/*
    * 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.omid.metrics;
  
  import org.apache.phoenix.thirdparty.com.google.common.base.Optional;
  
  import java.util.ArrayList;
  import java.util.List;
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.concurrent.ConcurrentMap;
  
  public class MetricsRegistryMap {
  
      private final ConcurrentMap<String, Metric> metrics = new ConcurrentHashMap<>();
  
      interface MetricBuilder<T extends Metric> {
  
          MetricBuilder<Gauge<? extends Number>> GAUGES = new MetricBuilder<Gauge<? extends Number>>() {
              @Override
              public boolean isInstance(Metric metric) {
                  return Gauge.class.isInstance(metric);
              }
          };
  
          MetricBuilder<Counter> COUNTERS = new MetricBuilder<Counter>() {
              @Override
              public boolean isInstance(Metric metric) {
                  return Counter.class.isInstance(metric);
              }
          };
  
          MetricBuilder<Timer> TIMERS = new MetricBuilder<Timer>() {
              @Override
              public boolean isInstance(Metric metric) {
                  return Timer.class.isInstance(metric);
              }
          };
  
          MetricBuilder<Meter> METERS = new MetricBuilder<Meter>() {
              @Override
              public boolean isInstance(Metric metric) {
                  return Meter.class.isInstance(metric);
              }
          };
  
          MetricBuilder<Histogram> HISTOGRAMS = new MetricBuilder<Histogram>() {
              @Override
              public boolean isInstance(Metric metric) {
                  return Histogram.class.isInstance(metric);
              }
          };
  
          boolean isInstance(Metric metric);
      }
  
      public Optional<? extends Metric> get(final String name,
                                            MetricBuilder<? extends Metric> builder,
                                            Class<? extends Metric> type) {
  
          final Metric metric = metrics.get(name);
          if (builder.isInstance(metric)) {
              return Optional.of(type.cast(metric));
          }
          return Optional.absent();
  
      }
  
      @SuppressWarnings("unchecked")
      public <T extends Metric, U extends Number> List<Gauge<U>> getGauges() {
          List<Gauge<U>> gaugesList = new ArrayList<>();
          for (Metric metric : metrics.values()) {
              if (metric instanceof Gauge) {
                  gaugesList.add((Gauge<U>) metric);
              }
          }
          return gaugesList;
      }
  
      public void register(String name, Metric metric) throws IllegalArgumentException {
          final Metric existing = metrics.putIfAbsent(name, metric);
          if (existing != null) {
              throw new IllegalArgumentException("A metric named " +
                      name +
                      " of class " +
                     metric.getClass().getCanonicalName() +
                     " already exists");
         }
     }
 
 }