@seeessence/stream/index.js

Two-way duplex stream

var EventEmitter = require('events').EventEmitter;
var PassThrough = require('stream').PassThrough;
var debug = require('./debug.js');

module.exports = function (arterial, venous, name) {
    
    var stream = new EventEmitter();
    
    if (arterial instanceof Function ||  typeof arterial === 'function') {
        
        arterial = (function (arterial) {
            return new PassThrough({
                objectMode: true,
                transform: function(object, encoding, callback) {
                    arterial(object, callback.bind(null));
                }
            });
        })(arterial);
    }
    
    if (venous instanceof Function ||  typeof venous === 'function') {
        
        venous = (function (venous) {
            
            return new PassThrough({
                objectMode: true,
                transform: function(object, encoding, callback) {
                    venous(object, callback.bind(null));
                }
            });
        })(venous);
        
    }
    
    process.env.npm_package_config_debug && debug(arterial, name, arguments.callee);
    process.env.npm_package_config_debug && debug(venous, name, arguments.callee);
    
    stream.pipe = function () {
        for (var argument in arguments)
            if (arguments.hasOwnProperty(argument))
                arterial.pipe(arguments[argument], {end: false});
                
        return stream;
    };
    
    var emit = true;
    
    arterial.on('pipe', function (source) {
        emit && source.unpipe(this);
        emit && source.pipe(venous);
        emit = true;
    });
    
    stream.on('pipe', function (source) {
        source.unpipe(this);
        emit = false;
        source.pipe(arterial);
        venous.pipe(source);
    });
    
    return stream;
};