function cssToTree (tree, css, selector, prelude) {
    var declarations = {};
    var hasDeclarations = false;
    var key, value;

    for (key in css) {
        value = css[key];
        if (typeof value !== 'object') {
            hasDeclarations = true;
            declarations[key] = value;
        }
    }

    if (hasDeclarations) {
        if (!tree[prelude]) tree[prelude] = {};
        tree[prelude][selector] = declarations;
    }

    for (key in css) {
        value = css[key];
        if (typeof value === 'object') {
            if (key[0] === '@') {
                cssToTree(tree, value, selector, key);
            } else {
                var hasCurrentSymbol = key.indexOf('&') > -1;
                var selectorParts = selector.split(',');
                if (hasCurrentSymbol) {
                    for (var i = 0; i < selectorParts.length; i++) {
                        selectorParts[i] = key.replace(/&/g, selectorParts[i]);
                    }
                } else {
                    for (var i = 0; i < selectorParts.length; i++) {
                        selectorParts[i] = selectorParts[i] + ' ' + key;
                    }
                }
                cssToTree(tree, value, selectorParts.join(','), prelude);
            }
        }
    }
};

exports.cssToTree = cssToTree;