package de.lmu.ifi.dbs.elki.index.tree;

/*
 This file is part of ELKI:
 Environment for Developing KDD-Applications Supported by Index-Structures

 Copyright (C) 2015
 Ludwig-Maximilians-Universität München
 Lehr- und Forschungseinheit für Datenbanksysteme
 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/>.
 */

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

import de.lmu.ifi.dbs.elki.database.ids.DBID;
import de.lmu.ifi.dbs.elki.database.ids.DBIDUtil;

/**
 * Abstract superclass for entries in an tree based index structure.
 * 
 * @author Elke Achtert
 * @since 0.2
 */
public abstract class AbstractLeafEntry implements LeafEntry {
  /**
   * Holds the id of the object (node or data object) represented by this entry.
   */
  private DBID id;

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

  /**
   * Constructor.
   * 
   * @param id the id of the object (node or data object) represented by this
   *        entry.
   */
  protected AbstractLeafEntry(DBID id) {
    this.id = id;
  }

  @Override
  public final boolean isLeafEntry() {
    return true;
  }

  @Override
  public DBID getDBID() {
    return id;
  }

  /**
   * Writes the id of the object (node or data object) that is represented by
   * this entry to the specified stream.
   */
  @Override
  public void writeExternal(ObjectOutput out) throws IOException {
    out.writeInt(DBIDUtil.asInteger(id));
  }

  /**
   * Restores the id of the object (node or data object) that is represented by
   * this entry from the specified stream.
   * 
   * @throws ClassNotFoundException If the class for an object being restored
   *         cannot be found.
   */
  @Override
  public void readExternal(ObjectInput in) throws IOException, ClassNotFoundException {
    this.id = DBIDUtil.importInteger(in.readInt());
  }

  /**
   * Indicates whether some other object is "equal to" this one.
   * 
   * @param o the object to be tested
   * @return true, if o is an AbstractEntry and has the same id as this entry.
   */
  @Override
  public boolean equals(Object o) {
    if(this == o) {
      return true;
    }
    if(o == null || getClass() != o.getClass()) {
      return false;
    }

    final AbstractLeafEntry that = (AbstractLeafEntry) o;

    return id == that.id;
  }

  /**
   * Returns as hash code for the entry its id.
   * 
   * @return the id of the entry
   */
  @Override
  public int hashCode() {
    return id.hashCode();
  }

  /**
   * Returns the id as a string representation of this entry.
   * 
   * @return a string representation of this entry
   */
  @Override
  public String toString() {
    return "o_" + id;
  }
}