// Copyright 2009-2012 by contributors, MIT License
// vim: ts=4 sts=4 sw=4 expandtab

// Module systems magic dance
(function (definition) {
    // RequireJS
    if (typeof define == "function") {
        define(definition);
    // YUI3
    } else if (typeof YUI == "function") {
        YUI.add("es5-sham", definition);
    // CommonJS and <script>
    } else {
        definition();
    }
})(function () {


var call = Function.prototype.call;
var prototypeOfObject = Object.prototype;
var owns = call.bind(prototypeOfObject.hasOwnProperty);

// If JS engine supports accessors creating shortcuts.
var defineGetter;
var defineSetter;
var lookupGetter;
var lookupSetter;
var supportsAccessors;
if ((supportsAccessors = owns(prototypeOfObject, "__defineGetter__"))) {
    defineGetter = call.bind(prototypeOfObject.__defineGetter__);
    defineSetter = call.bind(prototypeOfObject.__defineSetter__);
    lookupGetter = call.bind(prototypeOfObject.__lookupGetter__);
    lookupSetter = call.bind(prototypeOfObject.__lookupSetter__);
}

// ES5 15.2.3.2
// http://es5.github.com/#x15.2.3.2
if (!Object.getPrototypeOf) {
    // https://github.com/kriskowal/es5-shim/issues#issue/2
    // http://ejohn.org/blog/objectgetprototypeof/
    // recommended by fschaefer on github
    Object.getPrototypeOf = function getPrototypeOf(object) {
        return object.__proto__ || (
            object.constructor
                ? object.constructor.prototype
                : prototypeOfObject
        );
    };
}

//ES5 15.2.3.3
//http://es5.github.com/#x15.2.3.3

function doesGetOwnPropertyDescriptorWork(object) {
    try {
        object.sentinel = 0;
        return Object.getOwnPropertyDescriptor(
                object,
                "sentinel"
        ).value === 0;
    } catch (exception) {
        // returns falsy
    }
}

//check whether getOwnPropertyDescriptor works if it's given. Otherwise,
//shim partially.
if (Object.defineProperty) {
    var getOwnPropertyDescriptorWorksOnObject = 
        doesGetOwnPropertyDescriptorWork({});
    var getOwnPropertyDescriptorWorksOnDom = typeof document == "undefined" ||
    doesGetOwnPropertyDescriptorWork(document.createElement("div"));
    if (!getOwnPropertyDescriptorWorksOnDom || 
            !getOwnPropertyDescriptorWorksOnObject
    ) {
        var getOwnPropertyDescriptorFallback = Object.getOwnPropertyDescriptor;
    }
}

if (!Object.getOwnPropertyDescriptor || getOwnPropertyDescriptorFallback) {
    var ERR_NON_OBJECT = "Object.getOwnPropertyDescriptor called on a non-object: ";

    Object.getOwnPropertyDescriptor = function getOwnPropertyDescriptor(object, property) {
        if ((typeof object != "object" && typeof object != "function") || object === null) {
            throw new TypeError(ERR_NON_OBJECT + object);
        }

        // make a valiant attempt to use the real getOwnPropertyDescriptor
        // for I8's DOM elements.
        if (getOwnPropertyDescriptorFallback) {
            try {
                return getOwnPropertyDescriptorFallback.call(Object, object, property);
            } catch (exception) {
                // try the shim if the real one doesn't work
            }
        }

        // If object does not owns property return undefined immediately.
        if (!owns(object, property)) {
            return;
        }

        // If object has a property then it's for sure both `enumerable` and
        // `configurable`.
        var descriptor =  { enumerable: true, configurable: true };

        // If JS engine supports accessor properties then property may be a
        // getter or setter.
        if (supportsAccessors) {
            // Unfortunately `__lookupGetter__` will return a getter even
            // if object has own non getter property along with a same named
            // inherited getter. To avoid misbehavior we temporary remove
            // `__proto__` so that `__lookupGetter__` will return getter only
            // if it's owned by an object.
            var prototype = object.__proto__;
            object.__proto__ = prototypeOfObject;

            var getter = lookupGetter(object, property);
            var setter = lookupSetter(object, property);

            // Once we have getter and setter we can put values back.
            object.__proto__ = prototype;

            if (getter || setter) {
                if (getter) {
                    descriptor.get = getter;
                }
                if (setter) {
                    descriptor.set = setter;
                }
                // If it was accessor property we're done and return here
                // in order to avoid adding `value` to the descriptor.
                return descriptor;
            }
        }

        // If we got this far we know that object has an own property that is
        // not an accessor so we set it as a value and return descriptor.
        descriptor.value = object[property];
        descriptor.writable = true;
        return descriptor;
    };
}

// ES5 15.2.3.4
// http://es5.github.com/#x15.2.3.4
if (!Object.getOwnPropertyNames) {
    Object.getOwnPropertyNames = function getOwnPropertyNames(object) {
        return Object.keys(object);
    };
}

// ES5 15.2.3.5
// http://es5.github.com/#x15.2.3.5
if (!Object.create) {

    // Contributed by Brandon Benvie, October, 2012
    var createEmpty;
    var supportsProto = Object.prototype.__proto__ === null;
    if (supportsProto || typeof document == 'undefined') {
        createEmpty = function () {
            return { "__proto__": null };
        };
    } else {
        // In old IE __proto__ can't be used to manually set `null`, nor does
        // any other method exist to make an object that inherits from nothing,
        // aside from Object.prototype itself. Instead, create a new global
        // object and *steal* its Object.prototype and strip it bare. This is
        // used as the prototype to create nullary objects.
        createEmpty = function () {
            var iframe = document.createElement('iframe');
            var parent = document.body || document.documentElement;
            iframe.style.display = 'none';
            parent.appendChild(iframe);
            iframe.src = 'javascript:';
            var empty = iframe.contentWindow.Object.prototype;
            parent.removeChild(iframe);
            iframe = null;
            delete empty.constructor;
            delete empty.hasOwnProperty;
            delete empty.propertyIsEnumerable;
            delete empty.isPrototypeOf;
            delete empty.toLocaleString;
            delete empty.toString;
            delete empty.valueOf;
            empty.__proto__ = null;

            function Empty() {}
            Empty.prototype = empty;
            // short-circuit future calls
            createEmpty = function () {
                return new Empty();
            };
            return new Empty();
        };
    }

    Object.create = function create(prototype, properties) {

        var object;
        function Type() {}  // An empty constructor.

        if (prototype === null) {
            object = createEmpty();
        } else {
            if (typeof prototype !== "object" && typeof prototype !== "function") {
                // In the native implementation `parent` can be `null`
                // OR *any* `instanceof Object`  (Object|Function|Array|RegExp|etc)
                // Use `typeof` tho, b/c in old IE, DOM elements are not `instanceof Object`
                // like they are in modern browsers. Using `Object.create` on DOM elements
                // is...err...probably inappropriate, but the native version allows for it.
                throw new TypeError("Object prototype may only be an Object or null"); // same msg as Chrome
            }
            Type.prototype = prototype;
            object = new Type();
            // IE has no built-in implementation of `Object.getPrototypeOf`
            // neither `__proto__`, but this manually setting `__proto__` will
            // guarantee that `Object.getPrototypeOf` will work as expected with
            // objects created using `Object.create`
            object.__proto__ = prototype;
        }

        if (properties !== void 0) {
            Object.defineProperties(object, properties);
        }

        return object;
    };
}

// ES5 15.2.3.6
// http://es5.github.com/#x15.2.3.6

// Patch for WebKit and IE8 standard mode
// Designed by hax <hax.github.com>
// related issue: https://github.com/kriskowal/es5-shim/issues#issue/5
// IE8 Reference:
//     http://msdn.microsoft.com/en-us/library/dd282900.aspx
//     http://msdn.microsoft.com/en-us/library/dd229916.aspx
// WebKit Bugs:
//     https://bugs.webkit.org/show_bug.cgi?id=36423

function doesDefinePropertyWork(object) {
    try {
        Object.defineProperty(object, "sentinel", {});
        return "sentinel" in object;
    } catch (exception) {
        // returns falsy
    }
}

// check whether defineProperty works if it's given. Otherwise,
// shim partially.
if (Object.defineProperty) {
    var definePropertyWorksOnObject = doesDefinePropertyWork({});
    var definePropertyWorksOnDom = typeof document == "undefined" ||
        doesDefinePropertyWork(document.createElement("div"));
    if (!definePropertyWorksOnObject || !definePropertyWorksOnDom) {
        var definePropertyFallback = Object.defineProperty,
            definePropertiesFallback = Object.defineProperties;
    }
}

if (!Object.defineProperty || definePropertyFallback) {
    var ERR_NON_OBJECT_DESCRIPTOR = "Property description must be an object: ";
    var ERR_NON_OBJECT_TARGET = "Object.defineProperty called on non-object: "
    var ERR_ACCESSORS_NOT_SUPPORTED = "getters & setters can not be defined " +
                                      "on this javascript engine";

    Object.defineProperty = function defineProperty(object, property, descriptor) {
        if ((typeof object != "object" && typeof object != "function") || object === null) {
            throw new TypeError(ERR_NON_OBJECT_TARGET + object);
        }
        if ((typeof descriptor != "object" && typeof descriptor != "function") || descriptor === null) {
            throw new TypeError(ERR_NON_OBJECT_DESCRIPTOR + descriptor);
        }
        // make a valiant attempt to use the real defineProperty
        // for I8's DOM elements.
        if (definePropertyFallback) {
            try {
                return definePropertyFallback.call(Object, object, property, descriptor);
            } catch (exception) {
                // try the shim if the real one doesn't work
            }
        }

        // If it's a data property.
        if (owns(descriptor, "value")) {
            // fail silently if "writable", "enumerable", or "configurable"
            // are requested but not supported
            /*
            // alternate approach:
            if ( // can't implement these features; allow false but not true
                !(owns(descriptor, "writable") ? descriptor.writable : true) ||
                !(owns(descriptor, "enumerable") ? descriptor.enumerable : true) ||
                !(owns(descriptor, "configurable") ? descriptor.configurable : true)
            )
                throw new RangeError(
                    "This implementation of Object.defineProperty does not " +
                    "support configurable, enumerable, or writable."
                );
            */

            if (supportsAccessors && (lookupGetter(object, property) ||
                                      lookupSetter(object, property)))
            {
                // As accessors are supported only on engines implementing
                // `__proto__` we can safely override `__proto__` while defining
                // a property to make sure that we don't hit an inherited
                // accessor.
                var prototype = object.__proto__;
                object.__proto__ = prototypeOfObject;
                // Deleting a property anyway since getter / setter may be
                // defined on object itself.
                delete object[property];
                object[property] = descriptor.value;
                // Setting original `__proto__` back now.
                object.__proto__ = prototype;
            } else {
                object[property] = descriptor.value;
            }
        } else {
            if (!supportsAccessors) {
                throw new TypeError(ERR_ACCESSORS_NOT_SUPPORTED);
            }
            // If we got that far then getters and setters can be defined !!
            if (owns(descriptor, "get")) {
                defineGetter(object, property, descriptor.get);
            }
            if (owns(descriptor, "set")) {
                defineSetter(object, property, descriptor.set);
            }
        }
        return object;
    };
}

// ES5 15.2.3.7
// http://es5.github.com/#x15.2.3.7
if (!Object.defineProperties || definePropertiesFallback) {
    Object.defineProperties = function defineProperties(object, properties) {
        // make a valiant attempt to use the real defineProperties
        if (definePropertiesFallback) {
            try {
                return definePropertiesFallback.call(Object, object, properties);
            } catch (exception) {
                // try the shim if the real one doesn't work
            }
        }

        for (var property in properties) {
            if (owns(properties, property) && property != "__proto__") {
                Object.defineProperty(object, property, properties[property]);
            }
        }
        return object;
    };
}

// ES5 15.2.3.8
// http://es5.github.com/#x15.2.3.8
if (!Object.seal) {
    Object.seal = function seal(object) {
        // this is misleading and breaks feature-detection, but
        // allows "securable" code to "gracefully" degrade to working
        // but insecure code.
        return object;
    };
}

// ES5 15.2.3.9
// http://es5.github.com/#x15.2.3.9
if (!Object.freeze) {
    Object.freeze = function freeze(object) {
        // this is misleading and breaks feature-detection, but
        // allows "securable" code to "gracefully" degrade to working
        // but insecure code.
        return object;
    };
}

// detect a Rhino bug and patch it
try {
    Object.freeze(function () {});
} catch (exception) {
    Object.freeze = (function freeze(freezeObject) {
        return function freeze(object) {
            if (typeof object == "function") {
                return object;
            } else {
                return freezeObject(object);
            }
        };
    })(Object.freeze);
}

// ES5 15.2.3.10
// http://es5.github.com/#x15.2.3.10
if (!Object.preventExtensions) {
    Object.preventExtensions = function preventExtensions(object) {
        // this is misleading and breaks feature-detection, but
        // allows "securable" code to "gracefully" degrade to working
        // but insecure code.
        return object;
    };
}

// ES5 15.2.3.11
// http://es5.github.com/#x15.2.3.11
if (!Object.isSealed) {
    Object.isSealed = function isSealed(object) {
        return false;
    };
}

// ES5 15.2.3.12
// http://es5.github.com/#x15.2.3.12
if (!Object.isFrozen) {
    Object.isFrozen = function isFrozen(object) {
        return false;
    };
}

// ES5 15.2.3.13
// http://es5.github.com/#x15.2.3.13
if (!Object.isExtensible) {
    Object.isExtensible = function isExtensible(object) {
        // 1. If Type(O) is not Object throw a TypeError exception.
        if (Object(object) !== object) {
            throw new TypeError(); // TODO message
        }
        // 2. Return the Boolean value of the [[Extensible]] internal property of O.
        var name = '';
        while (owns(object, name)) {
            name += '?';
        }
        object[name] = true;
        var returnValue = owns(object, name);
        delete object[name];
        return returnValue;
    };
}

});
