// interface any visitor should extend
// define visit* function for all types
class Visitor {
  visitChannel(entity) {}

  visitApp(entity) {}

  visitGroup(entity) {}

  visitProgram(entity) {}
}

// specific implementation of visitor
// it encapsulates details of operation inside of a method
class EnterKeyVisitor extends Visitor {
  visitChannel(entity) {
    // conversion to domain entity may happen here e.g. new Channel(...)
    // or the domain entity may be taken from entity directly if it is "pre-cooked" there e.g. entity.actionData
    const actionPaylod = null;
    WatchFlow.watchChannel(actionPaylod);
  }

  vistApp(entity) {
    const actionPaylod = null; // same as above
    AppsActions.openApp(actionPaylod);
  }

  visitGroup(entity) {
    const actionPaylod = null; // same as above
    DPActions.openDetailPage(actionPaylod);
  }

  visitProgram(entity) {
    const actionPaylod = null; // same as above
    DPActions.openDetailPage(actionPaylod);
  }
}

class BaseSearchEntity {

  get primaryMetadata() {
    return '';
  }

  get secondaryMetadata() {
    return '';
  }

  visit(visitor) {
    return null;
  }

}

class ChannelViewEntity extends BaseSearchEntity {
  get primaryMetadata() {
    return this._data.chanelName;
  }

  get secondarMetadata() {
    return 'channel metadata';
  }

  visit(visitor) {
    return visitor.visitChannel(this);
  }
}

class SearchView extends BaseView {
   onKey(key) {
     const activeElement = this._list.getSelectedItemData();

     switch (key) {

       case Keys.Enter:
         return activeElement.visit(enterKeyVisitorInstance)

       case Keys.Play:
         return activeElement.visit(playKeyVisistorInstance);

       case Keys.Contextual:
         return activeElement.visit(contextualKeyVisitorInstance);
     }
   }
}