feat: add discovery

Signed-off-by: kjuulh <contact@kjuulh.io>

crates/churn/src/agent/event_handler.rs

@@ -0,0 +1,53 @@
+use notmad::{Component, MadError};
+
+use super::{agent_state::AgentState, config::AgentConfig, grpc_client::GrpcClient};
+
+#[derive(Clone)]
+pub struct EventHandler {
+    config: AgentConfig,
+    grpc: GrpcClient,
+}
+
+impl EventHandler {
+    pub fn new(state: impl Into<AgentState>) -> Self {
+        let state: AgentState = state.into();
+
+        Self {
+            config: state.config.clone(),
+            grpc: state.grpc.clone(),
+        }
+    }
+}
+
+#[async_trait::async_trait]
+impl Component for EventHandler {
+    fn name(&self) -> Option<String> {
+        Some("event_handler".into())
+    }
+
+    async fn run(
+        &self,
+        cancellation_token: tokio_util::sync::CancellationToken,
+    ) -> Result<(), notmad::MadError> {
+        tokio::select! {
+            _ = cancellation_token.cancelled() => {},
+            res = self.grpc.listen_events("agents", None::<String>, self.clone()) => {
+                res.map_err(MadError::Inner)?;
+            },
+            res = self.grpc.listen_events("agents", Some(&self.config.agent_id), self.clone()) => {
+                res.map_err(MadError::Inner)?;
+            }
+        }
+
+        Ok(())
+    }
+}
+
+#[async_trait::async_trait]
+impl super::grpc_client::ListenEventsExecutor for EventHandler {
+    async fn execute(&self, event: crate::grpc::ListenEventsResponse) -> anyhow::Result<()> {
+        tracing::info!(value = event.value, "received event");
+
+        Ok(())
+    }
+}