/**
    * 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.hadoop.hbase.master.procedure;
  
  import java.io.IOException;
  import java.io.InterruptedIOException;
  import java.util.concurrent.CountDownLatch;
  
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.hbase.classification.InterfaceStability;
  import org.apache.hadoop.hbase.client.VersionInfoUtil;
  import org.apache.hadoop.hbase.procedure2.Procedure;
  
  /**
   * Latch used by the Master to have the prepare() sync behaviour for old
   * clients, that can only get exceptions in a synchronous way.
   */
  @InterfaceAudience.Private
  @InterfaceStability.Evolving
  public abstract class ProcedurePrepareLatch {
    private static final NoopLatch noopLatch = new NoopLatch();
  
    public static ProcedurePrepareLatch createLatch() {
      // don't use the latch if we have procedure support
      return hasProcedureSupport() ? noopLatch : new CompatibilityLatch();
    }
  
    public static boolean hasProcedureSupport() {
      return VersionInfoUtil.currentClientHasMinimumVersion(1, 1);
    }
  
    protected abstract void countDown(final Procedure proc);
    public abstract void await() throws IOException;
  
    protected static void releaseLatch(final ProcedurePrepareLatch latch, final Procedure proc) {
      if (latch != null) {
        latch.countDown(proc);
      }
    }
  
    private static class NoopLatch extends ProcedurePrepareLatch {
      protected void countDown(final Procedure proc) {}
      public void await() throws IOException {}
    }
  
    protected static class CompatibilityLatch extends ProcedurePrepareLatch {
      private final CountDownLatch latch = new CountDownLatch(1);
  
      private IOException exception = null;
  
      protected void countDown(final Procedure proc) {
        if (proc.hasException()) {
          exception = proc.getException().unwrapRemoteException();
        }
        latch.countDown();
      }
  
      public void await() throws IOException {
        try {
          latch.await();
        } catch (InterruptedException e) {
          throw (InterruptedIOException)new InterruptedIOException().initCause(e);
        }
  
        if (exception != null) {
          throw exception;
        }
      }
    }
  }