marcog83/RoboJS

export class Signal {

    constructor() {
        this.listenerBoxes = [];


        this.listenersNeedCloning = false;
    }

    getNumListeners() {
        return this.listenerBoxes.length;
    }

    connect(slot, scope) {
        this.registerListener(slot, scope, false);
    }

    connectOnce(slot, scope) {
        this.registerListener(slot, scope, true);
    }

    disconnect(slot, scope) {
        if (this.listenersNeedCloning) {
            this.listenerBoxes = this.listenerBoxes.slice();
            this.listenersNeedCloning = false;
        }

        for (let i = this.listenerBoxes.length; i--;) {
            if (this.listenerBoxes[i].listener === slot && this.listenerBoxes[i].scope === scope) {
                this.listenerBoxes.splice(i, 1);
                return;
            }
        }
    }

    disconnectAll() {

        for (let i = this.listenerBoxes.length; i--;) {
            this.disconnect(this.listenerBoxes[i].listener, this.listenerBoxes[i].scope);
        }
    }

    emit(...args) {
        this.listenersNeedCloning = true;
        this.listenerBoxes.forEach(({scope, listener, once}) => {
            if (once) {
                this.disconnect(listener, scope);
            }
            listener.apply(scope, args);
        });

        this.listenersNeedCloning = false;
    }

    registerListener(listener, scope, once) {
        const _listeners = this.listenerBoxes.filter(box => box.listener === listener && box.scope === scope);

        if (!_listeners.length) {
            if (this.listenersNeedCloning) {
                this.listenerBoxes = this.listenerBoxes.slice();
            }

            this.listenerBoxes.push({listener, scope, once});
        } else {
            //
            const addOnce_add = _listeners.find(box => box.once && !once);
            const add_addOnce = _listeners.find(box => once && !box.once);

            if (addOnce_add) {
                throw new Error("You cannot addOnce() then try to add() the same listener " +
                    "without removing the relationship first.");
            }
            if (add_addOnce) {
                throw new Error("You cannot add() then addOnce() the same listener " +
                    "without removing the relationship first.");
            }
        }

    }
}