/**
    *
    * 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.metrics.impl;
  
  import java.util.Collection;
  import java.util.Collections;
  import java.util.Set;
  
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.hbase.metrics.MetricRegistries;
  import org.apache.hadoop.hbase.metrics.MetricRegistry;
  import org.apache.hadoop.hbase.metrics.MetricRegistryFactory;
  import org.apache.hadoop.hbase.metrics.MetricRegistryInfo;
  
  import com.google.common.base.Optional;
  import com.google.common.base.Supplier;
  
  /**
   * Implementation of MetricRegistries that does ref-counting.
   */
  @InterfaceAudience.Private
  public class MetricRegistriesImpl extends MetricRegistries {
    private final MetricRegistryFactory factory;
    private final RefCountingMap<MetricRegistryInfo, MetricRegistry> registries;
  
    public MetricRegistriesImpl() {
      this(new MetricRegistryFactoryImpl());
    }
  
    public MetricRegistriesImpl(MetricRegistryFactory factory) {
      this.factory = factory;
      this.registries = new RefCountingMap<>();
    }
  
    @Override
    public MetricRegistry create(final MetricRegistryInfo info) {
      return registries.put(info, new Supplier<MetricRegistry>() {
        @Override
        public MetricRegistry get() {
          return factory.create(info);
        }
      });
    }
  
    @Override
    public boolean remove(MetricRegistryInfo key) {
      return registries.remove(key) == null;
    }
  
    @Override
    public Optional<MetricRegistry> get(MetricRegistryInfo info) {
      return Optional.fromNullable(registries.get(info));
    }
  
    @Override
    public Collection<MetricRegistry> getMetricRegistries() {
      return Collections.unmodifiableCollection(registries.values());
    }
  
    @Override
    public void clear() {
      registries.clear();
    }
  
    @Override
    public Set<MetricRegistryInfo> getMetricRegistryInfos() {
      return Collections.unmodifiableSet(registries.keySet());
    }
  }