content: /**
   * 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.bigtop.datagenerators.weatherman.internal;
  
  import org.apache.bigtop.datagenerators.samplers.SeedFactory;
  import org.apache.bigtop.datagenerators.samplers.samplers.ConditionalSampler;
  import org.apache.bigtop.datagenerators.samplers.samplers.ExponentialSampler;
  import org.apache.bigtop.datagenerators.samplers.samplers.Sampler;
  
  public class PrecipitationSampler implements
          ConditionalSampler<WeatherRecordBuilder, WeatherRecordBuilder> {
    private final Sampler<Double> precipitationSampler;
  
    public PrecipitationSampler(double averagePrecipitation,
            SeedFactory seedFactory) {
      precipitationSampler = new ExponentialSampler(1.0 / averagePrecipitation,
              seedFactory);
    }
  
    public WeatherRecordBuilder sample(WeatherRecordBuilder record)
            throws Exception {
      double temp = record.getTemperature();
      double precipitation = precipitationSampler.sample();
      record.setPrecipitation(precipitation);
  
      double fractionRain = 1.0
              / (1.0 + Math.exp(-WeatherConstants.PRECIPITATION_A
                      * (temp - WeatherConstants.PRECIPITATION_B)));
  
      double rainfall = fractionRain * precipitation;
      double snowfall = WeatherConstants.PRECIPITATION_TO_SNOWFALL
              * (1.0 - fractionRain) * precipitation;
      record.setRainFall(rainfall);
      record.setSnowFall(snowfall);
  
      return record;
    }
  }
  