Complete log stream implementation

Sets up a watch channel to send tracing lines from tracing-subscriber to
receivers in a axum handler which streams Server Sent Events to any
number of connected /log/stream clients.

src/handlers/log.rs

@@ -1,13 +1,46 @@
-use axum::response::Response;
+use std::convert::Infallible;
+use std::time::Duration;
+
+use axum::extract::State;
+use axum::response::{
+    sse::{Event, Sse},
+    Response,
+};
+use bytes::Bytes;
 use maud::html;
+use tokio::sync::watch::Receiver;
+use tokio_stream::wrappers::WatchStream;
+use tokio_stream::Stream;
+use tokio_stream::StreamExt;
 
 use crate::error::Result;
-use crate::partials::layout::Layout;
 use crate::log::MEM_LOG;
+use crate::partials::layout::Layout;
 
 pub async fn get(layout: Layout) -> Result<Response> {
     let mem_buf = MEM_LOG.lock().unwrap();
     Ok(layout.render(html! {
-        pre { (std::str::from_utf8(mem_buf.as_slices().0).unwrap()) }
+        turbo-stream-source src="/log/stream" {}
+        pre id="log" { (std::str::from_utf8(mem_buf.as_slices().0).unwrap()) }
     }))
 }
+
+pub async fn stream(
+    State(log_receiver): State<Receiver<Bytes>>,
+) -> Sse<impl Stream<Item = Result<Event, Infallible>>> {
+    let log_stream = WatchStream::new(log_receiver);
+    let log_stream = log_stream.map(|line| {
+        Ok(Event::default().data(html! {
+            turbo-stream action="append" target="log" {
+                template {
+                    (std::str::from_utf8(&line).unwrap())
+                }
+            }
+        }.into_string()))
+    });
+    Sse::new(log_stream).keep_alive(
+        axum::response::sse::KeepAlive::new()
+            .interval(Duration::from_secs(15))
+            .text("keep-alive-text"),
+    )
+}