path: root/plugins/org.eclipse.emf.compare/src/org/eclipse/emf/compare/utils/EMFComparePredicates.java

/*******************************************************************************
 * Copyright (c) 2012, 2016 Obeo 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:
 *     Obeo - initial API and implementation
 *     Stefan Dirix - bug 441172
 *     Philip Langer - add additional predicates
 *     Tanja Mayerhofer - bug 501864
 *******************************************************************************/
package org.eclipse.emf.compare.utils;

import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.base.Predicates.and;
import static com.google.common.base.Predicates.not;
import static com.google.common.base.Predicates.or;
import static com.google.common.collect.Iterables.all;
import static com.google.common.collect.Iterables.any;
import static org.eclipse.emf.compare.ConflictKind.REAL;
import static org.eclipse.emf.compare.DifferenceKind.ADD;
import static org.eclipse.emf.compare.internal.utils.ComparisonUtil.isDeleteOrUnsetDiff;
import static org.eclipse.emf.compare.internal.utils.DiffUtil.getAllAtomicRefiningDiffs;
import static org.eclipse.emf.compare.internal.utils.DiffUtil.getAllRefiningDiffs;

import com.google.common.base.Predicate;

import java.util.Arrays;
import java.util.Iterator;
import java.util.Set;

import org.eclipse.emf.compare.AttributeChange;
import org.eclipse.emf.compare.Conflict;
import org.eclipse.emf.compare.ConflictKind;
import org.eclipse.emf.compare.Diff;
import org.eclipse.emf.compare.DifferenceKind;
import org.eclipse.emf.compare.DifferenceSource;
import org.eclipse.emf.compare.DifferenceState;
import org.eclipse.emf.compare.FeatureMapChange;
import org.eclipse.emf.compare.Match;
import org.eclipse.emf.compare.ReferenceChange;
import org.eclipse.emf.compare.ResourceLocationChange;
import org.eclipse.emf.ecore.EAttribute;
import org.eclipse.emf.ecore.EGenericType;
import org.eclipse.emf.ecore.ENamedElement;
import org.eclipse.emf.ecore.EObject;
import org.eclipse.emf.ecore.EReference;
import org.eclipse.emf.ecore.EStructuralFeature;
import org.eclipse.emf.ecore.EcorePackage;
import org.eclipse.emf.ecore.util.FeatureMap;

/**
 * This class will provide a number of Predicates that can be used to retrieve particular {@link Diff}s from
 * an iterable.
 * 
 * @author <a href="mailto:laurent.goubet@obeo.fr">Laurent Goubet</a>
 */
public final class EMFComparePredicates {
	/**
	 * This can be used to test whether a given Diff has no conflict object associated.
	 * 
	 * @since 3.1
	 */
	public static final Predicate<? super Diff> WITHOUT_CONFLICT = new Predicate<Diff>() {
		public boolean apply(Diff input) {
			return input != null && input.getConflict() == null;
		}
	};

	/**
	 * This can be used to check whether a given diff is a containment reference change.
	 * 
	 * @since 3.1
	 */
	public static final Predicate<? super Diff> CONTAINMENT_REFERENCE_CHANGE = new Predicate<Diff>() {
		public boolean apply(Diff input) {
			return input instanceof ReferenceChange
					&& ((ReferenceChange)input).getReference().isContainment();
		}
	};

	/**
	 * Predicate used to know if the given EObject is an EGenericType without eTypeArguments. When an
	 * EGenericType has arguments, it seems that the mutually derived references are not applicable in this
	 * case.
	 * 
	 * @return true, if the given EObject is an EGenericType without eTypeArguments, false otherwise.
	 */
	public static final Predicate<? super EObject> IS_EGENERIC_TYPE_WITHOUT_PARAMETERS = new Predicate<EObject>() {
		public boolean apply(EObject input) {
			final boolean isEGenericWithoutParams;
			if (input instanceof EGenericType && ((EGenericType)input).getETypeArguments().isEmpty()) {
				if (input.eContainer() instanceof EGenericType) {
					EGenericType eGenericTypeContainer = (EGenericType)(input.eContainer());
					isEGenericWithoutParams = !(eGenericTypeContainer.getETypeArguments().contains(input)
							|| input.equals(eGenericTypeContainer.getELowerBound())
							|| input.equals(eGenericTypeContainer.getEUpperBound()));
				} else {
					isEGenericWithoutParams = true;
				}
			} else {
				isEGenericWithoutParams = false;
			}
			return isEGenericWithoutParams;
		}
	};

	/**
	 * This class does not need to be instantiated.
	 */
	private EMFComparePredicates() {
		// Hides default constructor
	}

	/**
	 * This predicate can be used to check whether a given Diff represents the modification of a single-valued
	 * reference going by the given {@code referenceName} on an EObject which name matches
	 * {@code qualifiedName}. This can be used both on three-way and two-way Diffs : if three-way, we'll
	 * consider that the {@code fromQualifiedName} can be either one of the right or origin values, and the
	 * {@code toQualifiedName} to be either left or right. on two-way diffs however, {@code fromQualifiedName}
	 * can only be the right value, and {@code toQualifiedName} will be the left one.
	 * <p>
	 * Note that in order for this to work, we expect the EObjects to have a "name" feature returning a String
	 * for us to compare it with the given qualified name.
	 * </p>
	 * 
	 * @param qualifiedName
	 *            Qualified name of the EObject which we expect to present a ReferenceChange.
	 * @param referenceName
	 *            Name of the single-valued reference on which we expect a change.
	 * @param fromQualifiedName
	 *            The original value of this reference.
	 * @param toQualifiedName
	 *            The value to which this reference has been changed.
	 * @return The created predicate.
	 */
	@SuppressWarnings("unchecked")
	public static Predicate<? super Diff> changedReference(final String qualifiedName,
			final String referenceName, final String fromQualifiedName, final String toQualifiedName) {
		final Predicate<? super Diff> valuesMatch = new ReferenceValuesMatch(referenceName, fromQualifiedName,
				toQualifiedName);
		return and(ofKind(DifferenceKind.CHANGE), onEObject(qualifiedName), valuesMatch);
	}

	/**
	 * This predicate can be used to check whether a given Diff represents the addition of a value in a
	 * multi-valued attribute going by {@code attributeName} on an EObject which name matches
	 * {@code qualifiedName}.
	 * <p>
	 * Note that in order for this to work, we expect the EObjects to have a "name" feature returning a String
	 * for us to compare it with the given qualified name.
	 * </p>
	 * 
	 * @param qualifiedName
	 *            Qualified name of the EObject which we expect to present an AttributeChange.
	 * @param attributeName
	 *            Name of the multi-valued attribute on which we expect a change.
	 * @param addedValue
	 *            The value we expect to have been added to this attribute.
	 * @return The created predicate.
	 */
	@SuppressWarnings("unchecked")
	public static Predicate<? super Diff> addedToAttribute(final String qualifiedName,
			final String attributeName, final Object addedValue) {
		// This is only meant for multi-valued attributes
		return and(ofKind(DifferenceKind.ADD), onEObject(qualifiedName),
				attributeValueMatch(attributeName, addedValue, true));
	}

	/**
	 * This predicate can be used to check whether a given Diff represents the addition of a value in a
	 * multi-valued reference going by {@code referenceName} on an EObject which name matches
	 * {@code qualifiedName}.
	 * <p>
	 * Note that in order for this to work, we expect the EObjects to have a "name" feature returning a String
	 * for us to compare it with the given qualified name.
	 * </p>
	 * 
	 * @param qualifiedName
	 *            Qualified name of the EObject which we expect to present a ReferenceChange.
	 * @param referenceName
	 *            Name of the multi-valued reference on which we expect a change.
	 * @param addedQualifiedName
	 *            Qualified name of the EObject which we expect to have been added to this reference.
	 * @return The created predicate.
	 */
	@SuppressWarnings("unchecked")
	public static Predicate<? super Diff> addedToReference(final String qualifiedName,
			final String referenceName, final String addedQualifiedName) {
		// This is only meant for multi-valued references
		return and(ofKind(DifferenceKind.ADD), onEObject(qualifiedName),
				referenceValueMatch(referenceName, addedQualifiedName, true));
	}

	/**
	 * This predicate can be used to check whether a given Diff represents the addition of a value in a
	 * multi-valued reference going by {@code referenceName} on an EObject which name matches
	 * {@code qualifiedName}.
	 * <p>
	 * Note that in order for this to work, we expect the EObjects to have a "name" feature returning a String
	 * for us to compare it with the given qualified name.
	 * </p>
	 * 
	 * @param qualifiedName
	 *            Qualified name of the EObject which we expect to present a ReferenceChange.
	 * @param referenceName
	 *            Name of the multi-valued reference on which we expect a change.
	 * @param addedQualifiedName
	 *            Qualified name of the EObject which we expect to have been added to this reference.
	 * @param featureDelegateForAddedName
	 *            The optional feature to define the name of the objects which we expect to have been added to
	 *            this reference. May be null.
	 * @return The created predicate.
	 */
	@SuppressWarnings("unchecked")
	public static Predicate<? super Diff> addedToReference(final String qualifiedName,
			final String referenceName, final String addedQualifiedName,
			final EStructuralFeature featureDelegateForAddedName) {
		// This is only meant for multi-valued references
		return and(ofKind(DifferenceKind.ADD), onEObject(qualifiedName),
				referenceValueMatch(referenceName, addedQualifiedName, true, featureDelegateForAddedName));
	}

	/**
	 * This predicate can be used to check whether a given Diff represents the moving of a value within a
	 * multi-valued attribute going by {@code attributeName} on an EObject which name matches
	 * {@code qualifiedName}.
	 * <p>
	 * Note that in order for this to work, we expect the EObjects to have a "name" feature returning a String
	 * for us to compare it with the given qualified name.
	 * </p>
	 * 
	 * @param qualifiedName
	 *            Qualified name of the EObject which we expect to present an AttributeChange.
	 * @param attributeName
	 *            Name of the multi-valued attribute on which we expect a change.
	 * @param removedValue
	 *            Value which we expect to have been moved within this attribute.
	 * @return The created predicate.
	 */
	@SuppressWarnings("unchecked")
	public static Predicate<? super Diff> movedInAttribute(final String qualifiedName,
			final String attributeName, final Object removedValue) {
		// This is only meant for multi-valued attributes
		return and(ofKind(DifferenceKind.MOVE), onEObject(qualifiedName),
				attributeValueMatch(attributeName, removedValue, true));
	}

	/**
	 * This predicate can be used to check whether a given Diff represents the moving of a value within a
	 * multi-valued reference going by {@code referenceName} on an EObject which name matches
	 * {@code qualifiedName}.
	 * <p>
	 * Note that in order for this to work, we expect the EObjects to have a "name" feature returning a String
	 * for us to compare it with the given qualified name.
	 * </p>
	 * 
	 * @param qualifiedName
	 *            Qualified name of the EObject which we expect to present a ReferenceChange.
	 * @param referenceName
	 *            Name of the multi-valued reference on which we expect a change.
	 * @param removedQualifiedName
	 *            Qualified name of the EObject which we expect to have been moved within this reference.
	 * @return The created predicate.
	 */
	@SuppressWarnings("unchecked")
	public static Predicate<? super Diff> movedInReference(final String qualifiedName,
			final String referenceName, final String removedQualifiedName) {
		// This is only meant for multi-valued references
		return and(ofKind(DifferenceKind.MOVE), onEObject(qualifiedName),
				referenceValueMatch(referenceName, removedQualifiedName, true));
	}

	/**
	 * This predicate can be used to check whether a given Diff is a {@link ReferenceChange} representing the
	 * eOpposite of the {@code diff} argument.
	 * 
	 * @param diff
	 *            The {@link ReferenceChange} against which is checked if an eOpposite relation exists.
	 * @return The created predicate.
	 * @since 3.2
	 */
	public static Predicate<Diff> isDiffOnEOppositeOf(final ReferenceChange diff) {
		return new Predicate<Diff>() {
			public boolean apply(Diff input) {
				return input instanceof ReferenceChange
						&& diff.getReference().getEOpposite() == ((ReferenceChange)input).getReference();
			}
		};
	}

	/**
	 * This predicate can be used to check whether a given Diff is equivalent to the {@code diff} argument.
	 * 
	 * @param diff
	 *            The {@link ReferenceChange} against which is checked if an equivalence relation exists.
	 * @return The created predicate.
	 * @since 3.2
	 */
	public static Predicate<Diff> isEquivalentTo(final Diff diff) {
		return new Predicate<Diff>() {
			public boolean apply(Diff input) {
				return input.getEquivalence() != null
						&& input.getEquivalence().getDifferences().contains(diff);
			}
		};
	}

	/**
	 * This predicate can be used to check whether a given Diff is a {@link ReferenceChange} with the same
	 * reference as the {@code diff} argument.
	 * 
	 * @param diff
	 *            The {@link ReferenceChange} against which is checked whether it has the same reference.
	 * @return The created predicate.
	 * @since 3.2
	 */
	public static Predicate<Diff> hasSameReferenceAs(final ReferenceChange diff) {
		return new Predicate<Diff>() {
			public boolean apply(Diff input) {
				return input instanceof ReferenceChange
						&& diff.getReference() == ((ReferenceChange)input).getReference();
			}
		};
	}

	/**
	 * This predicate can be used to check whether a given Diff represents the deletion of a value from a
	 * multi-valued attribute going by {@code attributeName} on an EObject which name matches
	 * {@code qualifiedName}.
	 * <p>
	 * Note that in order for this to work, we expect the EObjects to have a "name" feature returning a String
	 * for us to compare it with the given qualified name.
	 * </p>
	 * 
	 * @param qualifiedName
	 *            Qualified name of the EObject which we expect to present an AttributeChange.
	 * @param attributeName
	 *            Name of the multi-valued attribute on which we expect a change.
	 * @param removedValue
	 *            Value which we expect to have been removed from this attribute.
	 * @return The created predicate.
	 */
	@SuppressWarnings("unchecked")
	public static Predicate<? super Diff> removedFromAttribute(final String qualifiedName,
			final String attributeName, final Object removedValue) {
		// This is only meant for multi-valued attributes
		return and(ofKind(DifferenceKind.DELETE), onEObject(qualifiedName),
				attributeValueMatch(attributeName, removedValue, true));
	}

	/**
	 * Indicates whether a diff is part of a real add/add conflict.
	 * 
	 * @return a predicate to check if a diff belongs to an add/add conflict.
	 * @since 3.4
	 */
	public static Predicate<Diff> isInRealAddAddConflict() {
		return new Predicate<Diff>() {
			public boolean apply(Diff input) {
				Conflict conflict = input.getConflict();
				if (conflict != null) {
					if (conflict.getKind() != REAL) {
						return false;
					} else {
						if (all(conflict.getDifferences(), ofKind(ADD))) {
							return true;
						}
					}
				}
				return false;
			}
		};
	}

	/**
	 * This predicate can be used to check whether a given Diff represents the deletion of a value from a
	 * multi-valued reference going by {@code referenceName} on an EObject which name matches
	 * {@code qualifiedName}.
	 * <p>
	 * Note that in order for this to work, we expect the EObjects to have a "name" feature returning a String
	 * for us to compare it with the given qualified name.
	 * </p>
	 * 
	 * @param qualifiedName
	 *            Qualified name of the EObject which we expect to present a ReferenceChange.
	 * @param referenceName
	 *            Name of the multi-valued reference on which we expect a change.
	 * @param removedQualifiedName
	 *            Qualified name of the EObject which we expect to have been removed from this reference.
	 * @return The created predicate.
	 */
	@SuppressWarnings("unchecked")
	public static Predicate<? super Diff> removedFromReference(final String qualifiedName,
			final String referenceName, final String removedQualifiedName) {
		// This is only meant for multi-valued references
		return and(ofKind(DifferenceKind.DELETE), onEObject(qualifiedName),
				referenceValueMatch(referenceName, removedQualifiedName, true));
	}

	/**
	 * This predicate can be used to check whether a given Diff represents the deletion of a value from a
	 * multi-valued reference going by {@code referenceName} on an EObject which name matches
	 * {@code qualifiedName}.
	 * <p>
	 * Note that in order for this to work, we expect the EObjects to have a "name" feature returning a String
	 * for us to compare it with the given qualified name.
	 * </p>
	 * 
	 * @param qualifiedName
	 *            Qualified name of the EObject which we expect to present a ReferenceChange.
	 * @param referenceName
	 *            Name of the multi-valued reference on which we expect a change.
	 * @param removedQualifiedName
	 *            Qualified name of the EObject which we expect to have been removed from this reference.
	 * @param featureDelegateForRemovedName
	 *            The optional feature to define the name of the objects which we expect to have been removed
	 *            from this reference. May be null.
	 * @return The created predicate.
	 */
	@SuppressWarnings("unchecked")
	public static Predicate<? super Diff> removedFromReference(final String qualifiedName,
			final String referenceName, final String removedQualifiedName,
			final EStructuralFeature featureDelegateForRemovedName) {
		// This is only meant for multi-valued references
		return and(ofKind(DifferenceKind.DELETE), onEObject(qualifiedName), referenceValueMatch(referenceName,
				removedQualifiedName, true, featureDelegateForRemovedName));
	}

	/**
	 * This predicate can be used to check whether a given Diff represents the modification of a single-valued
	 * attribute going by the given {@code attributeName} on an EObject which name matches
	 * {@code qualifiedName}. This can be used both on three-way and two-way Diffs : if three-way, we'll
	 * consider that the {@code fromValue} can be either one of the right or origin values, and the
	 * {@code toValue} to be either left or right. on two-way diffs however, {@code fromValue} can only be the
	 * right value, and {@code toValue} will be the left one.
	 * <p>
	 * Note that in order for this to work, we expect the EObjects to have a "name" feature returning a String
	 * for us to compare it with the given qualified name.
	 * </p>
	 * 
	 * @param qualifiedName
	 *            Qualified name of the EObject which we expect to present an AttributeChange.
	 * @param attributeName
	 *            Name of the single-valued attribute on which we expect a change.
	 * @param fromValue
	 *            The original value of this attribute.
	 * @param toValue
	 *            The value to which this attribute has been changed.
	 * @return The created predicate.
	 */
	@SuppressWarnings("unchecked")
	public static Predicate<? super Diff> changedAttribute(final String qualifiedName,
			final String attributeName, final Object fromValue, final Object toValue) {
		final Predicate<? super Diff> valuesMatch = new AttributeValuesMatch(attributeName, fromValue,
				toValue);
		return and(ofKind(DifferenceKind.CHANGE), onEObject(qualifiedName), valuesMatch);
	}

	/**
	 * This predicate can be used to check whether a given Diff represents the addition of an EObject matching
	 * the given qualified name. Namely, it will check that that Diff is a ReferenceChange, that one of its
	 * Match sides correspond to the given qualified name's ancestors, and that its value correspond to the
	 * given qualified name's last segment.
	 * <p>
	 * For example, {@code added("extlibrary.BookCategory.Encyclopedia")} will check that an EObject named
	 * "Encyclopedia" has been added under the container "extlibrary.BookCategory". Note that
	 * {@code added("emf.compare.Match")} will <b>not</b> match a difference on the EObject
	 * "org.eclipse.emf.compare.Match". The qualified name must be absolute.
	 * </p>
	 * <p>
	 * Note that in order for this to work, we expect the EObjects to have a "name" feature returning a
	 * String.
	 * </p>
	 * 
	 * @param qualifiedName
	 *            The qualified name of the EObject we expect to have been added.
	 * @return The created predicate.
	 */
	@SuppressWarnings("unchecked")
	public static Predicate<? super Diff> added(final String qualifiedName) {
		final int parentEndIndex = qualifiedName.lastIndexOf('.');
		if (parentEndIndex >= 0) {
			final String ancestors = qualifiedName.substring(0, parentEndIndex);
			final String objectName = qualifiedName.substring(parentEndIndex + 1);
			return and(ofKind(DifferenceKind.ADD), onEObject(ancestors), valueNameMatches(objectName));
		}
		return and(valueNameMatches(qualifiedName), ofKind(DifferenceKind.ADD));
	}

	/**
	 * This predicate can be used to check whether a given Diff represents the move of an EObject matching the
	 * given qualified name. Namely, it will check that that Diff is a ReferenceChange, that one of its Match
	 * sides correspond to the given qualified name's ancestors, and that its value correspond to the given
	 * qualified name's last segment.
	 * <p>
	 * Note that in order for this to work, we expect the EObjects to have a "name" feature returning a
	 * String.
	 * </p>
	 * 
	 * @param qualifiedName
	 *            The qualified name of the EObject we expect to have been moved.
	 * @param referenceName
	 *            Name of the reference in which we expect a child to have been added.
	 * @return The created predicate.
	 */
	@SuppressWarnings("unchecked")
	public static Predicate<? super Diff> moved(final String qualifiedName, final String referenceName) {
		final int parentEndIndex = qualifiedName.lastIndexOf('.');
		if (parentEndIndex >= 0) {
			final String ancestors = qualifiedName.substring(0, parentEndIndex);
			final String objectName = qualifiedName.substring(parentEndIndex + 1);
			return and(ofKind(DifferenceKind.MOVE), onEObject(ancestors), onFeature(referenceName),
					valueNameMatches(objectName));
		}
		return and(ofKind(DifferenceKind.MOVE), valueNameMatches(qualifiedName), onFeature(referenceName));
	}

	/**
	 * This predicate can be used to check whether a given Diff represents the removal of an EObject matching
	 * the given qualified name. Namely, it will check that that Diff is a ReferenceChange, that one of its
	 * Match sides correspond to the given qualified name's ancestors, and that its value correspond to the
	 * given qualified name's last segment.
	 * <p>
	 * For example, {@code removed("extlibrary.BookCategory.Encyclopedia")} will check that an EObject named
	 * "Encyclopedia" has been removed from the container "extlibrary.BookCategory". Note that
	 * {@code removed("emf.compare.Match")} will <b>not</b> match a difference on the EObject
	 * "org.eclipse.emf.compare.Match". The qualified name must be absolute.
	 * </p>
	 * <p>
	 * Note that in order for this to work, we expect the EObjects to have a "name" feature returning a
	 * String.
	 * </p>
	 * 
	 * @param qualifiedName
	 *            The qualified name of the EObject we expect to have been removed.
	 * @return The created predicate.
	 */
	@SuppressWarnings("unchecked")
	public static Predicate<? super Diff> removed(final String qualifiedName) {
		final int parentEndIndex = qualifiedName.lastIndexOf('.');
		if (parentEndIndex >= 0) {
			final String ancestors = qualifiedName.substring(0, parentEndIndex);
			final String objectName = qualifiedName.substring(parentEndIndex + 1);
			return and(ofKind(DifferenceKind.DELETE), onEObject(ancestors), valueNameMatches(objectName));
		}
		return and(valueNameMatches(qualifiedName), ofKind(DifferenceKind.DELETE));
	}

	/**
	 * This can be used to check that a given Diff correspond to either an {@link AttributeChange}, a
	 * {@link FeatureMapChange} or a {@link ReferenceChange}, and that the corresponding reference or
	 * attribute matches the given {@code featureName}.
	 * 
	 * @param featureName
	 *            Name of the feature on which we expect a change.
	 * @return The created predicate.
	 */
	public static Predicate<? super Diff> onFeature(final String featureName) {
		return new Predicate<Diff>() {
			public boolean apply(Diff input) {
				final EStructuralFeature affectedFeature;
				if (input instanceof AttributeChange) {
					affectedFeature = ((AttributeChange)input).getAttribute();
				} else if (input instanceof ReferenceChange) {
					affectedFeature = ((ReferenceChange)input).getReference();
				} else if (input instanceof FeatureMapChange) {
					affectedFeature = ((FeatureMapChange)input).getAttribute();
				} else {
					return false;
				}
				return featureName.equals(affectedFeature.getName());
			}
		};
	}

	/**
	 * Accept only diffs that inherit either AttributeChange, ReferenceChange, or FeatureMapChange that
	 * concern the given feature.
	 * 
	 * @param feature
	 *            Feature to deal with
	 * @return a new predicate that accepts diffs that concern the given feature.
	 */
	public static Predicate<Diff> onFeature(EStructuralFeature feature) {
		return new OnFeature(feature);
	}

	/**
	 * This can be used to check that a given Diff originates from the given {@code source} side.
	 * 
	 * @param source
	 *            The side from which we expect this diff to originate.
	 * @return The created predicate.
	 */
	public static Predicate<? super Diff> fromSide(final DifferenceSource source) {
		return new Predicate<Diff>() {
			public boolean apply(Diff input) {
				return input != null && input.getSource() == source;
			}
		};
	}

	/**
	 * This can be used to check that a given Diff originates from the given {@code source} side.
	 * 
	 * @param diff
	 *            The diff the side of which will be used to filter.
	 * @return The created predicate.
	 */
	public static Predicate<Diff> sameSideAs(final Diff diff) {
		if (diff == null) {
			throw new IllegalArgumentException();
		}
		return new Predicate<Diff>() {
			public boolean apply(Diff input) {
				return input != null && input.getSource() == diff.getSource();
			}
		};
	}

	/**
	 * This can be used in order to check that a Diff has been detected on the given EObject.
	 * 
	 * @param eObject
	 *            The EObject which we expect the diff to concern.
	 * @return The created predicate.
	 */
	public static Predicate<? super Diff> onEObject(final EObject eObject) {
		return new Predicate<Diff>() {
			public boolean apply(Diff input) {
				if (input == null) {
					return false;
				}

				final Match match = input.getMatch();
				return match.getLeft() == eObject || match.getRight() == eObject
						|| match.getOrigin() == eObject;
			}
		};
	}

	/**
	 * This can be used in order to check whether a Diff has been detected on an EObject matching the given
	 * qualified name.
	 * <p>
	 * For this to work, we expect the EObjects to have a feature named "name" returning a String.
	 * </p>
	 * 
	 * @param qualifiedName
	 *            The qualified name of the EObject we expect that diff to concern.
	 * @return The created predicate.
	 */
	public static Predicate<? super Diff> onEObject(final String qualifiedName) {
		return new Predicate<Diff>() {
			public boolean apply(Diff input) {
				if (input == null || input instanceof ResourceLocationChange) {
					return false;
				}

				final Match match = input.getMatch();
				return match(match.getLeft(), qualifiedName, null)
						|| match(match.getRight(), qualifiedName, null)
						|| match(match.getOrigin(), qualifiedName, null);
			}
		};
	}

	/**
	 * This can be used in order to check whether a Diff has been detected on an EObject matching the given
	 * qualified name or the qualified name under the given feature.
	 * <p>
	 * For this to work, we expect the EObjects to have a feature named "name" returning a String or to have
	 * the given feature (String or EObject with a feature named "name").
	 * </p>
	 * 
	 * @param qualifiedName
	 *            The qualified name of the EObject we expect that diff to concern.
	 * @param featureDelegate
	 *            The optional feature to define the name of the objects. May be null.
	 * @return The created predicate.
	 */
	public static Predicate<? super Diff> onEObject(final String qualifiedName,
			final EStructuralFeature featureDelegate) {
		return new Predicate<Diff>() {
			public boolean apply(Diff input) {
				if (input == null) {
					return false;
				}

				final Match match = input.getMatch();
				return match(match.getLeft(), qualifiedName, featureDelegate)
						|| match(match.getRight(), qualifiedName, featureDelegate)
						|| match(match.getOrigin(), qualifiedName, featureDelegate);
			}
		};
	}

	/**
	 * This predicate can be used to check whether a particular diff is of the given {@code kind}. This is
	 * mainly used to differentiate additions from deletions.
	 * 
	 * @param kind
	 *            The kind we expect this diff to have.
	 * @return The created predicate.
	 */
	public static Predicate<? super Diff> ofKind(final DifferenceKind kind) {
		return new Predicate<Diff>() {
			public boolean apply(Diff input) {
				return input != null && input.getKind() == kind;
			}
		};
	}

	/**
	 * Accept only diffs of the given kinds.
	 * 
	 * @param kind1
	 *            first kind of diff to accept
	 * @param kind2
	 *            second kind of diff to accept
	 * @return The created predicate.
	 */
	public static Predicate<Diff> ofKind(final DifferenceKind kind1, final DifferenceKind kind2) {
		checkNotNull(kind1);
		checkNotNull(kind2);
		return new Predicate<Diff>() {
			public boolean apply(Diff input) {
				return input != null && (input.getKind() == kind1 || input.getKind() == kind2);
			}
		};
	}

	/**
	 * Accept only diffs whose value matches the given value.
	 * 
	 * @param helper
	 *            The helper to match values
	 * @param value
	 *            The value to match
	 * @return The created predicate.
	 */
	public static Predicate<Diff> valueMatches(final IEqualityHelper helper, final Object value) {
		return new Predicate<Diff>() {
			public boolean apply(Diff input) {
				if (input instanceof ReferenceChange) {
					return helper.matchingValues(value, ((ReferenceChange)input).getValue());
				} else if (input instanceof AttributeChange) {
					return helper.matchingValues(value, ((AttributeChange)input).getValue());
				} else if (input instanceof FeatureMapChange) {
					return helper.matchingValues(value,
							((FeatureMap.Entry)((FeatureMapChange)input).getValue()).getValue());
				}
				return false;
			}
		};
	}

	/**
	 * This predicate can be used in order to check that a particular Diff describes either a
	 * {@link ReferenceChange}, {@link AttributeChange} or {@link FeatureMapChange} for the given
	 * {@code expectedValue}.
	 * <p>
	 * For example, this could be used to check that the given value has indeed been added to a reference or
	 * attribute, though such checks are more easily performed through {@link #addedIn(EObject, EObject)} or
	 * {@link #removedFrom(EObject, EObject)}.
	 * </p>
	 * 
	 * @param expectedValue
	 *            The value which we expect to have changed and detected through a Diff.
	 * @return The created predicate.
	 */
	public static Predicate<? super Diff> valueIs(final Object expectedValue) {
		return new Predicate<Diff>() {
			public boolean apply(Diff input) {
				final Object value;
				if (input instanceof ReferenceChange) {
					value = ((ReferenceChange)input).getValue();
				} else if (input instanceof AttributeChange) {
					value = ((AttributeChange)input).getValue();
				} else if (input instanceof FeatureMapChange) {
					value = ((FeatureMapChange)input).getValue();
				} else {
					return false;
				}

				return value == expectedValue || (value != null && value.equals(expectedValue));
			}
		};
	}

	/**
	 * This predicate can be used to check whether a given Diff describes an AttributeChange with the given
	 * {@code attributeName} and which changed value corresponds to the given {@code expectedValue}.
	 * 
	 * @param attributeName
	 *            The name of the attribute for which we seek an AttributeChange.
	 * @param expectedValue
	 *            The value we expect to correspond to this AttributeChange.
	 * @param multiValued
	 *            Tells us to check for either multi- or single-valued reference changes.
	 * @return The created predicate.
	 */
	public static Predicate<? super Diff> attributeValueMatch(final String attributeName,
			final Object expectedValue, final boolean multiValued) {
		return new Predicate<Diff>() {
			public boolean apply(Diff input) {
				if (input instanceof AttributeChange
						&& ((AttributeChange)input).getAttribute().getName().equals(attributeName)
						&& ((AttributeChange)input).getAttribute().isMany() == multiValued) {
					final Object value = ((AttributeChange)input).getValue();
					return input.getMatch().getComparison().getEqualityHelper().matchingAttributeValues(value,
							expectedValue);
				}
				return false;
			}
		};
	}

	/**
	 * This predicate can be used to check whether a given Diff describes a ReferenceChange with the given
	 * {@code referenceName} and which changed value corresponds to the given {@code qualifiedName}.
	 * <p>
	 * For this to work, we expect the EObject to have a feature named "name" returning a String for us to try
	 * and match it.
	 * </p>
	 * 
	 * @param referenceName
	 *            The reference for which we seek a ReferenceChange.
	 * @param qualifiedName
	 *            The qualified name of the EObject on which we detected a change.
	 * @param multiValued
	 *            Tells us to check for either multi- or single-valued reference changes.
	 * @return The created predicate.
	 */
	public static Predicate<? super Diff> referenceValueMatch(final String referenceName,
			final String qualifiedName, final boolean multiValued) {
		return new Predicate<Diff>() {
			public boolean apply(Diff input) {
				if (input instanceof ReferenceChange
						&& ((ReferenceChange)input).getReference().getName().equals(referenceName)
						&& ((ReferenceChange)input).getReference().isMany() == multiValued) {
					final EObject value = ((ReferenceChange)input).getValue();
					return qualifiedName != null && match(value, qualifiedName, null);
				}
				return false;
			}
		};
	}

	/**
	 * This predicate can be used to check whether a given Diff describes a ReferenceChange with the given
	 * {@code referenceName} and which changed value corresponds to the given {@code qualifiedName} or the
	 * qualified name under the given {@code featureDelegate}.
	 * <p>
	 * For this to work, we expect the EObject to have a feature named "name" returning a String or to have
	 * the given feature (String or EObject with a feature named "name") for us to try and match it.
	 * </p>
	 * 
	 * @param referenceName
	 *            The reference for which we seek a ReferenceChange.
	 * @param qualifiedName
	 *            The qualified name of the EObject on which we detected a change.
	 * @param multiValued
	 *            Tells us to check for either multi- or single-valued reference changes.
	 * @param featureDelegate
	 *            The optional feature to define the name of the objects. May be null.
	 * @return The created predicate.
	 */
	public static Predicate<? super Diff> referenceValueMatch(final String referenceName,
			final String qualifiedName, final boolean multiValued, final EStructuralFeature featureDelegate) {
		return new Predicate<Diff>() {
			public boolean apply(Diff input) {
				if (input instanceof ReferenceChange
						&& ((ReferenceChange)input).getReference().getName().equals(referenceName)
						&& ((ReferenceChange)input).getReference().isMany() == multiValued) {
					final EObject value = ((ReferenceChange)input).getValue();
					return qualifiedName != null && match(value, qualifiedName, featureDelegate);
				}
				return false;
			}
		};
	}

	/**
	 * This can be used to check whether a given Diff describes either a {@link ReferenceChange} on an EObject
	 * which name is {@code expectedName}.
	 * <p>
	 * For this to work, we expect the EObject to have a feature named "name" returning a String for us to try
	 * and match it.
	 * </p>
	 * 
	 * @param expectedName
	 *            The name of the EObject which we expect as a changed reference value.
	 * @return The created predicate.
	 */
	public static Predicate<? super Diff> valueNameMatches(final String expectedName) {
		return new Predicate<Diff>() {
			public boolean apply(Diff input) {
				final EObject value;
				if (input instanceof ReferenceChange) {
					value = ((ReferenceChange)input).getValue();
				} else {
					return false;
				}
				return internalMatch(value, expectedName, null);
			}
		};
	}

	/**
	 * This can be used to check whether a given Diff describes either a {@link ReferenceChange} on an EObject
	 * which name is {@code expectedName} or which the given feature provides the {@code expectedName}.
	 * <p>
	 * For this to work, we expect the EObject to have a feature named "name" returning a String or to have
	 * the given feature (String or EObject with a feature named "name") for us to try and match it.
	 * </p>
	 * 
	 * @param expectedName
	 *            The name of the EObject which we expect as a changed reference value.
	 * @param featureDelegate
	 *            The optional feature to define the name of the objects. May be null.
	 * @return The created predicate.
	 */
	public static Predicate<? super Diff> valueNameMatches(final String expectedName,
			final EStructuralFeature featureDelegate) {
		return new Predicate<Diff>() {
			public boolean apply(Diff input) {
				final EObject value;
				if (input instanceof ReferenceChange) {
					value = ((ReferenceChange)input).getValue();
				} else {
					return false;
				}
				return internalMatch(value, expectedName, featureDelegate);
			}
		};
	}

	/**
	 * This can be used to check whether a given Diff has a conflict of one of the given type.
	 * 
	 * @param kinds
	 *            Type(s) of the conflict(s) we seek.
	 * @return The created predicate.
	 */
	public static Predicate<? super Diff> hasConflict(final ConflictKind... kinds) {
		return new Predicate<Diff>() {
			public boolean apply(Diff input) {
				return input != null && input.getConflict() != null
						&& Arrays.asList(kinds).contains(input.getConflict().getKind());
			}
		};
	}

	/**
	 * This can be used to check whether a given Diff is in (one of) the given state(s).
	 * 
	 * @param states
	 *            State(s) in which we need a Diff to be.
	 * @return The created predicate.
	 */
	public static Predicate<? super Diff> hasState(final DifferenceState... states) {
		return new Predicate<Diff>() {
			public boolean apply(Diff input) {
				return input != null && Arrays.asList(states).contains(input.getState());
			}
		};
	}

	/**
	 * Predicate builder for diffs that can conflict with the given diff.
	 * 
	 * @param diff
	 *            The diff
	 * @return A predicate that accepts diffs that might conflict with the given diff.
	 */
	public static Predicate<Diff> possiblyConflictingWith(Diff diff) {
		return new ConflictCandidateFilter(diff);
	}

	/**
	 * This can be used to check whether a given Conflict is of one of the given kind.
	 * 
	 * @param kinds
	 *            Type(s) of the conflict(s) we seek.
	 * @return The created predicate.
	 */
	public static Predicate<? super Conflict> containsConflictOfTypes(final ConflictKind... kinds) {
		return new Predicate<Conflict>() {
			public boolean apply(Conflict input) {
				return input != null && input.getKind() != null
						&& Arrays.asList(kinds).contains(input.getKind());
			}
		};
	}

	/**
	 * This can be used to check whether a given diff is a containment reference change.
	 * 
	 * @return The created predicate.
	 * @deprecated use {@link #CONTAINMENT_REFERENCE_CHANGE};
	 */
	@Deprecated
	public static Predicate<? super Diff> containmentReferenceChange() {
		return CONTAINMENT_REFERENCE_CHANGE;
	}

	/**
	 * This will be used to check that a given {@link EObject} corresponds to the given {@code qualifiedName}.
	 * <p>
	 * For example, {@code match("extlibrary.BookCategory.Encyclopedia")} will return {@code true} for an
	 * EObject named "Encyclopedia" under the container "extlibrary.BookCategory". Note, however that
	 * {@code match("emf.compare.Match")} will <b>not</b> match the EObject "org.eclipse.emf.compare.Match".
	 * The qualified name must be absolute.
	 * </p>
	 * <p>
	 * For this to work, we expect the EObject to have a feature named "name" returning a String or to have
	 * the given feature (String or EObject with a feature named "name") for us to try and match it. See also
	 * {@link #getNameFeature(EObject)}.
	 * </p>
	 * 
	 * @param eObject
	 *            The EObject which qualified name we are to check.
	 * @param qualifiedName
	 *            The expected, <b>absolute</b> qualified name of the given {@code eObject}.
	 * @param featureDelegate
	 *            The optional feature to define the name of the objects. May be null.
	 * @return {@code true} if the given {@code eObject} matches the given {@code qualifiedName},
	 *         {@code false} if not, or if we could not determine the "name" feature of that EObject.
	 * @see #getNameFeature(EObject)
	 */
	private static boolean match(EObject eObject, String qualifiedName, EStructuralFeature featureDelegate) {
		if (eObject == null || qualifiedName == null || qualifiedName.length() == 0) {
			return false;
		}
		final String[] names = qualifiedName.split("\\."); //$NON-NLS-1$

		int current = names.length - 1;
		boolean matches = internalMatch(eObject, names[current--], featureDelegate);
		if (matches) {
			EObject container = eObject.eContainer();
			while (matches && container != null && current >= 0) {
				matches = internalMatch(container, names[current--], featureDelegate);
				container = container.eContainer();
			}
			// This qualified name does not match if there was still a container "above"
			// "emf.compare.Match" does not match the EObject "org.eclipse.emf.compare.Match"
			matches = matches && container == null;
		}

		return matches;
	}

	/**
	 * This will be used to check whether a given Object matches the given {@code qualifiedName}, considering
	 * {@code null} as legal values. Namely, this will return {@code true} in the following cases :
	 * <ul>
	 * <li>both {@code eObject} and {@code qualifiedName} are {@code null}</li>
	 * <li>eObject is an instance of {@link EObject} and its qualified name matches the given
	 * {@code qualifiedName} according to the semantics of {@link #match(EObject, String)}</li>
	 * </ul>
	 * 
	 * @param eObject
	 *            The Object which qualified name we are to check. May be {@code null}.
	 * @param qualifiedName
	 *            The expected, <b>absolute</b> qualified name of the given {@code eObject}. May be
	 *            {@code null}.
	 * @return {@code true} if the given {@code eObject} matches the given {@code qualifiedName},
	 *         {@code false} if not, or if we could not determine the "name" feature of that EObject.
	 * @see #match(EObject, String)
	 */
	private static boolean matchAllowingNull(Object eObject, String qualifiedName) {
		if (eObject == null) {
			return qualifiedName == null;
		}
		return qualifiedName != null && eObject instanceof EObject
				&& match((EObject)eObject, qualifiedName, null);
	}

	/**
	 * Checks that the given {@code eObject}'s name is equal to {@code name}.
	 * <p>
	 * For this to work, we expect the EObject to have a feature named "name" returning a String or to have
	 * the given feature (String or EObject with a feature named "name") for us to try and match it. See also
	 * {@link #getNameFeature(EObject)}.
	 * </p>
	 * 
	 * @param eObject
	 *            the EObject which name we are to check.
	 * @param name
	 *            The expected name of {@code eObject}.
	 * @param featureDelegate
	 *            The optional feature to define the name of the objects. May be null.
	 * @return {@code true} if the given {@code eObject}'s name is equal to the given {@code name},
	 *         {@code false} if not, or if we could not determine the "name" feature of that EObject.
	 * @see #getNameFeature(EObject)
	 */
	private static boolean internalMatch(EObject eObject, String name, EStructuralFeature featureDelegate) {
		final EStructuralFeature nameFeature = getNameFeature(eObject);
		boolean match = false;
		if (nameFeature != null) {
			final Object featureValue = eObject.eGet(nameFeature);
			if (featureValue instanceof String) {
				match = featureValue.equals(name);
			}
		} else if (featureDelegate != null && !featureDelegate.isMany()) {
			final Object featureValue = ReferenceUtil.safeEGet(eObject, featureDelegate);
			if (featureValue instanceof String) {
				match = featureValue.equals(name);
			} else if (featureValue instanceof EObject) {
				match = internalMatch((EObject)featureValue, name, null);
			}
		}
		return match;
	}

	/**
	 * Tries and determine the "name" feature of the given EObject. By default, we only consider
	 * {@link ENamedElement#name} or a feature of the given {@code eObject}'s EClass which would be named
	 * "name".
	 * 
	 * @param eObject
	 *            The EObject for which we are trying to determine a name.
	 * @return The name feature of the given EObject if we could find one, {@code null} otherwise.
	 */
	private static EStructuralFeature getNameFeature(EObject eObject) {
		if (eObject instanceof ENamedElement) {
			return EcorePackage.eINSTANCE.getENamedElement_Name();
		}
		EStructuralFeature nameFeature = null;
		final Iterator<EStructuralFeature> features = eObject.eClass().getEAllStructuralFeatures().iterator();
		while (nameFeature == null && features.hasNext()) {
			final EStructuralFeature feature = features.next();
			if ("name".equals(feature.getName())) { //$NON-NLS-1$
				nameFeature = feature;
			}
		}
		return nameFeature;
	}

	/**
	 * This predicate can be used to check whether any refining diff of a given diff fulfills the given
	 * predicate.
	 * 
	 * @param predicate
	 *            The predicate to check.
	 * @return The predicate.
	 * @since 3.4
	 */
	public static Predicate<Diff> anyRefining(final Predicate<? super Diff> predicate) {
		return new Predicate<Diff>() {
			public boolean apply(Diff diff) {
				return diff != null && any(getAllRefiningDiffs(diff), predicate);
			}
		};
	}

	/**
	 * This predicate can be used to check whether any refined diff of a given diff fulfills the given
	 * predicate.
	 * 
	 * @param predicate
	 *            The predicate to check.
	 * @return The predicate.
	 * @since 3.4
	 */
	public static Predicate<Diff> anyRefined(final Predicate<? super Diff> predicate) {
		return new Predicate<Diff>() {
			public boolean apply(Diff input) {
				return input != null && any(input.getRefines(), predicate);
			}
		};
	}

	/**
	 * This predicate can be used to check whether a diff has refiningDiffs AND all these refining diffs
	 * fulfill the given predicate.
	 * <p>
	 * <b>BEWARE: If the given diff has no refining diff, the predicate returns <code>false</code>.</b>
	 * </p>
	 * 
	 * @param predicate
	 *            The predicate to check on each 'atomic' (i.e. not refined) refining diff.
	 * @return The predicate.
	 * @since 3.4
	 */
	public static Predicate<Diff> allAtomicRefining(final Predicate<? super Diff> predicate) {
		return new Predicate<Diff>() {
			public boolean apply(Diff diff) {
				Set<Diff> atomicRefiningDiffs = getAllAtomicRefiningDiffs(diff);
				if (atomicRefiningDiffs.isEmpty()) {
					return false;
				}
				return all(atomicRefiningDiffs, predicate);
			}
		};
	}

	/**
	 * This predicate can be used to check whether a diff is in a conflict directly or indirectly.
	 * <p>
	 * A diff is directly in a conflict if it {@link #hasConflict(ConflictKind...) has a conflict}. A diff is
	 * indirectly in a conflict, if one of its refining diffs is in a conflict.
	 * </p>
	 * 
	 * @param kinds
	 *            Type(s) of the conflict(s) we seek.
	 * @return The created predicate.
	 * @since 3.4
	 */
	public static Predicate<? super Diff> hasDirectOrIndirectConflict(final ConflictKind... kinds) {
		return or(hasConflict(kinds), anyRefining(hasConflict(kinds)));
	}

	/**
	 * This predicate can be used to check whether a diff is not in a conflict directly or indirectly.
	 * <p>
	 * A diff is directly in a conflict if it {@link #hasConflict(ConflictKind...) has a conflict}. A diff is
	 * indirectly in a conflict, if one of its refining diffs is in a conflict.
	 * </p>
	 * 
	 * @param kinds
	 *            Type(s) of the conflict(s) we seek.
	 * @return The created predicate.
	 * @since 3.4
	 */
	public static Predicate<? super Diff> hasNoDirectOrIndirectConflict(final ConflictKind... kinds) {
		return not(hasDirectOrIndirectConflict(kinds));
	}

	/**
	 * This particular predicate will be used to check that a given Diff corresponds to a ReferenceChange on a
	 * given reference, with known "original" and "changed" values.
	 * 
	 * @author <a href="mailto:laurent.goubet@obeo.fr">Laurent Goubet</a>
	 */
	private static final class ReferenceValuesMatch implements Predicate<Diff> {
		/** Name of the reference we expect to have been changed. */
		private final String referenceName;

		/** Qualified name of the expected original value of this reference. */
		private final String fromQualifiedName;

		/** Qualified name of the value to which this reference is expected to have changed. */
		private final String toQualifiedName;

		/**
		 * Instantiates this predicate given the values it is meant to match.
		 * 
		 * @param referenceName
		 *            Name of the single-valued reference on which we expect a change.
		 * @param fromQualifiedName
		 *            The original value of this reference.
		 * @param toQualifiedName
		 *            The value to which this reference has been changed.
		 */
		ReferenceValuesMatch(String referenceName, String fromQualifiedName, String toQualifiedName) {
			this.referenceName = referenceName;
			this.fromQualifiedName = fromQualifiedName;
			this.toQualifiedName = toQualifiedName;
		}

		/**
		 * {@inheritDoc}
		 * 
		 * @see com.google.common.base.Predicate#apply(java.lang.Object)
		 */
		public boolean apply(Diff input) {
			// Note that this is not meant for many-valued references
			if (input instanceof ReferenceChange
					&& ((ReferenceChange)input).getReference().getName().equals(referenceName)
					&& !((ReferenceChange)input).getReference().isMany()) {
				final EReference reference = ((ReferenceChange)input).getReference();
				final Match match = input.getMatch();
				final Object leftValue;
				if (match.getLeft() != null) {
					leftValue = match.getLeft().eGet(reference);
				} else {
					leftValue = null;
				}
				final Object rightValue;
				if (match.getRight() != null) {
					rightValue = match.getRight().eGet(reference);
				} else {
					rightValue = null;
				}
				final Object originValue;
				if (match.getOrigin() != null) {
					originValue = match.getOrigin().eGet(reference);
				} else {
					originValue = null;
				}

				// "from" is either right or origin
				boolean applies = false;
				if (matchAllowingNull(originValue, fromQualifiedName)) {
					// "from" is origin, "to" can be either left or right
					applies = matchAllowingNull(leftValue, toQualifiedName)
							|| matchAllowingNull(rightValue, toQualifiedName);
				} else if (matchAllowingNull(rightValue, fromQualifiedName)) {
					// "from" is right, "to" can only be left
					applies = matchAllowingNull(leftValue, toQualifiedName);
				}
				return applies;
			}
			return false;
		}
	}

	/**
	 * This particular predicate will be used to check that a given Diff corresponds to an AttributeChange on
	 * a given attribute, with known "original" and "changed" values.
	 * 
	 * @author <a href="mailto:laurent.goubet@obeo.fr">Laurent Goubet</a>
	 */
	private static final class AttributeValuesMatch implements Predicate<Diff> {
		/** Name of the attribute we expect to have been changed. */
		private final String attributeName;

		/** The expected original value of this attribute. */
		private final Object fromValue;

		/** The value to which this attribute is expected to have changed. */
		private final Object toValue;

		/**
		 * Instantiates this predicate given the values it is meant to match.
		 * 
		 * @param attributeName
		 *            Name of the single-valued attribute on which we expect a change.
		 * @param fromValue
		 *            The original value of this attribute.
		 * @param toValue
		 *            The value to which this attribute has been changed.
		 */
		AttributeValuesMatch(String attributeName, Object fromValue, Object toValue) {
			this.attributeName = attributeName;
			this.fromValue = fromValue;
			this.toValue = toValue;
		}

		/**
		 * Checks whether the two given Objects match : they are either both {@code null}, the same instance,
		 * or their "equals" returns {@code true}. If neither is {@code true}, we assume that these two
		 * Objects don't match.
		 * <p>
		 * Do note that "unset" values are in fact set to the empty String instead of {@code null}. We will
		 * thus consider {@code null} equal to the empty String here.
		 * </p>
		 * 
		 * @param attributeValue
		 *            The reference value, first of the two Objects to compare.
		 * @param expectedValue
		 *            The expected value, second of the two Objects to compare.
		 * @return {@code true} if these two Objects are equal, {@code false} otherwise.
		 */
		private static boolean equalAttributeValues(Object attributeValue, Object expectedValue) {
			// Using == to handle the "null" case
			boolean equal = expectedValue == attributeValue
					|| expectedValue != null && expectedValue.equals(attributeValue);
			// Consider that null is equal to the empty string (unset attributes)
			if (!equal) {
				equal = "".equals(attributeValue) && expectedValue == null || "".equals(expectedValue) //$NON-NLS-1$ //$NON-NLS-2$
						&& attributeValue == null;
			}
			return equal;
		}

		/**
		 * {@inheritDoc}
		 * 
		 * @see com.google.common.base.Predicate#apply(java.lang.Object)
		 */
		public boolean apply(Diff input) {
			// Note that this is not meant for multi-valued attributes
			if (input instanceof AttributeChange
					&& ((AttributeChange)input).getAttribute().getName().equals(attributeName)
					&& !((AttributeChange)input).getAttribute().isMany()) {
				final EAttribute attribute = ((AttributeChange)input).getAttribute();
				final Match match = input.getMatch();

				final Object leftValue;
				if (match.getLeft() != null) {
					leftValue = match.getLeft().eGet(attribute);
				} else {
					leftValue = attribute.getDefaultValue();
				}

				final Object rightValue;
				if (match.getRight() != null) {
					rightValue = match.getRight().eGet(attribute);
				} else {
					rightValue = attribute.getDefaultValue();
				}

				final Object originValue;
				if (match.getOrigin() != null) {
					originValue = match.getOrigin().eGet(attribute);
				} else {
					originValue = attribute.getDefaultValue();
				}

				final Object actualFrom;
				if (fromValue == null) {
					actualFrom = attribute.getDefaultValue();
				} else {
					actualFrom = fromValue;
				}
				final Object actualTo;
				if (toValue == null) {
					actualTo = attribute.getDefaultValue();
				} else {
					actualTo = toValue;
				}

				// "from" is either right or origin
				boolean applies = false;
				if (equalAttributeValues(actualFrom, originValue)) {
					// "from" is origin, "to" can be either left or right
					applies = equalAttributeValues(actualTo, leftValue)
							|| equalAttributeValues(actualTo, rightValue);
				} else if (equalAttributeValues(actualFrom, rightValue)) {
					// "from" is right, "to" can only be left
					applies = equalAttributeValues(actualTo, leftValue);
				}
				return applies;
			}
			return false;
		}
	}

	/**
	 * Predicate for diffs taht concern a given feature.
	 * 
	 * @author <a href="mailto:laurent.delaigue@obeo.fr">Laurent Delaigue</a>
	 */
	private static class OnFeature implements Predicate<Diff> {
		/** The feature. */
		private final EStructuralFeature feature;

		/**
		 * Constructor.
		 * 
		 * @param feature
		 *            the feature
		 */
		OnFeature(EStructuralFeature feature) {
			this.feature = checkNotNull(feature);
		}

		/**
		 * Apply the predicate.
		 * 
		 * @param input
		 *            The diff to filter.
		 * @return true if and only if input concerns the given feature.
		 */
		public boolean apply(Diff input) {
			if (input == null) {
				return false;
			}
			boolean apply = false;
			if (input instanceof ReferenceChange) {
				apply = ((ReferenceChange)input).getReference() == feature;
			} else if (input instanceof AttributeChange) {
				apply = ((AttributeChange)input).getAttribute() == feature;
			} else if (input instanceof FeatureMapChange) {
				apply = ((FeatureMapChange)input).getAttribute() == feature;
			}
			return apply;
		}
	}

	/**
	 * This will be used to filter out the list of potential candidates for conflict with a given Diff.
	 * 
	 * @author <a href="mailto:laurent.goubet@obeo.fr">Laurent Goubet</a>
	 */
	private static final class ConflictCandidateFilter implements Predicate<Diff> {
		/** The Diff for which we seek conflict candidates. */
		private final Diff diff;

		/**
		 * Instantiates our filtering Predicate given the reference Diff for which to seek potential
		 * conflicts.
		 * 
		 * @param diff
		 *            The Diff for which we seek conflict candidates, must not be null.
		 */
		ConflictCandidateFilter(Diff diff) {
			this.diff = checkNotNull(diff);
		}

		/**
		 * {@inheritDoc}
		 * 
		 * @see com.google.common.base.Predicate#apply(java.lang.Object)
		 */
		public boolean apply(Diff input) {
			return !(input instanceof ResourceLocationChange) && canConflictWith(input);
		}

		/**
		 * Checks if the given {@link Diff diff1} can be in conflict with the given {@link Diff diff2}.
		 * <p>
		 * Notably, we don't need to try and detect a conflict between two diffs if they're one and the same
		 * or if they have already been detected as a conflicting couple. Likewise, there can be no conflict
		 * if the two diffs originate from the same side.
		 * </p>
		 * <p>
		 * bug 381143 : we'll also remove any containment deletion diff on other Matches from here.
		 * </p>
		 * 
		 * @param other
		 *            candidate difference to consider for conflict detection.
		 * @return {@code true} if the two given diffs can conflict, {@code false} otherwise.
		 */
		private boolean canConflictWith(Diff other) {
			if (diff == other || diff.getSource() == other.getSource()) {
				return false;
			}
			final Conflict conflict = diff.getConflict();
			boolean canConflict = false;
			if (conflict == null || !conflict.getDifferences().contains(other)) {
				if (diff.getMatch() != other.getMatch() && other instanceof ReferenceChange
						&& ((ReferenceChange)other).getReference().isContainment()) {
					canConflict = !isDeleteOrUnsetDiff(other);
				} else {
					canConflict = true;
				}
			}
			return canConflict;
		}
	}

}