/**
    *
    * 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.util;
  
  import com.yammer.metrics.core.Histogram;
  import com.yammer.metrics.stats.Sample;
  import com.yammer.metrics.stats.Snapshot;
  
  import java.lang.reflect.Constructor;
  import java.text.DecimalFormat;
  
  /** Utility functions for working with Yammer Metrics. */
  public final class YammerHistogramUtils {
  
    // not for public consumption
    private YammerHistogramUtils() {}
  
    /**
     * Used formatting doubles so only two places after decimal point.
     */
    private static DecimalFormat DOUBLE_FORMAT = new DecimalFormat("#0.00");
  
    /**
     * Create a new {@link com.yammer.metrics.core.Histogram} instance. These constructors are
     * not public in 2.2.0, so we use reflection to find them.
     */
    public static Histogram newHistogram(Sample sample) {
      try {
        Constructor<?> ctor =
            Histogram.class.getDeclaredConstructor(Sample.class);
        ctor.setAccessible(true);
        return (Histogram) ctor.newInstance(sample);
      } catch (Exception e) {
        throw new RuntimeException(e);
      }
    }
  
    /** @return an abbreviated summary of {@code hist}. */
    public static String getShortHistogramReport(final Histogram hist) {
      Snapshot sn = hist.getSnapshot();
      return "mean=" + DOUBLE_FORMAT.format(hist.mean()) +
          ", min=" + DOUBLE_FORMAT.format(hist.min()) +
          ", max=" + DOUBLE_FORMAT.format(hist.max()) +
          ", stdDev=" + DOUBLE_FORMAT.format(hist.stdDev()) +
          ", 95th=" + DOUBLE_FORMAT.format(sn.get95thPercentile()) +
          ", 99th=" + DOUBLE_FORMAT.format(sn.get99thPercentile());
    }
  
    /** @return a summary of {@code hist}. */
    public static String getHistogramReport(final Histogram hist) {
      Snapshot sn = hist.getSnapshot();
      return ", mean=" + DOUBLE_FORMAT.format(hist.mean()) +
          ", min=" + DOUBLE_FORMAT.format(hist.min()) +
          ", max=" + DOUBLE_FORMAT.format(hist.max()) +
          ", stdDev=" + DOUBLE_FORMAT.format(hist.stdDev()) +
          ", 50th=" + DOUBLE_FORMAT.format(sn.getMedian()) +
          ", 75th=" + DOUBLE_FORMAT.format(sn.get75thPercentile()) +
          ", 95th=" + DOUBLE_FORMAT.format(sn.get95thPercentile()) +
          ", 99th=" + DOUBLE_FORMAT.format(sn.get99thPercentile()) +
          ", 99.9th=" + DOUBLE_FORMAT.format(sn.get999thPercentile()) +
          ", 99.99th=" + DOUBLE_FORMAT.format(sn.getValue(0.9999)) +
          ", 99.999th=" + DOUBLE_FORMAT.format(sn.getValue(0.99999));
    }
  }