'use strict';

var hasOwn = Object.prototype.hasOwnProperty; var toStr = Object.prototype.toString; var defineProperty = Object.defineProperty; var gOPD = Object.getOwnPropertyDescriptor;

var isArray = function isArray(arr) {

if (typeof Array.isArray === 'function') {
        return Array.isArray(arr);
}

return toStr.call(arr) === '[object Array]';

};

var isPlainObject = function isPlainObject(obj) {

if (!obj || toStr.call(obj) !== '[object Object]') {
        return false;
}

var hasOwnConstructor = hasOwn.call(obj, 'constructor');
var hasIsPrototypeOf = obj.constructor && obj.constructor.prototype && hasOwn.call(obj.constructor.prototype, 'isPrototypeOf');
// Not own constructor property must be Object
if (obj.constructor && !hasOwnConstructor && !hasIsPrototypeOf) {
        return false;
}

// Own properties are enumerated firstly, so to speed up,
// if last one is own, then all properties are own.
var key;
for (key in obj) { /**/ }

return typeof key === 'undefined' || hasOwn.call(obj, key);

};

// If name is '__proto__', and Object.defineProperty is available, define __proto__ as an own property on target var setProperty = function setProperty(target, options) {

if (defineProperty && options.name === '__proto__') {
        defineProperty(target, options.name, {
                enumerable: true,
                configurable: true,
                value: options.newValue,
                writable: true
        });
} else {
        target[options.name] = options.newValue;
}

};

// Return undefined instead of __proto__ if '__proto__' is not an own property var getProperty = function getProperty(obj, name) {

if (name === '__proto__') {
        if (!hasOwn.call(obj, name)) {
                return void 0;
        } else if (gOPD) {
                // In early versions of node, obj['__proto__'] is buggy when obj has
                // __proto__ as an own property. Object.getOwnPropertyDescriptor() works.
                return gOPD(obj, name).value;
        }
}

return obj[name];

};

module.exports = function extend() {

var options, name, src, copy, copyIsArray, clone;
var target = arguments[0];
var i = 1;
var length = arguments.length;
var deep = false;

// Handle a deep copy situation
if (typeof target === 'boolean') {
        deep = target;
        target = arguments[1] || {};
        // skip the boolean and the target
        i = 2;
}
if (target == null || (typeof target !== 'object' && typeof target !== 'function')) {
        target = {};
}

for (; i < length; ++i) {
        options = arguments[i];
        // Only deal with non-null/undefined values
        if (options != null) {
                // Extend the base object
                for (name in options) {
                        src = getProperty(target, name);
                        copy = getProperty(options, name);

                        // Prevent never-ending loop
                        if (target !== copy) {
                                // Recurse if we're merging plain objects or arrays
                                if (deep && copy && (isPlainObject(copy) || (copyIsArray = isArray(copy)))) {
                                        if (copyIsArray) {
                                                copyIsArray = false;
                                                clone = src && isArray(src) ? src : [];
                                        } else {
                                                clone = src && isPlainObject(src) ? src : {};
                                        }

                                        // Never move original objects, clone them
                                        setProperty(target, { name: name, newValue: extend(deep, clone, copy) });

                                // Don't bring in undefined values
                                } else if (typeof copy !== 'undefined') {
                                        setProperty(target, { name: name, newValue: copy });
                                }
                        }
                }
        }
}

// Return the modified object
return target;

};