/*
    * 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.giraph.metrics;
  
  import com.google.common.collect.ImmutableMap;
  
  import java.util.concurrent.TimeUnit;
  
  /**
   * A timer to record duration of an event in a given TimeUnit.
   * GiraphTimer is actually just a single-value Yammer Gauge that has some
   * methods to make timing things easier.
   */
  public class GiraphTimer extends ValueGauge<Long> {
    /** Mapping from TimeUnit to abbreviation used for printing */
    private static final ImmutableMap<TimeUnit, String> TIME_UNIT_TO_ABBREV =
        ImmutableMap.<TimeUnit, String>builder().
            put(TimeUnit.DAYS, "days").
            put(TimeUnit.HOURS, "hours").
            put(TimeUnit.MICROSECONDS, "us").
            put(TimeUnit.MILLISECONDS, "ms").
            put(TimeUnit.MINUTES, "mins").
            put(TimeUnit.NANOSECONDS, "ns").
            put(TimeUnit.SECONDS, "secs").build();
  
    /** dimension to measure things by */
    private TimeUnit timeUnit;
  
    /**
     * Create new timer, add it to the registry.
     *
     * @param registry GiraphMetricsRegistry to add timer to
     * @param name String name of timer
     * @param timeUnit TimeUnit to measure in
     */
    public GiraphTimer(GiraphMetricsRegistry registry, String name,
                       TimeUnit timeUnit) {
      super(registry, name);
      this.timeUnit = timeUnit;
      set(0L);
    }
  
    /**
     * Get TimeUnit used.
     *
     * @return TimeUnit being used.
     */
    public TimeUnit getTimeUnit() {
      return timeUnit;
    }
  
    /**
     * Begin timing an event.
     *
     * @return GiraphTimerContext. Use stop() to end timing the event.
     */
    public GiraphTimerContext time() {
      return new GiraphTimerContext(this);
    }
  
    /**
     * Set value from a given TimeUnit, converting to our TimeUnit.
     *
     * @param value long measurement taken.
     * @param valueTimeUnit TimeUnit measurement is in.
     * @return this
     */
    public GiraphTimer set(long value, TimeUnit valueTimeUnit) {
      set(timeUnit.convert(value, valueTimeUnit));
      return this;
    }
  
    /**
     * Get abbreviated string of TimeUnit.
     *
     * @return TimeUnit abbreviation.
     */
    public String getTimeUnitAbbrev() {
      return TIME_UNIT_TO_ABBREV.get(timeUnit);
    }
  
    /**
     * Get string representation of value
    *
    * @return String value and abbreviated time unit
    */
   public String valueAndUnit() {
     return "" + value() + " " + getTimeUnitAbbrev();
   }
 }