TF-3691 Support HTML escaping in search snippets

Signed-off-by: dab246 <tdvu@linagora.com>

core/test/utils/html_utils_test.dart

@@ -1,4 +1,5 @@
 import 'package:core/presentation/utils/html_transformer/dom/image_transformers.dart';
+import 'package:core/utils/html/html_utils.dart';
 import 'package:flutter_test/flutter_test.dart';
 
 void main() {
@@ -31,4 +32,112 @@ void main() {
       expect(result, null);
     });
   });
+
+  group('HtmlUtils.unescapeHtml', () {
+    test('should return original string when no HTML entities present', () {
+      const input = 'This is a normal string';
+      expect(HtmlUtils.unescapeHtml(input), equals(input));
+    });
+
+    test('should unescape basic HTML entities', () {
+      const input = '<div>Hello & Welcome</div>';
+      const expected = '<div>Hello & Welcome</div>';
+      expect(HtmlUtils.unescapeHtml(input), equals(expected));
+    });
+
+    test('should unescape numeric decimal HTML entities', () {
+      const input = '&#65;&#66;&#67;';
+      const expected = 'ABC';
+      expect(HtmlUtils.unescapeHtml(input), equals(expected));
+    });
+
+    test('should unescape numeric hexadecimal HTML entities', () {
+      const input = '&#x41;&#x42;&#x43;';
+      const expected = 'ABC';
+      expect(HtmlUtils.unescapeHtml(input), equals(expected));
+    });
+
+    test('should unescape special character entities', () {
+      const input = '&quot;Hello&apos; &copy; &reg; &trade;';
+      const expected = '"Hello\' © ® ™';
+      expect(HtmlUtils.unescapeHtml(input), equals(expected));
+    });
+
+    test('should handle empty string', () {
+      const input = '';
+      expect(HtmlUtils.unescapeHtml(input), isEmpty);
+    });
+
+    test('should handle string with only HTML entity', () {
+      const input = '&amp;';
+      const expected = '&';
+      expect(HtmlUtils.unescapeHtml(input), equals(expected));
+    });
+
+    test('should leave invalid HTML entities unchanged', () {
+      const input = 'This & is not an entity &invalid; &123';
+      const expected = 'This & is not an entity &invalid; &123';
+      expect(HtmlUtils.unescapeHtml(input), equals(expected));
+    });
+
+    test('should handle Unicode characters', () {
+      const input = '&lt;こんにちは&gt;'; // <こんにちは>
+      const expected = '<こんにちは>';
+      expect(HtmlUtils.unescapeHtml(input), equals(expected));
+    });
+
+    test('should handle complex mixed entities', () {
+      const input = '&lt;script&gt;alert(&quot;Hello&quot;);&lt;/script&gt;&amp;&#64;&#x40;';
+      const expected = '<script>alert("Hello");</script>&@@';
+      expect(HtmlUtils.unescapeHtml(input), equals(expected));
+    });
+  });
+
+  group('HtmlUtils.removeWhitespace', () {
+    test('should remove carriage returns (\\r)', () {
+      expect(HtmlUtils.removeWhitespace('Hello\rWorld'), equals('HelloWorld'));
+      expect(HtmlUtils.removeWhitespace('\r\r\r'), equals(''));
+      expect(HtmlUtils.removeWhitespace('a\rb\rc'), equals('abc'));
+    });
+
+    test('should remove newlines (\\n)', () {
+      expect(HtmlUtils.removeWhitespace('Hello\nWorld'), equals('HelloWorld'));
+      expect(HtmlUtils.removeWhitespace('\n\n\n'), equals(''));
+      expect(HtmlUtils.removeWhitespace('a\nb\nc'), equals('abc'));
+    });
+
+    test('should remove tabs (\\t)', () {
+      expect(HtmlUtils.removeWhitespace('Hello\tWorld'), equals('HelloWorld'));
+      expect(HtmlUtils.removeWhitespace('\t\t\t'), equals(''));
+      expect(HtmlUtils.removeWhitespace('a\tb\tc'), equals('abc'));
+    });
+
+    test('should remove all whitespace characters when combined', () {
+      expect(HtmlUtils.removeWhitespace('Hello\r\n\tWorld'), equals('HelloWorld'));
+      expect(HtmlUtils.removeWhitespace('a\rb\nc\td'), equals('abcd'));
+      expect(HtmlUtils.removeWhitespace('\r\n\t\r\n\t'), equals(''));
+    });
+
+    test('should return empty string for empty input', () {
+      expect(HtmlUtils.removeWhitespace(''), equals(''));
+    });
+
+    test('should leave string unchanged when no whitespace present', () {
+      expect(HtmlUtils.removeWhitespace('HelloWorld'), equals('HelloWorld'));
+      expect(HtmlUtils.removeWhitespace('12345'), equals('12345'));
+      expect(HtmlUtils.removeWhitespace('!@#\$%^'), equals('!@#\$%^'));
+    });
+
+    test('should preserve spaces if not configured to remove them', () {
+      expect(HtmlUtils.removeWhitespace('Hello World'), equals('Hello World'));
+      expect(HtmlUtils.removeWhitespace('a b c'), equals('a b c'));
+    });
+
+    test('should handle mixed content with various whitespace', () {
+      expect(
+        HtmlUtils.removeWhitespace('Text\rwith\nnew\tlines\r\nand\ttabs'),
+        equals('Textwithnewlinesandtabs'),
+      );
+    });
+  });
 }