def validate_app_data(name, server_id, existing_app_id=None):
    """
    Validate application data, checking for required fields and uniqueness

    Args:
        name: The application name
        server_id: The server ID
        existing_app_id: The ID of the application being edited (if any)

    Returns:
        tuple: (valid, error_message)
    """
    # Check for required fields
    if not name or not name.strip():
        return False, "Application name is required"

    if not server_id:
        return False, "Server is required"

    # Check name length
    if len(name) < 2:
        return False, "Application name must be at least 2 characters"

    # Check for uniqueness of name on the server
    from app.models import App

    query = App.query.filter(App.name == name, App.server_id == server_id)

    # If editing an existing app, exclude it from the uniqueness check
    if existing_app_id:
        query = query.filter(App.id != existing_app_id)

    existing_app = query.first()

    if existing_app:
        return False, f"Application '{name}' already exists on this server"

    return True, None