package org.apache.maven.surefire.util.internal;
   
   /*
    * 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.
   */
  
  import java.util.AbstractMap;
  import java.util.LinkedHashSet;
  import java.util.Map;
  import java.util.Set;
  
  import static java.util.Collections.unmodifiableSet;
  
  /**
   * Copies input map in {@link #ImmutableMap(Map) constructor}, and Entries are linked and thread-safe.
   * The map is immutable with linear list of entries.
   *
   * @param <K> key
   * @param <V> value
   * @since 2.20
   */
  public final class ImmutableMap<K, V>
          extends AbstractMap<K, V>
  {
      private final Node<K, V> first;
  
      public ImmutableMap( Map<K, V> map )
      {
          Node<K, V> first = null;
          Node<K, V> previous = null;
          for ( Entry<K, V> e : map.entrySet() )
          {
              Node<K, V> node = new Node<K, V>( e.getKey(), e.getValue() );
              if ( first == null )
              {
                  first = node;
              }
              else
              {
                  previous.next = node;
              }
              previous = node;
          }
          this.first = first;
      }
  
      @Override
      public Set<Entry<K, V>> entrySet()
      {
          Set<Entry<K, V>> entries = new LinkedHashSet<Entry<K, V>>();
          Node<K, V> node = first;
          while ( node != null )
          {
              entries.add( node );
              node = node.next;
          }
          return unmodifiableSet( entries );
      }
  
      static final class Node<K, V>
              implements Entry<K, V>
      {
          final K key;
          final V value;
          volatile Node<K, V> next;
  
          Node( K key, V value )
          {
              this.key = key;
              this.value = value;
          }
  
          @Override
          public K getKey()
          {
              return key;
          }
  
          @Override
          public V getValue()
          {
              return value;
          }
  
         @Override
         public V setValue( V value )
         {
             throw new UnsupportedOperationException();
         }
 
         @Override
         public boolean equals( Object o )
         {
             if ( this == o )
             {
                 return true;
             }
 
             if ( o == null || getClass() != o.getClass() )
             {
                 return false;
             }
 
             Node<?, ?> node = (Node<?, ?>) o;
 
             return getKey() != null ? getKey().equals( node.getKey() ) : node.getKey() == null
                            && getValue() != null ? getValue().equals( node.getValue() ) : node.getValue() == null;
 
         }
 
         @Override
         public int hashCode()
         {
             int result = getKey() != null ? getKey().hashCode() : 0;
             result = 31 * result + ( getValue() != null ? getValue().hashCode() : 0 );
             return result;
         }
     }
 }