// import the required libraries
const puppeteer = require('puppeteer');
const cheerio = require('cheerio');

(async () => {
	// launch Puppeteer instance and open new page
	const browser = await puppeteer.launch();
	const page = await browser.newPage();
	
	try {
		// navigate to target web page
    	await page.goto('https://scrapingclub.com/exercise/list_infinite_scroll/');

		// scroll to the bottom of the page
        await autoScroll(page);
 
        // retrieve HTML content
        const htmlContent = await page.content();
        // parse HTML using Cheerio
        const $ = cheerio.load(htmlContent);
 
        // extract desired data using Cheerio selectors
        $('.post').each((index, element) => {
            const title = $(element).find('h4').text().trim();
            const price = $(element).find('h5').text().trim();
            console.log(`item ${index + 1}: ${title}, ${price}`);
        });
 
    } catch (error) {
        console.error('Error:', error);
    } finally {
        await browser.close();
  }
})();


// function to automatically scroll to the bottom of the page
async function autoScroll(page) {
  await page.evaluate(async () => {
    // use Promise to handle asynchronous scrolling
    await new Promise((resolve, reject) => {
      let totalHeight = 0; // initialize total height scrolled
      const distance = 100; // set distance to scroll each time
      // set interval to continuously scroll the page
      const scrollInterval = setInterval(() => {
        // calculate the total scroll height of the page
        const scrollHeight = document.body.scrollHeight;
        // scroll the page by the specified distance
        window.scrollBy(0, distance);
        // update the total height scrolled
        totalHeight += distance;
        // check if the total height scrolled is equal to or exceeds the scroll height of the page
        if (totalHeight >= scrollHeight) {
          // if so, clear the interval to stop scrolling
          clearInterval(scrollInterval);
          // resolve the Promise to indicate scrolling is complete
          resolve();
        }
      }, 100); // set interval duration
    });
  });
}