#include "chess.h"
#include "data.h"
/* last modified 12/21/09 */
/*
 *******************************************************************************
 *                                                                             *
 *   Drawn() is used to answer the question "is this position a hopeless       *
 *   draw?"  Several considerations are included in making this decision, but  *
 *   the most basic one is simply the remaining material for each side.  If    *
 *   either side has pawns, it's not a draw.  With no pawns, equal material is *
 *   a draw.  Otherwise, the superior side must have enough material to be     *
 *   able to force a mate.                                                     *
 *                                                                             *
 *   Drawn() has 0 possible return values:                                     *
 *                                                                             *
 *   0:  Game is not a draw by rule or drawish in nature.                      *
 *                                                                             *
 *   1:  Game is a "technical draw" where material is even with no pawns and   *
 *       the search is also returning draw scores as the best outcome.         *
 *                                                                             *
 *   2:  Game is an "actual draw" by FIDE rules, such as KB vs K, where mate   *
 *       can't be forced, even with worst possible play by one side.           *
 *                                                                             *
 *******************************************************************************
 */
int Drawn(TREE * RESTRICT tree, int value) {
/*
 ************************************************************
 *                                                          *
 *  If either side has pawns, the game is not a draw for    *
 *  lack of material.                                       *
 *                                                          *
 ************************************************************
 */
  if (TotalPieces(white, pawn) || TotalPieces(black, pawn))
    return 0;
/*
 ************************************************************
 *                                                          *
 *  If the score suggests a mate has been found, this is    *
 *  not a draw.                                             *
 *                                                          *
 ************************************************************
 */
  if (MateScore(value))
    return 0;
/*
 ************************************************************
 *                                                          *
 *  If neither side has pawns, and one side has some sort   *
 *  of material superiority, then determine if the winning  *
 *  side has enough material to win.                        *
 *                                                          *
 ************************************************************
 */
  if (TotalPieces(white, occupied) + TotalPieces(black, occupied) < 4)
    return 2;
  if (TotalPieces(white, occupied) < 5 && TotalPieces(black, occupied) < 5)
    return 1;
  if (TotalPieces(white, occupied) == 5 || TotalPieces(white, occupied) > 6)
    return 0;
  if (TotalPieces(black, occupied) == 5 || TotalPieces(black, occupied) > 6)
    return 0;
  if ((TotalPieces(white, occupied) == 6 && !Bishops(white) && Material > 0)
      || (TotalPieces(black, occupied) == 6 && !Bishops(black)
          && Material < 0))
    return 1;
/*
 ************************************************************
 *                                                          *
 *  The search result must indicate a draw also, otherwise  *
 *  it could be a tactical win or loss, so we will skip     *
 *  calling an equal material (no pawns) position a draw to *
 *  make sure there is no mate that the search sees.        *
 *                                                          *
 *  If neither side has pawns, then one side must have some *
 *  sort of material superiority, otherwise it is a draw.   *
 *                                                          *
 ************************************************************
 */
  if (value != DrawScore(game_wtm))
    return 0;
  if (TotalPieces(white, occupied) == TotalPieces(black, occupied))
    return 1;
  return 0;
}