derma/src/facebook-api.js

const { graphql_endpoint } = require('./constants');
const {
  map_event,
  get_past_events_from_page,
  get_upcoming_events_from_page,
  get_page_info,
  get_edges,
  sleep,
} = require('./logic');
const fetch = require('node-fetch');
const last = require('ramda/src/last');

const do_request = async (doc_id, variables) => {
  const params = new URLSearchParams();
  params.append('doc_id', doc_id);
  params.append('variables', JSON.stringify(variables));

  const fetch_options = {
    headers: {
      'Content-Type': 'application/x-www-form-urlencoded',
    },
    body: params,
    method: 'POST',
  };

  let res = null;

  try {
    res = await fetch(graphql_endpoint, fetch_options);
  } catch (e) {
    console.error(e);
    return null;
  }

  if (!res.ok) {
    return null;
  }

  try {
    res = await res.json();
  } catch (e) {
    console.error(e);
    return null;
  }

  return res;
};

const do_events_request = async (page_id, doc_id, cursor = null) => {
  let variables = {
    pageID: `${page_id}`,
    allowedStates: ['PUBLISHED', 'CANCELED'],
    cacheBreaker: 0,
  };

  if (cursor !== null) {
    variables = { ...variables, count: 20, cursor };
  }

  const res = await do_request(doc_id, variables);
  return res;
};

const get_events = async (page_id, doc_id, get_events_from_page, events) => {
  let { edges, cursor } = events;
  let next = cursor !== null;
  while (next) {
    let page;
    page = await do_events_request(page_id, doc_id, cursor);
    const { has_next_page } = get_page_info(page);
    page = get_events_from_page(page);
    edges = [...edges, ...get_edges(page)];
    next = has_next_page;
    cursor = last(edges).cursor;
    if (next) {
      await sleep(2);
    }
  }
  return edges;
};

const get_upcoming_events = async (page_id, events) => {
  const doc_id = '3911675102281316';
  const upcoming_events = await get_events(
    page_id,
    doc_id,
    get_upcoming_events_from_page,
    events,
  );

  return upcoming_events;
};

const get_past_events = async (page_id, events) => {
  const doc_id = '3972530646159673';
  const past_events = await get_events(
    page_id,
    doc_id,
    get_past_events_from_page,
    events,
  );
  return past_events;
};

const get_reoccuring_events = () => {};

const init_scrape = async (page_id) => {
  const doc_id = '3636086023161977';
  const res = await do_events_request(page_id, doc_id);

  const upcoming_events = get_upcoming_events_from_page(res);
  const past_events = get_past_events_from_page(res);

  const upcoming_edges = get_edges(upcoming_events);
  const past_edges = get_edges(past_events);

  const upcoming_has_next_page = get_page_info(upcoming_events).has_next_page;
  const past_has_next_page = get_page_info(past_events).has_next_page;

  return {
    upcoming_events: {
      edges: upcoming_edges,
      cursor: upcoming_has_next_page ? last(upcoming_edges).cursor : null,
    },
    past_events: {
      cursor: past_has_next_page ? last(past_edges).cursor : null,
      edges: past_edges,
    },
  };
};

const get_page_events = async (opt) => {
  const { page_id } = opt;

  let { upcoming_events, past_events } = await init_scrape(page_id);

  if (opt.get_past_events) {
    await sleep(2);
    past_events = await get_past_events(page_id, past_events);
  } else {
    past_events = [];
  }

  if (opt.get_upcoming_events) {
    await sleep(2);
    upcoming_events = await get_upcoming_events(page_id, upcoming_events);
  } else {
    upcoming_events = [];
  }

  const nodes = [...upcoming_events, ...past_events];

  return nodes.map(map_event);
};

module.exports = {
  get_page_events,
};