change validator UNIQUE rule depend on METHOD

public function rules()
{
    $user = User::find($this->users);

    switch($this->method())
    {
        case 'GET':
        case 'DELETE':
        {
            return [];
        }
        case 'POST':
        {
            return [
                'user.name.first' => 'required',
                'user.name.last'  => 'required',
                'user.email'      => 'required|email|unique:users,email',
                'user.password'   => 'required|confirmed',
            ];
        }
        case 'PUT':
        case 'PATCH':
        {
            return [
                'user.name.first' => 'required',
                'user.name.last'  => 'required',
                'user.email'      => 'required|email|unique:users,email,'.$user->id,
                'user.password'   => 'required|confirmed',
            ];
        }
        default:break;
    }
}