/**
    * 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.
   */
  /*
   * Copyright 2016 Josh Elser
   *
   * Licensed 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.Map;
  
  import org.apache.commons.lang.StringUtils;
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hadoop.hbase.metrics.Counter;
  import org.apache.hadoop.hbase.metrics.Gauge;
  import org.apache.hadoop.hbase.metrics.Histogram;
  import org.apache.hadoop.hbase.metrics.Meter;
  import org.apache.hadoop.hbase.metrics.Metric;
  import org.apache.hadoop.hbase.metrics.MetricRegistry;
  import org.apache.hadoop.hbase.metrics.MetricRegistryInfo;
  import org.apache.hadoop.hbase.metrics.Timer;
  import org.apache.hadoop.metrics2.MetricsCollector;
  import org.apache.hadoop.metrics2.MetricsInfo;
  import org.apache.hadoop.metrics2.MetricsRecordBuilder;
  import org.apache.hadoop.metrics2.lib.Interns;
  import org.apache.hadoop.metrics2.lib.MutableHistogram;
  
  /**
   * This is the adapter from "HBase Metrics Framework", implemented in hbase-metrics-api and
   * hbase-metrics modules to the Hadoop Metrics2 framework. This adapter is not a metric source,
   * but a helper to be able to collect all of the Metric's in the MetricRegistry using the
   * MetricsCollector and MetricsRecordBuilder.
   *
   * Some of the code is forked from https://github.com/joshelser/dropwizard-hadoop-metrics2.
   */
  public class HBaseMetrics2HadoopMetricsAdapter {
    private static final Log LOG
        = LogFactory.getLog(HBaseMetrics2HadoopMetricsAdapter.class);
    private static final String EMPTY_STRING = "";
  
    public HBaseMetrics2HadoopMetricsAdapter() {
    }
  
    /**
     * Iterates over the MetricRegistry and adds them to the {@code collector}.
     *
     * @param collector A metrics collector
     */
    public void snapshotAllMetrics(MetricRegistry metricRegistry,
                                   MetricsCollector collector) {
      MetricRegistryInfo info = metricRegistry.getMetricRegistryInfo();
      MetricsRecordBuilder builder = collector.addRecord(Interns.info(info.getMetricsName(),
          info.getMetricsDescription()));
      builder.setContext(info.getMetricsContext());
  
      snapshotAllMetrics(metricRegistry, builder);
    }
  
    /**
     * Iterates over the MetricRegistry and adds them to the {@code builder}.
     *
     * @param builder A record builder
     */
    public void snapshotAllMetrics(MetricRegistry metricRegistry, MetricsRecordBuilder builder) {
      Map<String, Metric> metrics = metricRegistry.getMetrics();
  
      for (Map.Entry<String, Metric> e: metrics.entrySet()) {
        // Always capitalize the name
        String name = StringUtils.capitalize(e.getKey());
        Metric metric = e.getValue();
  
        if (metric instanceof Gauge) {
          addGauge(name, (Gauge<?>) metric, builder);
       } else if (metric instanceof Counter) {
         addCounter(name, (Counter)metric, builder);
       } else if (metric instanceof Histogram) {
         addHistogram(name, (Histogram)metric, builder);
       } else if (metric instanceof Meter) {
         addMeter(name, (Meter)metric, builder);
       } else if (metric instanceof Timer) {
         addTimer(name, (Timer)metric, builder);
       } else {
         LOG.info("Ignoring unknown Metric class " + metric.getClass().getName());
       }
     }
   }
 
   private void addGauge(String name, Gauge<?> gauge, MetricsRecordBuilder builder) {
     final MetricsInfo info = Interns.info(name, EMPTY_STRING);
     final Object o = gauge.getValue();
 
     // Figure out which gauge types metrics2 supports and call the right method
     if (o instanceof Integer) {
       builder.addGauge(info, (int) o);
     } else if (o instanceof Long) {
       builder.addGauge(info, (long) o);
     } else if (o instanceof Float) {
       builder.addGauge(info, (float) o);
     } else if (o instanceof Double) {
       builder.addGauge(info, (double) o);
     } else {
       LOG.warn("Ignoring Gauge (" + name + ") with unhandled type: " + o.getClass());
     }
   }
 
   private void addCounter(String name, Counter counter, MetricsRecordBuilder builder) {
     MetricsInfo info = Interns.info(name, EMPTY_STRING);
     builder.addCounter(info, counter.getCount());
   }
 
   /**
    * Add Histogram value-distribution data to a Hadoop-Metrics2 record building.
    *
    * @param name A base name for this record.
    * @param histogram A histogram to measure distribution of values.
    * @param builder A Hadoop-Metrics2 record builder.
    */
   private void addHistogram(String name, Histogram histogram, MetricsRecordBuilder builder) {
     MutableHistogram.snapshot(name, EMPTY_STRING, histogram, builder, true);
   }
 
   /**
    * Add Dropwizard-Metrics rate information to a Hadoop-Metrics2 record builder, converting the
    * rates to the appropriate unit.
    *
    * @param builder A Hadoop-Metrics2 record builder.
    * @param name A base name for this record.
    */
   private void addMeter(String name, Meter meter, MetricsRecordBuilder builder) {
     builder.addGauge(Interns.info(name + "_count", EMPTY_STRING), meter.getCount());
     builder.addGauge(Interns.info(name + "_mean_rate", EMPTY_STRING), meter.getMeanRate());
     builder.addGauge(Interns.info(name + "_1min_rate", EMPTY_STRING), meter.getOneMinuteRate());
     builder.addGauge(Interns.info(name + "_5min_rate", EMPTY_STRING), meter.getFiveMinuteRate());
     builder.addGauge(Interns.info(name + "_15min_rate", EMPTY_STRING),
         meter.getFifteenMinuteRate());
   }
 
   private void addTimer(String name, Timer timer, MetricsRecordBuilder builder) {
     addMeter(name, timer.getMeter(), builder);
     addHistogram(name, timer.getHistogram(), builder);
   }
 }