var Object_keys = function (obj) {
    if (Object.keys) return Object.keys(obj)
    else {
        var res = [];
        for (var key in obj) res.push(key)
        return res;
    }
};

var forEach = function (xs, fn) {
    if (xs.forEach) return xs.forEach(fn)
    else for (var i = 0; i < xs.length; i++) {
        fn(xs[i], i, xs);
    }
};

var Script = exports.Script = function NodeScript (code) {
    if (!(this instanceof Script)) return new Script(code);
    this.code = code;
};

Script.prototype.runInNewContext = function (context) {
    if (!context) context = {};
    
    var iframe = document.createElement('iframe');
    if (!iframe.style) iframe.style = {};
    iframe.style.display = 'none';
    
    document.body.appendChild(iframe);
    
    var win = iframe.contentWindow;
    
    forEach(Object_keys(context), function (key) {
        win[key] = context[key];
    });
     
    if (!win.eval && win.execScript) {
        // win.eval() magically appears when this is called in IE:
        win.execScript('null');
    }
    
    var res = win.eval(this.code);
    
    forEach(Object_keys(win), function (key) {
        context[key] = win[key];
    });
    
    document.body.removeChild(iframe);
    
    return res;
};

Script.prototype.runInThisContext = function () {
    return eval(this.code); // maybe...
};

Script.prototype.runInContext = function (context) {
    // seems to be just runInNewContext on magical context objects which are
    // otherwise indistinguishable from objects except plain old objects
    // for the parameter segfaults node
    return this.runInNewContext(context);
};

forEach(Object_keys(Script.prototype), function (name) {
    exports[name] = Script[name] = function (code) {
        var s = Script(code);
        return s[name].apply(s, [].slice.call(arguments, 1));
    };
});

exports.createScript = function (code) {
    return exports.Script(code);
};

exports.createContext = Script.createContext = function (context) {
    // not really sure what this one does
    // seems to just make a shallow copy
    var copy = {};
    if(typeof context === 'object') {
        forEach(Object_keys(context), function (key) {
            copy[key] = context[key];
        });
    }
    return copy;
};