Push events into a module structure consistent with the rest of the project.

1 files changed, 4 insertions, 107 deletions

diff --git a/src/channel/app.rs b/src/channel/app.rs
index 8ae0c3c..f9a75d7 100644
--- a/src/channel/app.rs
+++ b/src/channel/app.rs
@@ -1,6 +1,3 @@
-use std::collections::{hash_map::Entry, HashMap};
-use std::sync::{Arc, Mutex, MutexGuard};
-
 use chrono::TimeDelta;
 use futures::{
     future,
@@ -8,12 +5,13 @@ use futures::{
     Stream,
 };
 use sqlx::sqlite::SqlitePool;
-use tokio::sync::broadcast::{channel, Sender};
-use tokio_stream::wrappers::{errors::BroadcastStreamRecvError, BroadcastStream};
 
-use super::repo::broadcast::{self, Provider as _};
 use crate::{
     clock::DateTime,
+    events::{
+        app::Broadcaster,
+        repo::broadcast::{self, Provider as _},
+    },
     repo::{
         channel::{self, Channel, Provider as _},
         error::NotFound as _,
@@ -158,104 +156,3 @@ pub enum EventsError {
     #[error(transparent)]
     DatabaseError(#[from] sqlx::Error),
 }
-
-// Clones will share the same senders collection.
-#[derive(Clone)]
-pub struct Broadcaster {
-    // The use of std::sync::Mutex, and not tokio::sync::Mutex, follows Tokio's
-    // own advice: <https://tokio.rs/tokio/tutorial/shared-state>. Methods that
-    // lock it must be sync.
-    senders: Arc<Mutex<HashMap<channel::Id, Sender<broadcast::Message>>>>,
-}
-
-impl Broadcaster {
-    pub async fn from_database(db: &SqlitePool) -> Result<Self, sqlx::Error> {
-        let mut tx = db.begin().await?;
-        let channels = tx.channels().all().await?;
-        tx.commit().await?;
-
-        let channels = channels.iter().map(|c| &c.id);
-        let broadcaster = Self::new(channels);
-        Ok(broadcaster)
-    }
-
-    fn new<'i>(channels: impl IntoIterator<Item = &'i channel::Id>) -> Self {
-        let senders: HashMap<_, _> = channels
-            .into_iter()
-            .cloned()
-            .map(|id| (id, Self::make_sender()))
-            .collect();
-
-        Self {
-            senders: Arc::new(Mutex::new(senders)),
-        }
-    }
-
-    // panic: if ``channel`` is already registered.
-    pub fn register_channel(&self, channel: &channel::Id) {
-        match self.senders().entry(channel.clone()) {
-            // This ever happening indicates a serious logic error.
-            Entry::Occupied(_) => panic!("duplicate channel registration for channel {channel}"),
-            Entry::Vacant(entry) => {
-                entry.insert(Self::make_sender());
-            }
-        }
-    }
-
-    // panic: if ``channel`` has not been previously registered, and was not
-    // part of the initial set of channels.
-    pub fn broadcast(&self, channel: &channel::Id, message: broadcast::Message) {
-        let tx = self.sender(channel);
-
-        // Per the Tokio docs, the returned error is only used to indicate that
-        // there are no receivers. In this use case, that's fine; a lack of
-        // listening consumers (chat clients) when a message is sent isn't an
-        // error.
-        //
-        // The successful return value, which includes the number of active
-        // receivers, also isn't that interesting to us.
-        let _ = tx.send(message);
-    }
-
-    // panic: if ``channel`` has not been previously registered, and was not
-    // part of the initial set of channels.
-    pub fn listen(&self, channel: &channel::Id) -> impl Stream<Item = broadcast::Message> {
-        let rx = self.sender(channel).subscribe();
-
-        BroadcastStream::from(rx)
-            .take_while(|r| {
-                future::ready(match r {
-                    Ok(_) => true,
-                    // Stop the stream here. This will disconnect SSE clients
-                    // (see `routes.rs`), who will then resume from
-                    // `Last-Event-ID`, allowing them to catch up by reading
-                    // the skipped messages from the database.
-                    Err(BroadcastStreamRecvError::Lagged(_)) => false,
-                })
-            })
-            .map(|r| {
-                // Since the previous transform stops at the first error, this
-                // should always hold.
-                //
-                // See also <https://users.rust-lang.org/t/taking-from-stream-while-ok/48854>.
-                r.expect("after filtering, only `Ok` messages should remain")
-            })
-    }
-
-    // panic: if ``channel`` has not been previously registered, and was not
-    // part of the initial set of channels.
-    fn sender(&self, channel: &channel::Id) -> Sender<broadcast::Message> {
-        self.senders()[channel].clone()
-    }
-
-    fn senders(&self) -> MutexGuard<HashMap<channel::Id, Sender<broadcast::Message>>> {
-        self.senders.lock().unwrap() // propagate panics when mutex is poisoned
-    }
-
-    fn make_sender() -> Sender<broadcast::Message> {
-        // Queue depth of 16 chosen entirely arbitrarily. Don't read too much
-        // into it.
-        let (tx, _) = channel(16);
-        tx
-    }
-}