feat(proto): add frontend messages

proto/src/message/frontend.rs

@@ -0,0 +1,68 @@
+use crate::message::primitive::data::MessageData;
+use crate::message::primitive::pgstring::PgString;
+use crate::message::proto_message::ProtoMessage;
+use bincode::{Decode, Encode};
+
+#[derive(Debug)]
+pub enum FrontendMessage {
+    Query(QueryData),
+    Terminate,
+}
+
+impl ProtoMessage for FrontendMessage {
+    fn variant(&self) -> u8 {
+        match self {
+            FrontendMessage::Query(_) => b'Q',
+            FrontendMessage::Terminate => b'X',
+        }
+    }
+
+    fn serialize(&self) -> anyhow::Result<Vec<u8>> {
+        match self {
+            FrontendMessage::Query(data) => data.serialize(),
+            FrontendMessage::Terminate => Ok(Vec::with_capacity(0)),
+        }
+    }
+
+    fn deserialize(variant: u8, data: &[u8]) -> anyhow::Result<Self> {
+        match variant {
+            b'Q' => Ok(FrontendMessage::Query(QueryData::deserialize(data)?)),
+            b'X' => Ok(FrontendMessage::Terminate),
+            v => Err(anyhow::anyhow!("Unknown frontend message variant: {v}")),
+        }
+    }
+}
+
+#[derive(Debug, Clone, Encode, Decode)]
+pub struct QueryData {
+    pub query: PgString,
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_symmetric_query() {
+        let frontend = FrontendMessage::Query(QueryData {
+            query: PgString::from("SELECT * FROM foo WHERE bar = $1"),
+        });
+        let raw = frontend.serialize().unwrap();
+        let variant = frontend.variant();
+
+        let message = FrontendMessage::deserialize(variant, &raw).unwrap();
+        assert!(
+            matches!(message, FrontendMessage::Query(QueryData { query }) if query.as_str() == "SELECT * FROM foo WHERE bar = $1")
+        );
+    }
+
+    #[test]
+    fn test_symmetric_terminate() {
+        let frontend = FrontendMessage::Terminate;
+        let raw = frontend.serialize().unwrap();
+        let variant = frontend.variant();
+
+        let message = FrontendMessage::deserialize(variant, &raw).unwrap();
+        assert!(matches!(message, FrontendMessage::Terminate));
+    }
+}

proto/src/message/mod.rs

@@ -1,3 +1,4 @@
 pub mod backend;
+pub mod frontend;
 pub mod primitive;
 pub mod proto_message;