/*

  * Licensed to the Apache Software Foundation (ASF) under one or more

  * contributor license agreements.  See the NOTICE file distributed with

  * this work for additional information regarding copyright ownership.

  * The ASF licenses this file to You under the Apache License, Version 2.0

  * (the "License"); you may not use this file except in compliance with

  * the License.  You may obtain a copy of the License at

  *

  *  http://www.apache.org/licenses/LICENSE-2.0

  *

  * Unless required by applicable law or agreed to in writing, software

  * distributed under the License is distributed on an "AS IS" BASIS,

  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

  * See the License for the specific language governing permissions and

  * limitations under the License.

  */

 package org.apache.any23.extractor.xpath;

 import org.apache.any23.extractor.ExtractionResult;

 import org.openrdf.model.Resource;

 import org.openrdf.model.URI;

 import org.openrdf.model.Value;

 import java.util.Map;

 /**

  * This class models a <i>NQuads</i> template,

  * that is a quadruple in which any component

  * can be a variable.

  *

  * @author Michele Mostarda (mostarda@fbk.eu)

  */

 public class QuadTemplate {

     private final TemplateSubject subject;

     private final TemplatePredicate predicate;

     private final TemplateObject object;

     private final TemplateGraph graph;

     /**

      * Constructor.

      *

      * @param subject not <code>null</code> subject template.

      * @param predicate not <code>null</code> predicate template.

      * @param object not <code>null</code> object template.

      * @param graph graph template, can be <code>null</code>.

      */

     public QuadTemplate(

             TemplateSubject subject, TemplatePredicate predicate, TemplateObject object, TemplateGraph graph

     ) {

         if(subject == null) {

             throw new NullPointerException("subject term cannot be null.");

         }

         if(predicate == null) {

             throw new NullPointerException("predicate term cannot be null.");

         }

         if(object == null) {

             throw new NullPointerException("object term cannot be null.");

         }

         this.subject   = subject;

         this.predicate = predicate;

         this.object    = object;

         this.graph     = graph;

     }

     /**

      * Constructor for template with no graph.

      *

      * @param subject

      * @param predicate

      * @param object

      */

     public QuadTemplate(TemplateSubject subject, TemplatePredicate predicate, TemplateObject object) {

         this(subject, predicate, object, null);

     }

     /**

      * @return the template subject.

      */

     public TemplateSubject getSubject() {

         return subject;

     }

     /**

      * @return the template predicate.

      */

     public TemplatePredicate getPredicate() {

         return predicate;

     }

     /**

      * @return the template object.

      */

     public TemplateObject getObject() {

         return object;

     }

     /**

      * @return the template graph, can be <code>null</code>.

      */

     public TemplateGraph getGraph() {

         return graph;

     }

     /**

      * Prints out this quad template in the given {@link org.apache.any23.extractor.ExtractionResult}, using

      * the passed <i>variableAssignment</i> to expand variables.

      *

      * @param er extraction result instance on which write the quad produced by this template.

      * @param variableAssignment the assignment used to expand variables.

      */

     public void printOut(ExtractionResult er, Map<String,String> variableAssignment) {

         final Resource s = subject.getValue(variableAssignment);

         final URI p      = predicate.getValue(variableAssignment);

         final Value o    = object.getValue(variableAssignment);

         if(graph != null) {

             final URI g = graph.getValue(variableAssignment);

             er.writeTriple(s, p, o, g);

         } else {

             er.writeTriple(s, p, o);

         }

     }

     @Override

     public String toString() {

         return String.format("%s %s %s %s", subject, predicate, object, graph);

     }

 }