src/main/java/com/bazaarvoice/jless/ast/visitor/NestedMediaQueries.java
@Override
    public boolean enter(RuleSetNode ruleSetNode) {

        ScopeNode scopeNode = NodeTreeUtils.getFirstChild(ruleSetNode, ScopeNode.class);
        SelectorGroupNode selectorGroupNode = NodeTreeUtils.getFirstChild(ruleSetNode, SelectorGroupNode.class);

        if (selectorGroupNode == null) {
            return true;
        }

        List<SelectorNode> selectorNodes = NodeTreeUtils.getChildren(selectorGroupNode, SelectorNode.class);

        if (selectorNodes.size() < 0) {
            return true;
        }

        List<MediaQueryNode> mediaQueryNodes = NodeTreeUtils.getAndRemoveChildren(scopeNode, MediaQueryNode.class);

        for (MediaQueryNode mediaQueryNode : mediaQueryNodes) {
            ScopeNode mediaScopeNode = NodeTreeUtils.getFirstChild(mediaQueryNode, ScopeNode.class);

            List<RuleSetNode> nestedRuleSets = NodeTreeUtils.getAndRemoveChildren(mediaScopeNode, RuleSetNode.class);

            // if scope node for media query has anything more but whitespaces and rule sets than wrap it with rule set with the same selector group as outer rule set has
            if (mediaScopeNode.getChildren().size() > NodeTreeUtils.getChildren(mediaScopeNode, WhiteSpaceCollectionNode.class).size()) {
                RuleSetNode newRuleSetNode = new RuleSetNode();
                ScopeNode newScopeNode = new ScopeNode();
                newRuleSetNode.addChild(selectorGroupNode.clone());
                newRuleSetNode.addChild(newScopeNode);

                NodeTreeUtils.moveChildren(mediaScopeNode, newScopeNode);

                mediaScopeNode.clearChildren();
                mediaScopeNode.addChild(newRuleSetNode);
            }

            // adding outer selectors to every nested selectors
            for (RuleSetNode nestedRuleSet : nestedRuleSets) {
                List<SelectorGroupNode> nestedSelectorGroupNodes = NodeTreeUtils.getChildren(nestedRuleSet, SelectorGroupNode.class);

                for (SelectorGroupNode nestedSelectorGroupNode : nestedSelectorGroupNodes) {
                    List<SelectorNode> nestedSelectorNodes = NodeTreeUtils.getAndRemoveChildren(nestedSelectorGroupNode, SelectorNode.class);
                    NodeTreeUtils.getAndRemoveChildren(nestedSelectorGroupNode, SpacingNode.class);

                    for (SelectorNode selectorNode : selectorNodes) {
                        for (SelectorNode nestedSelectorNode : nestedSelectorNodes) {
                            if (nestedSelectorNode.getChildren().get(0) != null) {
                                if (nestedSelectorNode.getChildren().get(0) instanceof SelectorSegmentNode) {
                                    SelectorSegmentNode selectorSegmentNode = (SelectorSegmentNode) nestedSelectorNode.getChildren().get(0);
                                    selectorSegmentNode.setCombinator(" ");
                                }
                            }

                            for (int j = selectorNode.getChildren().size() - 1; j >= 0; j--) {
                                if (selectorNode.getChildren().get(j) instanceof SelectorSegmentNode) {
                                    SelectorSegmentNode selectorSegmentNode = (SelectorSegmentNode) selectorNode.getChildren().get(j).clone();

                                    nestedSelectorNode.addChild(0, selectorSegmentNode);
                                }
                            }

                            nestedSelectorGroupNode.addChild(nestedSelectorNode);
                            nestedSelectorGroupNode.addChild(new SpacingNode(" "));
                        }
                    }
                }
                mediaScopeNode.addChild(nestedRuleSet);
            }

            if (ruleSetNode.getParent() != null) {
                ruleSetNode.getParent().addChild(new SpacingNode("\n"));
                ruleSetNode.getParent().addChild(mediaQueryNode);
            }
        }

        return true;
    }
@Override
    public boolean enter(RuleSetNode ruleSetNode) {

        ScopeNode scopeNode = NodeTreeUtils.getFirstChild(ruleSetNode, ScopeNode.class);
        SelectorGroupNode selectorGroupNode = NodeTreeUtils.getFirstChild(ruleSetNode, SelectorGroupNode.class);

        if (selectorGroupNode == null) {
            return true;
        }

        List<SelectorNode> selectorNodes = NodeTreeUtils.getChildren(selectorGroupNode, SelectorNode.class);

        if (selectorNodes.size() < 0) {
            return true;
        }

        List<MediaQueryNode> mediaQueryNodes = NodeTreeUtils.getAndRemoveChildren(scopeNode, MediaQueryNode.class);

        for (MediaQueryNode mediaQueryNode : mediaQueryNodes) {
            ScopeNode mediaScopeNode = NodeTreeUtils.getFirstChild(mediaQueryNode, ScopeNode.class);

            List<RuleSetNode> nestedRuleSets = NodeTreeUtils.getAndRemoveChildren(mediaScopeNode, RuleSetNode.class);

            // if scope node for media query has anything more but whitespaces and rule sets than wrap it with rule set with the same selector group as outer rule set has
            if (mediaScopeNode.getChildren().size() > NodeTreeUtils.getChildren(mediaScopeNode, WhiteSpaceCollectionNode.class).size()) {
                RuleSetNode newRuleSetNode = new RuleSetNode();
                ScopeNode newScopeNode = new ScopeNode();
                newRuleSetNode.addChild(selectorGroupNode.clone());
                newRuleSetNode.addChild(newScopeNode);

                NodeTreeUtils.moveChildren(mediaScopeNode, newScopeNode);

                mediaScopeNode.clearChildren();
                mediaScopeNode.addChild(newRuleSetNode);
            }

            // adding outer selectors to every nested selectors
            for (RuleSetNode nestedRuleSet : nestedRuleSets) {
                List<SelectorGroupNode> nestedSelectorGroupNodes = NodeTreeUtils.getChildren(nestedRuleSet, SelectorGroupNode.class);

                for (SelectorGroupNode nestedSelectorGroupNode : nestedSelectorGroupNodes) {
                    List<SelectorNode> nestedSelectorNodes = NodeTreeUtils.getAndRemoveChildren(nestedSelectorGroupNode, SelectorNode.class);
                    NodeTreeUtils.getAndRemoveChildren(nestedSelectorGroupNode, SpacingNode.class);

                    for (SelectorNode selectorNode : selectorNodes) {
                        for (SelectorNode nestedSelectorNode : nestedSelectorNodes) {
                            if (nestedSelectorNode.getChildren().get(0) != null) {
                                if (nestedSelectorNode.getChildren().get(0) instanceof SelectorSegmentNode) {
                                    SelectorSegmentNode selectorSegmentNode = (SelectorSegmentNode) nestedSelectorNode.getChildren().get(0);
                                    selectorSegmentNode.setCombinator(" ");
                                }
                            }

                            for (int j = selectorNode.getChildren().size() - 1; j >= 0; j--) {
                                if (selectorNode.getChildren().get(j) instanceof SelectorSegmentNode) {
                                    SelectorSegmentNode selectorSegmentNode = (SelectorSegmentNode) selectorNode.getChildren().get(j).clone();

                                    nestedSelectorNode.addChild(0, selectorSegmentNode);
                                }
                            }

                            nestedSelectorGroupNode.addChild(nestedSelectorNode);
                            nestedSelectorGroupNode.addChild(new SpacingNode(" "));
                        }
                    }
                }
                mediaScopeNode.addChild(nestedRuleSet);
            }

            if (ruleSetNode.getParent() != null) {
                ruleSetNode.getParent().addChild(new SpacingNode("\n"));
                ruleSetNode.getParent().addChild(mediaQueryNode);
            }
        }

        return true;
    }
Locates nested MediaQueryNode inside RuleSetNode,
separates RuleSetNode and MediaQueryNode

If MediaQueryNode has nested RuleSetNodes than to every
nested selectors will added selector of input RuleSetNode

If MediaQueryNode has other nodes except WhiteSpaceCollectionNode and
RuleSetNode than all of that will be wrapped with new RuleSetNode with
the same selectors as has input RuleSetNode