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.solr.search.function;
  
  import org.apache.lucene.index.IndexReader;
  import org.apache.lucene.search.Searcher;
  
  import java.io.IOException;
  import java.util.Map;
  
  /**
   * Scales values to be between min and max.
   * <p>This implementation currently traverses all of the source values to obtain
   * their min and max.
   * <p>This implementation currently cannot distinguish when documents have been
   * deleted or documents that have no value, and 0.0 values will be used for
   * these cases.  This means that if values are normally all greater than 0.0, one can
   * still end up with 0.0 as the min value to map from.  In these cases, an
   * appropriate map() function could be used as a workaround to change 0.0
   * to a value in the real range.
   */
  public class ScaleFloatFunction extends ValueSource {
    protected final ValueSource source;
    protected final float min;
    protected final float max;
  
    public ScaleFloatFunction(ValueSource source, float min, float max) {
      this.source = source;
      this.min = min;
      this.max = max;
    }
  
    @Override
    public String description() {
      return "scale(" + source.description() + "," + min + "," + max + ")";
    }
  
    @Override
    public DocValues getValues(Map context, IndexReader reader) throws IOException {
      final DocValues vals =  source.getValues(context, reader);
      int maxDoc = reader.maxDoc();
  
      // this doesn't take into account deleted docs!
      float minVal=0.0f;
      float maxVal=0.0f;
  
      if (maxDoc>0) {
        minVal = maxVal = vals.floatVal(0);      
      }
  
      // Traverse the complete set of values to get the min and the max.
      // Future alternatives include being able to ask a DocValues for min/max
      // Another memory-intensive option is to cache the values in
      // a float[] on this first pass.
  
      for (int i=0; i<maxDoc; i++) {
        float val = vals.floatVal(i);
        if ((Float.floatToRawIntBits(val) & (0xff<<23)) == 0xff<<23) {
          // if the exponent in the float is all ones, then this is +Inf, -Inf or NaN
          // which don't make sense to factor into the scale function
          continue;
        }
        if (val < minVal) {
          minVal = val;
        } else if (val > maxVal) {
          maxVal = val;
        }
      }
  
      final float scale = (maxVal-minVal==0) ? 0 : (max-min)/(maxVal-minVal);
      final float minSource = minVal;
      final float maxSource = maxVal;
  
      return new DocValues() {
        @Override
        public float floatVal(int doc) {
  	return (vals.floatVal(doc) - minSource) * scale + min;
        }
        @Override
        public int intVal(int doc) {
          return (int)floatVal(doc);
        }
        @Override
        public long longVal(int doc) {
          return (long)floatVal(doc);
        }
        @Override
        public double doubleVal(int doc) {
          return (double)floatVal(doc);
        }
        @Override
        public String strVal(int doc) {
          return Float.toString(floatVal(doc));
        }
        @Override
        public String toString(int doc) {
  	return "scale(" + vals.toString(doc) + ",toMin=" + min + ",toMax=" + max
                  + ",fromMin=" + minSource
                  + ",fromMax=" + maxSource
                  + ")";
        }
      };
    }
  
    @Override
    public void createWeight(Map context, Searcher searcher) throws IOException {
      source.createWeight(context, searcher);
    }
  
    @Override
    public int hashCode() {
      int h = Float.floatToIntBits(min);
      h = h*29;
      h += Float.floatToIntBits(max);
      h = h*29;
      h += source.hashCode();
      return h;
    }
  
    @Override
    public boolean equals(Object o) {
      if (ScaleFloatFunction.class != o.getClass()) return false;
      ScaleFloatFunction other = (ScaleFloatFunction)o;
      return this.min == other.min
           && this.max == other.max
           && this.source.equals(other.source);
    }
  }
  