TF-3964 Fix text is not well displayed when preview email

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

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

@@ -6,6 +6,8 @@ import 'package:html/dom.dart';
 class NormalizeLineHeightInStyleTransformer extends DomTransformer {
   const NormalizeLineHeightInStyleTransformer();
 
+  static const _removableLineHeights = ['1px', '100%'];
+
   @override
   Future<void> process({
     required Document document,
@@ -13,19 +15,28 @@ class NormalizeLineHeightInStyleTransformer extends DomTransformer {
     Map<String, String>? mapUrlDownloadCID,
   }) async {
     try {
+      final pattern = RegExp(
+        r'line-height\s*:\s*(?:' + _removableLineHeights.join('|') + r')\s*;?',
+        caseSensitive: false,
+      );
+
       final elements = document.querySelectorAll('[style*="line-height"]');
 
       for (final element in elements) {
         final originalStyle = element.attributes['style'];
         if (originalStyle == null) continue;
 
-        final updatedStyle = originalStyle.replaceAllMapped(
-          RegExp(r'line-height\s*:\s*1px\s*;?', caseSensitive: false),
-          (match) => '',
-        );
+        var updatedStyle = originalStyle.replaceAll(pattern, '').trim();
+
+        // Remove extra spaces (>=2 spaces → 1 space)
+        updatedStyle = updatedStyle.replaceAll(RegExp(r'\s{2,}'), ' ');
 
         if (updatedStyle != originalStyle) {
-          element.attributes['style'] = updatedStyle;
+          if (updatedStyle.isEmpty) {
+            element.attributes.remove('style');
+          } else {
+            element.attributes['style'] = updatedStyle;
+          }
         }
       }
     } catch (e) {

core/test/utils/normalize_line_height_in_style_transformer_test.dart

@@ -0,0 +1,108 @@
+import 'package:core/presentation/utils/html_transformer/dom/normalize_line_height_in_style_transformer.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:html/parser.dart' show parse;
+import 'package:html/dom.dart';
+import 'package:core/data/network/dio_client.dart';
+import 'package:mockito/annotations.dart';
+
+import 'normalize_line_height_in_style_transformer_test.mocks.dart';
+
+@GenerateNiceMocks([MockSpec<DioClient>()])
+void main() {
+  group('NormalizeLineHeightInStyleTransformer', () {
+    const transformer = NormalizeLineHeightInStyleTransformer();
+    final dioClient = MockDioClient();
+
+    Future<Document> run(String html) async {
+      final doc = parse(html);
+      await transformer.process(document: doc, dioClient: dioClient);
+      return doc;
+    }
+
+    test('Should removes line-height:1px', () async {
+      final doc = await run('<p style="color:red; line-height:1px;">Hello</p>');
+      expect(doc.querySelector('p')!.attributes['style'], 'color:red;');
+    });
+
+    test('Should removes line-height:100%', () async {
+      final doc = await run(
+        '<p style="line-height:100%; font-size:14px;">Hi</p>',
+      );
+      expect(doc.querySelector('p')!.attributes['style'], 'font-size:14px;');
+    });
+
+    test('Should keeps other line-height values', () async {
+      final doc = await run(
+        '<p style="line-height:150%; font-weight:bold;">Hi</p>',
+      );
+      expect(
+        doc.querySelector('p')!.attributes['style'],
+        'line-height:150%; font-weight:bold;',
+      );
+    });
+
+    test('Should removes style attribute if only line-height existed',
+        () async {
+      final doc = await run('<div style="line-height:1px;"></div>');
+      expect(
+        doc.querySelector('div')!.attributes.containsKey('style'),
+        isFalse,
+      );
+    });
+
+    test('Should handles missing style gracefully', () async {
+      final doc = await run('<span>No style here</span>');
+      expect(
+        doc.querySelector('span')!.attributes.containsKey('style'),
+        isFalse,
+      );
+    });
+
+    test('Should removes multiple unwanted line-heights', () async {
+      final doc = await run(
+        '<p style="line-height:1px; color:blue; line-height:100%; font-size:12px;"></p>',
+      );
+      expect(
+        doc.querySelector('p')!.attributes['style'],
+        'color:blue; font-size:12px;',
+      );
+    });
+
+    test('Should removes line-height even with irregular spacing', () async {
+      final doc = await run(
+        '<p style="line-height :   1px ; color: green;"></p>',
+      );
+      expect(doc.querySelector('p')!.attributes['style'], 'color: green;');
+    });
+
+    test('Should keep line-height:auto', () async {
+      final doc = await run(
+        '<p style="line-height:auto; font-size:16px;"></p>',
+      );
+      expect(
+        doc.querySelector('p')!.attributes['style'],
+        'line-height:auto; font-size:16px;',
+      );
+    });
+
+    test('Should not touch unrelated CSS properties', () async {
+      final doc = await run(
+        '<p style="margin:0; padding:5px;"></p>',
+      );
+      expect(
+        doc.querySelector('p')!.attributes['style'],
+        'margin:0; padding:5px;',
+      );
+    });
+
+    test('Should trim trailing semicolon after removal', () async {
+      final doc = await run(
+        '<p style="line-height:1px;"></p>',
+      );
+      expect(
+        doc.querySelector('p')!.attributes.containsKey('style'),
+        isFalse,
+      );
+    });
+  });
+}