1 files changed, 53 insertions, 0 deletions
diff --git a/node_modules/csso/lib/restructure/2-initialMergeRuleset.js b/node_modules/csso/lib/restructure/2-initialMergeRuleset.js
new file mode 100644
index 00000000..c49abaa0
--- /dev/null
+++ b/node_modules/csso/lib/restructure/2-initialMergeRuleset.js
@@ -0,0 +1,53 @@
+import { walk } from 'css-tree';
+import {
+    unsafeToSkipNode,
+    isEqualSelectors,
+    isEqualDeclarations,
+    addSelectors,
+    hasSimilarSelectors
+} from './utils.js';
+
+function processRule(node, item, list) {
+    const selectors = node.prelude.children;
+    const declarations = node.block.children;
+
+    list.prevUntil(item.prev, function(prev) {
+        // skip non-ruleset node if safe
+        if (prev.type !== 'Rule') {
+            return unsafeToSkipNode.call(selectors, prev);
+        }
+
+        const prevSelectors = prev.prelude.children;
+        const prevDeclarations = prev.block.children;
+
+        // try to join rulesets with equal pseudo signature
+        if (node.pseudoSignature === prev.pseudoSignature) {
+            // try to join by selectors
+            if (isEqualSelectors(prevSelectors, selectors)) {
+                prevDeclarations.appendList(declarations);
+                list.remove(item);
+                return true;
+            }
+
+            // try to join by declarations
+            if (isEqualDeclarations(declarations, prevDeclarations)) {
+                addSelectors(prevSelectors, selectors);
+                list.remove(item);
+                return true;
+            }
+        }
+
+        // go to prev ruleset if has no selector similarities
+        return hasSimilarSelectors(selectors, prevSelectors);
+    });
+}
+
+// NOTE: direction should be left to right, since rulesets merge to left
+// ruleset. When direction right to left unmerged rulesets may prevent lookup
+// TODO: remove initial merge
+export default function initialMergeRule(ast) {
+    walk(ast, {
+        visit: 'Rule',
+        enter: processRule
+    });
+};