feat(sync): add typed presence projection

req: sync/001

req: sync/005

examples/kanban/src/main.rs

@@ -15,7 +15,7 @@ use hemx_axum::{
 use hemx_kanban_example::ui::board::{self as board};
 use hemx_kanban_example::ui::board_card as card_board;
 use hemx_kanban_example::ui::{self, board as board_ui};
-use hemx_sync::{Channel, SyncEffect};
+use hemx_sync::{Channel, PresenceScope, PresenceTracker, PresenceUpdate};
 use serde::{Deserialize, Serialize};
 use std::collections::BTreeMap;
 use std::convert::Infallible;
@@ -46,6 +46,7 @@ struct AppState {
     sync_store: Option<SyncStore>,
     sync_sessions: SyncSessionTokens,
     acknowledgement_heartbeat_interval: Duration,
+    presence: Mutex<PresenceTracker<String>>,
 }
 
 #[derive(Default)]
@@ -494,6 +495,7 @@ async fn main() {
             .filter(|milliseconds| *milliseconds > 0)
             .map(Duration::from_millis)
             .unwrap_or(ACKNOWLEDGEMENT_HEARTBEAT_INTERVAL),
+        presence: Mutex::new(PresenceTracker::default()),
     });
 
     let ordinary_routes = Router::new()
@@ -581,7 +583,28 @@ async fn interact(
 }
 
 // req: push/001 req: push/003 req: examples/001
-async fn sync_broadcast(Query(params): Query<BTreeMap<String, String>>) -> Response {
+struct PresenceSignal {
+    channel: Channel,
+    count: usize,
+}
+
+impl PresenceScope for PresenceSignal {
+    fn presence_channel(&self) -> Channel {
+        self.channel.clone()
+    }
+}
+
+#[hemx_sync::presence]
+fn presence_changed(signal: PresenceSignal) -> impl hemx::IntoEffect {
+    board::presence.put(&Presence {
+        count: u64::try_from(signal.count).expect("presence count fits u64"),
+    })
+}
+
+async fn sync_broadcast(
+    State(state): State<Arc<AppState>>,
+    Query(params): Query<BTreeMap<String, String>>,
+) -> Response {
     let Some(channel) = params
         .get("channel")
         .and_then(|channel| Channel::new(channel).ok())
@@ -591,10 +614,21 @@ async fn sync_broadcast(Query(params): Query<BTreeMap<String, String>>) -> Respo
     if channel.as_str() != "board" {
         return StatusCode::NOT_FOUND.into_response();
     }
-    let batch = board::presence
-        .put(&Presence { count: 7 })
-        .into_batch(ui::BUILD_FINGERPRINT);
-    let broadcast = SyncEffect::broadcast(channel, batch);
+    let member = params.get("member").cloned();
+    let count = {
+        let mut presence = state.presence.lock().unwrap();
+        match (params.get("action").map(String::as_str), member.as_ref()) {
+            (Some("join"), Some(member)) => presence.join(channel.clone(), member.clone()).count,
+            (Some("leave"), Some(member)) => presence.leave(&channel, member).count,
+            (None | Some("snapshot"), None) => presence.count(&channel),
+            _ => {
+                return (StatusCode::BAD_REQUEST, "invalid presence action or member")
+                    .into_response();
+            }
+        }
+    };
+    let broadcast =
+        presence_changed(PresenceSignal { channel, count }).into_broadcast(ui::BUILD_FINGERPRINT);
     let (_channel, effect_batch) = broadcast.into_parts();
     sse(stream::iter([Ok::<_, Infallible>(effect_batch)]).boxed()).into_response()
 }

examples/kanban/tests/browser_e2e.rs

@@ -2201,8 +2201,8 @@ async fn adversarial_wire_inputs_are_rejected_before_partial_application() -> We
 }
 
 #[tokio::test]
-async fn typed_broadcast_applies_generated_batch_over_sse() -> WebDriverResult<()> {
-    // test req: sync/004
+async fn typed_presence_join_leave_updates_generated_atom_over_sse() -> WebDriverResult<()> {
+    // test req: sync/001 req: sync/004 req: sync/005
     let app_port = available_port();
     let app_addr = format!("127.0.0.1:{app_port}");
     let mut app_command = Command::new(env!("CARGO_BIN_EXE_hemx-kanban-example"));
@@ -2222,25 +2222,57 @@ async fn typed_broadcast_applies_generated_batch_over_sse() -> WebDriverResult<(
 
     let result = async {
         driver.goto(&format!("http://{app_addr}/")).await?;
-        wait_until(
-            &driver,
-            "return document.body.textContent.includes('tick #7')",
-        )
-        .await?;
-        let resources = driver
-            .execute(
-                "return performance.getEntriesByType('resource').map(entry => entry.name).filter(name => name.includes('/sync/broadcast'))",
+        wait_until(&driver, "return document.body.textContent.includes('tick #0')").await?;
+        let proof = driver
+            .execute_async(
+                r#"
+                const done = arguments[arguments.length - 1];
+                (async () => {
+                  const root = document.querySelector('[data-hemx-root]');
+                  const apply = (url) => new Promise((resolve, reject) => {
+                    const source = new EventSource(url);
+                    const timeout = setTimeout(() => {
+                      source.close();
+                      reject(new Error(`presence event timed out: ${url}`));
+                    }, 5000);
+                    source.addEventListener('hemx', (event) => {
+                      clearTimeout(timeout);
+                      const normalized = event.data.replace(/-/g, '+').replace(/_/g, '/');
+                      const padded = normalized + '='.repeat((4 - normalized.length % 4) % 4);
+                      const raw = atob(padded);
+                      const bytes = Uint8Array.from(raw, (character) => character.charCodeAt(0));
+                      window.hemx.applyBatch(bytes.buffer, root);
+                      source.close();
+                      resolve(document.body.textContent);
+                    });
+                    source.onerror = () => {
+                      clearTimeout(timeout);
+                      source.close();
+                      reject(new Error(`presence event failed: ${url}`));
+                    };
+                  });
+                  const joinedAda = await apply('/sync/broadcast?channel=board&action=join&member=ada');
+                  const duplicateAda = await apply('/sync/broadcast?channel=board&action=join&member=ada');
+                  const joinedGrace = await apply('/sync/broadcast?channel=board&action=join&member=grace');
+                  const leftAda = await apply('/sync/broadcast?channel=board&action=leave&member=ada');
+                  done({
+                    joinedAda: joinedAda.includes('tick #1'),
+                    duplicateAda: duplicateAda.includes('tick #1'),
+                    joinedGrace: joinedGrace.includes('tick #2'),
+                    leftAda: leftAda.includes('tick #1'),
+                  });
+                })().catch((error) => done({ error: String(error), stack: error?.stack }));
+                "#,
                 Vec::new(),
             )
             .await?
             .json()
             .clone();
-        assert!(
-            resources
-                .as_array()
-                .is_some_and(|resources| !resources.is_empty()),
-            "typed broadcast SSE request was not observed: {resources}"
-        );
+        assert!(proof["error"].is_null(), "typed presence failed: {proof}");
+        assert_eq!(proof["joinedAda"], true, "{proof}");
+        assert_eq!(proof["duplicateAda"], true, "{proof}");
+        assert_eq!(proof["joinedGrace"], true, "{proof}");
+        assert_eq!(proof["leftAda"], true, "{proof}");
         Ok(())
     }
     .await;