From 0a05491930fb34ce7c93c33ea0b7599360483fc7 Mon Sep 17 00:00:00 2001
From: Owen Jacobson <owen@grimoire.ca>
Date: Fri, 20 Sep 2024 23:01:18 -0400
Subject: Push events into a module structure consistent with the rest of the
 project.

---
 src/events/routes.rs | 133 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 133 insertions(+)
 create mode 100644 src/events/routes.rs

(limited to 'src/events/routes.rs')

diff --git a/src/events/routes.rs b/src/events/routes.rs
new file mode 100644
index 0000000..f880c70
--- /dev/null
+++ b/src/events/routes.rs
@@ -0,0 +1,133 @@
+use axum::{
+    extract::State,
+    http::StatusCode,
+    response::{
+        sse::{self, Sse},
+        IntoResponse, Response,
+    },
+    routing::get,
+    Router,
+};
+use axum_extra::extract::Query;
+use chrono::{self, format::SecondsFormat, DateTime};
+use futures::stream::{self, Stream, StreamExt as _, TryStreamExt as _};
+
+use super::repo::broadcast;
+use crate::{
+    app::App,
+    channel::app::EventsError,
+    clock::RequestedAt,
+    error::InternalError,
+    header::LastEventId,
+    repo::{channel, login::Login},
+};
+
+pub fn router() -> Router<App> {
+    Router::new().route("/api/events", get(on_events))
+}
+
+#[derive(serde::Deserialize)]
+struct EventsQuery {
+    #[serde(default, rename = "channel")]
+    channels: Vec<channel::Id>,
+}
+
+async fn on_events(
+    State(app): State<App>,
+    RequestedAt(now): RequestedAt,
+    _: Login, // requires auth, but doesn't actually care who you are
+    last_event_id: Option<LastEventId>,
+    Query(query): Query<EventsQuery>,
+) -> Result<Events<impl Stream<Item = ChannelEvent<broadcast::Message>>>, ErrorResponse> {
+    let resume_at = last_event_id
+        .map(|LastEventId(header)| header)
+        .map(|header| DateTime::parse_from_rfc3339(&header))
+        .transpose()
+        // impl From would take more code; this is used once.
+        .map_err(ErrorResponse::LastEventIdError)?
+        .map(|ts| ts.to_utc());
+
+    let streams = stream::iter(query.channels)
+        .then(|channel| {
+            let app = app.clone();
+            async move {
+                let events = app
+                    .channels()
+                    .events(&channel, &now, resume_at.as_ref())
+                    .await?
+                    .map(ChannelEvent::wrap(channel));
+
+                Ok::<_, EventsError>(events)
+            }
+        })
+        .try_collect::<Vec<_>>()
+        .await
+        // impl From would take more code; this is used once.
+        .map_err(ErrorResponse::EventsError)?;
+
+    let stream = stream::select_all(streams);
+
+    Ok(Events(stream))
+}
+
+struct Events<S>(S);
+
+impl<S> IntoResponse for Events<S>
+where
+    S: Stream<Item = ChannelEvent<broadcast::Message>> + Send + 'static,
+{
+    fn into_response(self) -> Response {
+        let Self(stream) = self;
+        let stream = stream.map(to_sse_event);
+        Sse::new(stream)
+            .keep_alive(sse::KeepAlive::default())
+            .into_response()
+    }
+}
+
+enum ErrorResponse {
+    EventsError(EventsError),
+    LastEventIdError(chrono::ParseError),
+}
+
+impl IntoResponse for ErrorResponse {
+    fn into_response(self) -> Response {
+        match self {
+            Self::EventsError(not_found @ EventsError::ChannelNotFound(_)) => {
+                (StatusCode::NOT_FOUND, not_found.to_string()).into_response()
+            }
+            Self::EventsError(other) => InternalError::from(other).into_response(),
+            Self::LastEventIdError(other) => {
+                (StatusCode::BAD_REQUEST, other.to_string()).into_response()
+            }
+        }
+    }
+}
+
+fn to_sse_event(event: ChannelEvent<broadcast::Message>) -> Result<sse::Event, serde_json::Error> {
+    let data = serde_json::to_string_pretty(&event)?;
+    let event = sse::Event::default()
+        .id(event
+            .message
+            .sent_at
+            .to_rfc3339_opts(SecondsFormat::AutoSi, /* use_z */ true))
+        .data(&data);
+
+    Ok(event)
+}
+
+#[derive(serde::Serialize)]
+struct ChannelEvent<M> {
+    channel: channel::Id,
+    #[serde(flatten)]
+    message: M,
+}
+
+impl<M> ChannelEvent<M> {
+    fn wrap(channel: channel::Id) -> impl Fn(M) -> Self {
+        move |message| Self {
+            channel: channel.clone(),
+            message,
+        }
+    }
+}
-- 
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