(function (tree) {

tree.joinSelectorVisitor = function() {
    this.contexts = [[]];
    this._visitor = new tree.visitor(this);
};

tree.joinSelectorVisitor.prototype = {
    run: function (root) {
        return this._visitor.visit(root);
    },
    visitRule: function (ruleNode, visitArgs) {
        visitArgs.visitDeeper = false;
    },
    visitMixinDefinition: function (mixinDefinitionNode, visitArgs) {
        visitArgs.visitDeeper = false;
    },

    visitRuleset: function (rulesetNode, visitArgs) {
        var context = this.contexts[this.contexts.length - 1],
            paths = [], selectors;

        this.contexts.push(paths);

        if (! rulesetNode.root) {
            selectors = rulesetNode.selectors;
            if (selectors) {
                selectors = selectors.filter(function(selector) { return selector.getIsOutput(); });
                rulesetNode.selectors = selectors.length ? selectors : (selectors = null);
                if (selectors) { rulesetNode.joinSelectors(paths, context, selectors); }
            }
            if (!selectors) { rulesetNode.rules = null; }
            rulesetNode.paths = paths;
        }
    },
    visitRulesetOut: function (rulesetNode) {
        this.contexts.length = this.contexts.length - 1;
    },
    visitMedia: function (mediaNode, visitArgs) {
        var context = this.contexts[this.contexts.length - 1];
        mediaNode.rules[0].root = (context.length === 0 || context[0].multiMedia);
    }
};

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