diff --git a/gg-echo/src/main.rs b/gg-echo/src/main.rs
index 18c8ff9..de56082 100644
--- a/gg-echo/src/main.rs
+++ b/gg-echo/src/main.rs
@@ -1,49 +1,132 @@
 use maelstrom_protocol as proto;
 use proto::{Body, Message};
-use std::io::{BufRead, Write};
+use std::{
+    cell::OnceCell,
+    io::{BufRead, StdinLock, StdoutLock, Write},
+    sync::Mutex,
+};
 
 fn main() {
-    let mut out = std::io::stdout().lock();
+    let out = std::io::stdout().lock();
     let input = std::io::stdin().lock();
 
-    let mut mid = 1;
-
-    let mut node_id: String = "".to_string();
-
-    for line in input.lines() {
-        match line {
-            Ok(line) => {
-                if let Ok(msg) = serde_json::from_str::<proto::Message>(&line) {
-                    let typ = &msg.body.typ;
-                    match typ.as_str() {
-                        "init" => {
-                            let body = proto::init_ok(mid, msg.body.msg_id);
-                            mid += 1;
-                            let resp = message(&msg.src, &msg.dest, body);
-                            node_id = msg.dest;
-                            let resp = serde_json::to_string(&resp).unwrap();
-                            out.write_all(resp.as_bytes()).unwrap();
-                            out.write_all("\n".as_bytes()).unwrap();
-                            let _ = &mut out.flush().unwrap();
-                        }
-                        "echo" => {
-                            let body = Body::from_type("echo_ok")
-                                .with_msg_id(mid)
-                                .with_in_reply_to(msg.body.msg_id)
-                                .with_payload(msg.body.payload);
-                            mid += 1;
-                            let resp = message(&msg.src, &node_id, body);
-                            let resp = serde_json::to_string(&resp).unwrap();
-                            out.write_all(resp.as_bytes()).unwrap();
-                            out.write_all("\n".as_bytes()).unwrap();
-                            let _ = &mut out.flush().unwrap();
-                        }
-                        _ => {}
-                    }
-                }
+    let runner = &Runner::new(out);
+    let handler = |msg: &Message| {
+        let typ = &msg.body.typ;
+        match typ.as_str() {
+            "echo" => {
+                let body = Body::from_type("echo_ok").with_payload(msg.body.payload.clone());
+                runner.reply(&msg, body);
             }
             _ => {}
         }
+    };
+    runner.run(input, &handler);
+}
+
+struct Runner<'io> {
+    msg_id: Mutex<u64>,
+    node_id: OnceCell<String>,
+    nodes: OnceCell<Vec<String>>,
+    output: Mutex<StdoutLock<'io>>,
+}
+
+impl<'io> Runner<'io> {
+    pub fn new(output: StdoutLock<'io>) -> Self {
+        Runner {
+            output: Mutex::new(output),
+            msg_id: Mutex::new(1),
+            nodes: OnceCell::new(),
+            node_id: OnceCell::new(),
+        }
+    }
+
+    pub fn run(&self, input: StdinLock, handler: &dyn Fn(&Message)) {
+        for line in input.lines() {
+            match line {
+                Ok(line) => {
+                    if let Ok(msg) = serde_json::from_str::<proto::Message>(&line) {
+                        let typ = &msg.body.typ;
+                        match typ.as_str() {
+                            "init" => {
+                                self.init(&msg);
+
+                                let body = Body::from_type("init_ok");
+                                self.reply(&msg, body);
+                            }
+                            _ => {
+                                handler(&msg);
+                            }
+                        }
+                    }
+                }
+                _ => {}
+            }
+        }
+    }
+
+    pub fn node_id(&self) -> String {
+        self.node_id.get().cloned().unwrap_or("".to_string())
+    }
+
+    pub fn msg_id(&self) -> u64 {
+        *self.msg_id.lock().unwrap()
+    }
+
+    pub fn init(&self, msg: &Message) {
+        let node_id = msg
+            .body
+            .payload
+            .get("node_id")
+            .unwrap()
+            .as_str()
+            .unwrap()
+            .to_owned();
+        let nodes = msg
+            .body
+            .payload
+            .get("node_ids")
+            .unwrap()
+            .as_array()
+            .unwrap()
+            .iter()
+            .map(|s| s.as_str().unwrap().to_string())
+            .collect::<Vec<_>>();
+
+        let _ = self.node_id.get_or_init(|| node_id.to_owned());
+        let _ = self.nodes.get_or_init(|| nodes.to_vec());
+    }
+
+    pub fn reply(&self, req: &Message, body: Body) {
+        let mut body = body;
+        let src = self.node_id.get().unwrap().to_owned();
+        let dest = req.src.clone();
+        let in_reply_to = req.body.msg_id;
+        body.in_reply_to = in_reply_to;
+        let msg = Message { src, dest, body };
+        self.send(msg);
+    }
+
+    pub fn send(&self, msg: Message) {
+        let mut msg = msg;
+        if msg.body.msg_id == 0 {
+            let mid = {
+                let mut g = self.msg_id.lock().unwrap();
+                let m = *g;
+                *g += 1;
+                m
+            };
+            msg.body.msg_id = mid;
+        }
+        let msg = serde_json::to_string(&msg).unwrap();
+        let msg = format!("{msg}\n");
+        self.writeln(&msg);
+    }
+
+    fn writeln(&self, msg: &str) {
+        let mut out = self.output.lock().unwrap();
+        out.write_all(msg.as_bytes()).unwrap();
+        out.flush().unwrap();
     }
 }