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src/bin/axum_docs.rs

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+use axum::{
+    body::Body,
+    extract::{Query, State},
+    http::StatusCode,
+    response::sse::{Event, Sse},
+    routing::get,
+    Router,
+};
+use futures::{stream::Stream, StreamExt, TryStreamExt};
+use mcp_server::{ByteTransport, Server};
+use std::collections::HashMap;
+use tokio_util::codec::FramedRead;
+use tracing_subscriber::{layer::SubscriberExt, util::SubscriberInitExt};
+
+use anyhow::Result;
+use mcp_server::router::RouterService;
+use rust_doc_server::{jsonrpc_frame_codec::JsonRpcFrameCodec, DocRouter};
+use std::sync::Arc;
+use tokio::{
+    io::{self, AsyncWriteExt},
+    sync::Mutex,
+};
+use tracing_subscriber::{self};
+
+type C2SWriter = Arc<Mutex<io::WriteHalf<io::SimplexStream>>>;
+type SessionId = Arc<str>;
+
+const BIND_ADDRESS: &str = "127.0.0.1:8080";
+
+#[derive(Clone, Default)]
+pub struct App {
+    txs: Arc<tokio::sync::RwLock<HashMap<SessionId, C2SWriter>>>,
+}
+
+impl App {
+    pub fn new() -> Self {
+        Self {
+            txs: Default::default(),
+        }
+    }
+    pub fn router(&self) -> Router {
+        Router::new()
+            .route("/sse", get(sse_handler).post(post_event_handler))
+            .with_state(self.clone())
+    }
+}
+
+fn session_id() -> SessionId {
+    let id = format!("{:016x}", rand::random::<u128>());
+    Arc::from(id)
+}
+
+#[derive(Debug, serde::Deserialize)]
+#[serde(rename_all = "camelCase")]
+pub struct PostEventQuery {
+    pub session_id: String,
+}
+
+async fn post_event_handler(
+    State(app): State<App>,
+    Query(PostEventQuery { session_id }): Query<PostEventQuery>,
+    body: Body,
+) -> Result<StatusCode, StatusCode> {
+    const BODY_BYTES_LIMIT: usize = 1 << 22;
+    let write_stream = {
+        let rg = app.txs.read().await;
+        rg.get(session_id.as_str())
+            .ok_or(StatusCode::NOT_FOUND)?
+            .clone()
+    };
+    let mut write_stream = write_stream.lock().await;
+    let mut body = body.into_data_stream();
+    if let (_, Some(size)) = body.size_hint() {
+        if size > BODY_BYTES_LIMIT {
+            return Err(StatusCode::PAYLOAD_TOO_LARGE);
+        }
+    }
+    // calculate the body size
+    let mut size = 0;
+    while let Some(chunk) = body.next().await {
+        let Ok(chunk) = chunk else {
+            return Err(StatusCode::BAD_REQUEST);
+        };
+        size += chunk.len();
+        if size > BODY_BYTES_LIMIT {
+            return Err(StatusCode::PAYLOAD_TOO_LARGE);
+        }
+        write_stream
+            .write_all(&chunk)
+            .await
+            .map_err(|_| StatusCode::INTERNAL_SERVER_ERROR)?;
+    }
+    write_stream
+        .write_u8(b'\n')
+        .await
+        .map_err(|_| StatusCode::INTERNAL_SERVER_ERROR)?;
+    Ok(StatusCode::ACCEPTED)
+}
+
+async fn sse_handler(State(app): State<App>) -> Sse<impl Stream<Item = Result<Event, io::Error>>> {
+    // it's 4KB
+    const BUFFER_SIZE: usize = 1 << 12;
+    let session = session_id();
+    tracing::info!(%session, "sse connection");
+    let (c2s_read, c2s_write) = tokio::io::simplex(BUFFER_SIZE);
+    let (s2c_read, s2c_write) = tokio::io::simplex(BUFFER_SIZE);
+    app.txs
+        .write()
+        .await
+        .insert(session.clone(), Arc::new(Mutex::new(c2s_write)));
+    {
+        let app_clone = app.clone();
+        let session = session.clone();
+        tokio::spawn(async move {
+            let router = RouterService(DocRouter::new());
+            let server = Server::new(router);
+            let bytes_transport = ByteTransport::new(c2s_read, s2c_write);
+            let _result = server
+                .run(bytes_transport)
+                .await
+                .inspect_err(|e| tracing::error!(?e, "server run error"));
+            app_clone.txs.write().await.remove(&session);
+        });
+    }
+
+    let stream = futures::stream::once(futures::future::ok(
+        Event::default()
+            .event("endpoint")
+            .data(format!("?sessionId={session}")),
+    ))
+    .chain(
+        FramedRead::new(s2c_read, JsonRpcFrameCodec)
+            .map_err(|e| io::Error::new(io::ErrorKind::InvalidData, e))
+            .and_then(move |bytes| match std::str::from_utf8(&bytes) {
+                Ok(message) => futures::future::ok(Event::default().event("message").data(message)),
+                Err(e) => futures::future::err(io::Error::new(io::ErrorKind::InvalidData, e)),
+            }),
+    );
+    Sse::new(stream)
+}
+
+#[tokio::main]
+async fn main() -> io::Result<()> {
+    tracing_subscriber::registry()
+        .with(
+            tracing_subscriber::EnvFilter::try_from_default_env()
+                .unwrap_or_else(|_| format!("info,{}=debug", env!("CARGO_CRATE_NAME")).into()),
+        )
+        .with(tracing_subscriber::fmt::layer())
+        .init();
+    let listener = tokio::net::TcpListener::bind(BIND_ADDRESS).await?;
+
+    tracing::debug!("Rust Documentation Server listening on {}", listener.local_addr()?);
+    tracing::info!("Access the Rust Documentation Server at http://{}/sse", BIND_ADDRESS);
+    axum::serve(listener, App::new().router()).await
+}