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/*
 * 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.druid.sql.hook;

import com.google.inject.Inject;
import org.apache.druid.guice.LazySingleton;
import org.apache.druid.sql.calcite.planner.PlannerContext;
import org.apache.druid.sql.hook.DruidHook.HookKey;

import java.io.Closeable;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

/**
 * Dispatcher for Druid hooks.
 *
 * A single instance should live in the system and be used to dispatch hooks.
 * Usual way to dispatch should be via
 * {@link PlannerContext#dispatchHook(HookKey, Object)}. Access to this class is
 * also possible thru DruidConnectionExtras.
 */
@LazySingleton
public class DruidHookDispatcher
{
  Map, List>> hooks = new HashMap<>();

  @Inject
  public DruidHookDispatcher()
  {
  }

  public void register(HookKey label, DruidHook hook)
  {
    hooks.computeIfAbsent(label, k -> new ArrayList<>()).add(hook);
  }

  public void unregister(HookKey key, DruidHook hook)
  {
    hooks.get(key).remove(hook);
  }

  public  Closeable withHook(HookKey key, DruidHook hook)
  {
    register(key, hook);
    return new Closeable()
    {
      @Override
      public void close()
      {
        unregister(key, hook);
      }
    };
  }

  @SuppressWarnings({"rawtypes", "unchecked"})
  public  void dispatch(HookKey key, T object)
  {
    List> currentHooks = hooks.get(key);
    if (currentHooks != null) {
      for (DruidHook hook : currentHooks) {
        hook.invoke(key, object);
      }
    }
  }

}