/*
    * 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.maven.surefire.api.util.internal;
  
  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<>(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<>();
          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;
         }
     }
 }