import {Observable} from '../Observable';
import {Subscription} from '../Subscription';
import {tryCatch} from '../util/tryCatch';
import {errorObject} from '../util/errorObject';
import {Subscriber} from '../Subscriber';

/**
 * We need this JSDoc comment for affecting ESDoc.
 * @extends {Ignored}
 * @hide true
 */
export class FromEventPatternObservable<T, R> extends Observable<T> {

  /**
   * @param addHandler
   * @param removeHandler
   * @param selector
   * @return {FromEventPatternObservable}
   * @static true
   * @name fromEventPattern
   * @owner Observable
   */
  static create<T>(addHandler: (handler: Function) => any,
                   removeHandler: (handler: Function) => void,
                   selector?: (...args: Array<any>) => T) {
    return new FromEventPatternObservable(addHandler, removeHandler, selector);
  }

  constructor(private addHandler: (handler: Function) => any,
              private removeHandler: (handler: Function) => void,
              private selector?: (...args: Array<any>) => T) {
    super();
  }

  protected _subscribe(subscriber: Subscriber<T>) {
    const addHandler = this.addHandler;
    const removeHandler = this.removeHandler;
    const selector = this.selector;

    const handler = selector ? function(e: any) {
      let result = tryCatch(selector).apply(null, arguments);
      if (result === errorObject) {
        subscriber.error(result.e);
      } else {
        subscriber.next(result);
      }
    } : function(e: any) { subscriber.next(e); };

    let result = tryCatch(addHandler)(handler);
    if (result === errorObject) {
      subscriber.error(result.e);
    }
    subscriber.add(new Subscription(() => {
      //TODO: determine whether or not to forward to error handler
      removeHandler(handler);
    }));
  }
}