1 files changed, 137 insertions, 0 deletions

diff --git a/language-web/src/main/java/tools/refinery/language/web/xtext/servlet/TransactionExecutor.java b/language-web/src/main/java/tools/refinery/language/web/xtext/servlet/TransactionExecutor.java
new file mode 100644
index 00000000..08687097
--- /dev/null
+++ b/language-web/src/main/java/tools/refinery/language/web/xtext/servlet/TransactionExecutor.java
@@ -0,0 +1,137 @@
+package tools.refinery.language.web.xtext.servlet;
+
+import java.io.IOException;
+
+import org.eclipse.emf.common.util.URI;
+import org.eclipse.xtext.resource.IResourceServiceProvider;
+import org.eclipse.xtext.web.server.IServiceResult;
+import org.eclipse.xtext.web.server.ISession;
+import org.eclipse.xtext.web.server.InvalidRequestException;
+import org.eclipse.xtext.web.server.InvalidRequestException.UnknownLanguageException;
+import org.eclipse.xtext.web.server.ServiceConflictResult;
+import org.eclipse.xtext.web.server.XtextServiceDispatcher;
+import org.eclipse.xtext.web.server.contentassist.ContentAssistResult;
+import org.eclipse.xtext.web.server.formatting.FormattingResult;
+import org.eclipse.xtext.web.server.hover.HoverResult;
+import org.eclipse.xtext.web.server.model.DocumentStateResult;
+import org.eclipse.xtext.web.server.occurrences.OccurrencesResult;
+import org.eclipse.xtext.web.server.persistence.ResourceContentResult;
+
+import com.google.common.base.Strings;
+import com.google.inject.Injector;
+
+public class TransactionExecutor {
+        private final ISession session;
+
+        private final IResourceServiceProvider.Registry resourceServiceProviderRegistry;
+
+        public TransactionExecutor(ISession session, IResourceServiceProvider.Registry resourceServiceProviderRegistry) {
+                this.session = session;
+                this.resourceServiceProviderRegistry = resourceServiceProviderRegistry;
+        }
+
+        public void handleRequest(XtextWebSocketRequest request, ResponseHandler handler) throws IOException {
+                var requestData = request.getRequestData();
+                if (requestData == null || requestData.isEmpty()) {
+                        // Nothing to do.
+                        return;
+                }
+                int nCalls = requestData.size();
+                int lastCall = handleTransaction(request, handler);
+                for (int index = lastCall + 1; index < nCalls; index++) {
+                        handler.onResponse(
+                                        new XtextWebSocketErrorResponse(request, index, XtextWebSocketErrorKind.TRANSACTION_CANCELLED));
+                }
+        }
+
+        protected int handleTransaction(XtextWebSocketRequest request, ResponseHandler handler) throws IOException {
+                var requestData = request.getRequestData();
+                var stateId = request.getRequiredStateId();
+                int index = 0;
+                try {
+                        var injector = getInjector(request);
+                        var serviceDispatcher = injector.getInstance(XtextServiceDispatcher.class);
+                        int nCalls = requestData.size();
+                        for (; index < nCalls; index++) {
+                                var serviceContext = SimpleServiceContext.ofTransaction(session, request, stateId, index);
+                                var service = serviceDispatcher.getService(serviceContext);
+                                var serviceResult = service.getService().apply();
+                                handler.onResponse(new XtextWebSocketOkResponse(request, index, serviceResult));
+                                if (serviceResult instanceof ServiceConflictResult) {
+                                        break;
+                                }
+                                var nextStateId = getNextStateId(serviceResult);
+                                if (nextStateId != null) {
+                                        stateId = nextStateId;
+                                }
+                        }
+                } catch (InvalidRequestException e) {
+                        handler.onResponse(
+                                        new XtextWebSocketErrorResponse(request, index, XtextWebSocketErrorKind.REQUEST_ERROR, e));
+                } catch (RuntimeException e) {
+                        handler.onResponse(
+                                        new XtextWebSocketErrorResponse(request, index, XtextWebSocketErrorKind.SERVER_ERROR, e));
+                }
+                return index;
+        }
+
+        /**
+         * Get the injector to satisfy the request in the {@code serviceContext}.
+         * 
+         * Based on {@link org.eclipse.xtext.web.servlet.XtextServlet#getInjector}.
+         * 
+         * @param serviceContext the Xtext service context of the request
+         * @return the injector for the Xtext language in the request
+         * @throws UnknownLanguageException if the Xtext language cannot be determined
+         */
+        protected Injector getInjector(XtextWebSocketRequest request) {
+                IResourceServiceProvider resourceServiceProvider = null;
+                var resourceName = request.getResourceName();
+                if (resourceName == null) {
+                        resourceName = "";
+                }
+                var emfURI = URI.createURI(resourceName);
+                var contentType = request.getContentType();
+                if (Strings.isNullOrEmpty(contentType)) {
+                        resourceServiceProvider = resourceServiceProviderRegistry.getResourceServiceProvider(emfURI);
+                        if (resourceServiceProvider == null) {
+                                if (emfURI.toString().isEmpty()) {
+                                        throw new UnknownLanguageException(
+                                                        "Unable to identify the Xtext language: missing parameter 'resource' or 'contentType'.");
+                                } else {
+                                        throw new UnknownLanguageException(
+                                                        "Unable to identify the Xtext language for resource " + emfURI + ".");
+                                }
+                        }
+                } else {
+                        resourceServiceProvider = resourceServiceProviderRegistry.getResourceServiceProvider(emfURI, contentType);
+                        if (resourceServiceProvider == null) {
+                                throw new UnknownLanguageException(
+                                                "Unable to identify the Xtext language for contentType " + contentType + ".");
+                        }
+                }
+                return resourceServiceProvider.get(Injector.class);
+        }
+
+        protected String getNextStateId(IServiceResult serviceResult) {
+                if (serviceResult instanceof ContentAssistResult contentAssistResult) {
+                        return contentAssistResult.getStateId();
+                }
+                if (serviceResult instanceof DocumentStateResult documentStateResult) {
+                        return documentStateResult.getStateId();
+                }
+                if (serviceResult instanceof FormattingResult formattingResult) {
+                        return formattingResult.getStateId();
+                }
+                if (serviceResult instanceof HoverResult hoverResult) {
+                        return hoverResult.getStateId();
+                }
+                if (serviceResult instanceof OccurrencesResult occurrencesResult) {
+                        return occurrencesResult.getStateId();
+                }
+                if (serviceResult instanceof ResourceContentResult resourceContentResult) {
+                        return resourceContentResult.getStateId();
+                }
+                return null;
+        }
+}