export class CallbackHolder {
    constructor() {

    }
    private root = (Math.random() + 1).toString(36).substring(7);
    private inc = 0
    private callbacks = new Map<string, Function>()
    private newId() {
        return this.root + (this.inc++).toString(36)
    }
    addCallback(callback: Function) {
        return this.callbacks.set(this.newId(), callback);
    }
    callCallback(index: string, args: any[]): Promise<unknown> {
        const callback = this.callbacks.get(index)
        if (!callback) throw new Error(`Callback ${index} does not exist`)        
        this.callbacks.delete(index)
        return Promise.resolve().then(() => callback(...args))
    }
}