Simplify webhook module: deduplicate PEM decoding, extract delivery_id, remove redundant state

- Reuse jwt_auth::decode_pem_env in read_github_private_key instead of duplicating base64/PEM logic
- Extract delivery_id once at top of webhook_handler instead of 3 separate times
- Remove redundant funnel_port field from WebhookManager (derive from listener.port())
- Gate parse_event_metadata behind debug log level to avoid full JSON parse on every webhook

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

crates/arc-api/src/github_webhooks.rs

@@ -43,26 +43,23 @@ async fn webhook_handler(
     headers: HeaderMap,
     body: Bytes,
 ) -> StatusCode {
+    let delivery_id = headers
+        .get("x-github-delivery")
+        .and_then(|v| v.to_str().ok())
+        .unwrap_or("unknown");
+
     let signature = match headers
         .get("x-hub-signature-256")
         .and_then(|v| v.to_str().ok())
     {
         Some(s) => s,
         None => {
-            let delivery_id = headers
-                .get("x-github-delivery")
-                .and_then(|v| v.to_str().ok())
-                .unwrap_or("unknown");
             warn!(delivery = %delivery_id, "Webhook signature verification failed");
             return StatusCode::UNAUTHORIZED;
         }
     };
 
     if !verify_signature(&state.secret, &body, signature) {
-        let delivery_id = headers
-            .get("x-github-delivery")
-            .and_then(|v| v.to_str().ok())
-            .unwrap_or("unknown");
         warn!(delivery = %delivery_id, "Webhook signature verification failed");
         return StatusCode::UNAUTHORIZED;
     }
@@ -71,20 +68,23 @@ async fn webhook_handler(
         .get("x-github-event")
         .and_then(|v| v.to_str().ok())
         .unwrap_or("unknown");
-    let delivery_id = headers
-        .get("x-github-delivery")
-        .and_then(|v| v.to_str().ok())
-        .unwrap_or("unknown");
 
-    let (repo, action) = parse_event_metadata(&body);
-
-    debug!(
-        event = %event_type,
-        delivery = %delivery_id,
-        repo = %repo,
-        action = %action,
-        "Webhook received"
-    );
+    if tracing::enabled!(tracing::Level::DEBUG) {
+        let (repo, action) = parse_event_metadata(&body);
+        debug!(
+            event = %event_type,
+            delivery = %delivery_id,
+            repo = %repo,
+            action = %action,
+            "Webhook received"
+        );
+    } else {
+        info!(
+            event = %event_type,
+            delivery = %delivery_id,
+            "Webhook received"
+        );
+    }
 
     StatusCode::OK
 }
@@ -151,7 +151,6 @@ pub async fn spawn_webhook_listener(secret: Vec<u8>) -> anyhow::Result<WebhookLi
 /// Manage the full webhook lifecycle: listener + tailscale funnel + GitHub API.
 pub struct WebhookManager {
     listener: WebhookListener,
-    funnel_port: u16,
 }
 
 impl WebhookManager {
@@ -188,15 +187,12 @@ impl WebhookManager {
 
         info!(url = %webhook_url, "GitHub App webhook URL updated");
 
-        Ok(Self {
-            listener,
-            funnel_port: port,
-        })
+        Ok(Self { listener })
     }
 
     /// Shut down: disable funnel, stop listener.
     pub async fn shutdown(self) {
-        disable_tailscale_funnel(self.funnel_port).await;
+        disable_tailscale_funnel(self.listener.port()).await;
         self.listener.shutdown();
     }
 }

crates/arc-api/src/jwt_auth.rs

@@ -53,7 +53,7 @@ pub enum AuthMode {
 pub struct PeerCertificates(pub Option<Vec<CertificateDer<'static>>>);
 
 /// Decode a PEM env var that may be raw PEM or base64-encoded PEM.
-fn decode_pem_env(name: &str, value: &str) -> String {
+pub fn decode_pem_env(name: &str, value: &str) -> String {
     if value.starts_with("-----") {
         return value.to_string();
     }

crates/arc-api/src/serve.rs

@@ -307,13 +307,10 @@ fn resolve_model_provider(
 /// Read the GitHub App private key from the environment, decoding base64 if needed.
 fn read_github_private_key() -> Option<String> {
     let raw = std::env::var("GITHUB_APP_PRIVATE_KEY").ok()?;
-    if raw.starts_with("-----") {
-        Some(raw)
-    } else {
-        let pem_bytes =
-            base64::Engine::decode(&base64::engine::general_purpose::STANDARD, &raw).ok()?;
-        String::from_utf8(pem_bytes).ok()
-    }
+    Some(crate::jwt_auth::decode_pem_env(
+        "GITHUB_APP_PRIVATE_KEY",
+        &raw,
+    ))
 }
 
 /// Derive client certificate verification mode from the resolved auth strategies.