Observable.ts

export function AddObservable<
    Events extends string,
    T extends {
        new (...args: any[]): {
            _notify(e: Events): void;
            _get(e: Events): any;
        };
    },
>(constructor: T) {
    return class extends constructor {
        private readonly _listeners: Record<Events, Array<() => void>>;

        constructor(...args: any[]) {
            super(...args);

            this._listeners = {} as Record<Events, Array<() => void>>;
        }

        public _notify = (event: Events) => {
            if (this._listeners[event]) {
                this._listeners[event].forEach((f) => f());
            }
        };

        private _on = (event: Events, fn: () => void) => {
            if (!this._listeners[event]) {
                this._listeners[event] = [];
            }

            this._listeners[event].push(fn);

            return () => {
                const index = this._listeners[event].indexOf(fn);

                if (index > -1) {
                    this._listeners[event].splice(index, 1);
                }
            };
        };
    };
}