fixup! TF-4224 Reduce ReDoS vulnerability

core/lib/presentation/utils/html_transformer/base/dom_transformer.dart

@@ -2,6 +2,7 @@
 import 'package:core/data/network/dio_client.dart';
 import 'package:core/utils/app_logger.dart';
 import 'package:dartz/dartz.dart';
+import 'package:flutter/widgets.dart' show visibleForTesting;
 import 'package:html/dom.dart';
 
 /// Transforms the HTML DOM.
@@ -11,6 +12,9 @@ abstract class DomTransformer {
 
   static final _backgroundImageRegex = RegExp(r'''\bbackground-image\s*:\s*url\(\s*['"]?([^' ")]+)['"]?\s*\)''');
 
+  @visibleForTesting
+  static RegExp get backgroundImageRegex => _backgroundImageRegex;
+
   /// Uses the `DOM` [document] to transform the `document`.
   ///
   /// All changes will be visible to subsequent transformers.

core/lib/presentation/utils/html_transformer/dom/normalize_line_height_in_style_transformer.dart

@@ -1,6 +1,7 @@
 import 'package:core/data/network/dio_client.dart';
 import 'package:core/presentation/utils/html_transformer/base/dom_transformer.dart';
 import 'package:core/utils/app_logger.dart';
+import 'package:flutter/widgets.dart' show visibleForTesting;
 import 'package:html/dom.dart';
 
 class NormalizeLineHeightInStyleTransformer extends DomTransformer {
@@ -15,6 +16,9 @@ class NormalizeLineHeightInStyleTransformer extends DomTransformer {
     caseSensitive: false,
   );
 
+  @visibleForTesting
+  static RegExp get lineHeightPattern => _lineHeightPattern;
+
   @override
   Future<void> process({
     required Document document,

core/lib/utils/html/html_utils.dart

@@ -39,6 +39,15 @@ class HtmlUtils {
     caseSensitive: false,
   );
 
+  @visibleForTesting
+  static RegExp get htmlStartTagRegex => _htmlStartTagRegex;
+
+  @visibleForTesting
+  static RegExp get htmlEndTagRegex => _htmlEndTagRegex;
+
+  @visibleForTesting
+  static RegExp get urlRegex => _urlRegex;
+
   static const removeLineHeight1px = (
     script: '''
       document.querySelectorAll('[style*="line-height"]').forEach(el => {

core/test/utils/redos_vulnerability_test.dart

@@ -1,4 +1,5 @@
 import 'package:core/data/network/dio_client.dart';
+import 'package:core/presentation/utils/html_transformer/base/dom_transformer.dart';
 import 'package:core/presentation/utils/html_transformer/dom/image_transformers.dart';
 import 'package:core/presentation/utils/html_transformer/dom/normalize_line_height_in_style_transformer.dart';
 import 'package:core/utils/html/html_utils.dart';
@@ -684,10 +685,47 @@ void main() {
 
     group('Regex initialization optimization', () {
       test('regex patterns should be reused, not recreated', () {
-        // This test verifies that regex patterns are static and reused
-        final regex1 = StringConvert.base64ValidationRegex;
-        final regex2 = StringConvert.base64ValidationRegex;
-        expect(identical(regex1, regex2), true);
+        // This test verifies that all refactored regex patterns are static and reused
+        // across multiple calls, preventing unnecessary regex compilation overhead
+
+        // StringConvert patterns
+        final base64_1 = StringConvert.base64ValidationRegex;
+        final base64_2 = StringConvert.base64ValidationRegex;
+        expect(identical(base64_1, base64_2), true,
+            reason: 'base64ValidationRegex should be static and reused');
+
+        final emailLocalhost1 = StringConvert.emailLocalhostRegex;
+        final emailLocalhost2 = StringConvert.emailLocalhostRegex;
+        expect(identical(emailLocalhost1, emailLocalhost2), true,
+            reason: 'emailLocalhostRegex should be static and reused');
+
+        // DomTransformer patterns
+        final bgImage1 = DomTransformer.backgroundImageRegex;
+        final bgImage2 = DomTransformer.backgroundImageRegex;
+        expect(identical(bgImage1, bgImage2), true,
+            reason: 'backgroundImageRegex should be static and reused');
+
+        // NormalizeLineHeightInStyleTransformer patterns
+        final lineHeight1 = NormalizeLineHeightInStyleTransformer.lineHeightPattern;
+        final lineHeight2 = NormalizeLineHeightInStyleTransformer.lineHeightPattern;
+        expect(identical(lineHeight1, lineHeight2), true,
+            reason: 'lineHeightPattern should be static and reused');
+
+        // HtmlUtils patterns
+        final htmlStartTag1 = HtmlUtils.htmlStartTagRegex;
+        final htmlStartTag2 = HtmlUtils.htmlStartTagRegex;
+        expect(identical(htmlStartTag1, htmlStartTag2), true,
+            reason: 'htmlStartTagRegex should be static and reused');
+
+        final htmlEndTag1 = HtmlUtils.htmlEndTagRegex;
+        final htmlEndTag2 = HtmlUtils.htmlEndTagRegex;
+        expect(identical(htmlEndTag1, htmlEndTag2), true,
+            reason: 'htmlEndTagRegex should be static and reused');
+
+        final urlRegex1 = HtmlUtils.urlRegex;
+        final urlRegex2 = HtmlUtils.urlRegex;
+        expect(identical(urlRegex1, urlRegex2), true,
+            reason: 'urlRegex should be static and reused');
       });
     });
   });