/*
 * 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.index.tree.spatial;

import java.io.IOException;
import java.io.ObjectInput;
import java.io.ObjectOutput;

import elki.data.ModifiableHyperBoundingBox;
import elki.data.spatial.SpatialComparable;
import elki.index.tree.DirectoryEntry;

/**
 * Represents an entry in a directory node of a spatial index.
 * 
 * A SpatialDirectoryEntry consists of an id (representing the unique id of the
 * underlying spatial node) and the minimum bounding rectangle of the underlying
 * spatial node.
 * 
 * @author Elke Achtert
 * @since 0.1
 */
public class SpatialDirectoryEntry implements DirectoryEntry, SpatialEntry {
  /**
   * Serialization version.
   */
  private static final long serialVersionUID = 2;

  /**
   * Holds the id of the object (node or data object) represented by this entry.
   */
  private int id;

  /**
   * The minimum bounding rectangle of the underlying spatial node.
   */
  private ModifiableHyperBoundingBox mbr;

  /**
   * Empty constructor for serialization purposes.
   */
  public SpatialDirectoryEntry() {
    // empty constructor
  }

  /**
   * Constructs a new SpatialDirectoryEntry object with the given parameters.
   * 
   * @param id the unique id of the underlying spatial node
   * @param mbr the minimum bounding rectangle of the underlying spatial node
   */
  public SpatialDirectoryEntry(int id, ModifiableHyperBoundingBox mbr) {
    super();
    this.id = id;
    this.mbr = mbr;
  }

  @Override
  public int getPageID() {
    return id;
  }

  @Override
  public int getDimensionality() {
    return mbr.getDimensionality();
  }

  /**
   * @return the coordinate at the specified dimension of the minimum hyper
   *         point of the MBR of the underlying node
   */
  @Override
  public double getMin(int dimension) {
    return mbr.getMin(dimension);
  }

  /**
   * @return the coordinate at the specified dimension of the maximum hyper
   *         point of the MBR of the underlying node
   */
  @Override
  public double getMax(int dimension) {
    return mbr.getMax(dimension);
  }

  /**
   * Test whether this entry already has an MBR.
   * 
   * @return True when an MBR exists.
   */
  public boolean hasMBR() {
    return (this.mbr != null);
  }

  /**
   * Sets the MBR of this entry.
   * 
   * @param mbr the MBR to be set
   */
  public void setMBR(ModifiableHyperBoundingBox mbr) {
    this.mbr = mbr;
  }

  /**
   * Calls the super method and writes the MBR object of this entry to the
   * specified output stream.
   * 
   * @param out the stream to write the object to
   * @throws java.io.IOException Includes any I/O exceptions that may occur
   */
  @Override
  public void writeExternal(ObjectOutput out) throws IOException {
    out.writeInt(id);
    mbr.writeExternal(out);
  }

  /**
   * Calls the super method and reads the MBR object of this entry from the
   * specified input stream.
   * 
   * @param in the stream to read data from in order to restore the object
   * @throws java.io.IOException if I/O errors occur
   * @throws ClassNotFoundException If the class for an object being restored
   *         cannot be found.
   */
  @Override
  public void readExternal(ObjectInput in) throws IOException, ClassNotFoundException {
    this.id = in.readInt();
    this.mbr = new ModifiableHyperBoundingBox();
    this.mbr.readExternal(in);
  }

  /**
   * Extend the MBR of this node.
   * 
   * @param responsibleMBR
   * @return true when the MBR changed
   */
  public boolean extendMBR(SpatialComparable responsibleMBR) {
    return this.mbr.extend(responsibleMBR);
  }

  @Override
  public String toString() {
    return "SpatialDirectoryEntry(" + id + " mbr=" + (mbr != null ? mbr.toString() : null) + ")";
  }

  @Override
  public boolean equals(Object o) {
    // Note: we deliberately use the ID only for comparison.
    return this == o || (o != null && getClass() == o.getClass() && id == ((SpatialDirectoryEntry) o).id);
  }

  @Override
  public int hashCode() {
    return id;
  }
}
