/*!

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

var chai = require('../../chai'); var flag = require('./flag'); var isProxyEnabled = require('./isProxyEnabled'); var transferFlags = require('./transferFlags');

/**

* ### .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 addProperty(ctx, name, getter) {

getter = getter === undefined ? function () {} : getter;

Object.defineProperty(ctx, name,
  { get: function propertyGetter() {
      // Setting the `ssfi` flag to `propertyGetter` causes this function to
      // be the starting point for removing implementation frames from the
      // stack trace of a failed assertion.
      //
      // However, we only want to use this function as the starting point if
      // the `lockSsfi` flag isn't set and proxy protection is disabled.
      //
      // If the `lockSsfi` flag is set, then either this assertion has been
      // overwritten by another assertion, or this assertion is being invoked
      // from inside of another assertion. In the first case, the `ssfi` flag
      // has already been set by the overwriting assertion. In the second
      // case, the `ssfi` flag has already been set by the outer assertion.
      //
      // If proxy protection is enabled, then the `ssfi` flag has already been
      // set by the proxy getter.
      if (!isProxyEnabled() && !flag(this, 'lockSsfi')) {
        flag(this, 'ssfi', propertyGetter);
      }

      var result = getter.call(this);
      if (result !== undefined)
        return result;

      var newAssertion = new chai.Assertion();
      transferFlags(this, newAssertion);
      return newAssertion;
    }
  , configurable: true
});

};