package de.lmu.ifi.dbs.elki.utilities.datastructures.heap;

/*
 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 de.lmu.ifi.dbs.elki.utilities.datastructures.iterator.Iter;

/**
 * Basic in-memory heap interface, for double keys and V values.
 * 
 * @author Erich Schubert
 * @since 0.5.5
 * 
 * @apiviz.has UnsortedIter
 * @param <V> Value type
 */
public interface DoubleObjectHeap<V> {
  /**
   * Add a key-value pair to the heap
   * 
   * @param key Key
   * @param val Value
   */
  void add(double key, V val);

  /**
   * Add a key-value pair to the heap if it improves the top.
   * 
   * @param key Key
   * @param val Value
   * @param k Desired maximum size
   */
  void add(double key, V val, int k);

  /**
   * Combined operation that removes the top element, and inserts a new element
   * instead.
   * 
   * @param key Key of new element
   * @param val Value of new element
   */
  void replaceTopElement(double key, V val);

  /**
   * Get the current top key
   * 
   * @return Top key
   */
  double peekKey();

  /**
   * Get the current top value
   * 
   * @return Value
   */
  V peekValue();

  /**
   * Remove the first element
   */
  void poll();

  /**
   * Clear the heap contents.
   */
  void clear();

  /**
   * Query the size
   * 
   * @return Size
   */
  public int size();
  
  /**
   * Is the heap empty?
   * 
   * @return {@code true} when the size is 0.
   */
  public boolean isEmpty();

  /**
   * Get an unsorted iterator to inspect the heap.
   * 
   * @return Iterator
   */
  UnsortedIter<V> unsortedIter();

  /**
   * Unsorted iterator - in heap order. Does not poll the heap.
   * 
   * @author Erich Schubert
 * @param <V> Value type
   */
  public static interface UnsortedIter<V> extends Iter {
    /**
     * Get the current key
     * 
     * @return Current key
     */
    double getKey();

    /**
     * Get the current value
     * 
     * @return Current value
     */
    V getValue();
  }
}
