'use strict';

var value = require('./valid-value')
  , mixin = require('./mixin')

  , defineProperty = Object.defineProperty
  , getOwnPropertyDescriptor = Object.getOwnPropertyDescriptor
  , getOwnPropertyNames = Object.getOwnPropertyNames
  , getPrototypeOf = Object.getPrototypeOf
  , hasOwnProperty = Object.prototype.hasOwnProperty;

module.exports = function (target, source) {
	var error, end, define;
	target = Object(value(target));
	source = Object(value(source));
	end = getPrototypeOf(target);
	if (source === end) return target;
	try {
		mixin(target, source);
	} catch (e) { error = e; }
	source = getPrototypeOf(source);
	define = function (name) {
		if (hasOwnProperty.call(target, name)) return;
		try {
			defineProperty(target, name, getOwnPropertyDescriptor(source, name));
		} catch (e) { error = e; }
	};
	while (source && (source !== end)) {
		getOwnPropertyNames(source).forEach(define);
		source = getPrototypeOf(source);
	}
	if (error) throw error;
	return target;
};