/* Yo Emacs, this -*- C++ -*-
 *******************************************************************
 *******************************************************************
 *
 *
 * KREVERSI
 *
 *
 *******************************************************************
 *
 * A Reversi (or sometimes called Othello) game
 *
 *******************************************************************
 *
 * Created 1997 by Mario Weilguni <mweilguni@sime.com>. This file 
 * is ported from Mats Luthman's <Mats.Luthman@sylog.se> JAVA applet. 
 * Many thanks to Mr. Luthman who has allowed me to put this port 
 * under the GNU GPL. Without his wonderful game engine kreversi 
 * would be just another of those Reversi programs a five year old 
 * child could beat easily. But with it it's a worthy opponent!
 *
 * If you are interested on the JAVA applet of Mr. Luthman take a
 * look at http://www.sylog.se/~mats/
 *
 *******************************************************************
 *
 * This file is part of the KDE project "KREVERSI"
 *
 * KREVERSI is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2, or (at your option)
 * any later version.
 *
 * KREVERSI 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with KREVERSI; see the file COPYING.  If not, write to
 * the Free Software Foundation, 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 *
 *******************************************************************
 */

// The class Engine produces moves from a Game object through calls to the
// function ComputeMove().
//
// First of all: this is meant to be a simple example of a game playing
// program. Not everything is done in the most clever way, particularly not
// the way the moves are searched, but it is hopefully made in a way that makes
// it easy to understand. The function ComputeMove2() that does all the work
// is actually not much more than a hundred lines. Much could be done to
// make the search faster though, I'm perfectly aware of that. Feel free
// to experiment.
//
// The method used to generate the moves is called minimax tree search with
// alpha-beta pruning to a fixed depth. In short this means that all possible
// moves a predefined number of moves ahead are either searched or refuted
// with a method called alpha-beta pruning. A more thorough explanation of
// this method could be found at the world wide web at http:
// //yoda.cis.temple.edu:8080/UGAIWWW/lectures96/search/minimax/alpha-beta.html
// at the time this was written. Searching for "minimax" would also point
// you to information on this subject. It is probably possible to understand
// this method by reading the source code though, it is not that complicated.
//
// At every leaf node at the search tree, the resulting position is evaluated.
// Two things are considered when evaluating a position: the number of pieces
// of each color and at which squares the pieces are located. Pieces at the
// corners are valuable and give a high value, and having pieces at squares
// next to a corner is not very good and they give a lower value. In the
// beginning of a game it is more important to have pieces on "good" squares,
// but towards the end the total number of pieces of each color is given a
// higher weight. Other things, like how many legal moves that can be made in a
// position, and the number of pieces that can never be turned would probably
// make the program stronger if they were considered in evaluating a position,
// but that would make things more complicated (this was meant to be very
// simple example) and would also slow down computation (considerably?).
//
// The member m_board[10][10]) holds the current position during the
// computation. It is initiated at the start of ComputeMove() and
// every move that is made during the search is made on this board. It should
// be noted that 1 to 8 is used for the actual board, but 0 and 9 can be
// used too (they are always empty). This is practical when turning pieces
// when moves are made on the board. Every piece that is put on the board
// or turned is saved in the stack m_squarestack (see class SquareStack) so
// every move can easily be reversed after the search in a node is completed.
//
// The member m_bc_board[][] holds board control values for each square
// and is initiated by a call to the function private void SetupBcBoard()
// from Engines constructor. It is used in evaluation of positions except
// when the game tree is searched all the way to the end of the game.
//
// The two members m_coord_bit[9][9] and m_neighbor_bits[9][9] are used to
// speed up the tree search. This goes against the principle of keeping things
// simple, but to understand the program you do not need to understand them
// at all. They are there to make it possible to throw away moves where
// the piece that is played is not adjacent to a piece of opposite color
// at an early stage (because they could never be legal). It should be
// pointed out that not all moves that pass this test are legal, there will
// just be fewer moves that have to be tested in a more time consuming way.
//
// There are also two other members that should be mentioned: Score m_score
// and Score m_bc_score. They hold the number of pieces of each color and
// the sum of the board control values for each color during the search
// (this is faster than counting at every leaf node).
//

// The classes SquareStackEntry and SquareStack implement a
// stack that is used by Engine to store pieces that are turned during
// searching (see ComputeMove()).
//
// The class MoveAndValue is used by Engine to store all possible moves
// at the first level and the values that were calculated for them.
// This makes it possible to select a random move among those with equal
// or nearly equal value after the search is completed.

#ifndef __ENGINE__H__
#define __ENGINE__H__

#include "misc.h"
#include "SuperEngine.h"
#include "Position.h"
#include "Game.h"
#include "Move.h"
#include "Score.h"
#include "qarray.h"
#include <sys/times.h>
#include "misc.h"
#include <qbitarray.h>

#if defined(__GNUC__)
#define ULONG64 unsigned long long int
#else
class ULONG64 : public QBitArray {
public:
  ULONG64();
  ULONG64( unsigned int );
  void shl();
};
#endif



class SquareStackEntry
{
public:
  SquareStackEntry();

  void setXY(int x, int y);

public:
  int m_x, m_y;
};


class SquareStack
{
public:
  SquareStack();
  SquareStack(int size);

  void resize(int size);
  void init(int size);
  SquareStackEntry Pop();
  void Push(int x, int y);

private:
  QArray<SquareStackEntry> m_squarestack;
  int m_top;
};


class MoveAndValue
{
public:
  MoveAndValue();
  MoveAndValue(int x, int y, int value);  
  void setXYV(int x, int y, int value);

public:  
  int m_x, m_y, m_value;
};


class Engine : public SuperEngine {
public:
  Engine(int st, int sd);
  Engine(int st);
  Engine();
  virtual ~Engine() {};

  Move ComputeMove(Game g);
  Move ComputeFirstMove(Game g);
  int ComputeMove2(int xplay, int yplay, int player, int level,
    int cutoffval, ULONG64 playerbits, ULONG64 opponentbits);

  int TryAllMoves(int opponent, int level, int cutoffval,
		  ULONG64 opponentbits, ULONG64 playerbits);

  int EvaluatePosition(int player);
  void SetupBcBoard();
  void SetupBits();
  int CalcBcScore(int player);
  ULONG64 ComputeOccupiedBits(int player);

  void yield();

private:
  static const int LARGEINT;
  static const int ILLEGAL_VALUE;
  static const int BC_WEIGHT;
  int  m_board[10][10];
  int  m_bc_board[9][9];
  Score m_score;
  Score m_bc_score;
  SquareStack m_squarestack;
  int  m_depth;
  int  m_coeff;
  int  m_nodes_searched;
  bool m_exhaustive;
  ULONG64 m_coord_bit[9][9];
  ULONG64 m_neighbor_bits[9][9];
  long lastYield;
};

#endif
