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

interface HotkeyOptions {
    element: any;
    description: string | undefined;
    keys: string;
}

@Injectable({
    providedIn: 'root'
})
export class TTHotkeys {
    hotkeys = new Map();
    defaults: Partial<HotkeyOptions> = {
        element: document
    };

    constructor(private eventManager: EventManager) {
    }

    addShortcut(options: Partial<HotkeyOptions>) {
        const merged = { ...this.defaults, ...options };
        if (merged.keys.indexOf('ctrl') > -1) {
            merged.keys = merged.keys.replace('ctrl', 'control');
        }
        const event = `keydown.${merged.keys}`;

        if (merged.description) {
            this.hotkeys.set(merged.keys, merged.description);
        }

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

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

            return () => {
                dispose();
                this.hotkeys.delete(merged.keys);
            };
        });
    }

}