import {Inject, Injectable} from '@angular/core';
import {EventManager} from '@angular/platform-browser';
import {DOCUMENT} from '@angular/common';
import {Observable} from 'rxjs';


type Options = {
  element: any;
  keys: string;
}

@Injectable({
  providedIn: 'root'
})
export class HotkeysService {

  private subscriptions: Map<string, Subscription> = new Map<string, Subscription>();

  defaults: Partial<Options> = {
    element: this.document
  };

  constructor(private eventManager: EventManager,
              @Inject(DOCUMENT) private document: Document) { }

  addShortcut(options: Partial<Options>) {
    const merged = { ...this.defaults, ...options };
    const event = `keydown.${merged.keys}`;

    const observable = new Observable(observer => {
      const handler = (e) => {
        e.preventDefault();
        observer.next(e);
      };

      const dispose = this.eventManager.addEventListener(
        merged.element, event, handler
      );

      return () => {
        dispose();
      };
    })
	this.subscriptions.set(event, observable);
    return observable;
  }

  removeShortcut(options: Partial<Options>){
  	const subscription = this.subscriptions.get(`keydown.${options.keys}`);
    if(subscription != null){
        subscription.unsubscribe();
    }
  }
}