Use idiomatic undertow/websocket maps instead of raw WebSocket API

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

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

@@ -4,11 +4,12 @@
 
 (defn- wrap-nil-guard
   "Discard responses with no :status — these are artifacts of ring-defaults
-   middleware wrapping a nil response (e.g., from a raw WebSocket upgrade)."
+   middleware wrapping a nil response (e.g., from a raw WebSocket upgrade).
+   Passes through :undertow/websocket responses for the adapter to handle."
   [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]}]
   (fn [handler]

src/clj/pmagnus/btcprice/web/routes/ws_proxy.clj

@@ -3,9 +3,7 @@
    [clojure.tools.logging :as log]
    [integrant.core :as ig])
   (:import
-   [io.undertow.server HttpServerExchange]
-   [io.undertow.websockets WebSocketConnectionCallback WebSocketProtocolHandshakeHandler]
-   [io.undertow.websockets.core AbstractReceiveListener WebSockets WebSocketChannel]
+   [io.undertow.websockets.core WebSockets WebSocketChannel]
    [java.net URI]
    [java.net.http HttpClient WebSocket$Builder WebSocket$Listener]
    [java.util.concurrent CompletableFuture]))
@@ -47,24 +45,19 @@
         (.buildAsync (URI. btcdata-ws-url) listener)
         (.join))))
 
-(defn- ws-proxy-handler [{:keys [btcdata-url]} req]
-  (let [^HttpServerExchange exchange (:server-exchange req)
-        btcdata-ws-url (str (.replaceFirst ^String btcdata-url "^http" "ws")
+(defn- ws-proxy-handler [{:keys [btcdata-url]} _req]
+  (let [btcdata-ws-url (str (.replaceFirst ^String btcdata-url "^http" "ws")
                             "/api/price/ws")
-        callback (proxy [WebSocketConnectionCallback] []
-                   (onConnect [_ws-exchange browser-ch]
+        upstream-atom  (atom nil)]
+    {:undertow/websocket
+     {:on-open
+      (fn [{:keys [^WebSocketChannel channel]}]
         (log/info "Browser connected, proxying to" btcdata-ws-url)
-                     (let [upstream (connect-upstream btcdata-ws-url browser-ch)]
-                       ;; Listen for browser close to tear down upstream
-                       (.set (.getReceiveSetter ^WebSocketChannel browser-ch)
-                             (proxy [AbstractReceiveListener] []
-                               (onCloseMessage [_this _msg _ch]
+        (reset! upstream-atom (connect-upstream btcdata-ws-url channel)))
+      :on-close-message
+      (fn [_]
         (log/debug "Browser closed")
-                                 (close-upstream-quietly upstream))))
-                       (.resumeReceives ^WebSocketChannel browser-ch))))
-        handler (WebSocketProtocolHandshakeHandler. callback)]
-    (.handleRequest handler exchange)
-    nil))
+        (close-upstream-quietly @upstream-atom))}}))
 
 (defn- ws-proxy-routes [opts]
   [["/ws/price"