derma/scrape.js

const puppeteer = require('puppeteer');
const { pathOr, unionWith, prop, eqBy, maxBy } = require('ramda');
const parse_args = require('minimist');
const url = require('url');
const path = require('path');
const fs = require('fs').promises;
const gm = require('gm').subClass({ imageMagick: true });

const graphql_endpoint = 'https://www.facebook.com/api/graphql/';
const facebook_event_url = (event_id) =>
  `https://www.facebook.com/events/${event_id}/`;

const get_upcoming_events = pathOr(
  null,
  'data.page.upcoming_events'.split('.'),
);

const merge_edges = unionWith(eqBy(prop('event_id')));

const load_event = async (page, event_id) => {
  try {
    const image_data = new Promise((resolve, reject) => {
      const images = [];
      page.on('response', async (response) => {
        const response_url = response.request().url();
        const { pathname } = new URL(response_url);
        const ext = path.extname(pathname);
        if (ext === '.jpg') {
          const image = await response.buffer();
          images.push(image);
        }
      });
      page.on('domcontentloaded', async () => {
        resolve(images);
      });
    });

    await page.goto(facebook_event_url(event_id));
    const images = await image_data;
    const image = images.reduce((res, image) =>
      maxBy((item) => item.length, res, image),
    );
    return { image };
  } catch (e) {
    console.error(e);
  }
};

const write_image = (path, image) =>
  fs.writeFile(path, image, { encoding: null });

const gm_write = (image, path) => {
  return new Promise((resolve, reject) =>
    image.write(path, (err) => (!err ? resolve() : reject(err))),
  );
};

const write_resized = async (image_path, original) => {
  const image = gm(original);
  const size = await new Promise((resolve, reject) => {
    image.size((err, value) => (!err ? resolve(value) : resolve(null)));
  });

  if (size === null) {
    throw new Error('Could not get image.');
  }

  let { height: y, width: x } = size;

  if (y % 2 === 1) {
    y = y + 1;
  }

  if (x % 2 === 1) {
    x = x + 1;
  }

  image.resize(x, y);

  if (y > x) {
    const z = (y - x) / 2;
    image.crop(x, x, 0, z);
  }

  if (y < x) {
    const z = (x - y) / 2;
    image.crop(y, y, z, 0);
  }

  return gm_write(image, image_path);
};

const save_images = async ({ image = null, event_id }) => {
  if (image === null) {
    return [];
  }
  const original_path = `./events/img/${event_id}.jpg`;
  const resized_path = `./events/img/${event_id}-square.jpg`;
  const original = write_image(original_path, image);
  const resized_square = write_resized(resized_path, image);
  try {
    const res = await Promise.all([original, resized_square]);
    return { original: original_path, square: resized_path };
  } catch (err) {
    console.error(err);
    return { original: null };
  }
};

const get_city_name = (event) =>
  pathOr('', 'event_place.city.contextual_name'.split('.'), event);

const get_event_host = (event) =>
  pathOr('', 'event_place.contextual_name'.split('.'), event);

const edge_to_node = (edge) => edge.node;

const map_event = ({ node: event }) => {
  const ticket_url = pathOr('', ['event_buy_ticket_url'], event);
  const city = get_city_name(event);
  const host = get_event_host(event);
  return {
    date: event.time_range,
    name: event.name,
    event_id: event.id,
    ticket_url,
    location: {
      host: host,
      location: city,
    },
  };
};

const create_images_directory = (images_directory) =>
  fs.mkdir(images_directory, { recursive: true }).catch(console.error);

const open_browser = async (images_directory) => {
  const browser = await puppeteer.launch({
    headless: false,
    args: ['--disable-dev-shm-usage'],
  });
  return browser;
};

const argv = parse_args(process.argv.slice(2));
const page_ids = pathOr('', ['page_ids'], argv)
  .split(',')
  .filter((str) => str.length !== 0)
  .map((page_id) => `https://www.facebook.com/${page_id}/events/`);
const event_ids = pathOr('', ['event_ids'], argv)
  .split(',')
  .filter((str) => str.length !== 0)
  .map((event_id) => `https://www.facebook.com/events/${event_id}`);

const register_upcoming_events_listener = (endpoint, page) => {
  let responses = [];
  return new Promise((resolve, reject) => {
    page.on('response', async (response) => {
      if (endpoint === response.request().url()) {
        try {
          const json = await response.json();
          const upcoming_events = get_upcoming_events(json);
          if (upcoming_events !== null) {
            responses = [upcoming_events, ...responses];
            if (!upcoming_events.page_info.has_next_page) {
              resolve(responses);
            }
          }
        } catch (err) {
          reject(err);
        }
      }
    });
  });
};

(async () => {
  create_images_directory('./events/img');

  const browser = await open_browser();

  let events = [];

  for (let page_id of page_ids) {
    let scraping = true;
    const facebook_page = await browser.newPage();
    const upcoming_events = register_upcoming_events_listener(
      graphql_endpoint,
      facebook_page,
    )
      .then((upcoming_events) => {
        scraping = false;
        return upcoming_events;
      })
      .catch((err) => {
        console.error(err);
        scraping = false;
      });

    await facebook_page.goto(page_id);

    while (scraping) {
      await facebook_page.evaluate(() =>
        window.scrollBy(0, window.innerHeight),
      );
    }

    const responses = await upcoming_events;
    const nodes = responses.reduce(
      (res, current) => [...res, ...current.edges],
      [],
    );
    const new_events = nodes.map(map_event);

    events = merge_edges(new_events, events);

    events = await Promise.all(
      events.map(async (event) => {
        const event_page = await browser.newPage();
        const event_data = await load_event(event_page, event.event_id);
        return {
          ...event_data,
          ...event,
        };
      }),
    );
  }

  events = await Promise.all(
    events.map(async (event) => {
      const images = await save_images(event);
      delete event.image;
      return {
        images,
        ...event,
      };
    }),
  );

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