refactor(daemon): Refactor commands_loop to use handle_connection (#126)

- Extracted the main token processing loop body in `commands_loop` into `handle_connection` to resolve deep nesting and improve code readability.
- Improved request reading logic by using `(&mut stream).take(request_len as u64).read_to_end(&mut buffer)` to strictly bound allocation to `request_len` and prevent initialization overhead.
- Passed `cargo fmt` and `cargo clippy`.

Co-authored-by: google-labs-jules[bot] <161369871+google-labs-jules[bot]@users.noreply.github.com>

src/bin/daemon.rs

@@ -15,7 +15,7 @@ use std::os::unix::fs::PermissionsExt;
 use std::{fs, time::Duration};
 use tokio::{
     io::{AsyncReadExt, AsyncWriteExt},
-    net::UnixListener,
+    net::{UnixListener, UnixStream},
     time::sleep,
 };
 
@@ -83,83 +83,92 @@ async fn main() -> Result<()> {
 
 async fn commands_loop(listener: UnixListener) -> Result<()> {
     loop {
-        let (mut stream, _addr) = listener.accept().await?;
+        let (stream, _addr) = listener.accept().await?;
 
         tokio::spawn(async move {
-            // ---------- Read request (start) ----------
-            let mut len_bytes = [0u8; 4];
-            if stream.read_exact(&mut len_bytes).await.is_err() {
-                eprintln!("Failed to read message length from client!");
-                return;
-            }
+            handle_connection(stream).await;
+        });
+    }
+}
 
-            let request_len = u32::from_le_bytes(len_bytes) as usize;
+async fn handle_connection(mut stream: UnixStream) {
+    // ---------- Read request (start) ----------
+    let mut len_bytes = [0u8; 4];
+    if stream.read_exact(&mut len_bytes).await.is_err() {
+        eprintln!("Failed to read message length from client!");
+        return;
+    }
 
-            if request_len > MAX_MESSAGE_SIZE {
-                eprintln!(
-                    "Failed to read message from client: request too large ({} bytes)!",
-                    request_len
-                );
-                return;
-            }
+    let request_len = u32::from_le_bytes(len_bytes) as usize;
 
-            let mut buffer = vec![0u8; request_len];
-            if stream.read_exact(&mut buffer).await.is_err() {
-                eprintln!("Failed to read message from client!");
-                return;
-            }
+    if request_len > MAX_MESSAGE_SIZE {
+        eprintln!(
+            "Failed to read message from client: request too large ({} bytes)!",
+            request_len
+        );
+        return;
+    }
 
-            let request: Request = match serde_json::from_slice(&buffer) {
-                Ok(req) => req,
-                Err(err) => {
-                    let response =
-                        Response::new(false, format!("Failed to parse request: {}", err));
-                    let response_data = match serde_json::to_vec(&response) {
-                        Ok(data) => data,
-                        Err(_) => return, // Should not happen with this simple Response
-                    };
-                    let response_len = response_data.len() as u32;
-                    let _ = stream.write_all(&response_len.to_le_bytes()).await;
-                    let _ = stream.write_all(&response_data).await;
-                    return;
-                }
-            };
-            // ---------- Read request (end) ----------
+    let mut buffer = Vec::new();
+    if (&mut stream)
+        .take(request_len as u64)
+        .read_to_end(&mut buffer)
+        .await
+        .is_err()
+        || buffer.len() != request_len
+    {
+        eprintln!("Failed to read message from client!");
+        return;
+    }
 
-            // ---------- Generate response (start) ----------
-            let command = parse_command(&request);
-            let response: Response;
-            if let Some(command) = command {
-                response = command.execute().await;
-            } else {
-                response = Response::new(false, "Unknown command");
-            }
-            // ---------- Generate response (end) ----------
-
-            // ---------- Send response (start) ----------
+    let request: Request = match serde_json::from_slice(&buffer) {
+        Ok(req) => req,
+        Err(err) => {
+            let response = Response::new(false, format!("Failed to parse request: {}", err));
             let response_data = match serde_json::to_vec(&response) {
                 Ok(data) => data,
-                Err(err) => {
-                    eprintln!("Failed to serialize response: {}", err);
-                    return;
-                }
+                Err(_) => return, // Should not happen with this simple Response
             };
             let response_len = response_data.len() as u32;
+            let _ = stream.write_all(&response_len.to_le_bytes()).await;
+            let _ = stream.write_all(&response_data).await;
+            return;
+        }
+    };
+    // ---------- Read request (end) ----------
 
-            if stream.write_all(&response_len.to_le_bytes()).await.is_err() {
-                eprintln!("Failed to write response length to client!");
-                return;
-            }
-            if stream.write_all(&response_data).await.is_err() {
-                eprintln!("Failed to write response to client!");
-                return;
-            }
-            // ---------- Send response (end) ----------
+    // ---------- Generate response (start) ----------
+    let command = parse_command(&request);
+    let response: Response;
+    if let Some(command) = command {
+        response = command.execute().await;
+    } else {
+        response = Response::new(false, "Unknown command");
+    }
+    // ---------- Generate response (end) ----------
 
-            if response.status && response.message.eq("killed") {
-                std::process::exit(0);
-            }
-        });
+    // ---------- Send response (start) ----------
+    let response_data = match serde_json::to_vec(&response) {
+        Ok(data) => data,
+        Err(err) => {
+            eprintln!("Failed to serialize response: {}", err);
+            return;
+        }
+    };
+    let response_len = response_data.len() as u32;
+
+    if stream.write_all(&response_len.to_le_bytes()).await.is_err() {
+        eprintln!("Failed to write response length to client!");
+        return;
+    }
+    if stream.write_all(&response_data).await.is_err() {
+        eprintln!("Failed to write response to client!");
+        return;
+    }
+    // ---------- Send response (end) ----------
+
+    if response.status && response.message.eq("killed") {
+        std::process::exit(0);
     }
 }