content: /*
   * 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.asterix.common.metadata;
  
  import java.util.ArrayList;
  import java.util.HashMap;
  import java.util.List;
  import java.util.Map;
  
  import org.apache.asterix.common.exceptions.AsterixException;
  import org.apache.asterix.common.exceptions.ErrorCode;
  import org.apache.asterix.common.metadata.IMetadataLock.Mode;
  import org.apache.commons.lang3.tuple.MutablePair;
  import org.apache.hyracks.algebricks.common.exceptions.AlgebricksException;
  
  /**
   * The LockList is used for two phase locking.
   */
  public class LockList {
      private final List<MutablePair<IMetadataLock, IMetadataLock.Mode>> locks = new ArrayList<>();
      private final Map<IMetadataLock.LockKey, Integer> indexes = new HashMap<>();
      private boolean lockPhase = true;
  
      /**
       * Acquires a lock.
       *
       * @param mode
       *            the lock mode.
       * @param lock
       *            the lock object.
       */
      public void add(IMetadataLock.Mode mode, IMetadataLock lock) throws AsterixException {
          if (isContained(mode, lock)) {
              return;
          }
          try {
              lock.lock(mode);
          } catch (InterruptedException e) {
              Thread.currentThread().interrupt();
              throw new AsterixException(e);
          }
          indexes.put(lock.getKey(), locks.size());
          locks.add(MutablePair.of(lock, mode));
      }
  
      private boolean isContained(Mode mode, IMetadataLock lock) throws AsterixException {
          if (!lockPhase) {
              throw new AsterixException(ErrorCode.COMPILATION_TWO_PHASE_LOCKING_VIOLATION);
          }
          Integer index = indexes.get(lock.getKey());
          if (index != null) {
              Mode acquired = locks.get(index).right;
              if (!acquired.contains(mode)) {
                  throw new AsterixException(ErrorCode.LOCK_WAS_ACQUIRED_DIFFERENT_OPERATION, mode, acquired);
              }
              return true;
          }
          return false;
      }
  
      public void upgrade(Mode to, IMetadataLock lock) throws AlgebricksException {
          if (!lockPhase) {
              throw new AsterixException(ErrorCode.COMPILATION_TWO_PHASE_LOCKING_VIOLATION);
          }
          Integer index = indexes.get(lock.getKey());
          if (index == null) {
              throw new AsterixException(ErrorCode.UPGRADE_FAILED_LOCK_WAS_NOT_ACQUIRED);
          }
          MutablePair<IMetadataLock, Mode> pair = locks.get(index);
          Mode from = pair.getRight();
          if (from == to) {
              return;
          }
          lock.upgrade(from, to);
          pair.setRight(to);
      }
  
      public void downgrade(Mode mode, IMetadataLock lock) throws AlgebricksException {
          if (!lockPhase) {
              throw new AsterixException(ErrorCode.COMPILATION_TWO_PHASE_LOCKING_VIOLATION);
          }
          Integer index = indexes.get(lock.getKey());
          if (index == null) {
              throw new AsterixException(ErrorCode.DOWNGRADE_FAILED_LOCK_WAS_NOT_ACQUIRED);
          }
          MutablePair<IMetadataLock, Mode> pair = locks.get(index);
          Mode acquired = pair.getRight();
          lock.downgrade(acquired, mode);
          pair.setRight(mode);
      }
  
      /**
       * Once unlock() is called, no caller can call add(IMetadataLock.Mode mode, IMetadataLock lock),
       * except that reset() is called.
       */
      public void unlock() {
          for (int i = locks.size() - 1; i >= 0; i--) {
              MutablePair<IMetadataLock, Mode> pair = locks.get(i);
              pair.getLeft().unlock(pair.getRight());
          }
          locks.clear();
          indexes.clear();
          lockPhase = false;
      }
  
      /**
       * Clears the state and starts another pass of two phase locking again.
       */
      public void reset() {
          unlock();
          lockPhase = true;
      }
  
      @Override
      public String toString() {
          return "{\"phase\" : \"" + (lockPhase ? "lock" : "unlock") + "\", \"locks\" : " + locks + "}";
      }
  }
  