gistfile1.txt

import EventEmitter from 'events';

class Dispatcher {
    constructor(actions) {
        this.subscribers = {};
        this.subscriptionId = 0;
        this.idPrefix = '____dispatch____';
        this.actions = actions;
        this.queue = [];
        this.isBusy = false;

        for(var action in this.actions) {
            this.subscribers[action] = {};
        }
    }

    dispatch(action, payload) {
        this._verify(action);

        if(this.isBusy) {
            throw "Can't dispatch while dispatching, use enqueue instead.";
        }

        this._dispatch(action, payload);

        if(this.queue.length > 0) {
            var oldQueue = this.queue;
            this.queue = [];
            for(var i = 0; i < this.queue.length; i++) {
                var action = queue[i].action;
                var payload = queue[i].payload;
                this._dispatch(action, payload);
                oldQueue = oldQueue.concat(this.queue);
                this.queue = [];
            }
        }
    }

    _dispatch(action, payload) {
        this.isBusy = true;
        for(var id in this.subscribers[action]) {
            this.subscribers[action][id](payload);
        }
        this.isBusy = false;
    }

    enqueue(action, payload) {
        this._verify(action);

        if(this.isBusy) {
            this.queue.push({action, payload});
        } else {
            this.dispatch(action, payload);
        }
    }


    subscribe(action, listener, id = this.idPrefix + this.subscriptionId++) {
        this._verify(action);
        this.subscribers[action][id] = listener;
        return id;
    }

    unsubscribe(action, id) {
        this._verify(action);
        delete this.subscribers[action][id];
    }

    _verify(action) {
        if(!this.actions[action]) {
            throw "No such action: " + action;
        }
    }
}


export default Dispatcher;