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 },
+    )
+}

crates/presentation/Cargo.toml

@@ -28,6 +28,7 @@ poster-storage = { workspace = true }
 sqlite = { workspace = true }
 sqlx = { workspace = true }
 template-askama = { workspace = true }
+event-publisher = { workspace = true }
 rss = { workspace = true }
 
 [dev-dependencies]

crates/presentation/src/main.rs

@@ -1,8 +1,7 @@
 use std::sync::Arc;
 
 use anyhow::Context;
-use async_trait::async_trait;
-use domain::{errors::DomainError, events::DomainEvent, ports::EventPublisher};
+use event_publisher::{EventPublisherConfig, create_event_channel};
 use sqlx::SqlitePool;
 use tokio::net::TcpListener;
 use tracing_subscriber::{layer::SubscriberExt, util::SubscriberInitExt};
@@ -18,15 +17,6 @@ use template_askama::AskamaHtmlRenderer;
 
 use presentation::{routes, state::AppState};
 
-struct StubEventPublisher;
-
-#[async_trait]
-impl EventPublisher for StubEventPublisher {
-    async fn publish(&self, _event: &DomainEvent) -> Result<(), DomainError> {
-        Ok(())
-    }
-}
-
 #[tokio::main]
 async fn main() -> anyhow::Result<()> {
     dotenvy::dotenv().ok();
@@ -64,12 +54,15 @@ async fn wire_dependencies() -> anyhow::Result<AppState> {
 
     let user_repo = SqliteUserRepository::new(pool);
 
+    let (event_publisher, event_worker) = create_event_channel(EventPublisherConfig::from_env());
+    tokio::spawn(event_worker.run());
+
     let app_ctx = AppContext {
         repository: Arc::new(movie_repo),
         metadata_client: Arc::new(MetadataClientImpl::new_omdb(omdb_api_key)),
         poster_fetcher: Arc::new(ReqwestPosterFetcher::new(PosterFetcherConfig::from_env())?),
         poster_storage: Arc::new(PosterStorageAdapter::from_config(storage_config)?),
-        event_publisher: Arc::new(StubEventPublisher),
+        event_publisher: Arc::new(event_publisher),
         auth_service: Arc::new(JwtAuthService::new(auth_config)),
         password_hasher: Arc::new(Argon2PasswordHasher),
         user_repository: Arc::new(user_repo),