content: package com.airbnb.aerosolve.core.transforms;
  
  import com.airbnb.aerosolve.core.FeatureVector;
  import com.airbnb.aerosolve.core.util.Util;
  
  import com.typesafe.config.Config;
  
  import java.util.HashMap;
  import java.util.List;
  import java.util.Set;
  import java.util.HashSet;
  import java.util.Map;
  import java.util.Map.Entry;
  
  /**
   * output = field1 - field2.key
   */
  public class SubtractTransform implements Transform {
    private String fieldName1;
    private String fieldName2;
    private List<String> keys;
    private String key2;
    private String outputName;
  
    @Override
    public void configure(Config config, String key) {
      fieldName1 = config.getString(key + ".field1");
      fieldName2 = config.getString(key + ".field2");
      keys = config.getStringList(key + ".keys");
      key2 = config.getString(key + ".key2");
      outputName = config.getString(key + ".output");
    }
  
    @Override
    public void doTransform(FeatureVector featureVector) {
      Map<String, Map<String, Double>> floatFeatures = featureVector.getFloatFeatures();
  
      if (floatFeatures == null) {
        return;
      }
  
      Map<String, Double> feature1 = floatFeatures.get(fieldName1);
      if (feature1 == null) {
        return;
      }
  
      Map<String, Double> feature2 = floatFeatures.get(fieldName2);
      if (feature2 == null) {
        return;
      }
      Double sub = feature2.get(key2);
      if (sub == null) {
        return;
      }
  
      Map<String, Double> output = Util.getOrCreateFloatFeature(outputName, floatFeatures);
  
      for (String key : keys) {
        if (feature1.containsKey(key)) {
          Double val = feature1.get(key);
          if (val != null) {
            output.put(key + '-' + key2, val - sub);
          }
        }
      }
    }
  }
  