legos/lib/lego-fn.js

Snap your streams together

'use strict';
/*
 *          _______
 *         /\      \
 *        /  \      \        _
 *       / O  \      \      | |
 *      /      \      \     | |     ___  __ _  ___  ___
 *     /      O \______\    | |    / _ \/ _` |/ _ \/ __|
 *     \ O      /      /    | |___|  __/ (_| | (_) \__ \
 *      \      /      /     |______\___|\__, |\___/|___/
 *       \  O /      /                   __/ |
 *        \  /      /                   |___/
 *         \/______/
 */

/*
	Simple function handler for legos.

	Pass the constructor a function; this function receives the item
	as the first parameter, and a callback function as the second parameter.
	This callback function can be called multiple times, and takes an item
	itself. This item is written to all outputs.

	If passed value is not a function, defaults to a passthrough function.
*/

var util = require('util');
var Lego = require('./lego');

function LegoFn(fn) {
	Lego.call(this);

	if (!(fn instanceof Function)) {
		throw new Error('argument must be a function');
	}

	// defining a property because this is
	// more of a base-class to begin with
	Object.defineProperty(this, 'fn', {
		value: fn
	});
}

util.inherits(LegoFn, Lego);

LegoFn.prototype.write = function write(item) {
	if (!this._open) {
		throw new Error('lego is not open');
	}

	var self = this;
	this.fn(item, function (item) {
		Lego.prototype.write.call(self, item);
	});

	return this;
};

module.exports = LegoFn;