/**
    * 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.commons.rdf.simple;
  
  import org.apache.commons.rdf.api.BlankNodeOrIRI;
  import org.apache.commons.rdf.api.IRI;
  import org.apache.commons.rdf.api.Quad;
  import org.apache.commons.rdf.api.RDFTerm;
  import org.apache.commons.rdf.api.Triple;
  
  import java.util.Objects;
  import java.util.Optional;
  
  /**
   * A simple implementation of Quad.
   */
  final class QuadImpl implements Quad {
  
      private final BlankNodeOrIRI graphName;
      private final BlankNodeOrIRI subject;
      private final IRI predicate;
      private final RDFTerm object;
  
      /**
       * Construct Quad from its constituent parts.
       * <p>
       * The objects are not changed. All mapping of BNode objects is done in
       * {@link SimpleRDF#createQuad(BlankNodeOrIRI, BlankNodeOrIRI, IRI, RDFTerm)}.
       *
       * @param graphName
       *            graphName of triple
       * @param subject
       *            subject of triple
       * @param predicate
       *            predicate of triple
       * @param object
       *            object of triple
       */
      public QuadImpl(final BlankNodeOrIRI graphName, final BlankNodeOrIRI subject, final IRI predicate, final RDFTerm object) {
          this.graphName = graphName; // possibly null
          this.subject = Objects.requireNonNull(subject);
          this.predicate = Objects.requireNonNull(predicate);
          this.object = Objects.requireNonNull(object);
      }
  
      @Override
      public Optional<BlankNodeOrIRI> getGraphName() {
          return Optional.ofNullable(graphName);
      }
  
      @Override
      public BlankNodeOrIRI getSubject() {
          return subject;
      }
  
      @Override
      public IRI getPredicate() {
          return predicate;
      }
  
      @Override
      public RDFTerm getObject() {
          return object;
      }
  
      @Override
      public String toString() {
          return getSubject().ntriplesString() + " " + getPredicate().ntriplesString() + " "
                  + getObject().ntriplesString() + " " + getGraphName().map(g -> g.ntriplesString() + " ").orElse("")
                  + ".";
      }
  
      @Override
      public int hashCode() {
          return Objects.hash(subject, predicate, object, graphName);
      }
  
      @Override
      public boolean equals(final Object obj) {
          if (!(obj instanceof Quad)) {
              return false;
          }
          final Quad other = (Quad) obj;
          return getGraphName().equals(other.getGraphName()) && getSubject().equals(other.getSubject())
                 && getPredicate().equals(other.getPredicate()) && getObject().equals(other.getObject());
     }
 
     @Override
     public Triple asTriple() {
         return new TripleImpl(getSubject(), getPredicate(), getObject());
     }
 
 }