class EventBus{
    constructor(){
        this.listeners = {}
    }
    on(eventName, callback){
        if(!this.listeners[eventName]){
            this.listeners[eventName] = [];
        }
        this.listeners[eventName].push(callback);
        return ()=>{
            this.off(eventName, callback);
        }
    }
    emit(eventName, data){
        if(!this.listeners[eventName]){
            return;
        }
        this.listeners[eventName].forEach((callback)=>{
            callback(data);
        })
    }
    async emitAsync(eventName, data){
        if(!this.listeners[eventName]){
            return Promise.resolve();
        }
        const callBackPromises = this.listeners[eventName].map((callback)=>{
            return Promise.resolve(callback(data));
        })
        await Promise.all(callBackPromises);
    }
    off(eventName, callback){
        if(!this.listeners[eventName]){
            return;
        }
        this.listeners[eventName] = this.listeners[eventName].filter(listener => listener !== callback);
    }
}