feat(event-publisher): add event publisher adapter with configuration and integration

crates/adapters/event-publisher/Cargo.toml

@@ -0,0 +1,10 @@
+[package]
+name = "event-publisher"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]
+domain      = { workspace = true }
+async-trait = { workspace = true }
+tokio       = { workspace = true }
+tracing     = { workspace = true }

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

@@ -0,0 +1,79 @@
+use async_trait::async_trait;
+use domain::{errors::DomainError, events::DomainEvent, ports::EventPublisher};
+use tokio::sync::mpsc;
+
+pub struct EventPublisherConfig {
+    pub channel_buffer: usize,
+}
+
+impl EventPublisherConfig {
+    pub fn from_env() -> Self {
+        let channel_buffer = std::env::var("EVENT_CHANNEL_BUFFER")
+            .ok()
+            .and_then(|v| v.parse().ok())
+            .unwrap_or(128);
+        Self { channel_buffer }
+    }
+}
+
+pub struct ChannelEventPublisher {
+    sender: mpsc::Sender<DomainEvent>,
+}
+
+#[async_trait]
+impl EventPublisher for ChannelEventPublisher {
+    async fn publish(&self, event: &DomainEvent) -> Result<(), DomainError> {
+        self.sender
+            .send(event.clone())
+            .await
+            .map_err(|e| DomainError::InfrastructureError(e.to_string()))
+    }
+}
+
+pub struct EventWorker {
+    receiver: mpsc::Receiver<DomainEvent>,
+}
+
+impl EventWorker {
+    pub async fn run(mut self) {
+        while let Some(event) = self.receiver.recv().await {
+            match &event {
+                DomainEvent::ReviewLogged {
+                    review_id,
+                    movie_id,
+                    user_id,
+                    rating,
+                    watched_at,
+                } => {
+                    tracing::info!(
+                        review_id  = %review_id.value(),
+                        movie_id   = %movie_id.value(),
+                        user_id    = %user_id.value(),
+                        rating     = rating.value(),
+                        watched_at = %watched_at,
+                        "event: review_logged"
+                    );
+                }
+                DomainEvent::MovieDiscovered {
+                    movie_id,
+                    external_metadata_id,
+                } => {
+                    tracing::info!(
+                        movie_id    = %movie_id.value(),
+                        external_id = external_metadata_id.value(),
+                        "event: movie_discovered"
+                    );
+                }
+            }
+        }
+        tracing::info!("event worker shut down");
+    }
+}
+
+pub fn create_event_channel(config: EventPublisherConfig) -> (ChannelEventPublisher, EventWorker) {
+    let (tx, rx) = mpsc::channel(config.channel_buffer);
+    (
+        ChannelEventPublisher { sender: tx },
+        EventWorker { receiver: rx },
+    )
+}