diffusion/src/node_modules/events/emitter.js

Diffusion JavaScript client

/*eslint valid-jsdoc: "off"*/
var functions = require('util/function');
var array = require('util/array');

var Stream = require('events/stream');

/**
 * <P>
 * An internal class to construct implementations of {@link events.Stream} with
 * a privately scoped emit function.
 * <P>
 * This allows safe construction of event-based interfaces without exposing the
 * means of emitting events.
 *
 * @class Emitter
 */
function Emitter(e, fn, events) {
    var listeners = {};

    var listener = function() { };
    var closed = false;

    var emit = function(event, args) {
        args = args || [];

        var dispatch = function(listener) {
            functions.callWithArguments(listener, args);
        };

        process.nextTick(function() {
            if (listeners[event]) {
                listeners[event].forEach(dispatch);
            }
        });

        listener(event, args);
    };

    // A safer, publicly exposed version of emit
    var publicEmit = function(event) {
        if (closed || !event) {
            return;
        }

        var args = array.argumentsToArray(arguments);
        args.shift();

        emit(event, args);
    };

    var error = function(reason) {
        emit('error', [reason]);
        close();
    };

    var close = function(reason) {
        if (closed) {
            return;
        }

        closed = true;
        emit('close', [reason]);
    };

    var stream = new Stream(listeners, error, close, events);

    if (e !== undefined) {
        stream.on(e, fn);
    }

    this.listen = function(fn) {
        listener = fn;
    };

    this.get = function() {
        return stream;
    };

    this.close = close;
    this.error = error;
    this.emit = publicEmit;

    this.assign = function(instance) {
        for (var k in stream) {
            instance[k] = stream[k];
        }
    };
}

/**
 * Create an emitter for an existing object instance.
 *
 * @param {Object} instance - The instance to assign to
 * @returns {Emitter} The emitter for the provided instance
 */
Emitter.assign = function(instance) {
    var emitter = new Emitter();
    var s = emitter.get();

    for (var k in s) {
        instance[k] = s[k];
    }

    return emitter;
};

module.exports = Emitter;