const express = require('express');
const puppeteer = require('puppeteer-core');

const app = express();
const port = process.env.PORT || 4000;
const wsEndpoint = process.env.BROWSER_WS_ENDPOINT;
const poolSize = parseInt(process.env.MAX_CONCURRENCY, 10) || 5;
const renderTimeout = parseInt(process.env.RENDER_TIMEOUT_MS, 10) || 10000;

let browser, context;
let isReady = false;
const pagePool = [];
const pageQueue = [];

// 初始化单个页面拦截和加载空白页
async function initializePage(page) {
  await page.setRequestInterception(true);
  page.on('request', req => {
    const url = req.url();
    if (/\.(png|jpg|jpeg|gif|svg|woff2?|ttf)$/.test(url) || /analytics|gtag|ads|doubleclick/i.test(url)) {
      req.abort();
    } else {
      req.continue();
    }
  });
  await page.goto('about:blank', { timeout: 5000, waitUntil: 'networkidle2' });
}

// 创建新的浏览器上下文和页面池
async function createContextAndPages() {
  if (context) {
    try {
      await context.close();
    } catch {}
  }
  context = await browser.createIncognitoBrowserContext();

  pagePool.length = 0;
  for (let i = 0; i < poolSize; i++) {
    const page = await context.newPage();
    await initializePage(page);
    pagePool.push(page);
  }
  console.log(`Created new context and initialized ${pagePool.length} pages`);
}

// 定时重启浏览器上下文，避免 browserless 自动关闭
async function periodicContextRestart() {
  try {
    console.log('Periodic context restart started...');
    isReady = false;
    await createContextAndPages();
    isReady = true;
    console.log('Periodic context restart done.');
  } catch (err) {
    console.error('Error during periodic context restart:', err);
  }
}

// 连接并初始化浏览器和上下文
async function initializeBrowser() {
  browser = await puppeteer.connect({ browserWSEndpoint: wsEndpoint });
  browser.on('disconnected', () => {
    console.warn('Browser disconnected, marking not ready and reconnecting...');
    isReady = false;
    reconnectBrowser();
  });
  await createContextAndPages();
  isReady = true;
  console.log('Browser connected and ready');
}

// 重连逻辑，失败最多重试5次，失败后退出进程
let reconnectCount = 0;
async function reconnectBrowser() {
  if (browser) {
    try {
      await browser.close();
    } catch {}
  }
  reconnectCount++;
  if (reconnectCount > 5) {
    console.error('Reconnect failed 5 times, exiting process');
    process.exit(1);
  }

  console.log(`Reconnect attempt #${reconnectCount}...`);
  try {
    await initializeBrowser();
    reconnectCount = 0; // 成功重连后计数归零
  } catch (err) {
    console.error('Reconnect failed:', err.message);
    setTimeout(reconnectBrowser, 3000);
  }
}

// 页面池获取
function acquirePage() {
  return new Promise(resolve => {
    if (pagePool.length > 0) {
      resolve(pagePool.pop());
    } else {
      pageQueue.push(resolve);
    }
  });
}

// 页面释放
function releasePage(page) {
  if (page.isClosed()) return;
  if (pageQueue.length > 0) {
    const next = pageQueue.shift();
    next(page);
  } else {
    pagePool.push(page);
  }
}

// 启动服务主流程
(async () => {
  try {
    await initializeBrowser();

    // 每7分钟重启一次上下文，避开 browserless 10分钟超时关闭
    setInterval(periodicContextRestart, 7 * 60 * 1000);
  } catch (err) {
    console.error('Startup failed:', err.message);
    reconnectBrowser();
  }
})();

app.get('/healthz', (req, res) => {
  res.json({ ready: isReady, poolSize, queueLength: pageQueue.length });
});

app.get('/', (req, res) => {
  res.send(isReady ? 'Renderer running' : 'Renderer not ready');
});

app.get('/render', async (req, res) => {
  if (!isReady) return res.status(503).send('Renderer not ready');
  const url = req.query.url;
  if (!url) return res.status(400).send('Missing url parameter');

  let page;
  try {
    page = await acquirePage();

    await page.goto('about:blank', { waitUntil: 'networkidle2', timeout: 5000 });
    await page.goto(url, { waitUntil: 'networkidle2', timeout: renderTimeout });
    await page.waitForFunction('document.readyState === "complete"', { timeout: 5000 });

    const html = await page.content();
    res.set('Content-Type', 'text/html; charset=utf-8');
    res.send(html);
  } catch (err) {
    console.error('Render error:', err.message);
    res.status(504).send('Render failed: ' + err.message);
  } finally {
    if (page && !page.isClosed()) {
      try {
        releasePage(page);
      } catch (e) {
        console.warn('Release page error:', e.message);
        await page.close().catch(() => {});
      }
    }
  }
});

app.listen(port, () => {
  console.log(`Renderer listening on port ${port}`);
});