1 files changed, 94 insertions, 0 deletions

diff --git a/language-web/src/main/java/tools/refinery/language/web/xtext/servlet/XtextWebSocket.java b/language-web/src/main/java/tools/refinery/language/web/xtext/servlet/XtextWebSocket.java
new file mode 100644
index 00000000..25f67545
--- /dev/null
+++ b/language-web/src/main/java/tools/refinery/language/web/xtext/servlet/XtextWebSocket.java
@@ -0,0 +1,94 @@
+package tools.refinery.language.web.xtext.servlet;
+
+import java.io.IOException;
+import java.io.Reader;
+
+import org.eclipse.jetty.websocket.api.Session;
+import org.eclipse.jetty.websocket.api.StatusCode;
+import org.eclipse.jetty.websocket.api.WriteCallback;
+import org.eclipse.jetty.websocket.api.annotations.OnWebSocketClose;
+import org.eclipse.jetty.websocket.api.annotations.OnWebSocketConnect;
+import org.eclipse.jetty.websocket.api.annotations.OnWebSocketError;
+import org.eclipse.jetty.websocket.api.annotations.OnWebSocketMessage;
+import org.eclipse.jetty.websocket.api.annotations.WebSocket;
+import org.eclipse.xtext.resource.IResourceServiceProvider;
+import org.eclipse.xtext.web.server.ISession;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import com.google.gson.Gson;
+import com.google.gson.JsonIOException;
+import com.google.gson.JsonParseException;
+
+@WebSocket
+public class XtextWebSocket {
+        private static final Logger LOG = LoggerFactory.getLogger(XtextWebSocket.class);
+
+        private final Gson gson = new Gson();
+
+        private final TransactionExecutor executor;
+
+        public XtextWebSocket(TransactionExecutor executor) {
+                this.executor = executor;
+        }
+
+        public XtextWebSocket(ISession session, IResourceServiceProvider.Registry resourceServiceProviderRegistry) {
+                this(new TransactionExecutor(session, resourceServiceProviderRegistry));
+        }
+
+        @OnWebSocketConnect
+        public void onConnect(Session webSocketSession) {
+                LOG.debug("New websocket connection from {}", webSocketSession.getRemoteAddress());
+        }
+
+        @OnWebSocketClose
+        public void onClose(Session webSocketSession, int statusCode, String reason) {
+                if (statusCode == StatusCode.NORMAL) {
+                        LOG.debug("{} closed connection normally: {}", webSocketSession.getRemoteAddress(), reason);
+                } else {
+                        LOG.warn("{} closed connection with status code {}: {}", webSocketSession.getRemoteAddress(), statusCode,
+                                        reason);
+                }
+        }
+
+        @OnWebSocketError
+        public void onError(Session webSocketSession, Throwable error) {
+                LOG.error("Internal websocket error in connection from" + webSocketSession.getRemoteAddress(), error);
+        }
+
+        @OnWebSocketMessage
+        public void onMessage(Session webSocketSession, Reader reader) {
+                XtextWebSocketRequest request;
+                try {
+                        request = gson.fromJson(reader, XtextWebSocketRequest.class);
+                } catch (JsonIOException e) {
+                        LOG.error("Cannot read from websocket from" + webSocketSession.getRemoteAddress(), e);
+                        if (webSocketSession.isOpen()) {
+                                webSocketSession.close(StatusCode.SERVER_ERROR, "Cannot read payload");
+                        }
+                        return;
+                } catch (JsonParseException e) {
+                        LOG.warn("Malformed websocket request from" + webSocketSession.getRemoteAddress(), e);
+                        webSocketSession.close(XtextStatusCode.INVALID_JSON, "Invalid JSON payload");
+                        return;
+                }
+                try {
+                        executor.handleRequest(request, response -> sendResponse(webSocketSession, response));
+                } catch (IOException e) {
+                        LOG.warn("Cannot initiaite async write to websocket " + webSocketSession.getRemoteAddress(), e);
+                        if (webSocketSession.isOpen()) {
+                                webSocketSession.close(StatusCode.SERVER_ERROR, "Cannot write payload");
+                        }
+                }
+        }
+
+        protected void sendResponse(Session webSocketSession, XtextWebSocketResponse response) throws IOException {
+                var responseString = gson.toJson(response);
+                webSocketSession.getRemote().sendPartialString(responseString, true, new WriteCallback() {
+                        @Override
+                        public void writeFailed(Throwable x) {
+                                LOG.warn("Cannot complete async write to websocket " + webSocketSession.getRemoteAddress(), x);
+                        }
+                });
+        }
+}