1 files changed, 93 insertions, 0 deletions
diff --git a/plugins/infra/core/org.eclipse.papyrus.infra.core.sashwindows.di/src/org/eclipse/papyrus/infra/core/sashwindows/di/util/PageRemovalValidator.java b/plugins/infra/core/org.eclipse.papyrus.infra.core.sashwindows.di/src/org/eclipse/papyrus/infra/core/sashwindows/di/util/PageRemovalValidator.java
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index 00000000000..13746ad2f59
--- /dev/null
+++ b/plugins/infra/core/org.eclipse.papyrus.infra.core.sashwindows.di/src/org/eclipse/papyrus/infra/core/sashwindows/di/util/PageRemovalValidator.java
@@ -0,0 +1,93 @@
+/*****************************************************************************
+ * Copyright (c) 2015 Christian W. Damus and others.
+ * 
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ *
+ * Contributors:
+ *   Christian W. Damus - Initial API and implementation
+ *   
+ *****************************************************************************/
+
+package org.eclipse.papyrus.infra.core.sashwindows.di.util;
+
+import java.util.Collection;
+import java.util.stream.Collectors;
+
+import org.eclipse.emf.common.notify.Notifier;
+import org.eclipse.papyrus.infra.core.sashwindows.di.PageRef;
+
+/**
+ * A protocol for an adapter that can be attached to the Sash model to validate
+ * the closing of pages.
+ */
+@FunctionalInterface
+public interface PageRemovalValidator {
+	/** A validator that always permits removing the page. */
+	PageRemovalValidator ALWAYS_REMOVE = new PageRemovalValidator() {
+
+		@Override
+		public boolean canRemovePage(PageRef page) {
+			return true;
+		}
+
+		@Override
+		public Collection<? extends PageRef> filterRemovablePages(Collection<? extends PageRef> pages) {
+			return pages;
+		}
+	};
+
+	/**
+	 * Queries whether the given page may be closed.
+	 * 
+	 * @param page
+	 *            the page to be closed
+	 * 
+	 * @return whether the page may be closed
+	 */
+	boolean canRemovePage(PageRef page);
+
+	/**
+	 * Filters a set of pages to be closed, returning those that actually may be closed.
+	 * This accounts for the possibility where a page may be closeable on its own,
+	 * but not if some other pages are also to be closed.
+	 * 
+	 * @param pages
+	 *            a collection of pages to be closed
+	 * 
+	 * @return the subset (possibly all or none) of the pages that may be closed
+	 */
+	default Collection<? extends PageRef> filterRemovablePages(Collection<? extends PageRef> pages) {
+		return pages.stream().filter(this::canRemovePage).collect(Collectors.toList());
+	}
+
+	/**
+	 * Composes myself with an{@code other} removal validator.
+	 * 
+	 * @param other
+	 *            another removal validator
+	 * 
+	 * @return a removal validator that applies my filtering and the {@code other}'s, both
+	 */
+	default PageRemovalValidator compose(PageRemovalValidator other) {
+		return new CompositePageRemovalValidator(this, other);
+	}
+
+	/**
+	 * Obtains the page removal validator for the given {@code notifier}.
+	 * 
+	 * @param notifier
+	 *            an element of (usually) the Sash model
+	 * 
+	 * @return the appropriate removal validator, never {@code null} (though perhaps the
+	 *         {@link #ALWAYS_REMOVE} instance)
+	 */
+	static PageRemovalValidator getInstance(Notifier notifier) {
+		return notifier.eAdapters().stream()
+				.filter(PageRemovalValidator.class::isInstance).map(PageRemovalValidator.class::cast)
+				.reduce(PageRemovalValidator::compose)
+				.orElse(ALWAYS_REMOVE);
+	}
+}