let STUN_TURN_DICT;
let MAPPED_STUN_TURN_DICT;
let TURN_CACHE_VALID_UNTIL = Math.floor(Date.now() / 1000);
let HAS_SEEN_TURN_SERVER = false;

const fetchStunTurnServers = function (sessionToken) {
  const now = Math.floor(Date.now() / 1000);
  const MEDIA = window.meetingClientSettings.public.media;
  const CACHE_STUN_TURN = MEDIA.cacheStunTurnServers;

  if (STUN_TURN_DICT && CACHE_STUN_TURN && now < TURN_CACHE_VALID_UNTIL) return Promise.resolve(STUN_TURN_DICT);

  const handleStunTurnResponse = ({ stunServers, turnServers }) => {
    if (!stunServers && !turnServers) {
      return Promise.reject(new Error('Could not fetch STUN/TURN servers'));
    }

    const turnReply = [];
    let max_ttl = null;
    turnServers.forEach((turnEntry) => {
      const { password, url, username } = turnEntry;
      const valid_until = parseInt(username.split(':')[0]);
      if (!max_ttl) {
        max_ttl = valid_until;
      } else if (valid_until < max_ttl) {
        max_ttl = valid_until;
      }
      turnReply.push({
        urls: url,
        password,
        username,
      });
      HAS_SEEN_TURN_SERVER = true;
    });
    TURN_CACHE_VALID_UNTIL = max_ttl;

    const stDictionary = {
      stun: stunServers.map(server => server.url),
      turn: turnReply,
    };

    STUN_TURN_DICT = stDictionary;

    return Promise.resolve(stDictionary);
  };

  const STUN_TURN_FETCH_URL = window.meetingClientSettings.public.media.stunTurnServersFetchAddress;

  const url = `${STUN_TURN_FETCH_URL}?sessionToken=${sessionToken}`;
  return fetch(url, { credentials: 'include' })
    .then(res => res.json())
    .then(handleStunTurnResponse);
};

const mapStunTurn = ({ stun, turn }) => {
  const rtcStuns = stun.map(url => ({ urls: url }));
  const rtcTurns = turn.map(t => ({ urls: t.urls, credential: t.password, username: t.username }));
  return rtcStuns.concat(rtcTurns);
};

const getFallbackStun = () => {
  const FALLBACK_STUN_SERVER = window.meetingClientSettings.public.media.fallbackStunServer;

  const stun = FALLBACK_STUN_SERVER ? [FALLBACK_STUN_SERVER] : [];
  return { stun, turn: [] };
};

const getMappedFallbackStun = () => {
  const FALLBACK_STUN_SERVER = window.meetingClientSettings.public.media.fallbackStunServer;

  return (FALLBACK_STUN_SERVER ? [{ urls: FALLBACK_STUN_SERVER }] : []);
};

const fetchWebRTCMappedStunTurnServers = function (sessionToken) {
  const MEDIA = window.meetingClientSettings.public.media;
  const CACHE_STUN_TURN = MEDIA.cacheStunTurnServers;

  return new Promise(async (resolve, reject) => {
    try {
      const now = Math.floor(Date.now() / 1000);
      if (MAPPED_STUN_TURN_DICT && CACHE_STUN_TURN && now < TURN_CACHE_VALID_UNTIL) {
        return resolve(MAPPED_STUN_TURN_DICT);
      }

      const stDictionary = await fetchStunTurnServers(sessionToken);

      MAPPED_STUN_TURN_DICT = mapStunTurn(stDictionary);
      return resolve(MAPPED_STUN_TURN_DICT);
    } catch (error) {
      return reject(error);
    }
  });
};

const hasTurnServer = () => {
  return HAS_SEEN_TURN_SERVER;
}

export {
  fetchStunTurnServers,
  fetchWebRTCMappedStunTurnServers,
  getFallbackStun,
  getMappedFallbackStun,
  hasTurnServer,
};