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/**

Copyright (C) SYSTAP, LLC DBA Blazegraph 2006-2016.  All rights reserved.

Contact:
     SYSTAP, LLC DBA Blazegraph
     2501 Calvert ST NW #106
     Washington, DC 20008
     [email protected]

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*/
/* Portions of this code are:
 *
 * Copyright Aduna (http://www.aduna-software.com/) (c) 1997-2007.
 *
 * Licensed under the Aduna BSD-style license.
 */
/*
 * Created on Aug 21, 2011
 */

package com.bigdata.rdf.sail.sparql;

import java.util.Map;

import org.openrdf.model.Value;
import org.openrdf.model.vocabulary.RDF;

import com.bigdata.rdf.model.BigdataValue;
import com.bigdata.rdf.model.BigdataValueFactory;
import com.bigdata.rdf.model.BigdataValueFactoryImpl;
import com.bigdata.rdf.sail.sparql.ast.VisitorException;
import com.bigdata.rdf.sparql.ast.ConstantNode;
import com.bigdata.rdf.sparql.ast.VarNode;

/**
 * Object provides context required in various stages of parsing queries or
 * updates.
 * 
 * @author Bryan Thompson
 * @openrdf
 */
public class BigdataASTContext {

    protected final BigdataValueFactory valueFactory;

    /**
     * A mapping of parsed RDF Values and well known vocabulary items used when
     * generating the AST to resolved {@link BigdataValue}s. This includes
     * everything which was parsed plus certain well-known items such as
     * {@link RDF#FIRST}, {@link RDF#REST}, and {@link RDF#NIL} which are only
     * used when handling syntactic sugar constructions.
     */
    protected final Map vocab;
    
    /**
     * Counter used to generate unique (within query) variable names.
     */
    private int constantVarID = 1;

	/**
	 * 
	 * @param values
	 *            A map from the distinct RDF {@link Value} objects in the QUERY
	 *            or UPDATE request to the corresponding {@link BigdataValue}
	 *            objects that will be used to process the request.
	 */
    public BigdataASTContext(final Map values) {

    	this.valueFactory = BigdataValueFactoryImpl.getInstance("");
        
    	this.vocab = values;

    }

    /**
     * Create an anonymous variable. The variable name will be unique (within
     * the scope of the query parser) and {@link VarNode#isAnonymous()} will
     * return true.
     * 
     * @param varName
     *            The prefix of the name of an anonymous variable. This should
     *            have the pattern -foo-. An unique (within query)
     *            variable identifier will be appended to the prefix.
     * 
     * @return The anonymous variable.
     */
    protected VarNode createAnonVar(final String varName) {

        final VarNode var = new VarNode(varName + constantVarID++);
        
        var.setAnonymous(true);
        
        return var;
        
    }

    /**
     * Return a constant for a pre-defined vocabulary item.
     * 
     * @throws VisitorException
     */
    protected ConstantNode createConstVar(final Value value)
            throws VisitorException {

        final BigdataValue v = vocab.get(value);

        if (v == null)
            throw new VisitorException("Undefined vocabulary: " + value);

        return new ConstantNode(v.getIV());

    }

    /**
	 * Return a new variable for a SID (Statement Identifier)
	 * 
	 * @see 
	 *      Reification Done Right
	 */
    protected VarNode createSidVar() {
    	
    		final VarNode var = new VarNode("-sid-" + constantVarID++);
        
        return var;
    	
    }
    
}