From a1337f9c6c32e036d8ffe64fcefbd9fb0add4e3c Mon Sep 17 00:00:00 2001
From: Will Crichton <wcrichto@cs.stanford.edu>
Date: Mon, 12 Aug 2024 15:09:45 -0700
Subject: [PATCH] Message passing solution

---
 crates/server/src/main.rs | 33 +++++++++++++++++++++++++--------
 1 file changed, 25 insertions(+), 8 deletions(-)

diff --git a/crates/server/src/main.rs b/crates/server/src/main.rs
index 9fa73ce..a94f6a8 100644
--- a/crates/server/src/main.rs
+++ b/crates/server/src/main.rs
@@ -1,8 +1,11 @@
-use std::sync::Arc;
+use std::sync::{Arc, LazyLock};
 
 use miniserve::{http::StatusCode, Content, Request, Response};
 use serde::{Deserialize, Serialize};
-use tokio::join;
+use tokio::{
+    join,
+    sync::{mpsc, oneshot},
+};
 
 async fn index(_req: Request) -> Response {
     let content = include_str!("../index.html").to_string();
@@ -14,6 +17,25 @@ struct Messages {
     messages: Vec<String>,
 }
 
+async fn query_chat(messages: &Arc<Vec<String>>) -> Vec<String> {
+    type Payload = (Arc<Vec<String>>, oneshot::Sender<Vec<String>>);
+    static SENDER: LazyLock<mpsc::Sender<Payload>> = LazyLock::new(|| {
+        let (tx, mut rx) = mpsc::channel::<Payload>(1024);
+        tokio::spawn(async move {
+            let mut chatbot = chatbot::Chatbot::new(vec![":-)".into(), "^^".into()]);
+            while let Some((messages, responder)) = rx.recv().await {
+                let response = chatbot.query_chat(&messages).await;
+                responder.send(response).unwrap();
+            }
+        });
+        tx
+    });
+
+    let (tx, rx) = oneshot::channel();
+    SENDER.send((Arc::clone(messages), tx)).await.unwrap();
+    rx.await.unwrap()
+}
+
 async fn chat(req: Request) -> Response {
     let Request::Post(body) = req else {
         return Err(StatusCode::METHOD_NOT_ALLOWED);
@@ -23,12 +45,7 @@ async fn chat(req: Request) -> Response {
     };
 
     let messages = Arc::new(data.messages);
-    let messages_ref = Arc::clone(&messages);
-    let (i, responses) = join!(
-        chatbot::gen_random_number(),
-        tokio::spawn(async move { chatbot::query_chat(&messages_ref).await })
-    );
-    let mut responses = responses.unwrap();
+    let (i, mut responses) = join!(chatbot::gen_random_number(), query_chat(&messages));
 
     let response = responses.remove(i % responses.len());
     data.messages = Arc::into_inner(messages).unwrap();