refactor (v2): better arch

Co-authored-by: Copilot <copilot@github.com>

crates/adapters/nats/src/lib.rs

@@ -0,0 +1,92 @@
+pub mod consumer;
+pub mod publisher;
+
+use std::time::Duration;
+
+use async_nats::jetstream::{self, consumer as nats_consumer, consumer::pull};
+
+use crate::{consumer::NatsEventConsumer, publisher::NatsEventPublisher};
+
+// ── Subject routing ───────────────────────────────────────────────────────────
+
+pub(crate) fn subject_for(event: &domain::events::DomainEvent) -> &'static str {
+    use domain::events::DomainEvent;
+    match event {
+        DomainEvent::NoteCreated { .. } => "knotes.note.created",
+        DomainEvent::NoteUpdated { .. } => "knotes.note.updated",
+        DomainEvent::NoteDeleted { .. } => "knotes.note.deleted",
+    }
+}
+
+pub(crate) const SUBSCRIBE_SUBJECT: &str = "knotes.note.>";
+
+// ── Config ────────────────────────────────────────────────────────────────────
+
+/// Configuration for the JetStream stream and durable pull consumer.
+///
+/// **Dead-letter queue**: after `max_deliver` failed attempts NATS stops
+/// redelivering and publishes an advisory to
+/// `$JS.EVENT.ADVISORY.CONSUMER.MAX_DELIVERIES.{stream}.{consumer}`.
+/// Subscribe to those with a monitoring consumer or NATS dashboard to
+/// observe dead messages.
+#[derive(Debug, Clone)]
+pub struct JetStreamConfig {
+    /// Name of the JetStream stream (created on first use if absent).
+    pub stream_name: String,
+    /// Durable consumer name — survives worker restarts.
+    pub consumer_name: String,
+    /// Maximum delivery attempts before the message is considered dead.
+    pub max_deliver: i64,
+    /// How long JetStream waits for an ack before redelivering.
+    pub ack_wait: Duration,
+}
+
+impl Default for JetStreamConfig {
+    fn default() -> Self {
+        Self {
+            stream_name: "KNOTES".into(),
+            consumer_name: "knotes-worker".into(),
+            max_deliver: 5,
+            ack_wait: Duration::from_secs(30),
+        }
+    }
+}
+
+// ── Setup ─────────────────────────────────────────────────────────────────────
+
+/// Connect to NATS and initialise both the publisher and consumer.
+/// Creates the JetStream stream and durable pull consumer if they do not exist.
+pub async fn setup(
+    url: &str,
+    config: JetStreamConfig,
+) -> Result<(NatsEventPublisher, NatsEventConsumer), Box<dyn std::error::Error + Send + Sync>> {
+    let client = async_nats::connect(url).await?;
+    let js = jetstream::new(client);
+
+    let stream = js
+        .get_or_create_stream(jetstream::stream::Config {
+            name: config.stream_name.clone(),
+            subjects: vec![SUBSCRIBE_SUBJECT.into()],
+            ..Default::default()
+        })
+        .await?;
+
+    let nats_consumer: nats_consumer::Consumer<pull::Config> = stream
+        .get_or_create_consumer(
+            &config.consumer_name,
+            pull::Config {
+                durable_name: Some(config.consumer_name.clone()),
+                ack_policy: jetstream::consumer::AckPolicy::Explicit,
+                max_deliver: config.max_deliver,
+                ack_wait: config.ack_wait,
+                filter_subject: SUBSCRIBE_SUBJECT.into(),
+                ..Default::default()
+            },
+        )
+        .await?;
+
+    Ok((
+        NatsEventPublisher::new(js),
+        NatsEventConsumer::new(nats_consumer),
+    ))
+}