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headless-services/commons/commons-java/src/main/java/org/springframework/ide/vscode/commons/languageserver/java/FutureProjectFinder.java

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+package org.springframework.ide.vscode.commons.languageserver.java;
+
+import java.net.URI;
+import java.util.Map;
+import java.util.Optional;
+import java.util.WeakHashMap;
+import java.util.concurrent.CompletableFuture;
+
+import org.eclipse.lsp4j.TextDocumentIdentifier;
+import org.springframework.beans.factory.DisposableBean;
+import org.springframework.ide.vscode.commons.java.IJavaProject;
+import org.springframework.ide.vscode.commons.languageserver.java.ProjectObserver.Listener;
+
+public class FutureProjectFinder implements DisposableBean {
+	
+	private JavaProjectFinder projectFinder;
+	private ProjectObserver projectObserver;
+	
+	private WeakHashMap<URI, CompletableFuture<IJavaProject>> pendingFindProjectRequests = new WeakHashMap<>();
+	
+	private final Listener LISTENER = new Listener() {
+		
+		@Override
+		public void deleted(IJavaProject project) {
+		}
+		
+		@Override
+		public void created(IJavaProject project) {
+			resolvePendingRequests(project);
+		}
+		
+		@Override
+		public void changed(IJavaProject project) {
+		}
+	};
+	
+	
+	public FutureProjectFinder(JavaProjectFinder projectFinder, Optional<ProjectObserver> projectObserver) {
+		this.projectFinder = projectFinder;
+		this.projectObserver = projectObserver.orElse(null);
+		if (this.projectObserver != null) {
+			this.projectObserver.addListener(LISTENER);
+		}
+	}
+
+	synchronized private void resolvePendingRequests(IJavaProject project) {
+		for (Map.Entry<URI, CompletableFuture<IJavaProject>> e : pendingFindProjectRequests.entrySet()) {
+			Optional<IJavaProject> jp = projectFinder.find(new TextDocumentIdentifier(e.getKey().toString()));
+			if (jp.isPresent()) {
+				e.getValue().complete(jp.get());
+				pendingFindProjectRequests.remove(e.getKey());
+			}
+		}
+	}
+
+	@Override
+	public void destroy() throws Exception {
+		if (projectObserver != null) {
+			projectObserver.removeListener(LISTENER);
+		}
+	}
+	
+	synchronized public CompletableFuture<IJavaProject> findFuture(URI uri) {		
+		TextDocumentIdentifier id = new TextDocumentIdentifier(uri.toString());
+		Optional<IJavaProject> jp = projectFinder.find(id);
+		if (jp.isPresent()) {
+			return CompletableFuture.completedFuture(jp.get());
+		} else {
+			if (projectObserver == null) {
+				throw new IllegalStateException("Future project lookup not supported without ProjectObserver bean present");
+			}
+			CompletableFuture<IJavaProject> cf = pendingFindProjectRequests.get(uri);
+			if (cf == null) {
+				cf = new CompletableFuture<IJavaProject>();
+				pendingFindProjectRequests.put(uri, cf);
+			}
+			return cf;
+		}
+	}
+
+
+}