package de.tud.plt.r43ples.existentobjects;
   
   import de.tud.plt.r43ples.exception.InternalErrorException;
   import de.tud.plt.r43ples.management.Config;
   import de.tud.plt.r43ples.triplestoreInterface.TripleStoreInterfaceSingleton;
   import org.apache.jena.query.QuerySolution;
   import org.apache.jena.query.ResultSet;
   import org.apache.logging.log4j.LogManager;
   import org.apache.logging.log4j.Logger;
  
  /**
   * Provides information of an already existent statement.
   *
   * @author Stephan Hensel
   */
  public class Statement {
  
      /** The logger. **/
      private Logger logger = LogManager.getLogger(Statement.class);
  
      /** The statement URI. */
      private String statementURI;
      /** The subject. */
      private String subject;
      /** The predicate. */
      private String predicate;
      /** The object. */
      private String object;
      /** The identification whether the object is a resource (true) or a literal (false). */
      private boolean isResource;
  
      /** The revision graph URI. */
      private String revisionGraphURI;
      /** The corresponding revision graph. */
      private RevisionGraph revisionGraph;
  
  
      /**
       * The constructor.
       *
       * @param revisionGraph the revision graph
       * @param statementURI the statement URI
       * @throws InternalErrorException
       */
      public Statement(RevisionGraph revisionGraph, String statementURI) throws InternalErrorException {
          this.revisionGraph = revisionGraph;
          this.revisionGraphURI = this.revisionGraph.getRevisionGraphUri();
          this.statementURI = statementURI;
  
          retrieveAdditionalInformation();
      }
  
      /**
       * The constructor.
       *
       * @param revisionGraph the revision graph
       * @param statementURI the statement URI
       * @param subject the subject
       * @param predicate the predicate
       * @param object the object
       * @param isResource the identification whether the object is a resource (true) or a literal (false)
       */
      public Statement(RevisionGraph revisionGraph, String statementURI, String subject, String predicate, String object, boolean isResource) {
          this.revisionGraph = revisionGraph;
          this.revisionGraphURI = this.revisionGraph.getRevisionGraphUri();
          this.statementURI = statementURI;
          this.subject = subject;
          this.predicate = predicate;
          this.object = object;
          this.isResource = isResource;
      }
  
      /**
       * Calculate additional information of the current statement and store this information to local variables.
       *
       * @throws InternalErrorException
       */
      private void retrieveAdditionalInformation() throws InternalErrorException {
          logger.info("Get additional information of current statement URI " + statementURI + ".");
          String query = Config.prefixes + String.format(""
                  + "SELECT ?subject ?predicate ?object "
                  + "WHERE { GRAPH  <%s> {"
                  + "	<%s> a rdf:Statement; "
                  + "	 rdf:subject ?subject; "
                  + "  rdf:predicate ?predicate; "
                  + "  rdf:object ?object. "
                  + "} }", revisionGraphURI, statementURI);
          this.logger.debug(query);
          ResultSet resultSet = TripleStoreInterfaceSingleton.get().executeSelectQuery(query);
          if (resultSet.hasNext()) {
              QuerySolution qs = resultSet.next();
              subject = qs.getResource("?subject").toString();
              predicate = qs.getResource("?predicate").toString();
              if (qs.getResource("?object") != null) {
                  object = qs.getResource("?object").toString();
                  isResource = true;
              } else {
                  if (qs.getLiteral("?object") != null) {
                      object = qs.getLiteral("?object").toString();
                     isResource = false;
                 }
             }
         } else {
             throw new InternalErrorException("No additional information found for statement URI " + statementURI + ".");
         }
     }
 
     /**
      * Get the statement URI.
      *
      * @return the statement URI
      */
     public String getStatementURI() {
         return statementURI;
     }
 
     /**
      * Get the subject.
      *
      * @return the subject
      */
     public String getSubject() {
         return subject;
     }
 
     /**
      * Get the predicate.
      *
      * @return the predicate
      */
     public String getPredicate() {
         return predicate;
     }
 
     /**
      * Get the object.
      *
      * @return the object
      */
     public String getObject() {
         return object;
     }
 
     /**
      * Get the identification whether the object is a resource (true) or a literal (false).
      *
      * @return true if the object is a resource and false if the object is a literal
      */
     public boolean isResource() {
         return isResource;
     }
 
     /**
      * Get the revision graph.
      *
      * @return the revision graph
      */
     public RevisionGraph getRevisionGraph() {
         return revisionGraph;
     }
 
 }