server/www/room.js

function Room(modules) {

  function Player(key, name, alone) {
    this.key = key;
    this.name = name;
    this.alone = alone;
    this.dom = modules.dom.make('li', {textContent: name});
    this.position = null;
  }

  var players = {};
  var sortedKeys = [];
  var session = {
    key: null,
    loggedIn: false,
    selected: null
  };

  modules.messaging.addEventListener(["Welcome"], function(o) {
    for(var key in o.room) {
      enter(parseInt(key), o.room[key]);
    }
  });

  modules.messaging.addEventListener(["Update"], function(o) {
    o.alone.forEach(function(key) {players[key].alone = true;});
    o.paired.forEach(function(key) {players[key].alone = false;});
  });

  modules.messaging.addEventListener(["Relay", "LogIn"], function(o) {
    enter(o.from, o.message);
  });

  modules.messaging.addEventListener(["Relay", "LogOut"], function(o) {
    leave(o.from);
  });

  var compareKeysByLogin = modules.fun.map(function(key) {return players[key].name;}, modules.fun.defaultCompare);

  return {
    filter: filter,
    enter: enter,
    leave: leave,
    name: name
  };

  function filter(name) {
    if(modules.session.isLoggedIn()) {
      var keep = function(player) {
        return player.name.match(name) && !modules.session.is(player.key) && player.alone;
      };
    } else {
      var keep = function(player) {return player.name.match(name);};
    }
    return modules.fun.mapFilter(modules.fun.of(players), keep)(sortedKeys);
  }

  function enter(key, obj) {
    var name = obj.name || "anon";
    var alone = obj.alone != undefined ? obj.alone : true;
    var player = new Player(key, name, alone);
    players[key] = player;
    player.position = modules.fun.insert(key, sortedKeys, compareKeysByLogin);
    sortedKeys.splice(player.position, 0, key);
  }

  function leave(key) {
    var player = players[key];
    if(player != undefined) {
      sortedKeys.splice(player.position, 1);
      delete players[key];
    }
  }

  function name(key) {
    player = players[key];
    return player && player.name;
  }
}