Core hook of the Facebook Sixth Sense Chrome extension

sixth-sense.js

function getUserId(fbid) {
  return fbid.split(':')[1];
}

requireLazy(
  ['MercuryTypingReceiver', 'MercuryThreads', 'ShortProfiles'],
  (MercuryTypingReceiver, MercuryThreads, ShortProfiles) => {

    MercuryTypingReceiver
      .get()
      .addRetroactiveListener('state-changed', onStateChanged);

    // Called every time a user starts or stops typing in a thread
    function onStateChanged(state) {

      // State is a dictionary that maps thread ids to the list of the
      // currently typing users ids'
      const threadIds = Object.keys(state);

      // Walk through all threads in order to retrieve a list of all
      // user ids
      const userIds = threadIds.reduce(
        (res, threadId) => res.concat(state[threadId].map(getUserId)),
        []
      );

      MercuryThreads.get().getMultiThreadMeta(threadIds, threads => {
        ShortProfiles.getMulti(userIds, users => {
          // Now that we've retrieved all the information we need
          // about the threads and the users, we send it to the
          // Chrome application to process and display it to the user.
          window.postMessage({
            type: 'update',
            threads,
            users,
            state,
          }, '*');
        });
      });

    }
  }

);