/*******************************************************************************
 * Copyright (c) 2007, 2010 Association for Decentralized Information Management
 * in Industry THTH ry.
 * 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:
 *     VTT Technical Research Centre of Finland - initial API and implementation
 *******************************************************************************/
package org.simantics.layer0.utils.binaryPredicates;

import java.util.ArrayDeque;
import java.util.Collection;
import java.util.Deque;
import java.util.HashSet;
import java.util.Set;

import org.simantics.db.Resource;
import org.simantics.db.ReadGraph;
import org.simantics.db.WriteGraph;
import org.simantics.db.exception.DatabaseException;
import org.simantics.utils.datastructures.Pair;

public class TransitiveClosure extends BinaryPredicate {
	IBinaryPredicate predicate;
	

	public TransitiveClosure(IBinaryPredicate predicate) {
		this.predicate = predicate;
	}

	@Override
	public void add(WriteGraph g, Resource subject, Resource object) throws DatabaseException {
		if(!has(g, subject, object))
			predicate.add(g, subject, object);
	}

	@Override
	public Collection<Resource> getObjects(ReadGraph g, Resource subject) throws DatabaseException {
		Deque<Resource> unprocessed = new ArrayDeque<Resource>();
		unprocessed.add(subject);
		Set<Resource> result = new HashSet<Resource>();
		while(!unprocessed.isEmpty())
			for(Resource r : predicate.getObjects(g, unprocessed.pop()))
				if(result.add(r))
					unprocessed.push(r);
		return result;
	}

	@Override
	public Collection<Pair<Resource, Resource>> getStatements(ReadGraph g) {
		// TODO Auto-generated method stub
		return null;
	}

	@Override
	public Collection<Resource> getSubjects(ReadGraph g, Resource object) throws DatabaseException {
		Deque<Resource> unprocessed = new ArrayDeque<Resource>();
		unprocessed.add(object);
		Set<Resource> result = new HashSet<Resource>();
		while(!unprocessed.isEmpty())
			for(Resource r : predicate.getSubjects(g, unprocessed.pop()))
				if(result.add(r))
					unprocessed.push(r);
		return result;
	}

	@Override
	public boolean has(ReadGraph g, Resource subject, Resource object) throws DatabaseException {
		Deque<Resource> unprocessed = new ArrayDeque<Resource>();
		unprocessed.add(subject);
		Set<Resource> objects = new HashSet<Resource>();
		while(!unprocessed.isEmpty())
			for(Resource r : predicate.getObjects(g, unprocessed.pop()))
				if(r.equals(object))
					return true;
				else if(objects.add(r))
					unprocessed.push(r);
		return false;
	}

	@Override
	public void remove(WriteGraph g, Resource subject, Resource object) {
		throw new UnsupportedOperationException();
	}

	@Override
	public boolean supportsAdditions() {
		return predicate.supportsAdditions();
	}

	@Override
	public boolean supportsGetObjects() {
		return predicate.supportsGetObjects();
	}

	@Override
	public boolean supportsGetStatements() {
		return false; // FIXME: just unimplemented
	}

	@Override
	public boolean supportsGetSubjects() {
		return predicate.supportsGetSubjects();
	}

	@Override
	public boolean supportsRemovals() {
		return false;
	}

	@Override
	public int hashCode() {
		final int prime = 31;
		int result = 1;
		result = prime * result
				+ ((predicate == null) ? 0 : predicate.hashCode());
		return result;
	}

	@Override
	public boolean equals(Object obj) {
		if (this == obj)
			return true;
		if (obj == null)
			return false;
		if (getClass() != obj.getClass())
			return false;
		TransitiveClosure other = (TransitiveClosure) obj;
		if (predicate == null) {
			if (other.predicate != null)
				return false;
		} else if (!predicate.equals(other.predicate))
			return false;
		return true;
	}
	
}