Fix the regexp performance issue

Also move the addHoverClass implementation into the rebuild stage.
So if there is still some corner case we have not handled, it will
only affect the replayer part of rrweb.

src/rebuild.ts

@@ -115,6 +115,22 @@ function getTagName(n: elementNode): string {
   return tagName;
 }
 
+const CSS_SELECTOR = /([^\r\n,{}]+)(,(?=[^}]*{)|\s*{)/g;
+const HOVER_SELECTOR = /([^\\]):hover/g;
+export function addHoverClass(cssText: string): string {
+  return cssText.replace(CSS_SELECTOR, (match, p1: string, p2: string) => {
+    if (HOVER_SELECTOR.test(p1)) {
+      const newSelector = p1.replace(HOVER_SELECTOR, '$1.\\:hover');
+      return `${p1.replace(/\s*$/, '')}, ${newSelector.replace(
+        /^\s*/,
+        '',
+      )}${p2}`;
+    } else {
+      return match;
+    }
+  });
+}
+
 function buildNode(n: serializedNodeWithId, doc: Document): Node | null {
   switch (n.type) {
     case NodeType.Document:
@@ -139,6 +155,9 @@ function buildNode(n: serializedNodeWithId, doc: Document): Node | null {
           value = typeof value === 'boolean' ? '' : value;
           const isTextarea = tagName === 'textarea' && name === 'value';
           const isRemoteCss = tagName === 'style' && name === '_cssText';
+          if (isRemoteCss) {
+            value = addHoverClass(value);
+          }
           if (isTextarea || isRemoteCss) {
             const child = doc.createTextNode(value);
             node.appendChild(child);
@@ -152,7 +171,9 @@ function buildNode(n: serializedNodeWithId, doc: Document): Node | null {
       }
       return node;
     case NodeType.Text:
-      return doc.createTextNode(n.textContent);
+      return doc.createTextNode(
+        n.isStyle ? addHoverClass(n.textContent) : n.textContent,
+      );
     case NodeType.CDATA:
       return doc.createCDATASection(n.textContent);
     case NodeType.Comment: