dsf/org.eclipse.cdt.dsf.ui/src/org/eclipse/cdt/dsf/debug/ui/viewmodel/expression/AbstractExpressionVMNode.java

/*******************************************************************************
 * Copyright (c) 2007, 2012 Wind River Systems and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     Wind River Systems - initial API and implementation
 *******************************************************************************/
package org.eclipse.cdt.dsf.debug.ui.viewmodel.expression;

import java.util.List;

import org.eclipse.cdt.dsf.concurrent.ConfinedToDsfExecutor;
import org.eclipse.cdt.dsf.concurrent.DataRequestMonitor;
import org.eclipse.cdt.dsf.concurrent.IDsfStatusConstants;
import org.eclipse.cdt.dsf.concurrent.MultiRequestMonitor;
import org.eclipse.cdt.dsf.datamodel.IDMContext;
import org.eclipse.cdt.dsf.internal.ui.DsfUIPlugin;
import org.eclipse.cdt.dsf.service.DsfSession;
import org.eclipse.cdt.dsf.ui.concurrent.ViewerDataRequestMonitor;
import org.eclipse.cdt.dsf.ui.viewmodel.IVMContext;
import org.eclipse.cdt.dsf.ui.viewmodel.VMChildrenUpdate;
import org.eclipse.cdt.dsf.ui.viewmodel.datamodel.AbstractDMVMNode;
import org.eclipse.cdt.dsf.ui.viewmodel.datamodel.AbstractDMVMProvider;
import org.eclipse.core.runtime.IStatus;
import org.eclipse.core.runtime.Status;
import org.eclipse.debug.core.model.IExpression;
import org.eclipse.debug.internal.ui.viewers.model.provisional.IChildrenUpdate;

/**
 * Base class for VM Nodes which can be used in the expressions view.
 * <p>
 * This base class uses the methods {@link #canParseExpression(IExpression)} and
 * {@link #update(IChildrenUpdate[])} to implement the
 * {@link IExpressionVMNode#update(IExpressionUpdate)}
 * method.  Two additional abstract protected methods need to be implemented
 * by the sub-class as well.
 * </p>
 */
public abstract class AbstractExpressionVMNode extends AbstractDMVMNode implements IExpressionVMNode {
	/**
	 * @since 2.0
	 */
	protected static final String PROP_ELEMENT_EXPRESSION = "element_expression"; //$NON-NLS-1$

	public AbstractExpressionVMNode(AbstractDMVMProvider provider, DsfSession session,
			Class<? extends IDMContext> dmcClassType) {
		super(provider, session, dmcClassType);
	}

	@Override
	public void update(final IExpressionUpdate update) {
		if (!canParseExpression(update.getExpression())) {
			// This method should not be called if canParseExpression() returns false.
			// Return an internal error status.
			update.setStatus(new Status(IStatus.ERROR, DsfUIPlugin.PLUGIN_ID, IDsfStatusConstants.INTERNAL_ERROR,
					"Cannot parse expression", null)); //$NON-NLS-1$
			update.done();
			return;
		}

		// Retrieve the list of all elements from the sub-class.  Then compare
		// each returned element to the expression in the update, using
		// testElementForExpression().  The element that matches the expression
		// is returned to the client.
		// If no matching element is found, the createInvalidExpressionVMContext()
		// method is called to a special context.
		update(new IChildrenUpdate[] {
				new VMChildrenUpdate(update, -1, -1, new ViewerDataRequestMonitor<List<Object>>(getExecutor(), update) {
					@Override
					protected void handleSuccess() {
						if (getData().size() == 0) {
							update.setExpressionElement(createInvalidExpressionVMContext(update.getExpression()));
							update.done();
						} else {
							final List<Object> elements = getData();

							final MultiRequestMonitor<DataRequestMonitor<Boolean>> multiRm = new MultiRequestMonitor<>(
									getExecutor(), null) {
								@Override
								protected void handleCompleted() {
									if (isSuccess()) {
										boolean foundMatchingContext = false;
										for (int i = 0; i < getRequestMonitors().size(); i++) {
											if (getRequestMonitors().get(i).getData()) {
												Object element = elements.get(i);
												associateExpression(element, update.getExpression());
												update.setExpressionElement(element);
												foundMatchingContext = true;
												break;
											}
										}
										if (!foundMatchingContext) {
											update.setExpressionElement(
													createInvalidExpressionVMContext(update.getExpression()));
										}
									} else {
										update.setStatus(getStatus());
									}
									update.done();
								}
							};
							multiRm.requireDoneAdding();

							for (Object element : elements) {
								testElementForExpression(element, update.getExpression(),
										multiRm.add(new DataRequestMonitor<Boolean>(getExecutor(), null) {
											@Override
											protected void handleCompleted() {
												multiRm.requestMonitorDone(this);
											}
										}));
							}
							multiRm.doneAdding();
						}
					}

					@Override
					protected void handleFailure() {
						update.setStatus(getStatus());
						update.done();
					}
				}) });

	}

	/**
	 * Tests whether the given element matches the given expression.
	 *
	 * @param element Element to test against the given expression.
	 * @param expression Expression to use to check if the element is matching.
	 * @param rm The request monitor for the result.
	 */
	@ConfinedToDsfExecutor("#getSession#getExecutor")
	protected void testElementForExpression(Object element, IExpression expression,
			final DataRequestMonitor<Boolean> rm) {
		rm.setData(false);
		rm.done();
	}

	/**
	 * Sets the given expression as the expression belonging to the given
	 * element.
	 * <p>
	 * This base class creates VM context elements using the extending class's
	 * {@link #update(IChildrenUpdate[])} method.  The element matching the
	 * expression is found using {@link #testElementForExpression(Object, IExpression, DataRequestMonitor)}.
	 * Once the matching element is found it needs to be linked to the expression
	 * so that it can be distinguished from other contexts created for identical
	 * but distinct expressions.  This method accomplishes this task.  Elements
	 * which are associated with expressions should use the expression object
	 * for implementation of {@link #equals(Object)} and {@link #hashCode()}
	 * methods.
	 * </p>
	 *
	 * @param element
	 * @param expression
	 */
	protected void associateExpression(Object element, IExpression expression) {
	}

	/**
	 * Create a place holder for an invalid expression.  If for a given expression,
	 * this VM node returns true from {@link #canParseExpression(IExpression)}, which
	 * indicates that the expression matches the node's expected format, but the node
	 * then is not able to find the element represented by the expression, then an
	 * "invalid" expression context needs to be created.
	 * <p>
	 * This method can be overriden to provide a node-specific invalid expression
	 * context.
	 * </p>
	 *
	 * @param expression Expression to create the context for.
	 * @return Returns a VM context object representing an invalid expression with
	 *
	 * @since 1.1
	 */
	protected IVMContext createInvalidExpressionVMContext(IExpression expression) {
		return new InvalidExpressionVMContext(this, expression);
	}
}