refactor: consolidate nvim crates, extract server library, and update workspace dependencies

mcp-stdio/src/lib.rs

@@ -29,7 +29,9 @@ pub async fn read_mcp_message<R: tokio::io::AsyncRead + Unpin>(
         }
     }
 
-    if length == 0 {
+    const MAX_MESSAGE_BYTES: usize = 50 * 1024 * 1024; // 50MB safety cap
+
+    if length == 0 || length > MAX_MESSAGE_BYTES {
         return None;
     }
 
@@ -40,3 +42,59 @@ pub async fn read_mcp_message<R: tokio::io::AsyncRead + Unpin>(
 
     String::from_utf8(buffer).ok()
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::io::Cursor;
+
+    #[tokio::test]
+    async fn test_read_ndjson_message() {
+        let input = "{\"jsonrpc\":\"2.0\",\"id\":1,\"method\":\"ping\"}\n";
+        let mut reader = BufReader::new(Cursor::new(input));
+        let msg = read_mcp_message(&mut reader).await;
+        assert_eq!(msg, Some("{\"jsonrpc\":\"2.0\",\"id\":1,\"method\":\"ping\"}".to_string()));
+    }
+
+    #[tokio::test]
+    async fn test_read_content_length_message() {
+        let payload = "{\"jsonrpc\":\"2.0\",\"id\":2}";
+        let input = format!("Content-Length: {}\r\n\r\n{}", payload.len(), payload);
+        let mut reader = BufReader::new(Cursor::new(input));
+        let msg = read_mcp_message(&mut reader).await;
+        assert_eq!(msg, Some(payload.to_string()));
+    }
+
+    #[tokio::test]
+    async fn test_read_mcp_message_eof() {
+        let input = "";
+        let mut reader = BufReader::new(Cursor::new(input));
+        let msg = read_mcp_message(&mut reader).await;
+        assert_eq!(msg, None);
+    }
+
+    #[tokio::test]
+    async fn test_read_mcp_message_zero_content_length() {
+        let input = "Content-Length: 0\r\n\r\n";
+        let mut reader = BufReader::new(Cursor::new(input));
+        let msg = read_mcp_message(&mut reader).await;
+        assert_eq!(msg, None);
+    }
+
+    #[tokio::test]
+    async fn test_read_mcp_message_exceeds_max_bytes() {
+        let input = "Content-Length: 60000000\r\n\r\n";
+        let mut reader = BufReader::new(Cursor::new(input));
+        let msg = read_mcp_message(&mut reader).await;
+        assert_eq!(msg, None);
+    }
+
+    #[tokio::test]
+    async fn test_read_mcp_message_read_exact_error() {
+        let input = "Content-Length: 1000\r\n\r\nshort";
+        let mut reader = BufReader::new(Cursor::new(input));
+        let msg = read_mcp_message(&mut reader).await;
+        assert_eq!(msg, None);
+    }
+}
+