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

/*******************************************************************************
 * Copyright (c) 2007, 2009 IBM Corporation 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:
 *     IBM Corporation - initial API and implementation
 *     Matthew Hall - bugs 220700, 271148, 278550
 *******************************************************************************/

package org.eclipse.core.databinding;

import org.eclipse.core.databinding.observable.ObservableTracker;
import org.eclipse.core.databinding.observable.value.IObservableValue;
import org.eclipse.core.databinding.observable.value.IValueChangeListener;
import org.eclipse.core.databinding.observable.value.ValueChangeEvent;
import org.eclipse.core.databinding.observable.value.WritableValue;
import org.eclipse.core.databinding.util.Policy;
import org.eclipse.core.internal.databinding.BindingStatus;
import org.eclipse.core.internal.databinding.Util;
import org.eclipse.core.runtime.IStatus;
import org.eclipse.core.runtime.MultiStatus;
import org.eclipse.core.runtime.Status;

/**
 * @since 1.0
 * 
 */
class ValueBinding<M, T> extends
		Binding<IObservableValue<M>, IObservableValue<T>> {
	private final UpdateValueStrategy<T, M> targetToModel;
	private final UpdateValueStrategy<M, T> modelToTarget;
	private WritableValue<IStatus> validationStatusObservable;
	private IObservableValue<T> target;
	private IObservableValue<M> model;

	private boolean updatingTarget;
	private boolean updatingModel;
	private IValueChangeListener<T> targetChangeListener = new IValueChangeListener<T>() {
		public void handleValueChange(ValueChangeEvent<T> event) {
			if (!updatingTarget
					&& !Util.equals(event.diff.getOldValue(),
							event.diff.getNewValue())) {
				doUpdate(target, model, targetToModel, false, false);
			}
		}
	};
	private IValueChangeListener<M> modelChangeListener = new IValueChangeListener<M>() {
		public void handleValueChange(ValueChangeEvent<M> event) {
			if (!updatingModel
					&& !Util.equals(event.diff.getOldValue(),
							event.diff.getNewValue())) {
				doUpdate(model, target, modelToTarget, false, false);
			}
		}
	};

	/**
	 * @param targetObservableValue
	 * @param modelObservableValue
	 * @param targetToModel
	 * @param modelToTarget
	 */
	public ValueBinding(IObservableValue<T> targetObservableValue,
			IObservableValue<M> modelObservableValue,
			UpdateValueStrategy<T, M> targetToModel,
			UpdateValueStrategy<M, T> modelToTarget) {
		super(targetObservableValue, modelObservableValue);
		this.target = targetObservableValue;
		this.model = modelObservableValue;
		this.targetToModel = targetToModel;
		this.modelToTarget = modelToTarget;
		if ((targetToModel.getUpdatePolicy() & (UpdateValueStrategy.POLICY_CONVERT | UpdateValueStrategy.POLICY_UPDATE)) != 0) {
			target.addValueChangeListener(targetChangeListener);
		} else {
			targetChangeListener = null;
		}
		if ((modelToTarget.getUpdatePolicy() & (UpdateValueStrategy.POLICY_CONVERT | UpdateValueStrategy.POLICY_UPDATE)) != 0) {
			model.addValueChangeListener(modelChangeListener);
		} else {
			modelChangeListener = null;
		}
	}

	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() == UpdateValueStrategy.POLICY_UPDATE) {
			updateModelToTarget();
		} else if (modelToTarget.getUpdatePolicy() == UpdateValueStrategy.POLICY_CONVERT) {
			validateModelToTarget();
		}
		if (targetToModel.getUpdatePolicy() == UpdateValueStrategy.POLICY_UPDATE
				|| targetToModel.getUpdatePolicy() == UpdateValueStrategy.POLICY_CONVERT) {
			validateTargetToModel();
		}
	}

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

	public void updateTargetToModel() {
		doUpdate(target, model, targetToModel, true, false);
	}

	public void updateModelToTarget() {
		doUpdate(model, target, modelToTarget, true, false);
	}

	/**
	 * Incorporates the provided <code>newStats</code> into the
	 * <code>multieStatus</code>.
	 * 
	 * @param multiStatus
	 * @param newStatus
	 * @return <code>true</code> if the update should proceed
	 */
	/* package */boolean mergeStatus(MultiStatus multiStatus, IStatus newStatus) {
		if (!newStatus.isOK()) {
			multiStatus.add(newStatus);
			return multiStatus.getSeverity() < IStatus.ERROR;
		}
		return true;
	}

	/*
	 * This method may be moved to UpdateValueStrategy in the future if clients
	 * need more control over how the source value is copied to the destination
	 * observable.
	 */
	private <S, D> void doUpdate(final IObservableValue<S> source,
			final IObservableValue<D> destination,
			final UpdateValueStrategy<S, D> updateValueStrategy,
			final boolean explicit, final boolean validateOnly) {

		final int policy = updateValueStrategy.getUpdatePolicy();
		if (policy == UpdateValueStrategy.POLICY_NEVER)
			return;
		if (policy == UpdateValueStrategy.POLICY_ON_REQUEST && !explicit)
			return;

		source.getRealm().exec(new Runnable() {
			public void run() {
				boolean destinationRealmReached = false;
				final MultiStatus multiStatus = BindingStatus.ok();
				try {
					// Get value
					S value = source.getValue();

					// Validate after get
					IStatus status = updateValueStrategy
							.validateAfterGet(value);
					if (!mergeStatus(multiStatus, status))
						return;

					// Convert value
					final D convertedValue = updateValueStrategy.convert(value);

					// Validate after convert
					status = updateValueStrategy
							.validateAfterConvert(convertedValue);
					if (!mergeStatus(multiStatus, status))
						return;
					if (policy == UpdateValueStrategy.POLICY_CONVERT
							&& !explicit)
						return;

					// Validate before set
					status = updateValueStrategy
							.validateBeforeSet(convertedValue);
					if (!mergeStatus(multiStatus, status))
						return;
					if (validateOnly)
						return;

					// Set value
					destinationRealmReached = true;
					destination.getRealm().exec(new Runnable() {
						public void run() {
							if (destination == target) {
								updatingTarget = true;
							} else {
								updatingModel = true;
							}
							try {
								IStatus setterStatus = updateValueStrategy
										.doSet(destination, convertedValue);

								mergeStatus(multiStatus, setterStatus);
							} finally {
								if (destination == target) {
									updatingTarget = false;
								} else {
									updatingModel = false;
								}
								setValidationStatus(multiStatus);
							}
						}
					});
				} catch (Exception ex) {
					// This check is necessary as in 3.2.2 Status
					// doesn't accept a null message (bug 177264).
					String message = (ex.getMessage() != null) ? ex
							.getMessage() : ""; //$NON-NLS-1$

					mergeStatus(multiStatus, new Status(IStatus.ERROR,
							Policy.JFACE_DATABINDING, IStatus.ERROR, message,
							ex));
				} finally {
					if (!destinationRealmReached) {
						setValidationStatus(multiStatus);
					}

				}
			}
		});
	}

	public void validateModelToTarget() {
		doUpdate(model, target, modelToTarget, true, true);
	}

	public void validateTargetToModel() {
		doUpdate(target, model, targetToModel, true, true);
	}

	private void setValidationStatus(final IStatus status) {
		validationStatusObservable.getRealm().exec(new Runnable() {
			public void run() {
				validationStatusObservable.setValue(status);
			}
		});
	}

	public void dispose() {
		if (targetChangeListener != null) {
			target.removeValueChangeListener(targetChangeListener);
			targetChangeListener = null;
		}
		if (modelChangeListener != null) {
			model.removeValueChangeListener(modelChangeListener);
			modelChangeListener = null;
		}
		target = null;
		model = null;
		super.dispose();
	}

}