export type Listener = ( event?: DispatcherEvent ) => void;

export interface DispatcherEvent {
	type: string;
	[ key: string ]: any;
}

export class EventDispatcher {

	private _listeners: { [ type: string ]: Listener[] } = {};

	addEventListener( type: string, listener: Listener ): void {

		const listeners = this._listeners;

		if ( listeners[ type ] === undefined ) listeners[ type ] = [];

		if ( listeners[ type ].indexOf( listener ) === - 1 ) listeners[ type ].push( listener );

	}

	// hasEventListener( type: string, listener: Listener ): boolean {

	// 	const listeners = this._listeners;

	// 	return listeners[ type ] !== undefined && listeners[ type ].indexOf( listener ) !== - 1;

	// }

	removeEventListener( type: string, listener: Listener ): void {

		const listeners = this._listeners;
		const listenerArray = listeners[ type ];

		if ( listenerArray !== undefined ) {

			const index = listenerArray.indexOf( listener );

			if ( index !== - 1 ) listenerArray.splice( index, 1 );

		}

	}

	// removeAllEventListeners( type?: string ): void {

	// 	if ( ! type ) {

	// 		this._listeners = {};
	// 		return;

	// 	}

	// 	if ( Array.isArray( this._listeners[ type ] ) ) this._listeners[ type ].length = 0;

	// }

	dispatchEvent( event: DispatcherEvent ): void {

		const listeners = this._listeners;
		const listenerArray = listeners[ event.type ];

		if ( listenerArray !== undefined ) {

			event.target = this;
			const array = listenerArray.slice( 0 );

			for ( let i = 0, l = array.length; i < l; i ++ ) {

				array[ i ].call( this, event );

			}

		}

	}

}