const puppeteer = require('puppeteer');

const POOL_SIZE = parseInt(process.env.BROWSER_POOL_SIZE) || 5;
const VIEWPORT_WIDTH = 3240;
const VIEWPORT_HEIGHT = 3240;

let browsers = [];
let availableBrowsers = [];
let initPromise = null;


async function initPool() {
    if (initPromise) return initPromise;

    initPromise = (async () => {
        console.log(`Initializing browser pool with ${POOL_SIZE} instances...`);

        for (let i = 0; i < POOL_SIZE; i++) {
            const browser = await puppeteer.launch({
                headless: true,
                args: ['--no-sandbox', '--disable-setuid-sandbox']
            });

            browsers.push(browser);
            availableBrowsers.push(browser);
        }

        console.log(`Browser pool ready with ${POOL_SIZE} browsers`);
    })();

    return initPromise;
}

async function acquireBrowser() {
    await initPool();

    // wait for available browser
    while (availableBrowsers.length === 0) {
        await new Promise(resolve => setTimeout(resolve, 50));
    }

    return availableBrowsers.pop();
}

function releaseBrowser(browser) {
    availableBrowsers.push(browser);
}

// renders html and returns screenshot as buffer
async function renderHtml(html, waitTime = 1000) {
    const browser = await acquireBrowser();
    let page = null;

    try {
        page = await browser.newPage();
        await page.setViewport({
            width: VIEWPORT_WIDTH,
            height: VIEWPORT_HEIGHT
        });

        await page.setContent(html, { waitUntil: ['load', 'domcontentloaded', 'networkidle0'] });

        // wait for body to be ready
        await page.waitForSelector('body');

        // wait for any animations or laoding
        await new Promise(resolve => setTimeout(resolve, waitTime));

        const screenshot = await page.screenshot({
            type: 'png',
            fullPage: false,
            encoding: 'binary'
        });

        return Buffer.from(screenshot);
    } finally {
        if (page) await page.close();
        releaseBrowser(browser);
    }
}


async function shutdownPool() {
    console.log('Shutting down browser pool...');

    for (const browser of browsers) {
        await browser.close();
    }

    browsers = [];
    availableBrowsers = [];
    initPromise = null;

    console.log('Browser pool shut down');
}

// Graceful shutdown handlers
process.on('SIGINT', async () => {
    await shutdownPool();
    process.exit(0);
});

process.on('SIGTERM', async () => {
    await shutdownPool();
    process.exit(0);
});

module.exports = {
    initPool,
    renderHtml,
    shutdownPool,
    POOL_SIZE
};