topTweeters.js

/* 3/13/2015 NH2
 * topTweeters.js
 * For a given topic, finds and sets the top (size) tweeters
 */
var stream = require('readable-stream')
var util = require('util')

var TopTweeters = module.exports = function (options) {
  options || (options = {})
  var hwm = options.hwm || 16

  stream.Transform.call(this, {objectMode: true, highWaterMark: hwm})

  this.size = options.size || 1000
}

util.inherits(TopTweeters, stream.Transform)

TopTweeters.prototype._transform = function (topic, encoding, callback) {

  var lists = topic.Lists

  var authorities = lists.map(function (list) {
    return list.Authorities
  }).reduce(function (bigArray, smallArray) {
    return bigArray.concat(smallArray)
  })

  var rankedAuthorities = authorities.reduce(function (ranked, authority) {
    if (ranked[authority.id]) {
      ranked[authority.id].rank += 1
    } else {
      authority.rank = 1
      ranked[authority.id] = authority
    }
    return ranked
  }, {})

  var sortedAuthorities = Object.keys(rankedAuthorities).map(function (key) {
    return rankedAuthorities[key]
  }).sort(function (a, b) {
    return b.rank - a.rank
  })

  var topAuthorities = sortedAuthorities.splice(0, this.size)

  var topTweeterIds = topAuthorities.map(function (authority) {
    return authority.id
  })

  topic.setTopTweeters(topTweeterIds).then(function () {
    callback(null, topic);
  })

};


TopTweeters.prototype._flush = function (callback) {
  callback();
};