/*
    * 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.eclipse.aether;
  
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.concurrent.ConcurrentMap;
  import java.util.function.Supplier;
  
  import static java.util.Objects.requireNonNull;
  
  /**
   * A simple session data storage backed by a thread-safe map.
   */
  public final class DefaultSessionData implements SessionData {
  
      private final ConcurrentMap<Object, Object> data;
  
      /**
       * Creates a new session data instance.
       */
      public DefaultSessionData() {
          data = new ConcurrentHashMap<>();
      }
  
      public void set(Object key, Object value) {
          requireNonNull(key, "key cannot be null");
  
          if (value != null) {
              data.put(key, value);
          } else {
              data.remove(key);
          }
      }
  
      public boolean set(Object key, Object oldValue, Object newValue) {
          requireNonNull(key, "key cannot be null");
  
          if (newValue != null) {
              if (oldValue == null) {
                  return data.putIfAbsent(key, newValue) == null;
              }
              return data.replace(key, oldValue, newValue);
          } else {
              if (oldValue == null) {
                  return !data.containsKey(key);
              }
              return data.remove(key, oldValue);
          }
      }
  
      public Object get(Object key) {
          requireNonNull(key, "key cannot be null");
  
          return data.get(key);
      }
  
      public Object computeIfAbsent(Object key, Supplier<Object> supplier) {
          return data.computeIfAbsent(key, k -> supplier.get());
      }
  }