feat: v2 rewrite — hexagonal arch, ActivityPub federation, NATS, deployment-ready (#1)

crates/adapters/event-transport/Cargo.toml

@@ -0,0 +1,15 @@
+[package]
+name = "event-transport"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+domain        = { workspace = true }
+event-payload = { workspace = true }
+serde_json    = { workspace = true }
+async-trait   = { workspace = true }
+tracing       = { workspace = true }
+futures       = { workspace = true }
+
+[dev-dependencies]
+tokio = { workspace = true, features = ["full"] }

crates/adapters/event-transport/src/lib.rs

@@ -0,0 +1,236 @@
+use async_trait::async_trait;
+use domain::{
+    errors::DomainError,
+    events::{DomainEvent, EventEnvelope},
+    ports::{EventConsumer, EventPublisher},
+};
+use event_payload::EventPayload;
+use futures::stream::BoxStream;
+
+/// Abstraction over any pub/sub transport backend.
+/// Implement this for NATS, Kafka, Redis Streams, etc.
+/// The adapter calls `publish_bytes(subject, bytes)` — subjects come from `EventPayload::subject()`.
+#[async_trait]
+pub trait Transport: Send + Sync {
+    async fn publish_bytes(&self, subject: &str, bytes: &[u8]) -> Result<(), DomainError>;
+}
+
+/// Routes domain events to a transport backend.
+///
+/// Converts: `DomainEvent` → `EventPayload` → JSON bytes → `transport.publish_bytes(subject, bytes)`
+///
+/// To swap transports (e.g. NATS → Kafka), replace the `T` at the composition root.
+pub struct EventPublisherAdapter<T: Transport> {
+    transport: T,
+}
+
+impl<T: Transport> EventPublisherAdapter<T> {
+    pub fn new(transport: T) -> Self {
+        Self { transport }
+    }
+}
+
+#[async_trait]
+impl<T: Transport> EventPublisher for EventPublisherAdapter<T> {
+    async fn publish(&self, event: &DomainEvent) -> Result<(), DomainError> {
+        let payload = EventPayload::from(event);
+        let subject = payload.subject();
+        let bytes =
+            serde_json::to_vec(&payload).map_err(|e| DomainError::Internal(e.to_string()))?;
+        tracing::debug!(subject, "publishing event");
+        self.transport.publish_bytes(subject, &bytes).await
+    }
+}
+
+/// A raw inbound message from a transport backend.
+/// `ack` and `nack` are transport-level acknowledgements (e.g. Kafka offset commit).
+/// For at-most-once transports (basic NATS), both are no-ops.
+pub struct RawMessage {
+    pub subject: String,
+    pub payload: Vec<u8>,
+    pub delivery_count: u64,
+    pub ack: Box<dyn Fn() + Send + Sync>,
+    pub nack: Box<dyn Fn() + Send + Sync>,
+}
+
+/// Abstraction over any subscribe/consume backend.
+pub trait MessageSource: Send + Sync {
+    fn messages(&self) -> BoxStream<'_, Result<RawMessage, DomainError>>;
+}
+
+/// Deserializes raw transport messages into domain `EventEnvelope`s.
+/// Invalid or unknown messages are skipped with a warning — stream continues.
+pub struct EventConsumerAdapter<S: MessageSource> {
+    source: S,
+}
+
+impl<S: MessageSource> EventConsumerAdapter<S> {
+    pub fn new(source: S) -> Self {
+        Self { source }
+    }
+}
+
+impl<S: MessageSource> EventConsumer for EventConsumerAdapter<S> {
+    fn consume(&self) -> BoxStream<'_, Result<EventEnvelope, DomainError>> {
+        use futures::StreamExt;
+        let stream = self.source.messages();
+        Box::pin(stream.filter_map(|result| async move {
+            match result {
+                Err(e) => {
+                    tracing::warn!("transport error: {e}");
+                    None
+                }
+                Ok(msg) => {
+                    let payload = match serde_json::from_slice::<EventPayload>(&msg.payload) {
+                        Ok(p) => p,
+                        Err(e) => {
+                            tracing::warn!("failed to deserialize event payload — acking to prevent orphan: {e}");
+                            (msg.ack)();
+                            return None;
+                        }
+                    };
+                    let event = match DomainEvent::try_from(payload) {
+                        Ok(e) => e,
+                        Err(e) => {
+                            tracing::warn!("unknown or malformed event type — acking to prevent orphan: {e}");
+                            (msg.ack)();
+                            return None;
+                        }
+                    };
+                    Some(Ok(EventEnvelope {
+                        event,
+                        delivery_count: msg.delivery_count,
+                        ack: msg.ack,
+                        nack: msg.nack,
+                    }))
+                }
+            }
+        }))
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use async_trait::async_trait;
+    use domain::value_objects::{ThoughtId, UserId};
+    use std::sync::{Arc, Mutex};
+
+    struct SpyTransport {
+        calls: Arc<Mutex<Vec<(String, Vec<u8>)>>>,
+    }
+    impl SpyTransport {
+        fn new() -> (Self, Arc<Mutex<Vec<(String, Vec<u8>)>>>) {
+            let calls = Arc::new(Mutex::new(vec![]));
+            (
+                Self {
+                    calls: calls.clone(),
+                },
+                calls,
+            )
+        }
+    }
+    #[async_trait]
+    impl Transport for SpyTransport {
+        async fn publish_bytes(&self, subject: &str, bytes: &[u8]) -> Result<(), DomainError> {
+            self.calls
+                .lock()
+                .unwrap()
+                .push((subject.to_string(), bytes.to_vec()));
+            Ok(())
+        }
+    }
+
+    #[tokio::test]
+    async fn thought_created_routes_to_correct_subject() {
+        let (spy, calls) = SpyTransport::new();
+        let publisher = EventPublisherAdapter::new(spy);
+        publisher
+            .publish(&DomainEvent::ThoughtCreated {
+                thought_id: ThoughtId::new(),
+                user_id: UserId::new(),
+                in_reply_to_id: None,
+            })
+            .await
+            .unwrap();
+        let calls = calls.lock().unwrap();
+        assert_eq!(calls.len(), 1);
+        assert_eq!(calls[0].0, "thoughts.created");
+    }
+
+    #[tokio::test]
+    async fn serialized_payload_is_valid_json() {
+        let (spy, calls) = SpyTransport::new();
+        let publisher = EventPublisherAdapter::new(spy);
+        publisher
+            .publish(&DomainEvent::UserBlocked {
+                blocker_id: UserId::new(),
+                blocked_id: UserId::new(),
+            })
+            .await
+            .unwrap();
+        let bytes = calls.lock().unwrap()[0].1.clone();
+        let json: serde_json::Value = serde_json::from_slice(&bytes).expect("valid JSON");
+        assert_eq!(json["type"], "UserBlocked");
+    }
+
+    #[tokio::test]
+    async fn consumer_adapter_deserializes_and_yields_event() {
+        use domain::value_objects::ThoughtId;
+        use futures::StreamExt;
+
+        let event = DomainEvent::ThoughtCreated {
+            thought_id: ThoughtId::new(),
+            user_id: UserId::new(),
+            in_reply_to_id: None,
+        };
+        let payload = EventPayload::from(&event);
+        let bytes = serde_json::to_vec(&payload).unwrap();
+
+        struct OneMessageSource {
+            bytes: Vec<u8>,
+        }
+        #[async_trait::async_trait]
+        impl MessageSource for OneMessageSource {
+            fn messages(&self) -> futures::stream::BoxStream<'_, Result<RawMessage, DomainError>> {
+                let msg = RawMessage {
+                    subject: "thoughts.created".to_string(),
+                    payload: self.bytes.clone(),
+                    delivery_count: 1,
+                    ack: Box::new(|| {}),
+                    nack: Box::new(|| {}),
+                };
+                Box::pin(futures::stream::once(async { Ok(msg) }))
+            }
+        }
+
+        let adapter = EventConsumerAdapter::new(OneMessageSource { bytes });
+        let mut stream = adapter.consume();
+        let envelope = stream.next().await.unwrap().unwrap();
+        assert!(matches!(envelope.event, DomainEvent::ThoughtCreated { .. }));
+    }
+
+    #[tokio::test]
+    async fn consumer_adapter_skips_invalid_payloads() {
+        use futures::StreamExt;
+
+        struct BadMessageSource;
+        #[async_trait::async_trait]
+        impl MessageSource for BadMessageSource {
+            fn messages(&self) -> futures::stream::BoxStream<'_, Result<RawMessage, DomainError>> {
+                let msg = RawMessage {
+                    subject: "bad".to_string(),
+                    payload: b"not valid json".to_vec(),
+                    delivery_count: 1,
+                    ack: Box::new(|| {}),
+                    nack: Box::new(|| {}),
+                };
+                Box::pin(futures::stream::once(async { Ok(msg) }))
+            }
+        }
+
+        let adapter = EventConsumerAdapter::new(BadMessageSource);
+        let mut stream = adapter.consume();
+        assert!(stream.next().await.is_none());
+    }
+}