/*
 * General MVC stuff
 */
var OMVC = {};

OMVC.makeObservableSubject = function () {
  var observers = [];
  var addObserver = function (o) {
    if (typeof o !== 'function') {
      throw new Error('observer must be a function');
    }
    for (var i = 0, ilen = observers.length; i < ilen; i += 1) {
      var observer = observers[i];
      if (observer === o) {
        throw new Error('observer already in the list');
      }
    }
    observers.push(o);
  };
  var removeObserver = function (o) {
    for (var i = 0, ilen = observers.length; i < ilen; i += 1) {
      var observer = observers[i];
      if (observer === o) {
        observers.splice(i, 1);
        return;
      }
    }
    throw new Error('could not find observer in list of observers');
  };
  var notifyObservers = function (data) {
    // Make a copy of observer list in case the list
    // is mutated during the notifications.
    var observersSnapshot = observers.slice(0);
    for (var i = 0, ilen = observersSnapshot.length; i < ilen; i += 1) {
      observersSnapshot[i](data);
    }
  };
  return {
    addObserver: addObserver,
    removeObserver: removeObserver,
    notifyObservers: notifyObservers,
    notify: notifyObservers
  };
};