[MM-61619]: Added aria-live property for message sent status (#29720)

* [MA-22]: Added aria-live property for message sent status

* Review Fixes: Updated the logic to programmatically change status element's content.

* [MA-22]: Rebased with master

webapp/channels/src/components/advanced_text_editor/advanced_text_editor.tsx

@@ -20,6 +20,7 @@ import {haveIChannelPermission} from 'mattermost-redux/selectors/entities/roles'
 import {getCurrentUserId, isCurrentUserGuestUser, getStatusForUserId, makeGetDisplayName} from 'mattermost-redux/selectors/entities/users';
 
 import * as GlobalActions from 'actions/global_actions';
+import type {CreatePostOptions} from 'actions/post_actions';
 import {actionOnGlobalItemsWithPrefix} from 'actions/storage';
 import type {SubmitPostReturnType} from 'actions/views/create_comment';
 import {removeDraft, updateDraft} from 'actions/views/drafts';
@@ -197,6 +198,7 @@ const AdvancedTextEditor = ({
     const draftRef = useRef(draftFromStore);
     const storedDrafts = useRef<Record<string, PostDraft | undefined>>({});
     const lastBlurAt = useRef(0);
+    const messageStatusRef = useRef<HTMLDivElement | null>(null);
 
     const [draft, setDraft] = useState(draftFromStore);
     const [caretPosition, setCaretPosition] = useState(draft.message.length);
@@ -338,6 +340,19 @@ const AdvancedTextEditor = ({
         isInEditMode,
     );
 
+    const handleSubmitWithErrorHandling = useCallback((submittingDraft?: PostDraft, schedulingInfo?: SchedulingInfo, options?: CreatePostOptions) => {
+        handleSubmit(submittingDraft, schedulingInfo, options);
+        if (!errorClass) {
+            const messageStatusElement = messageStatusRef.current;
+            const messageStatusInnerText = messageStatusElement?.textContent;
+            if (messageStatusInnerText === 'Message Sent') {
+                messageStatusElement!.textContent = 'Message Sent &nbsp;';
+            } else {
+                messageStatusElement!.textContent = 'Message Sent';
+            }
+        }
+    }, [errorClass, handleSubmit]);
+
     const handleCancel = useCallback(() => {
         handleDraftChange({
             message: '',
@@ -392,8 +407,8 @@ const AdvancedTextEditor = ({
             handleFileChangesOnSave(draft);
         }
 
-        handleSubmit();
+        handleSubmitWithErrorHandling();
-    }, [dispatch, draft, handleFileChangesOnSave, handleSubmit, isInEditMode, isRHS]);
+    }, [dispatch, draft, handleFileChangesOnSave, handleSubmitWithErrorHandling, isInEditMode, isRHS]);
 
     const [handleKeyDown, postMsgKeyPress] = useKeyHandler(
         draft,
@@ -418,8 +433,8 @@ const AdvancedTextEditor = ({
 
     const handleSubmitWithEvent = useCallback((e: React.FormEvent) => {
         e.preventDefault();
-        handleSubmit();
+        handleSubmitWithErrorHandling();
-    }, [handleSubmit]);
+    }, [handleSubmitWithErrorHandling]);
 
     const handlePostError = useCallback((err: React.ReactNode) => {
         setPostError(err);
@@ -573,7 +588,9 @@ const AdvancedTextEditor = ({
         draftRef.current = draft;
     }, [draft]);
 
-    const handleSubmitPostAndScheduledMessage = useCallback((schedulingInfo?: SchedulingInfo) => handleSubmit(undefined, schedulingInfo), [handleSubmit]);
+    const handleSubmitPostAndScheduledMessage = useCallback((schedulingInfo?: SchedulingInfo) => {
+        handleSubmitWithErrorHandling(undefined, schedulingInfo);
+    }, [handleSubmitWithErrorHandling]);
 
     // Set the draft from store when changing post or channels, and store the previous one
     useEffect(() => {
@@ -865,6 +882,11 @@ const AdvancedTextEditor = ({
                     onCancel={handleCancel}
                 />
             )}
+            <div
+                ref={messageStatusRef}
+                aria-live='assertive'
+                className='sr-only'
+            />
         </form>
     );
 };