package org.djutils.stats.summarizers.quantileaccumulator;
   
   import org.djutils.exceptions.Throw;
   import org.djutils.stats.summarizers.Tally;
   
   import com.tdunning.math.stats.TDigest;
   
   /**
    * TDigestAccumulator.java. <br>
   * <br>
   * Copyright (c) 2020-2022 Delft University of Technology, Jaffalaan 5, 2628 BX Delft, the Netherlands. All rights reserved. See
   * for project information <a href="https://djutils.org" target="_blank"> https://djutils.org</a>. The DJUTILS project is
   * distributed under a three-clause BSD-style license, which can be found at
   * <a href="https://djutils.org/docs/license.html" target="_blank"> https://djutils.org/docs/license.html</a>. <br>
   * @author <a href="https://www.tudelft.nl/averbraeck">Alexander Verbraeck</a>
   * @author <a href="https://www.tudelft.nl/pknoppers">Peter Knoppers</a>
   */
  public class TDigestAccumulator implements QuantileAccumulator
  {
      /** The TDigest that accumulates the ingested data into bins. */
      private TDigest tDigest;
  
      /** The compression used to create the TDigest (required to re-initialize). */
      private final int compression;
  
      /** The compression used by the parameter-less constructor. */
      public static final int DEFAULT_COMPRESSION = 100;
  
      /**
       * Construct a new TDigestAccumulator.
       * @param compression int; the number of bins to compress the data into
       */
      public TDigestAccumulator(final int compression)
      {
          this.compression = compression;
          initialize();
      }
  
      /**
       * Construct a new TDigestAccumulator with compression set to <code>DEFAULT_COMPRESSION</code>.
       */
      public TDigestAccumulator()
      {
          this(DEFAULT_COMPRESSION);
      }
  
      /** {@inheritDoc} */
      @Override
      public double register(final double value)
      {
          Throw.when(Double.isNaN(value), IllegalArgumentException.class, "accumulator can not accumlate NaN value");
          this.tDigest.add(value);
          return value;
      }
  
      /** {@inheritDoc} */
      @Override
      public double getQuantile(final Tally tally, final double probability)
      {
          Throw.whenNull(tally, "tally cannot be null");
          Throw.when(probability < 0 || probability > 1, IllegalArgumentException.class,
                  "probability should be between 0 and 1 (inclusive)");
          return this.tDigest.quantile(probability);
      }
  
      /** {@inheritDoc} */
      @Override
      public double getCumulativeProbability(final Tally tally, final double quantile)
      {
          return this.tDigest.cdf(quantile);
      }
  
      /** {@inheritDoc} */
      @Override
      public void initialize()
      {
          this.tDigest = TDigest.createDigest(this.compression);
      }
  
      /** {@inheritDoc} */
      @Override
      public final String toString()
      {
          return "TDigestAccumulator [tDigest=" + this.tDigest + ", compression=" + this.compression + "]";
      }
  
  }