/**
    * 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.rdf4j.impl;
  
  import java.nio.charset.StandardCharsets;
  import java.util.UUID;
  
  import org.apache.commons.rdf.api.BlankNode;
  import org.apache.commons.rdf.rdf4j.RDF4JBlankNode;
  import org.eclipse.rdf4j.model.BNode;
  import org.eclipse.rdf4j.rio.turtle.TurtleUtil;
  
  final class BlankNodeImpl extends AbstractRDFTerm<BNode> implements RDF4JBlankNode {
  
      private transient int hashCode = 0;
      private final long saltUUIDleast;
      private final long saltUUIDmost;
  
      BlankNodeImpl(final BNode bNode, final UUID salt) {
          super(bNode);
          // Space-efficient storage of salt UUID
          saltUUIDmost = salt.getMostSignificantBits();
          saltUUIDleast = salt.getLeastSignificantBits();
      }
  
      @Override
      public boolean equals(final Object obj) {
          if (obj == this) {
              return true;
          }
          // NOTE: Do NOT use Bnode.equals() as it has a more generous
          // equality based only on the value.getID();
          if (obj instanceof BlankNode) {
              final BlankNode blankNode = (BlankNode) obj;
              return uniqueReference().equals(blankNode.uniqueReference());
          }
          return false;
      }
  
      @Override
      public int hashCode() {
          if (hashCode != 0) {
              return hashCode;
          }
          return hashCode = uniqueReference().hashCode();
      }
  
      private boolean isValidBlankNodeLabel(final String id) {
          // FIXME: Replace with a regular expression?
          if (id.isEmpty()) {
              return false;
          }
          if (!TurtleUtil.isBLANK_NODE_LABEL_StartChar(id.codePointAt(0))) {
              return false;
          }
          for (int i = 1; i < id.length(); i++) {
              if (!TurtleUtil.isBLANK_NODE_LABEL_Char(id.codePointAt(i))) {
                  return false;
              }
          }
          return true;
      }
  
      @Override
      public String ntriplesString() {
          if (isValidBlankNodeLabel(value.getID())) {
              return "_:" + value.getID();
          }
          return "_:" + UUID.nameUUIDFromBytes(value.getID().getBytes(StandardCharsets.UTF_8));
      }
  
      @Override
      public String uniqueReference() {
          final UUID uuid = new UUID(saltUUIDmost, saltUUIDleast);
          return "urn:uuid:" + uuid + "#" + value.getID();
      }
  
      @Override
      public String toString() {
          return ntriplesString() + " [" + uniqueReference() + "]";
      }
  }