/*
    * 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.named.support;
  
  import java.util.ArrayDeque;
  import java.util.Deque;
  import java.util.concurrent.TimeUnit;
  import java.util.concurrent.locks.ReadWriteLock;
  
  import org.eclipse.aether.named.NamedLockKey;
  
  /**
   * Named lock support implementation that is using {@link ReadWriteLock} instances. The adapted lock MUST SUPPORT
   * reentrancy, non re-entrant locks will NOT work. It is the responsibility of an adapting lock, to ensure that
   * above lock requirement stands.
   */
  public class ReadWriteLockNamedLock extends NamedLockSupport {
      private enum Step {
          /**
           * Step when {@link ReadWriteLock#readLock()} was locked
           */
          SHARED,
  
          /**
           * Step when {@link ReadWriteLock#writeLock()} was locked
           */
          EXCLUSIVE
      }
  
      private final ThreadLocal<Deque<Step>> threadSteps;
  
      private final ReadWriteLock readWriteLock;
  
      public ReadWriteLockNamedLock(
              final NamedLockKey key, final NamedLockFactorySupport factory, final ReadWriteLock readWriteLock) {
          super(key, factory);
          this.threadSteps = ThreadLocal.withInitial(ArrayDeque::new);
          this.readWriteLock = readWriteLock;
      }
  
      @Override
      protected boolean doLockShared(final long time, final TimeUnit unit) throws InterruptedException {
          Deque<Step> steps = threadSteps.get();
          if (readWriteLock.readLock().tryLock(time, unit)) {
              steps.push(Step.SHARED);
              return true;
          }
          return false;
      }
  
      @Override
      protected boolean doLockExclusively(final long time, final TimeUnit unit) throws InterruptedException {
          Deque<Step> steps = threadSteps.get();
          if (!steps.isEmpty()) { // we already own shared or exclusive lock
              if (!steps.contains(Step.EXCLUSIVE)) {
                  throw new LockUpgradeNotSupportedException(this); // Lock upgrade not supported
              }
          }
          if (readWriteLock.writeLock().tryLock(time, unit)) {
              steps.push(Step.EXCLUSIVE);
              return true;
          }
          return false;
      }
  
      @Override
      protected void doUnlock() {
          Deque<Step> steps = threadSteps.get();
          if (steps.isEmpty()) {
              throw new IllegalStateException("Wrong API usage: unlock without lock");
          }
          Step step = steps.pop();
          if (Step.SHARED == step) {
              readWriteLock.readLock().unlock();
          } else if (Step.EXCLUSIVE == step) {
              readWriteLock.writeLock().unlock();
          }
      }
  }