Add toggle read/unread action with 'u' keybinding in mail app

src/services/himalaya/client.py

@@ -312,6 +312,49 @@ async def mark_as_read(
         return str(e), False
 
 
+async def mark_as_unread(
+    message_id: int,
+    folder: Optional[str] = None,
+    account: Optional[str] = None,
+) -> Tuple[Optional[str], bool]:
+    """
+    Mark a message as unread by removing the 'seen' flag.
+
+    Args:
+        message_id: The ID of the message to mark as unread
+        folder: The folder containing the message
+        account: The account to use
+
+    Returns:
+        Tuple containing:
+        - Result message or error
+        - Success status (True if operation was successful)
+    """
+    try:
+        cmd = f"himalaya flag remove seen {message_id}"
+        if folder:
+            cmd += f" -f '{folder}'"
+        if account:
+            cmd += f" -a '{account}'"
+
+        process = await asyncio.create_subprocess_shell(
+            cmd,
+            stdout=asyncio.subprocess.PIPE,
+            stderr=asyncio.subprocess.PIPE,
+        )
+        stdout, stderr = await process.communicate()
+
+        if process.returncode == 0:
+            return stdout.decode().strip() or "Marked as unread", True
+        else:
+            error_msg = stderr.decode().strip()
+            logging.error(f"Error marking message as unread: {error_msg}")
+            return error_msg or "Unknown error", False
+    except Exception as e:
+        logging.error(f"Exception during marking message as unread: {e}")
+        return str(e), False
+
+
 async def search_envelopes(
     query: str,
     folder: Optional[str] = None,