Ex

SIEngine.Scene = function () {
  this.componentDictionary = {};
  this.systemList = [];
};

SIEngine.Scene.prototype = Object.create(Object.prototype, {
  constructor: {
    value: SIEngine.Scene
  },
  componentDictionary: {
    enumerable: true, configurable: true, writable: true
  },
  systemList: {
    enumerable: true, configurable: true, writable: true
  }
});

SIEngine.Scene.prototype.getComponentDictionary = function () {
  return this.componentDictionary;
}

SIEngine.Scene.prototype.getSystemList = function () {
  return this.systemList;
}

SIEngine.Scene.prototype.addComponent = function (entity, component) {
  var entityIdentifier = entity.getIdentifier();
  var componentType = component.getType();

  var componentDictionary = this.getComponentDictionary();

  component.setParentEntity(entity);

  if (!(componentType in componentDictionary)) {
    componentDictionary[componentType] = {};
  }

  componentDictionary[componentType][entityIdentifier] = component;
};

SIEngine.Scene.prototype.removeComponent = function (entity, component) {
  var entityIdentifier = entity.getIdentifier();
  var componentType = component.getType();

  var componentDictionary = this.getComponentDictionary();

  component.deleteParentEntity();

  delete componentDictionary[componentType][entityIdentifier];

  if (Object.keys(componentDictionary[componentType]).length === 0) {
    delete componentDictionary[componentType];
  }
};

SIEngine.Scene.prototype.removeEntity = function (entity) {
  var entityIdentifier = entity.getIdentifier();

  var componentDictionary = this.getComponentDictionary();

  for (var componentType in componentDictionary) {
    delete componentDictionary[componentType][entity];

    if (Object.keys(componentDictionary[componentType]).length === 0) {
      delete componentDictionary[componentType];
    }
  }
};

SIEngine.Scene.prototype.addSystem = function (system) {
  var systemList = this.getSystemList();

  system.setParentScene(this);

  systemList.push(system);
  systemList.sort(function(a, b) {return a.getPriority() - b.getPriority()});
};

SIEngine.Scene.prototype.removeSystem = function (system) {
  var systemList = this.getSystemList();
  var systemIndex = systemList.indexOf(system);

  if (systemIndex !== -1) {
    system.deleteParentScene();

    systemList.splice(systemIndex, 1);
  }
};

SIEngine.Scene.prototype.updateSystems = function () {
  var systemList = this.getSystemList();

  for (var i = 0; i < systemList.length; i++) {
    systemList[i].update();
  }
};