farmcontrol-api/src/templates/pdffactory.js

import log4js from 'log4js';
import puppeteer from 'puppeteer';
import config from '../config.js';
import { getPuppeteerLaunchOptions } from '../puppeteerLaunchOptions.js';

const logger = log4js.getLogger('PDF Factory');
logger.level = config.server.logLevel;

let browser = null;
let launchPromise = null;
let shutdownRegistered = false;

function isBrowserConnected() {
  return browser != null && browser.connected;
}

async function launchBrowser() {
  logger.info('Launching persistent Puppeteer browser...');
  const instance = await puppeteer.launch(getPuppeteerLaunchOptions());
  instance.on('disconnected', () => {
    if (browser === instance) {
      logger.warn('Puppeteer browser disconnected');
      browser = null;
      launchPromise = null;
    }
  });
  logger.info('Persistent Puppeteer browser ready');
  return instance;
}

function registerShutdownHandlers() {
  if (shutdownRegistered) {
    return;
  }
  shutdownRegistered = true;

  const shutdown = async () => {
    await closePDFBrowser();
  };

  process.once('SIGINT', shutdown);
  process.once('SIGTERM', shutdown);
  process.once('beforeExit', shutdown);
}

export async function startPDFBrowser() {
  if (process.env.NODE_ENV !== 'test') {
    registerShutdownHandlers();
  }

  if (isBrowserConnected()) {
    return browser;
  }

  if (launchPromise == null) {
    launchPromise = launchBrowser()
      .then((instance) => {
        browser = instance;
        return instance;
      })
      .catch((error) => {
        launchPromise = null;
        throw error;
      });
  }

  return launchPromise;
}

export async function closePDFBrowser() {
  const instance = browser;
  browser = null;
  launchPromise = null;
  if (instance != null) {
    try {
      await instance.close();
    } catch (error) {
      logger.warn('Error closing Puppeteer browser:', error.message);
    }
  }
}

async function withPage(run) {
  let page;
  try {
    const instance = await startPDFBrowser();
    page = await instance.newPage();
    return await run(page);
  } catch (error) {
    if (page == null && isBrowserConnected() === false) {
      const instance = await startPDFBrowser();
      page = await instance.newPage();
      return await run(page);
    }
    throw error;
  } finally {
    if (page != null) {
      await page.close().catch(() => {});
    }
  }
}

/**
 * Generates a PDF from HTML content using a persistent Puppeteer browser
 * @param {string} html - The HTML content to convert to PDF
 * @param {Object} options - PDF generation options
 * @param {number} options.width - Document width in mm
 * @param {number|string} options.height - Document height in mm, or 'auto'
 * @returns {Promise<Buffer>} The PDF buffer
 */
export async function generatePDF(html, options = {}) {
  try {
    return await withPage(async (page) => {
      await page.setContent(html, {
        waitUntil: 'domcontentloaded',
      });

      var height = options?.height || '50';

      if (options.height == 'auto') {
        const calculatedHeight = await page.evaluate(() => {
          return document.getElementById('content').scrollHeight;
        });

        height = calculatedHeight;
      }

      return page.pdf({
        printBackground: true,
        preferCSSPageSize: true,
        width: options.width ? `${options.width}mm` : undefined,
        height: height ? (options.height == 'auto' ? `${height + 2}px` : `${height}mm`) : undefined,
        margin: {
          top: '0mm',
          right: '0mm',
          bottom: '0mm',
          left: '0mm',
        },
      });
    });
  } catch (error) {
    logger.error('Error generating PDF:', error.message);
    throw error;
  }
}