derma/scrape.js

const puppeteer = require('puppeteer');
const { JSDOM } = require('jsdom');
const event_page = 'https://www.facebook.com/KulturVarsel/events';

// const event_page = 'https://www.facebook.com/pg/bandmaldito/events';
// const event_page = 'file:///home/zalox/src/kultar-events/index.chrome.html';

const upcoming_event_id = 'upcoming_events_card';
const upcoming_event_selector = `#upcoming_events_card > div > div:nth-child(2) > table > tbody > tr`;

const month_name_to_number = (month_name) => {
  switch (month_name.toUpperCase()) {
  case "JAN": return 1;
  case "FEB": return 2;
  case "MAR": return 3;
  case "APR": return 4;
  case "MAY": return 5;
  case "JUN": return 6;
  case "JUL": return 7;
  case "AUG": return 8;
  case "SEP": return 9;
  case "OCT": return 10;
  case "NOV": return 10;
  case "DEC": return 12;
  }
}

const parse_event_time = (event_time_text) => {
  const reversed_text = event_time_text.split("").reverse().join("");
  if (!(reversed_text.substr(2, 1) == '+')) {
    return null;
  }

  const timezone = reversed_text.substr(0,6).split("").reverse().join("");
  const minutes = reversed_text.substr(7,2).split("").reverse().join("");
  const hour = reversed_text.substr(10,2).split("").reverse().join("").trim();
  return {
    tz: timezone,
    min: minutes,
    hour,
  }
}

const parse_ticket_location = (row) => {
  const host = row.children[2].firstChild.firstChild.firstChild.innerHTML
  const location = row.children[2].firstChild.lastChild.innerHTML
  return {
    host,
    location,
  };
}

const parse_event_date = (row) => {
  const date_column = row.firstChild.firstChild;
  const month_text = new String(date_column.firstChild.innerHTML);
  const month = new Number(month_name_to_number(month_text)) - 1;
  const day = new Number(date_column.lastChild.innerHTML);
  const event_time_text = row.children[1].lastChild.getElementsByTagName('span')[1].innerHTML;
  const event_time = parse_event_time(event_time_text);

  if (event_time === null) {
    return new Date(2020, month, day);
  }

  return new Date(2020, month, day, event_time.hour, event_time.min);
}

const parse_event_link = (row) => {
  const link_text = row.children[1].firstChild.getElementsByTagName('a')[0].href;
  const event_id = link_text.split('/')[2];
  return event_id;
}

const parse_ticket_url = (row) => {
  const link_text = row.lastChild.firstChild.firstChild;

  if (link_text.children.length === 0) {
    return null;
  }

  const url = new URL(link_text.getElementsByTagName('a')[0].href)
        .searchParams
        .get('u');

  return url;
}

const parse_event_name = (row) =>  {
  const event_name = row.children[1].firstChild.getElementsByTagName('span')[0].innerHTML;
  return event_name.trim();
}

const load_page = async () => {
  try {
    const browser = await puppeteer.launch({ headless: true });

    const page = await browser.newPage();

    await page.goto(event_page);
    await page.waitForSelector(upcoming_event_selector);

    await page.evaluate(() => {
      window.scrollBy(0, window.innerHeight);
    });

    await page.waitFor(1000);

    let get_events = (upcoming_event_id) => {
      const upcoming_events_element = document.getElementById(upcoming_event_id);

      if (upcoming_events_element === null) {
        throw new Error(`Element ${upcoming_event_id} was not found.`);
      }

      if (upcoming_events_element.firstChild === null) {
        throw new Error(`Element ${upcoming_event_id} firstChild was not found.`);
      }

      if (upcoming_events_element.firstChild.children === null) {
        throw new Error(`Element ${upcoming_event_id} children not found.`);
      }

      return Array.from(upcoming_events_element.firstChild.children).map(item => item.innerHTML);
    };


    const events = await page.evaluate(get_events, upcoming_event_id);

    const htmlToTableRowElement = (table) => {
      const { document } = (new JSDOM(table)).window;
      return Array.from(document.body.getElementsByTagName('tr'))[0];
    }

    const emptyArrays = item => item;

    const parseRowToEvents = table_row => {
      const date = parse_event_date(table_row);
      const name = parse_event_name(table_row);
      const event_id = parse_event_link(table_row);
      const ticket_url = parse_ticket_url(table_row);
      const location = parse_ticket_location(table_row);
      return {
        date,
        name,
        event_id,
        ticket_url,
        location,
      };
    };

    const parsed_events = events
          .map(htmlToTableRowElement)
          .filter(emptyArrays)
          .map(parseRowToEvents)
    ;

    console.log(JSON.stringify(parsed_events));
  }

  catch(e) {
    console.error(e);
  }
};

(
  async () => {
    await load_page();
    process.exit();
  }
)();