/*
 * This file is part of ELKI:
 * Environment for Developing KDD-Applications Supported by Index-Structures
 *
 * Copyright (C) 2022
 * ELKI Development Team
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 */
package elki.utilities.datastructures.histogram;

import java.util.Arrays;

/**
 * Histogram class storing double values.
 * <p>
 * The histogram will start with "bin" bins, but it can grow dynamically to the
 * left and right.
 * 
 * @author Erich Schubert
 * @since 0.5.5
 */
public class DoubleHistogram extends AbstractStaticHistogram {
  /**
   * Constructor.
   * 
   * @param bins Number of bins
   * @param min Cover minimum
   * @param max Cover maximum
   */
  public DoubleHistogram(int bins, double min, double max) {
    super(bins, min, max);
    data = bins >= 0 ? new double[bins] : null;
  }

  /**
   * Data store
   */
  double[] data;

  /**
   * Increment the value of a bin.
   * 
   * @param coord Coordinate
   * @param val Value
   */
  public void increment(double coord, double val) {
    int bin = getBinNr(coord);
    if(bin < 0) {
      if(size - bin > data.length) {
        // Reallocate.
        double[] tmpdata = new double[growSize(data.length, size - bin)];
        System.arraycopy(data, 0, tmpdata, -bin, size);
        data = tmpdata;
      }
      else {
        // Shift in place and clear head
        System.arraycopy(data, 0, data, -bin, size);
        Arrays.fill(data, 0, -bin, (double) 0);
      }
      data[0] = val;
      // Note that bin is negative, -bin is the shift offset!
      assert (data.length >= size - bin);
      offset -= bin;
      size -= bin;
      // TODO: modCounter++; and have iterators fast-fail
    }
    else if(bin >= data.length) {
      double[] tmpdata = new double[growSize(data.length, bin + 1)];
      System.arraycopy(data, 0, tmpdata, 0, size);
      tmpdata[bin] = val;
      data = tmpdata;
      size = bin + 1;
      // TODO: modCounter++; and have iterators fast-fail
      // Unset max value when resizing
      max = Double.MAX_VALUE;
    }
    else {
      if(bin >= size) {
        // TODO: reset bins to 0 first?
        size = bin + 1;
      }
      data[bin] += val;
    }
  }

  /**
   * Get the value at a particular position.
   * 
   * @param coord Coordinate
   * @return Value
   */
  public double get(double coord) {
    int bin = getBinNr(coord);
    return (bin < 0 || bin >= size) ? 0 : data[bin];
  }

  @Override
  public Iter iter() {
    return new Iter();
  }

  /**
   * Iterator class.
   * 
   * @author Erich Schubert
   */
  public class Iter extends AbstractStaticHistogram.Iter implements Histogram.Iter {
    /**
     * Get the value of the bin.
     * 
     * @return Bin value
     */
    public double getValue() {
      return data[bin];
    }

    @Override
    public Iter advance() {
      super.advance();
      return this;
    }

    @Override
    public Iter advance(int count) {
      super.advance(count);
      return this;
    }

    @Override
    public Iter retract() {
      super.retract();
      return this;
    }

    @Override
    public Iter seek(int off) {
      super.seek(off);
      return this;
    }
  }
}
