feat: add discovery

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

crates/churn/src/api.rs

@@ -1,6 +1,12 @@
 use std::net::SocketAddr;
 
-use axum::{extract::MatchedPath, http::Request, routing::get, Router};
+use axum::{
+    extract::{MatchedPath, State},
+    http::Request,
+    routing::get,
+    Json, Router,
+};
+use serde::{Deserialize, Serialize};
 use tokio_util::sync::CancellationToken;
 use tower_http::trace::TraceLayer;
 
@@ -22,6 +28,7 @@ impl Api {
     pub async fn serve(&self) -> anyhow::Result<()> {
         let app = Router::new()
             .route("/", get(root))
+            .route("/discovery", get(discovery))
             .with_state(self.state.clone())
             .layer(
                 TraceLayer::new_for_http().make_span_with(|request: &Request<_>| {
@@ -55,6 +62,28 @@ async fn root() -> &'static str {
     "Hello, churn!"
 }
 
+#[derive(Serialize, Deserialize)]
+pub struct Discovery {
+    pub external_host: String,
+    pub process_host: String,
+}
+
+impl Discovery {
+    pub async fn get_from_host(host: &str) -> anyhow::Result<Self> {
+        let resp = reqwest::get(format!("{}/discovery", host.trim_end_matches('/'))).await?;
+        let s: Self = resp.json().await?;
+
+        Ok(s)
+    }
+}
+
+async fn discovery(State(state): State<SharedState>) -> Json<Discovery> {
+    Json(Discovery {
+        external_host: state.config.external_host.clone(),
+        process_host: state.config.process_host.clone(),
+    })
+}
+
 #[async_trait::async_trait]
 impl notmad::Component for Api {
     async fn run(&self, _cancellation_token: CancellationToken) -> Result<(), notmad::MadError> {