(function (tree) {

tree.URL = function (val, paths) {

if (val.data) {
    this.attrs = val;
} else {
    // Add the base path if the URL is relative and we are in the browser
    if (typeof(window) !== 'undefined' && !/^(?:https?:\/\/|file:\/\/|data:|\/)/.test(val.value) && paths.length > 0) {
        val.value = paths[0] + (val.value.charAt(0) === '/' ? val.value.slice(1) : val.value);
    }
    this.value = val;
    this.paths = paths;
}

}; tree.URL.prototype = {

toCSS: function () {
    return "url(" + (this.attrs ? 'data:' + this.attrs.mime + this.attrs.charset + this.attrs.base64 + this.attrs.data
                                : this.value.toCSS()) + ")";
},
eval: function (ctx) {
    return this.attrs ? this : new(tree.URL)(this.value.eval(ctx), this.paths);
}

};

})(require('../tree'));