feat(proto): add server handshake handler

proto/src/handshake/mod.rs

@@ -0,0 +1 @@
+pub mod server;

proto/src/handshake/server.rs

@@ -0,0 +1,59 @@
+use crate::message::backend::{
+    AuthenticationOkData, BackendKeyDataData, BackendMessage, ParameterStatusData,
+    ReadyForQueryData,
+};
+use crate::message::special::{SpecialMessage, StartupMessageData};
+use crate::reader::frontend::FrontendProtoReader;
+use crate::writer::backend::BackendProtoWriter;
+use crate::writer::protowriter::ProtoFlush;
+
+pub async fn do_server_handshake(
+    writer: &mut (impl BackendProtoWriter + ProtoFlush),
+    reader: &mut impl FrontendProtoReader,
+    name: &str,
+    process: i32,
+    secret: i32,
+) -> anyhow::Result<StartupMessageData> {
+    match &reader.peek_special_message().await? {
+        Some(msg @ SpecialMessage::SSLRequest) => {
+            reader.consume_special_message(msg).await?;
+            writer.write_ssl_reject().await?;
+            writer.flush().await?;
+        }
+        _ => {
+            //  No SSL request
+        }
+    }
+
+    let startup_message = match &reader.peek_special_message().await? {
+        Some(msg @ SpecialMessage::StartupMessage(data)) => {
+            reader.consume_special_message(msg).await?;
+            data.clone()
+        }
+        _ => {
+            return Err(anyhow::anyhow!("Expected Startup Message"));
+        }
+    };
+
+    writer
+        .write_proto(BackendMessage::from(AuthenticationOkData { status: 0 }))
+        .await?;
+
+    writer
+        .write_proto(BackendMessage::from(ParameterStatusData {
+            name: "server_version".to_string().into(),
+            value: format!("16.0 ({name})").into(),
+        }))
+        .await?;
+
+    writer
+        .write_proto(BackendMessage::from(BackendKeyDataData { process, secret }))
+        .await?;
+
+    writer
+        .write_proto(BackendMessage::from(ReadyForQueryData { status: b'I' }))
+        .await?;
+
+    writer.flush().await?;
+    Ok(startup_message)
+}

proto/src/lib.rs

@@ -1,3 +1,4 @@
+pub mod handshake;
 pub mod message;
 pub mod reader;
 pub mod writer;