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 /* This Source Code Form is subject to the terms of the Mozilla Public

  * License, v. 2.0. If a copy of the MPL was not distributed with this

  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

 "use strict";

 module.metadata = {

   "stability": "deprecated"

 };

 // `var` is being used in the module in order to make it reusable in

 // environments in which `let` and `const` is not yet supported.

 // Returns `object`'s property value, where `name` is a name of the property.

 function get(object, name) {

   return object[name];

 }

 // Assigns `value` to the `object`'s property, where `name` is the name of the

 // property.

 function set(object, name, value) {

   return object[name] = value;

 }

 /**

  * Given an `object` containing a property with the given `name`, create

  * a property descriptor that can be used to define alias/proxy properties

  * on other objects.  A change in the value of an alias will propagate

  * to the aliased property and vice versa.

  */

 function createAliasProperty(object, name) {

   // Getting own property descriptor of an `object` for the given `name` as

   // we are going to create proxy analog.

   var property = Object.getOwnPropertyDescriptor(object, name);

   var descriptor = {

     configurable: property.configurable,

     enumerable: property.enumerable,

     alias: true

   };

   // If the original property has a getter and/or setter, bind a

   // corresponding getter/setter in the alias descriptor to the original

   // object, so the `this` object in the getter/setter is the original object

   // rather than the alias.

   if ("get" in property && property.get)

     descriptor.get = property.get.bind(object);

   if ("set" in property && property.set)

     descriptor.set = property.set.bind(object);

   // If original property was a value property.

   if ("value" in property) {

     // If original property is a method using it's `object` bounded copy.

     if (typeof property.value === "function") {

       descriptor.value = property.value.bind(object);

       // Also preserving writability of the original property.

       descriptor.writable = property.writable;

     }

     // If the original property was just a data property, we create proxy

     // accessors using our custom get/set functions to propagate changes to the

     // original `object` and vice versa.

     else {

       descriptor.get = get.bind(null, object, name);

       descriptor.set = set.bind(null, object, name);

     }

   }

   return descriptor;

 }

 // Defines property on `object` object with a name `alias` if given if not

 // defaults to `name` that represents an alias of `source[name]`. If aliased

 // property was an assessor or a method `this` pseudo-variable will be `source`

 // when invoked. If aliased property was a data property changes on any of the

 // aliases will propagate to the `source[name]` and also other way round.

 function defineAlias(source, target, name, alias) {

   return Object.defineProperty(target, alias || name,

                                createAliasProperty(source, name));

 }

 /**

  * Function takes any `object` and returns a proxy for its own public

  * properties. By default properties are considered to be public if they don't

  * start with `"_"`, but default behavior can be overridden if needed, by

  * passing array of public property `names` as a second argument. By default

  * returned object will be direct decedent of the given `object`'s prototype,

  * but this can be overridden by passing third optional argument, that will be

  * used as `prototype` instead.

  * @param {Object} object

  *    Object to create cortex for.

  * @param {String[]} [names]

  *    Optional array of public property names.

  * @param {Object} [prototype]

  *    Optional argument that will be used as `prototype` of the returned object,

  *    if not provided `Object.getPrototypeOf(object)` is used instead.

  */

 exports.Cortex = function Cortex(object, names, prototype) {

   // Creating a cortex object from the given `prototype`, if one was not

   // provided then `prototype` of a given `object` is used. This allows

   // consumer to define expected behavior `instanceof`. In common case

   // `prototype` argument can be omitted to preserve same behavior of

   // `instanceof` as on original `object`.

   var cortex = Object.create(prototype || Object.getPrototypeOf(object));

   // Creating alias properties on the `cortex` object for all the own

   // properties of the original `object` that are contained in `names` array.

   // If `names` array is not provided then all the properties that don't

   // start with `"_"` are aliased.

   Object.getOwnPropertyNames(object).forEach(function (name) {

     if ((!names && "_" !== name.charAt(0)) || (names && ~names.indexOf(name)))

       defineAlias(object, cortex, name);

   });

   return cortex;

 }