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RDF2go is an implementation-independent Java API with the design goals: portability (hence the name), performance and ease of implementation. This project was started at FZI Forschungszentrum Informatik Karlsruhe, Germany - www.fzi.de
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/**
 * LICENSE INFORMATION
 * 
 * Copyright 2005-2008 by FZI (http://www.fzi.de). Licensed under a BSD license
 * (http://www.opensource.org/licenses/bsd-license.php)  = Max Völkel
 *  = FZI Forschungszentrum Informatik Karlsruhe, Karlsruhe,
 * Germany  = 2010
 * 
 * Further project information at http://semanticweb.org/wiki/RDF2Go
 */

package org.ontoware.rdf2go.model.impl;

import org.ontoware.rdf2go.model.Statement;
import org.ontoware.rdf2go.model.TriplePattern;
import org.ontoware.rdf2go.model.node.Node;
import org.ontoware.rdf2go.model.node.NodeOrVariable;
import org.ontoware.rdf2go.model.node.Resource;
import org.ontoware.rdf2go.model.node.ResourceOrVariable;
import org.ontoware.rdf2go.model.node.URI;
import org.ontoware.rdf2go.model.node.UriOrVariable;
import org.ontoware.rdf2go.model.node.Variable;
import org.ontoware.rdf2go.model.node.impl.PlainLiteralImpl;


/**
 * A statement with variables
 * 
 * @author voelkel
 * 
 */
public class TriplePatternImpl implements TriplePattern {
	
	/**
     * 
     */
	private static final long serialVersionUID = 7880656889564700726L;
	
	public enum SPO {
		SUBJECT, PREDICATE, OBJECT
	}
	
	private ResourceOrVariable subject;
	
	private UriOrVariable predicate;
	
	private NodeOrVariable object;
	
	public SPO extract;
	
	public TriplePatternImpl(ResourceOrVariable subject, UriOrVariable predicate,
	        NodeOrVariable object) {
		this.subject = subject;
		this.predicate = predicate;
		this.object = object;
	}
	
	public TriplePatternImpl(ResourceOrVariable subject, UriOrVariable predicate,
	        NodeOrVariable object, SPO extract) {
		this.subject = subject;
		this.predicate = predicate;
		this.object = object;
		this.extract = extract;
	}
	
	/**
	 * Convenience constructor
	 * 
	 * @param subject never null
	 * @param predicate never null
	 * @param object never null
	 */
	public TriplePatternImpl(ResourceOrVariable subject, URI predicate, String object) {
		this.subject = subject;
		this.predicate = predicate;
		this.object = new PlainLiteralImpl(object);
	}
	
	@Override
    public NodeOrVariable getObject() {
		return this.object;
	}
	
	@Override
    public UriOrVariable getPredicate() {
		return this.predicate;
	}
	
	@Override
    public ResourceOrVariable getSubject() {
		return this.subject;
	}
	
	/**
	 * @param statement an RDF2Go statement
	 * @return the part of the statement which should be extracted according to
	 *         this pattern
	 */
	public Node getExtract(Statement statement) {
		switch(this.extract) {
		case SUBJECT:
			return statement.getSubject();
		case PREDICATE:
			return statement.getPredicate();
		case OBJECT:
			return statement.getObject();
		default: {
			assert false;
			throw new RuntimeException();
		}
		}
	}
	
	@Override
	public boolean equals(Object o) {
		return ((o instanceof Statement) && (this.getSubject().equals(((Statement)o).getSubject()))
		        && (this.getPredicate().equals(((Statement)o).getPredicate())) && (this.getObject()
		        .equals(((Statement)o).getObject())));
	}
	
	@Override
	public int hashCode() {
		return this.object.hashCode() + this.predicate.hashCode() + this.object.hashCode();
	}
	
	public static TriplePatternImpl createObjectPattern(Resource resource, URI propertyURI) {
		return new TriplePatternImpl(resource, propertyURI, Variable.ANY, SPO.OBJECT);
	}
	
	public static TriplePatternImpl createSubjectPattern(URI propertyURI, Node objectNode) {
		return new TriplePatternImpl(Variable.ANY, propertyURI, objectNode, SPO.SUBJECT);
	}
	
	@Override
    public boolean matches(Statement statement) {
		boolean matchesSubject = statement.getSubject().equals(this.getSubject())
		        || this.getSubject() instanceof Variable;
		
		boolean matchesPredicate = statement.getPredicate().equals(this.getPredicate())
		        || this.getPredicate() instanceof Variable;
		
		boolean matchesObject = statement.getObject().equals(this.getObject())
		        || this.getObject() instanceof Variable;
		
		return matchesSubject && matchesPredicate && matchesObject;
	}
	
}