plugins/org.eclipse.mylyn.docs.intent.compare/src/org/eclipse/mylyn/docs/intent/compare/match/IntentSimilarityChecker.java

/*******************************************************************************
 * Copyright (c) 2010, 2011 Obeo.
 * 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
 *******************************************************************************/
package org.eclipse.mylyn.docs.intent.compare.match;

import org.eclipse.emf.compare.FactoryException;
import org.eclipse.emf.compare.match.statistic.MetamodelFilter;
import org.eclipse.emf.ecore.EObject;
import org.eclipse.mylyn.docs.intent.core.descriptionunit.DescriptionBloc;
import org.eclipse.mylyn.docs.intent.core.document.IntentSection;
import org.eclipse.mylyn.docs.intent.markup.markup.Block;

/**
 * Similarity checker using the Intent semantics to compare two Intent elements.
 * 
 * @author <a href="mailto:alex.lagarde@obeo.fr">Alex Lagarde</a>
 */
public class IntentSimilarityChecker extends StatisticBasedSimilarityChecker {

	/**
	 * Value taht represents a very strong similarity.
	 */
	private static final double MAX_SIMILARITY = 0.9999;

	private EObject localRoot;

	private EObject repositoryRoot;

	/**
	 * IntentSimilarityChecker constructor.
	 * 
	 * @param localRoot
	 *            the root of the local AST of a Intent Element.
	 * @param repositoryRoot
	 *            the root of the repository AST for a Intent Element
	 * @param metamodelFilter
	 *            a metamodel filter the checker can use to know whether a feature alwaas has the same value
	 *            or not in the models.
	 * @param bridge
	 *            utility class to keep API compatibility.
	 */
	public IntentSimilarityChecker(MetamodelFilter metamodelFilter,
			AbstractGenericMatchEngineToCheckerBridge bridge, EObject localRoot, EObject repositoryRoot) {
		super(metamodelFilter, bridge);
		this.localRoot = localRoot;
		this.repositoryRoot = repositoryRoot;
	}

	/**
	 * {@inheritDoc}
	 * 
	 * @see org.eclipse.mylyn.docs.intent.compare.match.matcher.StatisticBasedSimilarityChecker#isSimilar(org.eclipse.emf.ecore.EObject,
	 *      org.eclipse.emf.ecore.EObject)
	 */
	@Override
	public boolean isSimilar(EObject obj1, EObject obj2) throws FactoryException {

		boolean isSimilar = false;
		boolean haveSpecificMatcher = false;
		// If the two objects are the roots, we consider that they are similar in any circumstance
		if (areRoots(obj1, obj2)) {
			isSimilar = true;
			haveSpecificMatcher = true;
		} else {
			if (obj1 instanceof DescriptionBloc && obj2 instanceof DescriptionBloc) {
				isSimilar = areSimilarDescriptionBlocs((DescriptionBloc)obj1, (DescriptionBloc)obj2);
				haveSpecificMatcher = true;
			} else {
				if (obj1 instanceof IntentSection && obj2 instanceof IntentSection) {
					isSimilar = areSimilarSessions((IntentSection)obj1, (IntentSection)obj2);
					haveSpecificMatcher = true;
				}
			}
		}
		if (!haveSpecificMatcher) {
			isSimilar = super.isSimilar(obj1, obj2);
		}
		return isSimilar;
	}

	/**
	 * {@inheritDoc}
	 * 
	 * @see org.eclipse.emf.compare.match.engine.AbstractSimilarityChecker#fastLookup(org.eclipse.emf.ecore.EObject)
	 */
	@Override
	public EObject fastLookup(EObject obj1) {
		if (obj1 == localRoot) {
			return repositoryRoot;
		}
		return super.fastLookup(obj1);
	}

	/**
	 * {@inheritDoc}
	 * 
	 * @see org.eclipse.mylyn.docs.intent.compare.match.matcher.client.ui.editor.merger.match.StatisticBasedSimilarityChecker#absoluteMetric(org.eclipse.emf.ecore.EObject,
	 *      org.eclipse.emf.ecore.EObject)
	 */
	@Override
	public double absoluteMetric(EObject obj1, EObject obj2) throws FactoryException {
		// If the two objects are the roots, we consider that they are similar in any circumstance
		if (areRoots(obj1, obj2)) {
			return MAX_SIMILARITY;
		}
		return super.absoluteMetric(obj1, obj2);
	}

	/**
	 * Indicates if the two given objects represent the roots of the compared element.
	 * 
	 * @param obj1
	 *            the first element to determine if it's a root
	 * @param obj2
	 *            the second element to determine if it's a root
	 * @return true if the two given objects represent the roots of the compared element, false otherwise
	 */
	private boolean areRoots(EObject obj1, EObject obj2) {
		return (obj1 == localRoot) && (obj2 == repositoryRoot);
	}

	/**
	 * Indicates if the first session matches the second one.
	 * 
	 * @param session1
	 *            the session to match
	 * @param session2
	 *            the candidate session
	 * @return true if the first session matches the second one, false otherwise
	 * @throws FactoryException
	 *             - on error accessing features.
	 */
	protected boolean areSimilarSessions(IntentSection session1, IntentSection session2) //TODO FIXME [naming] section should be better than session
			throws FactoryException {
		// 2 session are equals if :
		// they have the same title
		Block title1 = session1.getTitle();
		Block title2 = session2.getTitle();
		// TODO FIXME if section don't have any title yet, NPE
		return isSimilar(title1, title2);
	}

	/**
	 * Indicates if the first description bloc matches the second one.
	 * 
	 * @param obj1
	 *            the description bloc to match
	 * @param obj2
	 *            the candidate description bloc
	 * @return true if the first description bloc matches the second one, false otherwise
	 */
	private boolean areSimilarDescriptionBlocs(DescriptionBloc obj1, DescriptionBloc obj2) {
		// FIXME : first verify that both description blocs are part of the same DU

		// Two description blocs are equals if they have the same position in their container
		int positionInContainer1 = obj1.eContainer().eContents().indexOf(obj1);
		int positionInContainer2 = obj2.eContainer().eContents().indexOf(obj2);
		boolean haveSamePositionInContainer = positionInContainer1 == positionInContainer2;
		return haveSamePositionInContainer;
	}
}