TF-4195 refactor: extract helpers for updating email label in memory

lib/features/email/presentation/extensions/handle_label_for_email_extension.dart

@@ -123,15 +123,52 @@ extension HandleLabelForEmailExtension on SingleEmailController {
     required KeyWordIdentifier labelKeyword,
     required bool isMobileThreadDisabled,
   }) {
-    if (isMobileThreadDisabled) {
-      final selectedEmail = mailboxDashBoardController.selectedEmail.value;
-      if (selectedEmail?.id == emailId) {
-        mailboxDashBoardController.selectedEmail.value?.keywords
-            ?.addKeyword(labelKeyword);
+    _updateLabelOnSelectedEmailIfNeeded(
+      emailId: emailId,
+      labelKeyword: labelKeyword,
+      isMobileThreadDisabled: isMobileThreadDisabled,
+    );
+
+    _updateLabelOnThreadIfNeeded(
+      emailId: emailId,
+      labelKeyword: labelKeyword,
+      isMobileThreadDisabled: isMobileThreadDisabled,
+    );
+
+    _updateLabelOnCurrentEmailLoaded(
+      emailId: emailId,
+      labelKeyword: labelKeyword,
+    );
+
+    _notifyLabelUpdated(
+      emailId: emailId,
+      labelKeyword: labelKeyword,
+    );
   }
-    } else {
+
+  void _updateLabelOnSelectedEmailIfNeeded({
+    required EmailId emailId,
+    required KeyWordIdentifier labelKeyword,
+    required bool isMobileThreadDisabled,
+  }) {
+    if (!isMobileThreadDisabled) return;
+
+    final selectedEmail = mailboxDashBoardController.selectedEmail.value;
+    if (selectedEmail?.id != emailId) return;
+
+    selectedEmail?.keywords?.addKeyword(labelKeyword);
+  }
+
+  void _updateLabelOnThreadIfNeeded({
+    required EmailId emailId,
+    required KeyWordIdentifier labelKeyword,
+    required bool isMobileThreadDisabled,
+  }) {
+    if (isMobileThreadDisabled) return;
+
     final controller = threadDetailController;
-      if (controller != null) {
+    if (controller == null) return;
+
     controller.emailIdsPresentation.value =
         controller.emailIdsPresentation.toggleEmailKeywordById(
       emailId: emailId,
@@ -146,10 +183,15 @@ extension HandleLabelForEmailExtension on SingleEmailController {
       remove: false,
     );
   }
-    }
 
+  void _updateLabelOnCurrentEmailLoaded({
+    required EmailId emailId,
+    required KeyWordIdentifier labelKeyword,
+  }) {
     final emailLoaded = currentEmailLoaded.value;
-    if (emailLoaded != null && emailLoaded.emailCurrent?.id == emailId) {
+    if (emailLoaded == null) return;
+    if (emailLoaded.emailCurrent?.id != emailId) return;
+
     currentEmailLoaded.value = emailLoaded.toggleEmailKeyword(
       emailId: emailId,
       keyword: labelKeyword,
@@ -157,6 +199,10 @@ extension HandleLabelForEmailExtension on SingleEmailController {
     );
   }
 
+  void _notifyLabelUpdated({
+    required EmailId emailId,
+    required KeyWordIdentifier labelKeyword,
+  }) {
     mailboxDashBoardController.updateEmailFlagByEmailIds(
       [emailId],
       isLabelAdded: true,