feat: add nesting addon

addon/nesting.js

@@ -0,0 +1,41 @@
+'use strict';
+
+module.addon = function (renderer) {
+    renderer.selector = function (parentSelectors, selector) {
+        var parents = parentSelectors.split(',');
+        var result = [];
+        var selectors = selector.split(',');
+        var len1 = parents.length;
+        var len2 = selectors.length;
+        var i, j, part1, part2, sel, pos, parent, replacedSelector;
+
+        for (i = 0; i < len2; i++) {
+            sel = selectors[i];
+            pos = sel.indexOf('&');
+
+            if (pos > -1) {
+                part1 = sel.substr(0, pos);
+                part2 = sel.substr(pos + 1);
+
+                for (j = 0; j < len1; j++) {
+                    parent = parents[j];
+                    replacedSelector = part1 + parent + part2;
+
+                    result.push(replacedSelector);
+                }
+            } else {
+                for (j = 0; j < len1; j++) {
+                    parent = parents[j];
+
+                    if (parent) {
+                        result.push(parent + ' ' + sel);
+                    } else {
+                        result.push(sel);
+                    }
+                }
+            }
+        }
+
+        return result.join(',');
+    };
+};