/*jslint indent: 2, nomen: true, maxlen: 120, sloppy: true, vars: true */
/*global module, require, exports */
// Excerpt from Backbone Helpers
// -------
// Backbone.js 1.0.0
//
// (c) 2010-2013 Jeremy Ashkenas, DocumentCloud Inc.
// Backbone may be freely distributed under the MIT license.
// For all details and documentation:
// http://backbonejs.org

var _ = require("underscore");

// Helper function to correctly set up the prototype chain, for subclasses.
// Similar to `goog.inherits`, but uses a hash of prototype properties and
// class properties to be extended.
exports.extend = function(protoProps, staticProps) {
  var parent = this;
  var child;

  // The constructor function for the new subclass is either defined by you
  // (the "constructor" property in your `extend` definition), or defaulted
  // by us to simply call the parent's constructor.
  if (protoProps && _.has(protoProps, 'constructor')) {
    child = protoProps.constructor;
  } else {
    child = function(){ return parent.apply(this, arguments); };
  }

  // Add static properties to the constructor function, if supplied.
  _.extend(child, parent, staticProps);

  // Set the prototype chain to inherit from `parent`, without calling
  // `parent`'s constructor function.
  var Surrogate = function(){ this.constructor = child; };
  Surrogate.prototype = parent.prototype;
  child.prototype = new Surrogate;

  // Add prototype properties (instance properties) to the subclass,
  // if supplied.
  if (protoProps) _.extend(child.prototype, protoProps);

  // Set a convenience property in case the parent's prototype is needed
  // later.
  child.__super__ = parent.prototype;

  return child;
};