Code for https://wondersofcode.wordpress.com/?p=120, part 2

FitbitUserRepository_improved.js

var Q = require('q');
var mongoFacade = require('mongoFacade');

/** For each user in our DB, fetch her stats from Fitbit */
var getUsersWithFitbitStats = function(){
  var deferredResults = Q.defer();

  mongoFacade.find({}, function(err, users){ // Async fetch from DB
    // Turn each user into a promise of user stats
    var userStatsPromisses = users.map(function(user){

      var userStatsPromise = Q.defer();
      
      Auth.oauth.getProtectedResource(
        'https://api.fitbit.com/1/user/-/activities.json',
        'GET',
        user.oauthAccessToken,
        user.oauthAccessTokenSecret,
        function (error, data, response) { // Async fetch stats from Fitbit

          if (error) {
            logError(error, user);
            userStatsPromise.reject(error); // don't hide the failure from the caller
            return;
          }

          var responseData = JSON.parse(data);
          
          // Deliver the promissed data
          userStatsPromise.resolve({
            user: {
              id: user.fitbitId,
              name: user.name
            },
            data: responseData
          });
        }
      );

      return userStatsPromise.promise; // return an element of the new array

    }); // users.map

    // Wait for all of the userStats promisses to finish, filter out failures,
    // return the rest as an array of user stats
    //userStatsPromisses; -> deferredResults
    Q.allSettled(userStatsPromisses).then(function (results) {

      var fulfilled = function(r) {
        return r.state === "fulfilled";
      };
      var getValue = function(r) {
        return r.value;
      };
      
      var goodUserStats = results.filter(fulfilled).map(getValue);

      deferredResults.resolve(goodUserStats);
    });

  }); // async mongoFacade.find
  return deferredResults.promise;
};

module.exports = {
  getUsersWithFitbitStats: getUsersWithFitbitStats
};