apollo/services/poll.js

const plex = require("./plex");
const logger = require("./logging")
const config = require("../config/configuration");

const lastPlaying = {};
const lastScrobbleTimes = {};

async function poll() {
  const now = Date.now();
  const playing = [];

  try {
    const data = await plex.getCurrentlyPlaying();
    playing.push.apply(playing, data);
  } catch (ex) {
    logger.error(ex, "Could not fetch currently playing data from Plex.");
    return;
  }

  for (let media of playing) {
    if (!lastScrobbleTimes[media.mediaKey]) {
      lastScrobbleTimes[media.mediaKey] = 1;
    }

    const lastTrack = lastPlaying[media.sessionKey];
    if (!lastTrack) {
      logger.info(media, "A new session has started.");
    } else {
      if (checkIfCanScrobble(media, lastTrack, now)) {
        logger.info(lastTrack, "Scrobble");
        lastScrobbleTimes[lastTrack.mediaKey] = now;
      }
    }

    lastPlaying[media.sessionKey] = media;
  }

  // Scrobble then remove lingering sessions
  for (let key in lastPlaying) {
    if (!playing.some(p => p.sessionKey == key)) {
      const track = lastPlaying[key];
      if (checkIfCanScrobble(null, track, now)) {
        logger.info(track, "Scrobble");
        lastScrobbleTimes[track.mediaKey] = now;
      }
      delete lastPlaying[key];
      logger.debug("Deleted old session.", key);
    }
  }
}

function checkIfCanScrobble(current, last, now) {
  const scrobbleDuration = isInt(config.scrobble.duration) ? Number(config.scrobble.duration) : 30;
  const scrobblePercent = isInt(config.scrobble.percent) ? Number(config.scrobble.percent) : 30;

  if (last) {
    const newPlayback = current == null || current.playtime < last.playtime;
    const canBeScrobbled = last.playtime > scrobbleDuration * 1000 || last.playtime / last.duration > scrobblePercent;

    if (newPlayback && canBeScrobbled) {
      const sameSong = current != null && current.mediaKey == last.mediaKey;
      const lastTime = lastScrobbleTimes[last.mediaKey];
      return !sameSong || !lastTime || now - lastTime > scrobbleDuration;
    }
  }
  return false;
}

function isInt(value) {
  return !isNaN(value) &&
    parseInt(Number(value)) == value &&
    !isNaN(parseInt(value, 10));
}

module.exports = poll;