1 files changed, 89 insertions, 0 deletions

diff --git a/language-web/src/main/java/tools/refinery/language/web/xtext/server/push/PushWebDocument.java b/language-web/src/main/java/tools/refinery/language/web/xtext/server/push/PushWebDocument.java
new file mode 100644
index 00000000..906b9e30
--- /dev/null
+++ b/language-web/src/main/java/tools/refinery/language/web/xtext/server/push/PushWebDocument.java
@@ -0,0 +1,89 @@
+package tools.refinery.language.web.xtext.server.push;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+import org.eclipse.xtext.util.CancelIndicator;
+import org.eclipse.xtext.web.server.IServiceResult;
+import org.eclipse.xtext.web.server.model.AbstractCachedService;
+import org.eclipse.xtext.web.server.model.DocumentSynchronizer;
+import org.eclipse.xtext.web.server.model.XtextWebDocument;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import com.google.common.collect.ImmutableList;
+
+import tools.refinery.language.web.xtext.server.ResponseHandlerException;
+
+public class PushWebDocument extends XtextWebDocument {
+        private static final Logger LOG = LoggerFactory.getLogger(PushWebDocument.class);
+
+        private final List<PrecomputationListener> precomputationListeners = new ArrayList<>();
+
+        private final Map<Class<?>, IServiceResult> precomputedServices = new HashMap<>();
+
+        public PushWebDocument(String resourceId, DocumentSynchronizer synchronizer) {
+                super(resourceId, synchronizer);
+                if (resourceId == null) {
+                        throw new IllegalArgumentException("resourceId must not be null");
+                }
+        }
+
+        public boolean addPrecomputationListener(PrecomputationListener listener) {
+                synchronized (precomputationListeners) {
+                        if (precomputationListeners.contains(listener)) {
+                                return false;
+                        }
+                        precomputationListeners.add(listener);
+                        listener.onSubscribeToPrecomputationEvents(getResourceId(), this);
+                        return true;
+                }
+        }
+
+        public boolean removePrecomputationListener(PrecomputationListener listener) {
+                synchronized (precomputationListeners) {
+                        return precomputationListeners.remove(listener);
+                }
+        }
+
+        public <T extends IServiceResult> void precomputeServiceResult(AbstractCachedService<T> service, String serviceName,
+                        CancelIndicator cancelIndicator, boolean logCacheMiss) {
+                var result = getCachedServiceResult(service, cancelIndicator, logCacheMiss);
+                if (result == null) {
+                        LOG.error("{} service returned null result", serviceName);
+                        return;
+                }
+                var serviceClass = service.getClass();
+                var previousResult = precomputedServices.get(serviceClass);
+                if (previousResult != null && previousResult.equals(result)) {
+                        return;
+                }
+                precomputedServices.put(serviceClass, result);
+                notifyPrecomputationListeners(serviceName, result);
+        }
+
+        private <T extends IServiceResult> void notifyPrecomputationListeners(String serviceName, T result) {
+                var resourceId = getResourceId();
+                var stateId = getStateId();
+                List<PrecomputationListener> copyOfListeners;
+                synchronized (precomputationListeners) {
+                        copyOfListeners = ImmutableList.copyOf(precomputationListeners);
+                }
+                var toRemove = new ArrayList<PrecomputationListener>();
+                for (var listener : copyOfListeners) {
+                        try {
+                                listener.onPrecomputedServiceResult(resourceId, stateId, serviceName, result);
+                        } catch (ResponseHandlerException e) {
+                                LOG.error("Delivering precomputation push message failed", e);
+                                toRemove.add(listener);
+                        }
+                }
+                if (!toRemove.isEmpty()) {
+                        synchronized (precomputationListeners) {
+                                precomputationListeners.removeAll(toRemove);
+                        }
+                }
+        }
+}