/**
 * @license
 * Copyright Google LLC All Rights Reserved.
 *
 * Use of this source code is governed by an MIT-style license that can be
 * found in the LICENSE file at https://angular.io/license
 */

import {Injectable, Optional, SkipSelf} from '@angular/core';


// Users of the Dispatcher never need to see this type, but TypeScript requires it to be exported.
export type UniqueSelectionDispatcherListener = (id: string, name: string) => void;

/**
 * Class to coordinate unique selection based on name.
 * Intended to be consumed as an Angular service.
 * This service is needed because native radio change events are only fired on the item currently
 * being selected, and we still need to uncheck the previous selection.
 *
 * This service does not *store* any IDs and names because they may change at any time, so it is
 * less error-prone if they are simply passed through when the events occur.
 */
@Injectable()
export class UniqueSelectionDispatcher {
  private _listeners: UniqueSelectionDispatcherListener[] = [];

  /**
   * Notify other items that selection for the given name has been set.
   * @param id ID of the item.
   * @param name Name of the item.
   */
  notify(id: string, name: string) {
    for (let listener of this._listeners) {
      listener(id, name);
    }
  }

  /**
   * Listen for future changes to item selection.
   * @return Function used to deregister listener
   */
  listen(listener: UniqueSelectionDispatcherListener): () => void {
    this._listeners.push(listener);
    return () => {
      this._listeners = this._listeners.filter((registered: UniqueSelectionDispatcherListener) => {
        return listener !== registered;
      });
    };
  }
}

/** @docs-private */
export function UNIQUE_SELECTION_DISPATCHER_PROVIDER_FACTORY(
    parentDispatcher: UniqueSelectionDispatcher) {
  return parentDispatcher || new UniqueSelectionDispatcher();
}

/** @docs-private */
export const UNIQUE_SELECTION_DISPATCHER_PROVIDER = {
  // If there is already a dispatcher available, use that. Otherwise, provide a new one.
  provide: UniqueSelectionDispatcher,
  deps: [[new Optional(), new SkipSelf(), UniqueSelectionDispatcher]],
  useFactory: UNIQUE_SELECTION_DISPATCHER_PROVIDER_FACTORY
};