import Callback from "./callback";
import * as Collections from '../utils/collections';
import CallbackTable from "./callback_table";

export default class CallbackRegistry {
  _callbacks: CallbackTable;

  constructor() {
    this._callbacks = {};
  }

  get(name : string) : Callback[] {
    return this._callbacks[prefix(name)];
  }

  add(name : string, callback : Function, context : any) {
    var prefixedEventName = prefix(name);
    this._callbacks[prefixedEventName] = this._callbacks[prefixedEventName] || [];
    this._callbacks[prefixedEventName].push({
      fn: callback,
      context: context
    });
  }

  remove(name?: string, callback?: Function, context?: any) {
    if (!name && !callback && !context) {
      this._callbacks = {};
      return;
    }

    var names = name ? [prefix(name)] : Collections.keys(this._callbacks);

    if (callback || context) {
      this.removeCallback(names, callback, context);
    } else {
      this.removeAllCallbacks(names);
    }
  }

  private removeCallback(names : string[], callback : Function, context : any) {
    Collections.apply(names, function(name) {
      this._callbacks[name] = Collections.filter(
        this._callbacks[name] || [],
        function(binding) {
          return (callback && callback !== binding.fn) ||
                 (context && context !== binding.context);
        }
      );
      if (this._callbacks[name].length === 0) {
        delete this._callbacks[name];
      }
    }, this);
  }

  private removeAllCallbacks(names : string[]) {
    Collections.apply(names, function(name) {
      delete this._callbacks[name];
    }, this);
  }
}

function prefix(name : string) : string {
  return "_" + name;
}