bundles/org.eclipse.core.databinding/src/org/eclipse/core/databinding/SetBinding.java

/*******************************************************************************
 * Copyright (c) 2008, 2009 Matthew Hall 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:
 *     Matthew Hall - initial API and implementation (bug 124684)
 *     IBM Corporation - through ListBinding.java
 *     Matthew Hall - bugs 271148, 278550
 ******************************************************************************/

package org.eclipse.core.databinding;

import java.util.Collections;
import java.util.Iterator;

import org.eclipse.core.databinding.observable.Diffs;
import org.eclipse.core.databinding.observable.ObservableTracker;
import org.eclipse.core.databinding.observable.set.IObservableSet;
import org.eclipse.core.databinding.observable.set.ISetChangeListener;
import org.eclipse.core.databinding.observable.set.SetChangeEvent;
import org.eclipse.core.databinding.observable.set.SetDiff;
import org.eclipse.core.databinding.observable.value.IObservableValue;
import org.eclipse.core.databinding.observable.value.WritableValue;
import org.eclipse.core.internal.databinding.BindingStatus;
import org.eclipse.core.runtime.IStatus;
import org.eclipse.core.runtime.MultiStatus;
import org.eclipse.core.runtime.Status;

/**
 * @param <T>
 *            the type of the elements in the set on the target side
 * @param <M>
 *            the type of the elements in the set on the model side
 * @since 1.1
 * 
 */
public class SetBinding<M, T> extends
		Binding<IObservableSet<M>, IObservableSet<T>> {

	private UpdateSetStrategy<T, M> targetToModel;
	private UpdateSetStrategy<M, T> modelToTarget;
	private IObservableValue<IStatus> validationStatusObservable;
	private boolean updatingTarget;
	private boolean updatingModel;

	private ISetChangeListener<T> targetChangeListener = new ISetChangeListener<T>() {
		public void handleSetChange(SetChangeEvent<T> event) {
			if (!updatingTarget) {
				doUpdate(getTarget(), getModel(), event.diff, targetToModel,
						false, false);
			}
		}
	};

	private ISetChangeListener<M> modelChangeListener = new ISetChangeListener<M>() {
		public void handleSetChange(SetChangeEvent<M> event) {
			if (!updatingModel) {
				doUpdate(getModel(), getTarget(), event.diff, modelToTarget,
						false, false);
			}
		}
	};

	/**
	 * @param target
	 * @param model
	 * @param modelToTargetStrategy
	 * @param targetToModelStrategy
	 */
	public SetBinding(IObservableSet<T> target, IObservableSet<M> model,
			UpdateSetStrategy<T, M> targetToModelStrategy,
			UpdateSetStrategy<M, T> modelToTargetStrategy) {
		super(target, model);
		this.targetToModel = targetToModelStrategy;
		this.modelToTarget = modelToTargetStrategy;
		if ((targetToModel.getUpdatePolicy() & UpdateSetStrategy.POLICY_UPDATE) != 0) {
			target.addSetChangeListener(targetChangeListener);
		} else {
			targetChangeListener = null;
		}
		if ((modelToTarget.getUpdatePolicy() & UpdateSetStrategy.POLICY_UPDATE) != 0) {
			model.addSetChangeListener(modelChangeListener);
		} else {
			modelChangeListener = null;
		}
	}

	public IObservableValue<IStatus> getValidationStatus() {
		return validationStatusObservable;
	}

	protected void preInit() {
		ObservableTracker.setIgnore(true);
		try {
			validationStatusObservable = new WritableValue<IStatus>(
					context.getValidationRealm(), Status.OK_STATUS,
					IStatus.class);
		} finally {
			ObservableTracker.setIgnore(false);
		}
	}

	protected void postInit() {
		if (modelToTarget.getUpdatePolicy() == UpdateSetStrategy.POLICY_UPDATE) {
			updateModelToTarget();
		}
		if (targetToModel.getUpdatePolicy() == UpdateSetStrategy.POLICY_UPDATE) {
			validateTargetToModel();
		}
	}

	public void updateModelToTarget() {
		final IObservableSet<M> modelSet = getModel();
		modelSet.getRealm().exec(new Runnable() {
			public void run() {
				SetDiff<M> diff = Diffs.computeSetDiff(
						Collections.<M> emptySet(), modelSet);
				doUpdate(modelSet, getTarget(), diff, modelToTarget, true, true);
			}
		});
	}

	public void updateTargetToModel() {
		final IObservableSet<T> targetSet = getTarget();
		targetSet.getRealm().exec(new Runnable() {
			public void run() {
				SetDiff<T> diff = Diffs.computeSetDiff(
						Collections.<T> emptySet(), targetSet);
				doUpdate(targetSet, getModel(), diff, targetToModel, true, true);
			}
		});
	}

	public void validateModelToTarget() {
		// nothing for now
	}

	public void validateTargetToModel() {
		// nothing for now
	}

	/*
	 * This method may be moved to UpdateSetStrategy in the future if clients
	 * need more control over how the two sets are kept in sync.
	 */
	private <S, D> void doUpdate(final IObservableSet<S> source,
			final IObservableSet<D> destination, final SetDiff<S> diff,
			final UpdateSetStrategy<S, D> updateSetStrategy,
			final boolean explicit, final boolean clearDestination) {
		final int policy = updateSetStrategy.getUpdatePolicy();
		if (policy == UpdateSetStrategy.POLICY_NEVER)
			return;
		if (policy == UpdateSetStrategy.POLICY_ON_REQUEST && !explicit)
			return;
		destination.getRealm().exec(new Runnable() {
			public void run() {
				if (destination == getTarget()) {
					updatingTarget = true;
				} else {
					updatingModel = true;
				}
				MultiStatus multiStatus = BindingStatus.ok();

				try {
					if (clearDestination) {
						destination.clear();
					}

					for (Iterator<S> iterator = diff.getRemovals().iterator(); iterator
							.hasNext();) {
						IStatus setterStatus = updateSetStrategy.doRemove(
								destination,
								updateSetStrategy.convert(iterator.next()));

						mergeStatus(multiStatus, setterStatus);
						// TODO - at this point, the two sets
						// will be out of sync if an error
						// occurred...
					}

					for (Iterator<S> iterator = diff.getAdditions().iterator(); iterator
							.hasNext();) {
						IStatus setterStatus = updateSetStrategy.doAdd(
								destination,
								updateSetStrategy.convert(iterator.next()));

						mergeStatus(multiStatus, setterStatus);
						// TODO - at this point, the two sets
						// will be out of sync if an error
						// occurred...
					}
				} finally {
					validationStatusObservable.setValue(multiStatus);

					if (destination == getTarget()) {
						updatingTarget = false;
					} else {
						updatingModel = false;
					}
				}
			}
		});
	}

	/**
	 * Merges the provided <code>newStatus</code> into the
	 * <code>multiStatus</code>.
	 * 
	 * @param multiStatus
	 * @param newStatus
	 */
	/* package */void mergeStatus(MultiStatus multiStatus, IStatus newStatus) {
		if (!newStatus.isOK()) {
			multiStatus.add(newStatus);
		}
	}

	public void dispose() {
		if (targetChangeListener != null) {
			getTarget().removeSetChangeListener(targetChangeListener);
			targetChangeListener = null;
		}
		if (modelChangeListener != null) {
			getModel().removeSetChangeListener(modelChangeListener);
			modelChangeListener = null;
		}
		super.dispose();
	}
}