/*!
 * Chai - overwriteMethod utility
 * Copyright(c) 2012-2013 Jake Luer <jake@alogicalparadox.com>
 * MIT Licensed
 */

/**
 * ### overwriteMethod (ctx, name, fn)
 *
 * Overwites an already existing method and provides
 * access to previous function. Must return function
 * to be used for name.
 *
 *     utils.overwriteMethod(chai.Assertion.prototype, 'equal', function (_super) {
 *       return function (str) {
 *         var obj = utils.flag(this, 'object');
 *         if (obj instanceof Foo) {
 *           new chai.Assertion(obj.value).to.equal(str);
 *         } else {
 *           _super.apply(this, arguments);
 *         }
 *       }
 *     });
 *
 * Can also be accessed directly from `chai.Assertion`.
 *
 *     chai.Assertion.overwriteMethod('foo', fn);
 *
 * Then can be used as any other assertion.
 *
 *     expect(myFoo).to.equal('bar');
 *
 * @param {Object} ctx object whose method is to be overwritten
 * @param {String} name of method to overwrite
 * @param {Function} method function that returns a function to be used for name
 * @name overwriteMethod
 * @api public
 */

module.exports = function (ctx, name, method) {
  var _method = ctx[name]
    , _super = function () { return this; };

  if (_method && 'function' === typeof _method)
    _super = _method;

  ctx[name] = function () {
    var result = method(_super).apply(this, arguments);
    return result === undefined ? this : result;
  }
};