1 files changed, 124 insertions, 0 deletions
diff --git a/src/utils.rs b/src/utils.rs
new file mode 100644
index 0000000..5a2407a
--- /dev/null
+++ b/src/utils.rs
@@ -0,0 +1,124 @@
+use std::convert::Infallible;
+
+use futures::Future;
+use rocket::{
+    fairing::{self, Fairing, Info, Kind},
+    http::Status,
+    request::{FromRequest, Outcome},
+    tokio::{
+        self,
+        sync::broadcast::{channel, Sender},
+        task::JoinHandle,
+    },
+    Request, Response, Sentinel,
+};
+
+// does the same as try_outcome!(...).map_forward(|_| data),
+// but without moving data in non-failure cases.
+macro_rules! try_outcome_data {
+    ($data:expr, $e:expr) => {
+        match $e {
+            ::rocket::outcome::Outcome::Success(val) => val,
+            ::rocket::outcome::Outcome::Failure(e) => {
+                return ::rocket::outcome::Outcome::Failure(::std::convert::From::from(e))
+            },
+            ::rocket::outcome::Outcome::Forward(()) => {
+                return ::rocket::outcome::Outcome::Forward($data)
+            },
+        }
+    };
+}
+
+pub trait CanBeLogged: Send + 'static {
+    fn into_message(self) -> Option<String>;
+    fn not_run() -> Self;
+}
+
+impl CanBeLogged for Result<(), anyhow::Error> {
+    fn into_message(self) -> Option<String> {
+        self.err().map(|e| e.to_string())
+    }
+    fn not_run() -> Self {
+        Ok(())
+    }
+}
+
+pub fn spawn_logged<T>(context: &'static str, future: T) -> JoinHandle<()>
+where
+    T: Future + Send + 'static,
+    T::Output: CanBeLogged + Send + 'static,
+{
+    tokio::spawn(async move {
+        if let Some(msg) = future.await.into_message() {
+            warn!("{context}: {msg}");
+        }
+    })
+}
+
+pub struct DeferredActions;
+struct HasDeferredActions;
+
+pub struct DeferAction(Sender<()>);
+
+#[async_trait]
+impl Fairing for DeferredActions {
+    fn info(&self) -> Info {
+        Info { name: "deferred actions", kind: Kind::Ignite | Kind::Response }
+    }
+
+    async fn on_ignite(&self, rocket: rocket::Rocket<rocket::Build>) -> fairing::Result {
+        Ok(rocket.manage(HasDeferredActions))
+    }
+
+    async fn on_response<'r>(&self, req: &'r Request<'_>, res: &mut Response<'r>) {
+        if res.status() == Status::Ok {
+            if let Some(DeferAction(tx)) = req.local_cache(|| None) {
+                // could have no receivers, that's not an error here
+                tx.send(()).ok();
+            }
+        }
+    }
+}
+
+impl<'r> Sentinel for &'r DeferAction {
+    fn abort(rocket: &rocket::Rocket<rocket::Ignite>) -> bool {
+        rocket.state::<HasDeferredActions>().is_none()
+    }
+}
+
+#[async_trait]
+impl<'r> FromRequest<'r> for &'r DeferAction {
+    type Error = Infallible;
+
+    async fn from_request(req: &'r Request<'_>) -> Outcome<Self, Self::Error> {
+        Outcome::Success(
+            req.local_cache(|| {
+                let (tx, _) = channel(1);
+                Some(DeferAction(tx))
+            })
+            .as_ref()
+            .unwrap(),
+        )
+    }
+}
+
+impl DeferAction {
+    pub fn spawn_after_success<T>(&self, context: &'static str, future: T)
+    where
+        T: Future + Send + 'static,
+        T::Output: CanBeLogged + Send + 'static,
+    {
+        let mut r = self.0.subscribe();
+        spawn_logged(context, async move {
+            match r.recv().await {
+                Ok(_) => {
+                    // the request finished with success, now wait for it to be dropped
+                    // to ensure that all other fairings have run to completion.
+                    r.recv().await.ok();
+                    future.await
+                },
+                Err(_) => CanBeLogged::not_run(),
+            }
+        });
+    }
+}