const puppeteer = require('puppeteer');
const { pathOr, maxBy } = require('ramda');
const path = require('path');
const fs = require('fs').promises;
const filesystem = require('fs');

const { graphql_endpoint } = require('./constants');
const {
  event_url,
  get_city_name,
  get_event_host,
  get_past_events,
  get_upcoming_events,
  merge_edges,
  parse_args,
  save_images,
} = require('./logic');

const load_event = async (page, event_id) => {
  try {
    const image_data = new Promise((resolve) => {
      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(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 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 () => {
  const browser = await puppeteer.launch({
    headless: true,
    args: ['--disable-dev-shm-usage'],
  });
  return browser;
};

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);
            }
          }
          const past_events = get_past_events(json);
          if (past_events !== null) {
            if (!past_events.page_info.has_next_page) {
              resolve(responses);
            }
          }
        } catch (err) {
          reject(err);
        }
      }
    });
  });
};

const { page_ids, output, events: event_file } = parse_args(
  process.argv.slice(2),
);

const read_previous_events = (path) => {
  if (path !== null) {
    if (filesystem.existsSync(path)) {
      return fs
        .readFile(path, { encoding: 'utf-8' })
        .then((content) => JSON.parse(content))
        .catch(console.error);
    }
  }
  return Promise.resolve([]);
};

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

  const previous_events = await read_previous_events(event_file);

  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 = events.filter(
      ({ event_id }) =>
        previous_events.find(
          (previous_event) => event_id === previous_event.event_id,
        ) === undefined,
    );

    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,
      };
    }),
  );

  if (output === null) {
    const all_events = [...events, ...previous_events]
      .map((event) => {
        const start = pathOr(null, ['date', 'start'], event);
        if (start !== null) {
          try {
            event.date.start = new Date(start);
          } catch (e) {
            console.error(e);
            return event;
          }
        }
        return event;
      })
      .sort((a, b) => {
        const b_date = b.date.start;
        const a_date = a.date.start;
        if (a_date > b_date) {
          return 1;
        }
        if (a_date == b_date) {
          return 0;
        }
        return -1;
      });

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

  process.exit();
})();