refactor(proto): reuse code in handshakes

proto/src/handshake/response.rs

@@ -0,0 +1,65 @@
+use crate::handshake::errors::ClientHandshakeError;
+use crate::message::backend::{BackendKeyDataData, BackendMessage, ParameterStatusData};
+
+pub struct HandshakeResponse {
+    pub version: String,
+    pub process_id: i32,
+    pub secret_key: i32,
+}
+
+impl HandshakeResponse {
+    pub fn new(name: &str, pid: i32, key: i32) -> Self {
+        Self {
+            version: format!("16.0 ({name})", name = name),
+            process_id: pid,
+            secret_key: key,
+        }
+    }
+}
+
+impl TryFrom<&[BackendMessage]> for HandshakeResponse {
+    type Error = ClientHandshakeError;
+
+    fn try_from(messages: &[BackendMessage]) -> Result<Self, Self::Error> {
+        let mut version = None;
+        let mut process_id = None;
+        let mut secret_key = None;
+
+        for message in messages {
+            match message {
+                BackendMessage::ParameterStatus(data) => {
+                    if data.name.as_str() == "server_version" {
+                        version = Some(String::from(data.value.as_str()));
+                    }
+                }
+                BackendMessage::BackendKeyData(data) => {
+                    process_id = Some(data.process);
+                    secret_key = Some(data.secret);
+                }
+                _ => {}
+            }
+        }
+
+        match (version, process_id, secret_key) {
+            (Some(version), Some(process_id), Some(secret_key)) => {
+                Ok(Self { version, process_id, secret_key })
+            }
+            _ => Err(ClientHandshakeError::UnexpectedResponse),
+        }
+    }
+}
+
+impl From<&HandshakeResponse> for Vec<BackendMessage> {
+    fn from(response: &HandshakeResponse) -> Self {
+        vec![
+            BackendMessage::ParameterStatus(ParameterStatusData {
+                name: "server_version".into(),
+                value: response.version.clone().into(),
+            }),
+            BackendMessage::BackendKeyData(BackendKeyDataData {
+                process: response.process_id,
+                secret: response.secret_key,
+            }),
+        ]
+    }
+}