import {MapWrapper} from 'angular2/src/facade/collection';
import {stringify} from 'angular2/src/facade/lang';

// TODO: uncoment `int` once https://github.com/angular/angular/issues/1414 is fixed

/**
 * A unique object used for retrieving items from the {@link Injector}.
 *
 * Keys have:
 * - a system-wide unique `id`.
 * - a `token`, usually the `Type` of the instance.
 *
 * Keys are used internally by the {@link Injector} because their system-wide unique `id`s allow the
 * injector to index in arrays rather than looking up items in maps.
 *
 * @exportedAs angular2/di
 */
export class Key {
  token;
  id/* :int */;
  constructor(token, id/* :int */) {
    this.token = token;
    this.id = id;
  }

  get displayName() {
    return stringify(this.token);
  }

  /**
   * Retrieves a `Key` for a token.
   */
  static get(token):Key {
    return _globalKeyRegistry.get(token);
  }

  /**
   * @returns the number of keys registered in the system.
   */
  static get numberOfKeys()/* :int */ {
    return _globalKeyRegistry.numberOfKeys;
  }
}

/**
 * @private
 */
export class KeyRegistry {
  _allKeys:Map;
  constructor() {
    this._allKeys = MapWrapper.create();
  }

  get(token):Key {
    if (token instanceof Key) return token;

    if (MapWrapper.contains(this._allKeys, token)) {
      return MapWrapper.get(this._allKeys, token);
    }

    var newKey = new Key(token, Key.numberOfKeys);
    MapWrapper.set(this._allKeys, token, newKey);
    return newKey;
  }

  get numberOfKeys()/* :int */ {
    return MapWrapper.size(this._allKeys);
  }
}

var _globalKeyRegistry = new KeyRegistry();