fix(ws): adjust WebSocket path handling for proxy scenarios to prevent connection errors

Author: OnlineDynamic

www/js/fpp.js

@@ -13063,16 +13063,23 @@ function startFppdWS () {
 		fppdWSReconnectTimer = null;
 	}
 	var proto = window.location.protocol === 'https:' ? 'wss:' : 'ws:';
-	// Keep whatever path prefix the current page is under, rather than hardcoding
-	// root - needed so this still reaches the right fppd when viewed through
-	// FPP's built-in /proxy/<ip>/ relay (etc/apache2.site), which serves another
+	// Keep the current page's path prefix ONLY when viewed through FPP's
+	// built-in /proxy/<host>/ relay (etc/apache2.site), which serves another
 	// FPP's pages under a path prefix instead of at the root. A plain '/fppdws'
-	// here connects to THIS Apache's own fppd instead of the one being proxied
+	// there connects to THIS Apache's own fppd instead of the one being proxied
 	// to; mod_proxy_html can't fix this the way it rewrites static markup,
 	// since this URL is only ever built at runtime in the browser. The /proxy/
 	// Directory block's own WebSocket-upgrade rule already relays a prefixed
 	// path (e.g. /proxy/<ip>/fppdws) correctly - it just never receives one.
-	var pathPrefix = window.location.pathname.substring(0, window.location.pathname.lastIndexOf('/') + 1);
+	//
+	// Anywhere else the prefix has to be dropped: fppd registers the socket at
+	// the root (WS_PATH_ADD("/fppdws") in src/StatusWebSocket.cpp) and Apache
+	// only ProxyPasses /fppdws, so a page living in a subdirectory - /api/ (the
+	// API docs) or /wled/ - asked for ws://<host>/api/fppdws, which nothing
+	// listens on. That connection was refused and then retried forever, filling
+	// the console with NS_ERROR_WEBSOCKET_CONNECTION_REFUSED on those pages.
+	var proxyPrefix = window.location.pathname.match(/^\/proxy\/[^\/]+\//);
+	var pathPrefix = proxyPrefix ? proxyPrefix[0] : '/';
 	var url = proto + '//' + window.location.host + pathPrefix + 'fppdws';
 	// Detach the socket being replaced.  Belt and suspenders for the generation
 	// check below: an abandoned socket is unreachable once nothing points at its