Use idiomatic undertow/websocket maps instead of raw WebSocket API

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

src/clj/pmagnus/btcdata/web/middleware/core.clj

@@ -22,7 +22,7 @@
   [handler]
   (fn [request]
     (let [resp (handler request)]
-      (when (:status resp) resp))))
+      (when (or (:status resp) (:undertow/websocket resp)) resp))))
 
 (defn wrap-base [{:keys [site-defaults-config cors-origin]}]
   (let [origin (or cors-origin

src/clj/pmagnus/btcdata/web/routes/api.clj

@@ -11,9 +11,7 @@
    [reitit.ring.middleware.parameters :as parameters]
    [reitit.swagger :as swagger])
   (:import
-   [io.undertow.server HttpServerExchange]
-   [io.undertow.websockets WebSocketConnectionCallback WebSocketProtocolHandshakeHandler]
-   [io.undertow.websockets.core AbstractReceiveListener WebSockets WebSocketChannel]
+   [io.undertow.websockets.core WebSockets WebSocketChannel]
    [java.time Instant ZoneId]
    [java.time.format DateTimeFormatter]
    [java.util Locale]
@@ -66,9 +64,6 @@
   (let [queue (LinkedBlockingQueue.)
         wkey  (keyword (gensym "ws-"))
         rkey  (keyword (gensym "ws-r-"))]
-    (.set (.getReceiveSetter channel)
-          (proxy [AbstractReceiveListener] []))
-    (.resumeReceives channel)
     (add-watch price-atom wkey
       (fn [_ _ _ _] (.offer queue :update)))
     (add-watch rates-atom rkey
@@ -91,16 +86,12 @@
           (when (.isOpen channel)
             (try (.close channel) (catch Exception _))))))))
 
-(defn- ws-price-handler [{:keys [binance frankfurter]} req]
-  (let [^HttpServerExchange exchange (:server-exchange req)
-        price-atom (:latest-price binance)
-        rates-atom (:rates frankfurter)
-        callback (proxy [WebSocketConnectionCallback] []
-                   (onConnect [_ws-exchange channel]
-                     (start-ws-send-loop! channel price-atom rates-atom)))
-        handler (WebSocketProtocolHandshakeHandler. callback)]
-    (.handleRequest handler exchange)
-    nil))
+(defn- ws-price-handler [{:keys [binance frankfurter]} _req]
+  (let [price-atom (:latest-price binance)
+        rates-atom (:rates frankfurter)]
+    {:undertow/websocket
+     {:on-open (fn [{:keys [^WebSocketChannel channel]}]
+                 (start-ws-send-loop! channel price-atom rates-atom))}}))
 
 (defn- latest-price-handler [{:keys [binance frankfurter]} _req]
   (let [price-atom (:latest-price binance)