/*!
 * Chai - addProperty utility
 * Copyright(c) 2012-2014 Jake Luer <jake@alogicalparadox.com>
 * MIT Licensed
 */

var config = require('../config');
var flag = require('./flag');

/**
 * ### addProperty (ctx, name, getter)
 *
 * Adds a property to the prototype of an object.
 *
 *     utils.addProperty(chai.Assertion.prototype, 'foo', function () {
 *       var obj = utils.flag(this, 'object');
 *       new chai.Assertion(obj).to.be.instanceof(Foo);
 *     });
 *
 * Can also be accessed directly from `chai.Assertion`.
 *
 *     chai.Assertion.addProperty('foo', fn);
 *
 * Then can be used as any other assertion.
 *
 *     expect(myFoo).to.be.foo;
 *
 * @param {Object} ctx object to which the property is added
 * @param {String} name of property to add
 * @param {Function} getter function to be used for name
 * @namespace Utils
 * @name addProperty
 * @api public
 */

module.exports = function (ctx, name, getter) {
  Object.defineProperty(ctx, name,
    { get: function addProperty() {
        var old_ssfi = flag(this, 'ssfi');
        if (old_ssfi && config.includeStack === false)
          flag(this, 'ssfi', addProperty);

        var result = getter.call(this);
        return result === undefined ? this : result;
      }
    , configurable: true
  });
};