--disable-setuid-sandbox',
        '--disable-dev-shm-usage',
        '--disable-gpu',
      ],
    });
  }
  return browser;
}

// ============================================
// Template Loading & Compilation
// ============================================
const pdfTemplatePath = path.join(__dirname, 'templates', 'invoice-pdf.hbs');
let pdfTemplate: Handlebars.TemplateDelegate;

function loadTemplates() {
  pdfTemplate = Handlebars.compile(
    fs.readFileSync(pdfTemplatePath, 'utf-8')
  );
}

// Register Handlebars helpers for formatting
Handlebars.registerHelper('formatCurrency', (value: number) => {
  return new Intl.NumberFormat('en-US', {
    style: 'currency',
    currency: 'USD',
  }).format(value);
});

Handlebars.registerHelper('formatDate', (date: string) => {
  return new Date(date).toLocaleDateString('en-US', {
    year: 'numeric',
    month: 'long',
    day: 'numeric',
  });
});

Handlebars.registerHelper('multiply', (a: number, b: number) => a * b);

// Load templates on module init
loadTemplates();

// ============================================
// PDF Generation with Puppeteer
// ============================================
export async function generateInvoicePDF(data: InvoiceData): Promise<Buffer> {
  const browser = await getBrowser();
  const page = await browser.newPage();

  try {
    // Render HTML from Handlebars template
    const html = pdfTemplate(data);

    // Set viewport for consistent rendering
    await page.setViewport({ width: 794, height: 1123 }); // A4 size

    // Set content and wait for resources
    await page.setContent(html, {
      waitUntil: 'networkidle0',
      timeout: 30000,
    });

    // Add custom styles for print
    await page.addStyleTag({
      content: `
        @page { margin: 0; }
        body { margin: 20mm; }
      `,
    });

    // Generate PDF buffer
    const pdfBuffer = await page.pdf({
      format: 'A4',
      printBackground: true,
      preferCSSPageSize: true,
      margin: {
        top: '20mm',
        right: '20mm',
        bottom: '20mm',
        left: '20mm',
      },
    });

    return Buffer.from(pdfBuffer);
  } catch (error) {
    throw new Error(`PDF generation failed: ${(error as Error).message}`);
  } finally {
    await page.close();
  }
}

// ============================================
// Save PDF to file or upload to S3
// ============================================
export async function saveInvoicePDF(data: InvoiceData): Promise<string> {
  try {
    if (!data.invoiceNumber) {
      throw new Error('Missing required invoice data');
    }

    console.log(`Generating PDF for invoice ${data.invoiceNumber}...`);
    const pdfBuffer = await generateInvoicePDF(data);

    // Save to file or upload to S3
    const filename = `invoice-${data.invoiceNumber}.pdf`;
    fs.writeFileSync(path.join(__dirname, 'output', filename), pdfBuffer);

    console.log(`Invoice PDF saved: ${filename}`);
    return filename;
  } catch (error) {
    console.error('Failed to generate invoice:', error);
    throw new Error(`PDF generation failed: ${(error as Error).message}`);
  }
}

// Cleanup on process exit
process.on('exit', async () => {
  if (browser) await browser.close();
});