rewrite

src/response.rs

@@ -0,0 +1,35 @@
+#[derive(Debug, Clone)]
+pub enum Response {
+    Pong,
+    Error(Error),
+}
+
+impl std::fmt::Display for Response {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Response::Pong => write!(f, "Pong"),
+            Response::Error(error) => write!(f, "!{}", error),
+        }
+    }
+}
+
+#[derive(Debug, Clone)]
+pub enum Error {
+    InvalidRequest,
+    InvalidMethod,
+    InvalidParameter,
+    ParameterNotFound,
+    InvalidSessionToken,
+}
+
+impl std::fmt::Display for Error {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Error::InvalidRequest => write!(f, "Invalid request"),
+            Error::InvalidMethod => write!(f, "Invalid method"),
+            Error::InvalidParameter => write!(f, "Invalid parameter"),
+            Error::ParameterNotFound => write!(f, "Parameter not found"),
+            Error::InvalidSessionToken => write!(f, "Invalid session token"),
+        }
+    }
+}