/* movecheck.c
 *
 */

/*
    fics - An internet chess server.
    Copyright (C) 1993  Richard V. Nash

    This program 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 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 General Public License for more details.
*/

/* Revision history:
   name		email		yy/mm/dd	Change
   Richard Nash                 93/10/22	Created
   Markus Uhlin                 23/12/14	Fixed compiler warnings
   Markus Uhlin                 23/12/17	Fixed compiler warnings
*/

#include "stdinclude.h"

#include "algcheck.h"
#include "board.h"
#include "common.h"
#include "gamedb.h"
#include "movecheck.h"
#include "network.h"
#include "playerdb.h"
#include "utils.h"

/* Simply tests if the input string is a move or not. */
/* If it matches patterns below */
/* Add to this list as you improve the move parser */
/* MS_COMP e2e4 */
/* MS_COMPDASH e2-e4 */
/* MS_CASTLE o-o, o-o-o */
/* Not done yet */
/* MS_ALG e4, Nd5 Ncd5 */
PUBLIC int is_move(char *mstr)
{
  int len = strlen(mstr);
  if ((len > 3) && (mstr[len - 2] == '='))
    len -= 2;

  if (len == 4) {		/* Test for e2e4 */
    if (isfile(mstr[0]) && isrank(mstr[1]) &&
	isfile(mstr[2]) && isrank(mstr[3])) {
      return MS_COMP;
    }
  }
  if (len == 5) {		/* Test for e2-e4 */
    if (isfile(mstr[0]) && isrank(mstr[1]) &&
	(mstr[2] == '-') &&
	isfile(mstr[3]) && isrank(mstr[4])) {
      return MS_COMPDASH;
    }
  }
  if (len == 3) {		/* Test for o-o */
    if ((mstr[0] == 'o') && (mstr[1] == '-') && (mstr[2] == 'o')) {
      return MS_KCASTLE;
    }
    if ((mstr[0] == 'O') && (mstr[1] == '-') && (mstr[2] == 'O')) {
      return MS_KCASTLE;
    }
    if ((mstr[0] == '0') && (mstr[1] == '-') && (mstr[2] == '0')) {
      return MS_KCASTLE;
    }
  }
  if (len == 2) {		/* Test for oo */
    if ((mstr[0] == 'o') && (mstr[1] == 'o')) {
      return MS_KCASTLE;
    }
    if ((mstr[0] == 'O') && (mstr[1] == 'O')) {
      return MS_KCASTLE;
    }
    if ((mstr[0] == '0') && (mstr[1] == '0')) {
      return MS_KCASTLE;
    }
  }
  if (len == 5) {		/* Test for o-o-o */
    if ((mstr[0] == 'o') && (mstr[1] == '-') && (mstr[2] == 'o') && (mstr[3] == '-') && (mstr[4] == 'o')) {
      return MS_QCASTLE;
    }
    if ((mstr[0] == 'O') && (mstr[1] == '-') && (mstr[2] == 'O') && (mstr[3] == '-') && (mstr[4] == 'O')) {
      return MS_QCASTLE;
    }
    if ((mstr[0] == '0') && (mstr[1] == '-') && (mstr[2] == '0') && (mstr[3] == '-') && (mstr[4] == '0')) {
      return MS_QCASTLE;
    }
  }
  if (len == 3) {		/* Test for ooo */
    if ((mstr[0] == 'o') && (mstr[1] == 'o') && (mstr[2] == 'o')) {
      return MS_QCASTLE;
    }
    if ((mstr[0] == 'O') && (mstr[1] == 'O') && (mstr[2] == 'O')) {
      return MS_QCASTLE;
    }
    if ((mstr[0] == '0') && (mstr[1] == '0') && (mstr[2] == '0')) {
      return MS_QCASTLE;
    }
  }
  return alg_is_move(mstr);
}


PUBLIC int NextPieceLoop(board_t b, int *f, int *r, int color)
{
  while (1) {
    (*r) = (*r) + 1;
    if (*r > 7) {
      *r = 0;
      *f = *f + 1;
      if (*f > 7)
	break;
    }
    if ((b[*f][*r] != NOPIECE) && iscolor(b[*f][*r], color))
      return 1;
  }
  return 0;
}

PUBLIC int InitPieceLoop(board_t b, int *f, int *r, int color)
{
  *f = 0;
  *r = -1;
  return 1;
}

/* All of the routines assume that the obvious problems have been checked */
/* See legal_move() */
PRIVATE int legal_pawn_move( game_state_t *gs, int ff, int fr, int tf, int tr )
{
  if (ff == tf) {
    if (gs->board[tf][tr] != NOPIECE) return 0;
    if (gs->onMove == WHITE) {
      if (tr - fr == 1) return 1;
      if ((fr == 1) && (tr - fr == 2) && gs->board[ff][2]==NOPIECE) return 1;
    } else {
      if (fr - tr == 1) return 1;
      if ((fr == 6) && (fr - tr == 2) && gs->board[ff][5]==NOPIECE) return 1;
    }
    return 0;
  }
  if (ff != tf) { /* Capture ? */
    if ((ff - tf != 1) && (tf - ff != 1)) return 0;
    if ((fr - tr != 1) && (tr - fr != 1)) return 0;
    if (gs->onMove == WHITE) {
      if (fr > tr) return 0;
      if ((gs->board[tf][tr] != NOPIECE) && iscolor(gs->board[tf][tr],BLACK))
        return 1;
      if (gs->ep_possible[0][ff] == 1) {
        if ((tf==ff+1) && (gs->board[ff+1][fr] == B_PAWN)) return 1;
      } else if (gs->ep_possible[0][ff] == -1) {
        if ((tf==ff-1) && (gs->board[ff-1][fr] == B_PAWN)) return 1;
      }
    } else {
      if (tr > fr) return 0;
      if ((gs->board[tf][tr] != NOPIECE) && iscolor(gs->board[tf][tr],WHITE))
        return 1;
      if (gs->ep_possible[1][ff] == 1) {
        if ((tf==ff+1) && (gs->board[ff+1][fr] == W_PAWN)) return 1;
      } else if (gs->ep_possible[1][ff] == -1) {
        if ((tf==ff-1) && (gs->board[ff-1][fr] == W_PAWN)) return 1;
      }
    }
  }
  return 0;
}

PRIVATE int legal_knight_move(game_state_t * gs, int ff, int fr, int tf, int tr)
{
  int dx, dy;

  dx = ff - tf;
  dy = fr - tr;
  if ((dx == 2) || (dx == -2)) {
    if ((dy == -1) || (dy == 1))
      return 1;
  }
  if ((dy == 2) || (dy == -2)) {
    if ((dx == -1) || (dx == 1))
      return 1;
  }
  return 0;
}

PRIVATE int legal_bishop_move(game_state_t * gs, int ff, int fr, int tf, int tr)
{
  int dx, dy, x, y;
  int startx, starty;
  int count;
  int incx, incy;

  if (ff > tf) {
    dx = ff - tf;
    incx = -1;
  } else {
    dx = tf - ff;
    incx = 1;
  }
  startx = ff + incx;
  if (fr > tr) {
    dy = fr - tr;
    incy = -1;
  } else {
    dy = tr - fr;
    incy = 1;
  }
  starty = fr + incy;
  if (dx != dy)
    return 0;			/* Not diagonal */
  if (dx == 1)
    return 1;			/* One square, ok */
  count = dx - 1;
  for (x = startx, y = starty; count; x += incx, y += incy, count--) {
    if (gs->board[x][y] != NOPIECE)
      return 0;
  }
  return 1;
}

PRIVATE int legal_rook_move(game_state_t * gs, int ff, int fr, int tf, int tr)
{
  int i;
  int start, stop;

  if (ff == tf) {
    if (((fr - tr) == 1) || ((tr - fr) == 1))
      return 1;
    if (fr < tr) {
      start = fr + 1;
      stop = tr - 1;
    } else {
      start = tr + 1;
      stop = fr - 1;
    }
    for (i = start; i <= stop; i++) {
      if (gs->board[ff][i] != NOPIECE)
	return 0;
    }
    return 1;
  } else if (fr == tr) {
    if (((ff - tf) == 1) || ((tf - ff) == 1))
      return 1;
    if (ff < tf) {
      start = ff + 1;
      stop = tf - 1;
    } else {
      start = tf + 1;
      stop = ff - 1;
    }
    for (i = start; i <= stop; i++) {
      if (gs->board[i][fr] != NOPIECE)
	return 0;
    }
    return 1;
  } else {
    return 0;
  }
}

PRIVATE int legal_queen_move(game_state_t * gs, int ff, int fr, int tf, int tr)
{
  return legal_rook_move(gs, ff, fr, tf, tr) || legal_bishop_move(gs, ff, fr, tf, tr);
}

/* Ckeck, if square (kf,kr) is attacked by enemy piece.
 * Used in castling from/through check testing.
 */

/* new one from soso: */
PRIVATE int is_square_attacked (game_state_t *gs, int kf, int kr)
{
  game_state_t fakeMove;

  fakeMove = *gs;
  fakeMove.board[4][kr] = NOPIECE;
  fakeMove.board[kf][kr] = KING | fakeMove.onMove;
  fakeMove.onMove = CToggle (fakeMove.onMove);
  if (in_check(&fakeMove)) return 1;
    else return 0;
}

/* old one:
PRIVATE int is_square_attacked(game_state_t * gs, int kf, int kr)
{
  int f, r;
  gs->onMove = CToggle(gs->onMove);

  for (InitPieceLoop(gs->board, &f, &r, gs->onMove);
       NextPieceLoop(gs->board, &f, &r, gs->onMove);) {
    if (legal_move(gs, f, r, kf, kr)) {
      gs->onMove = CToggle(gs->onMove);
      return 1;
    }
  }
  gs->onMove = CToggle(gs->onMove);
  return 0;
}
*/

PRIVATE int legal_king_move(game_state_t * gs, int ff, int fr, int tf, int tr)
{
  if (gs->onMove == WHITE) {
    /* King side castling */
    if ((fr == 0) && (tr == 0) && (ff == 4) && (tf == 6) && !gs->wkmoved
	&& (!gs->wkrmoved) && (gs->board[5][0] == NOPIECE) &&
	(gs->board[6][0] == NOPIECE) && (gs->board[7][0] == W_ROOK) &&
	(!is_square_attacked(gs, 4, 0)) && (!is_square_attacked(gs, 5, 0))) {
      return 1;
    }
    /* Queen side castling */
    if ((fr == 0) && (tr == 0) && (ff == 4) && (tf == 2) && !gs->wkmoved
	&& (!gs->wqrmoved) && (gs->board[3][0] == NOPIECE) &&
	(gs->board[2][0] == NOPIECE) && (gs->board[1][0] == NOPIECE) &&
	(gs->board[0][0] == W_ROOK) &&
	(!is_square_attacked(gs, 4, 0)) && (!is_square_attacked(gs, 3, 0))) {
      return 1;
    }
  } else {			/* Black */
    /* King side castling */
    if ((fr == 7) && (tr == 7) && (ff == 4) && (tf == 6) && !gs->bkmoved
	&& (!gs->bkrmoved) && (gs->board[5][7] == NOPIECE) &&
	(gs->board[6][7] == NOPIECE) && (gs->board[7][7] == B_ROOK) &&
	(!is_square_attacked(gs, 4, 7)) && (!is_square_attacked(gs, 5, 7))) {
      return 1;
    }
    /* Queen side castling */
    if ((fr == 7) && (tr == 7) && (ff == 4) && (tf == 2) && (!gs->bkmoved)
	&& (!gs->bqrmoved) && (gs->board[3][7] == NOPIECE) &&
	(gs->board[2][7] == NOPIECE) && (gs->board[1][7] == NOPIECE) &&
	(gs->board[0][7] == B_ROOK) &&
	(!is_square_attacked(gs, 4, 7)) && (!is_square_attacked(gs, 3, 7))) {
      return 1;
    }
  }
  if (((ff - tf) > 1) || ((tf - ff) > 1))
    return 0;
  if (((fr - tr) > 1) || ((tr - fr) > 1))
    return 0;
  return 1;
}

PRIVATE void add_pos(int tof, int tor, int *posf, int *posr, int *numpos)
{
  posf[*numpos] = tof;
  posr[*numpos] = tor;
  (*numpos)++;
}

PRIVATE void possible_pawn_moves(game_state_t * gs,
				  int onf, int onr,
				  int *posf, int *posr, int *numpos)
{
  if (gs->onMove == WHITE) {
    if (gs->board[onf][onr + 1] == NOPIECE) {
      add_pos(onf, onr + 1, posf, posr, numpos);
      if ((onr == 1) && (gs->board[onf][onr + 2] == NOPIECE))
	add_pos(onf, onr + 2, posf, posr, numpos);
    }
    if ((onf > 0) && (gs->board[onf - 1][onr + 1] != NOPIECE) &&
	(iscolor(gs->board[onf - 1][onr + 1], BLACK)))
      add_pos(onf - 1, onr + 1, posf, posr, numpos);
    if ((onf < 7) && (gs->board[onf + 1][onr + 1] != NOPIECE) &&
	(iscolor(gs->board[onf + 1][onr + 1], BLACK)))
      add_pos(onf + 1, onr + 1, posf, posr, numpos);
    if (gs->ep_possible[0][onf] == -1)
      add_pos(onf - 1, onr + 1, posf, posr, numpos);
    if (gs->ep_possible[0][onf] == 1)
      add_pos(onf + 1, onr + 1, posf, posr, numpos);
  } else {
    if (gs->board[onf][onr - 1] == NOPIECE) {
      add_pos(onf, onr - 1, posf, posr, numpos);
      if ((onr == 6) && (gs->board[onf][onr - 2] == NOPIECE))
	add_pos(onf, onr - 2, posf, posr, numpos);
    }
    if ((onf > 0) && (gs->board[onf - 1][onr - 1] != NOPIECE) &&
	(iscolor(gs->board[onf - 1][onr - 1], WHITE)))
      add_pos(onf - 1, onr - 1, posf, posr, numpos);
/* loon: changed what looks like a typo, here's the original line:
      add_pos(onf - 1, onr + 1, posf, posr, numpos);
*/
    if ((onf < 7) && (gs->board[onf + 1][onr - 1] != NOPIECE) &&
	(iscolor(gs->board[onf + 1][onr - 1], WHITE)))
      add_pos(onf + 1, onr - 1, posf, posr, numpos);
    if (gs->ep_possible[1][onf] == -1)
      add_pos(onf - 1, onr - 1, posf, posr, numpos);
    if (gs->ep_possible[1][onf] == 1)
      add_pos(onf + 1, onr - 1, posf, posr, numpos);
  }
}

PRIVATE void possible_knight_moves(game_state_t * gs,
				    int onf, int onr,
				    int *posf, int *posr, int *numpos)
{
  static int knightJumps[8][2] = {{-1, 2}, {1, 2}, {2, -1}, {2, 1},
  {-1, -2}, {1, -2}, {-2, 1}, {-2, -1}};
  int f, r;
  int j;

  for (j = 0; j < 8; j++) {
    f = knightJumps[j][0] + onf;
    r = knightJumps[j][1] + onr;
    if ((f < 0) || (f > 7))
      continue;
    if ((r < 0) || (r > 7))
      continue;
    if ((gs->board[f][r] == NOPIECE) ||
	(iscolor(gs->board[f][r], CToggle(gs->onMove))))
      add_pos(f, r, posf, posr, numpos);
  }
}

PRIVATE void possible_bishop_moves(game_state_t * gs,
				    int onf, int onr,
				    int *posf, int *posr, int *numpos)
{
  int f, r;

  /* Up Left */
  f = onf;
  r = onr;
  while (1) {
    f--;
    r++;
    if ((f < 0) || (f > 7))
      break;
    if ((r < 0) || (r > 7))
      break;
    if ((gs->board[f][r] != NOPIECE) && (iscolor(gs->board[f][r], gs->onMove)))
      break;
    add_pos(f, r, posf, posr, numpos);
    if (gs->board[f][r] != NOPIECE)
      break;
  }
  /* Up Right */
  f = onf;
  r = onr;
  while (1) {
    f++;
    r++;
    if ((f < 0) || (f > 7))
      break;
    if ((r < 0) || (r > 7))
      break;
    if ((gs->board[f][r] != NOPIECE) && (iscolor(gs->board[f][r], gs->onMove)))
      break;
    add_pos(f, r, posf, posr, numpos);
    if (gs->board[f][r] != NOPIECE)
      break;
  }
  /* Down Left */
  f = onf;
  r = onr;
  while (1) {
    f--;
    r--;
    if ((f < 0) || (f > 7))
      break;
    if ((r < 0) || (r > 7))
      break;
    if ((gs->board[f][r] != NOPIECE) && (iscolor(gs->board[f][r], gs->onMove)))
      break;
    add_pos(f, r, posf, posr, numpos);
    if (gs->board[f][r] != NOPIECE)
      break;
  }
  /* Down Right */
  f = onf;
  r = onr;
  while (1) {
    f++;
    r--;
    if ((f < 0) || (f > 7))
      break;
    if ((r < 0) || (r > 7))
      break;
    if ((gs->board[f][r] != NOPIECE) && (iscolor(gs->board[f][r], gs->onMove)))
      break;
    add_pos(f, r, posf, posr, numpos);
    if (gs->board[f][r] != NOPIECE)
      break;
  }
}

PRIVATE void possible_rook_moves(game_state_t * gs,
				  int onf, int onr,
				  int *posf, int *posr, int *numpos)
{
  int f, r;

  /* Left */
  f = onf;
  r = onr;
  while (1) {
    f--;
    if ((f < 0) || (f > 7))
      break;
    if ((r < 0) || (r > 7))
      break;
    if ((gs->board[f][r] != NOPIECE) && (iscolor(gs->board[f][r], gs->onMove)))
      break;
    add_pos(f, r, posf, posr, numpos);
    if (gs->board[f][r] != NOPIECE)
      break;
  }
  /* Right */
  f = onf;
  r = onr;
  while (1) {
    f++;
    if ((f < 0) || (f > 7))
      break;
    if ((r < 0) || (r > 7))
      break;
    if ((gs->board[f][r] != NOPIECE) && (iscolor(gs->board[f][r], gs->onMove)))
      break;
    add_pos(f, r, posf, posr, numpos);
    if (gs->board[f][r] != NOPIECE)
      break;
  }
  /* Up */
  f = onf;
  r = onr;
  while (1) {
    r++;
    if ((f < 0) || (f > 7))
      break;
    if ((r < 0) || (r > 7))
      break;
    if ((gs->board[f][r] != NOPIECE) && (iscolor(gs->board[f][r], gs->onMove)))
      break;
    add_pos(f, r, posf, posr, numpos);
    if (gs->board[f][r] != NOPIECE)
      break;
  }
  /* Down */
  f = onf;
  r = onr;
  while (1) {
    r--;
    if ((f < 0) || (f > 7))
      break;
    if ((r < 0) || (r > 7))
      break;
    if ((gs->board[f][r] != NOPIECE) && (iscolor(gs->board[f][r], gs->onMove)))
      break;
    add_pos(f, r, posf, posr, numpos);
    if (gs->board[f][r] != NOPIECE)
      break;
  }
}

PRIVATE void possible_queen_moves(game_state_t * gs,
				   int onf, int onr,
				   int *posf, int *posr, int *numpos)
{
  possible_rook_moves(gs, onf, onr, posf, posr, numpos);
  possible_bishop_moves(gs, onf, onr, posf, posr, numpos);
}

PRIVATE void possible_king_moves(game_state_t * gs,
				  int onf, int onr,
				  int *posf, int *posr, int *numpos)
{
  static int kingJumps[8][2] = {{-1, -1}, {0, -1}, {1, -1}, {-1, 1},
  {0, 1}, {1, 1}, {-1, 0}, {1, 0}};
  int f, r;
  int j;

  for (j = 0; j < 8; j++) {
    f = kingJumps[j][0] + onf;
    r = kingJumps[j][1] + onr;
    if ((f < 0) || (f > 7))
      continue;
    if ((r < 0) || (r > 7))
      continue;
    if ((gs->board[f][r] == NOPIECE) ||
	(iscolor(gs->board[f][r], CToggle(gs->onMove))))
      add_pos(f, r, posf, posr, numpos);
  }
}

/* Doesn't check for check */
PUBLIC int legal_move(game_state_t * gs,
		       int fFile, int fRank,
		       int tFile, int tRank)
{
  int move_piece;
  int legal;

  if (fFile == ALG_DROP) {
    move_piece = fRank;
    if (move_piece == KING)
      return 0;
    if (gs->holding[gs->onMove==WHITE ? 0 : 1][move_piece-1] == 0)
      return 0;
    if (gs->board[tFile][tRank] != NOPIECE)
      return 0;
    if (move_piece == PAWN && (tRank == 0 || tRank == 7))
      return 0;
    return 1;
  } else {
    move_piece = piecetype(gs->board[fFile][fRank]);
  }
  if (gs->board[fFile][fRank] == NOPIECE)
    return 0;
  if (!iscolor(gs->board[fFile][fRank], gs->onMove))	/* Wrong color */
    return 0;
  if ((gs->board[tFile][tRank] != NOPIECE) &&
      iscolor(gs->board[tFile][tRank], gs->onMove))	/* Can't capture own */
    return 0;
  if ((fFile == tFile) && (fRank == tRank))	/* Same square */
    return 0;
  switch (move_piece) {
  case PAWN:
    legal = legal_pawn_move(gs, fFile, fRank, tFile, tRank);
    break;
  case KNIGHT:
    legal = legal_knight_move(gs, fFile, fRank, tFile, tRank);
    break;
  case BISHOP:
    legal = legal_bishop_move(gs, fFile, fRank, tFile, tRank);
    break;
  case ROOK:
    legal = legal_rook_move(gs, fFile, fRank, tFile, tRank);
    break;
  case QUEEN:
    legal = legal_queen_move(gs, fFile, fRank, tFile, tRank);
    break;
  case KING:
    legal = legal_king_move(gs, fFile, fRank, tFile, tRank);
    break;
  default:
    return 0;
    break;
  }
  return legal;
}


/*
 * This fills in the rest of the mt structure once it is determined
 * that. (Returns 'MOVE_ILLEGAL' if move leaves you in check.)
 */
PRIVATE int
move_calculate(game_state_t *gs, move_t *mt, int promote)
{
	game_state_t	fakeMove;
	int		ret, too_long;

	mt->pieceCaptured	= gs->board[mt->toFile][mt->toRank];
	mt->enPassant		= 0;	// Don't know yet,
					// let execute move take care of it

	if (mt->fromFile == ALG_DROP) {
		mt->piecePromotionTo = NOPIECE;
		ret = snprintf(mt->moveString, sizeof mt->moveString,
		    "%s/%c%c-%c%d",
		    wpstring[mt->fromRank],
		    DROP_CHAR,
		    DROP_CHAR,
		    (mt->toFile + 'a'),
		    (mt->toRank + 1));

		too_long = (ret < 0 || (size_t)ret >= sizeof mt->moveString);

		if (too_long) { /* XXX */
			fprintf(stderr, "FICS: %s: warning: "
			    "snprintf truncated\n", __func__);
		}
	} else {
		if (piecetype(gs->board[mt->fromFile][mt->fromRank]) == PAWN &&
		    (mt->toRank == 0 || mt->toRank == 7)) {
			mt->piecePromotionTo = (promote |
			    colorval(gs->board[mt->fromFile][mt->fromRank]));
		} else {
			mt->piecePromotionTo = NOPIECE;
		}

		if (piecetype(gs->board[mt->fromFile][mt->fromRank]) == PAWN &&
		    (mt->fromRank - mt->toRank == 2 ||
		    mt->toRank - mt->fromRank == 2)) {
			mt->doublePawn = mt->fromFile;
		} else {
			mt->doublePawn = -1;
		}

		if (piecetype(gs->board[mt->fromFile][mt->fromRank]) == KING &&
		    mt->fromFile == 4 &&
		    mt->toFile == 2) {
			sprintf(mt->moveString, "o-o-o");
		} else if (piecetype(gs->board[mt->fromFile][mt->fromRank]) == KING &&
		    mt->fromFile == 4 &&
		    mt->toFile == 6) {
			sprintf(mt->moveString, "o-o");
		} else {
			ret = snprintf(mt->moveString, sizeof mt->moveString,
			    "%s/%c%d-%c%d",
			    wpstring[piecetype(gs->board[mt->fromFile][mt->fromRank])],
			    (mt->fromFile + 'a'),
			    (mt->fromRank + 1),
			    (mt->toFile + 'a'),
			    (mt->toRank + 1));

			too_long = (ret < 0 || (size_t)ret >= sizeof mt->moveString);

			if (too_long) { /* XXX */
				fprintf(stderr, "FICS: %s: warning: "
				    "snprintf truncated\n", __func__);
			}
		}
	}

	// Replace this with an algabraic de-parser
	snprintf(mt->algString, sizeof mt->algString, "%s",
	    alg_unparse(gs, mt));
	fakeMove = *gs;
	execute_move(&fakeMove, mt, 0); // Calculates enPassant also

	// Does making this move leave ME in check?
	if (in_check(&fakeMove))
		return MOVE_ILLEGAL;
	// IanO: bughouse variants: drop cannot be check/checkmate

	return MOVE_OK;
}

PUBLIC int legal_andcheck_move(game_state_t * gs,
			        int fFile, int fRank,
			        int tFile, int tRank)
{
  move_t mt;
  if (!legal_move(gs, fFile, fRank, tFile, tRank))
    return 0;
  mt.color = gs->onMove;
  mt.fromFile = fFile;
  mt.fromRank = fRank;
  mt.toFile = tFile;
  mt.toRank = tRank;
  /* This should take into account a pawn promoting to another piece */
  if (move_calculate(gs, &mt, QUEEN) == MOVE_OK)
    return 1;
  else
    return 0;
}

PUBLIC int in_check(game_state_t * gs)
{
  int f, r;
  int kf = -1, kr = -1;

  /* Find the king */
  if (gs->onMove == WHITE) {
    for (f = 0; f < 8 && kf < 0; f++)
      for (r = 0; r < 8 && kf < 0; r++)
	if (gs->board[f][r] == B_KING) {
	  kf = f;
	  kr = r;
	}
  } else {
    for (f = 0; f < 8 && kf < 0; f++)
      for (r = 0; r < 8 && kf < 0; r++)
	if (gs->board[f][r] == W_KING) {
	  kf = f;
	  kr = r;
	}
  }
  if (kf < 0) {
    fprintf(stderr, "FICS: Error game with no king!\n");
    return 0;
  }
  for (InitPieceLoop(gs->board, &f, &r, gs->onMove);
       NextPieceLoop(gs->board, &f, &r, gs->onMove);) {
    if (legal_move(gs, f, r, kf, kr)) {	/* In Check? */
      return 1;
    }
  }
  return 0;
}

PRIVATE int
has_legal_move(game_state_t *gs)
{
	int	f, r;
	int	i;
	int	kf = 0, kr = -1;
	int	kf_and_kr_set = 0;
	int	numpossible = 0;
	int	possiblef[500];
	int	possibler[500];

	for (InitPieceLoop(gs->board, &f, &r, gs->onMove);
	     NextPieceLoop(gs->board, &f, &r, gs->onMove);) {
		switch (piecetype(gs->board[f][r])) {
		case PAWN:
			possible_pawn_moves(gs, f, r, possiblef, possibler,
			    &numpossible);
			break;
		case KNIGHT:
			possible_knight_moves(gs, f, r, possiblef, possibler,
			    &numpossible);
			break;
		case BISHOP:
			possible_bishop_moves(gs, f, r, possiblef, possibler,
			    &numpossible);
			break;
		case ROOK:
			possible_rook_moves(gs, f, r, possiblef, possibler,
			    &numpossible);
			break;
		case QUEEN:
			possible_queen_moves(gs, f, r, possiblef, possibler,
			    &numpossible);
			break;
		case KING:
			kf = f;
			kr = r;
			kf_and_kr_set = 1;
			possible_king_moves(gs, f, r, possiblef, possibler,
			    &numpossible);
			break;
		}
		if (numpossible >= 500)
			fprintf(stderr, "FICS: Possible move overrun\n");
		for (i = 0; i < numpossible; i++) {
			if (legal_andcheck_move(gs, f, r, possiblef[i],
			    possibler[i]))
				return 1;
		}
	}

	if (!kf_and_kr_set && kf == 0 && kr == -1) {
		fprintf(stderr, "FICS: %s: 'kf_and_kr_set' is 0\n", __func__);
		return 0;
	}

	// IanO: if we got here, then kf and kr must be set
	if (gs->gameNum >= 0 && garray[gs->gameNum].link >= 0) {
		// bughouse: potential drops as check interpositions
		gs->holding[gs->onMove == WHITE ? 0 : 1][QUEEN - 1]++;
		for (f = kf - 1; f <= kf + 1; f++) {
			for (r = kr - 1; r <= kr + 1; r++) {
				if (f >= 0 &&
				    f < 8 &&
				    r >= 0 &&
				    r < 8 &&
				    gs->board[f][r] == NOPIECE) {
					// try a drop next to the king
					if (legal_andcheck_move(gs, ALG_DROP,
					    QUEEN, f, r)) {
						gs->holding[gs->onMove == WHITE
						    ? 0 : 1][QUEEN - 1]--;
						return 1;
					}
				}
			}
		}

		gs->holding[gs->onMove == WHITE ? 0 : 1][QUEEN - 1]--;
	}

	fprintf(stderr, "FICS: NO LEGAL MOVE!\n");
	return 0;
}

/* This will end up being a very complicated function */
PUBLIC int parse_move(char *mstr, game_state_t * gs, move_t * mt, int promote)
{
  int type = is_move(mstr);
  int result;

  mt->color = gs->onMove;
  switch (type) {
  case MS_NOTMOVE:
    return MOVE_ILLEGAL;
    break;
  case MS_COMP:
    mt->fromFile = mstr[0] - 'a';
    mt->fromRank = mstr[1] - '1';
    mt->toFile = mstr[2] - 'a';
    mt->toRank = mstr[3] - '1';
    break;
  case MS_COMPDASH:
    mt->fromFile = mstr[0] - 'a';
    mt->fromRank = mstr[1] - '1';
    mt->toFile = mstr[3] - 'a';
    mt->toRank = mstr[4] - '1';
    break;
  case MS_KCASTLE:
    mt->fromFile = 4;
    mt->toFile = 6;
    if (gs->onMove == WHITE) {
      mt->fromRank = 0;
      mt->toRank = 0;
    } else {
      mt->fromRank = 7;
      mt->toRank = 7;
    }
    break;
  case MS_QCASTLE:
    mt->fromFile = 4;
    mt->toFile = 2;
    if (gs->onMove == WHITE) {
      mt->fromRank = 0;
      mt->toRank = 0;
    } else {
      mt->fromRank = 7;
      mt->toRank = 7;
    }
    break;
  case MS_ALG:
    /* Fills in the mt structure */
    if ((result = alg_parse_move(mstr, gs, mt)) != MOVE_OK)
      return result;
    break;
  default:
    return MOVE_ILLEGAL;
    break;
  }
  if (!legal_move(gs, mt->fromFile, mt->fromRank, mt->toFile, mt->toRank)) {
    return MOVE_ILLEGAL;
  }
  return move_calculate(gs, mt, promote);
}

/* Returns MOVE_OK, MOVE_NOMATERIAL, MOVE_CHECKMATE, or MOVE_STALEMATE */
/* check_game_status prevents recursion */
PUBLIC int execute_move(game_state_t * gs, move_t * mt, int check_game_status)
{
  int movedPiece;
  int tookPiece;
  int i, j, foobar;

  if (mt->fromFile == ALG_DROP) {
    movedPiece = mt->fromRank;
    tookPiece = NOPIECE;
    gs->holding[gs->onMove==WHITE ? 0 : 1][movedPiece-1]--;
    gs->board[mt->toFile][mt->toRank] = movedPiece | gs->onMove;
    if (gs->gameNum >= 0)
      gs->lastIrreversable = garray[gs->gameNum].numHalfMoves;
  } else {
  movedPiece = gs->board[mt->fromFile][mt->fromRank];
  tookPiece = gs->board[mt->toFile][mt->toRank];
  if (mt->piecePromotionTo == NOPIECE) {
    gs->board[mt->toFile][mt->toRank] = gs->board[mt->fromFile][mt->fromRank];
  } else {
    gs->board[mt->toFile][mt->toRank] = mt->piecePromotionTo | gs->onMove;
  }
  gs->board[mt->fromFile][mt->fromRank] = NOPIECE;
  /* Check if irreversable */
  if ((piecetype(movedPiece) == PAWN) || (tookPiece != NOPIECE)) {
    if (gs->gameNum >= 0)
      gs->lastIrreversable = garray[gs->gameNum].numHalfMoves;
  }
  /* Check if this move is en-passant */
  if ((piecetype(movedPiece) == PAWN) && (mt->fromFile != mt->toFile) &&
      (tookPiece == NOPIECE)) {
    if (gs->onMove == WHITE) {
      mt->pieceCaptured = B_PAWN;
    } else {
      mt->pieceCaptured = W_PAWN;
    }
    if (mt->fromFile > mt->toFile) {
      mt->enPassant = -1;
    } else {
      mt->enPassant = 1;
    }
    gs->board[mt->toFile][mt->fromRank] = NOPIECE;
  }
  /* Check en-passant flags for next moves */
  for (i = 0; i < 8; i++) {
    gs->ep_possible[0][i] = 0;
    gs->ep_possible[1][i] = 0;
  }
/* Added by Sparky 3/16/95

   From soso@Viktoria.drp.fmph.uniba.sk Thu Mar 16 13:08:51 1995
   Subject: Re: To DAV: enpassant prob. again
   To: chess@caissa.onenet.net (ICS)
   Date: Thu, 16 Mar 1995 20:06:20 +0100 (MET)

   Yeah !
   There was bug in other part of code:

   movecheck.c , line about 800:

     if (gs->onMove == WHITE) {
        if ((mt->toFile+1 < 7 ) ....  should be : (mt->toFile < 7 ) }
*/

  if ((piecetype(movedPiece) == PAWN) &&
   ((mt->fromRank == mt->toRank + 2) || (mt->fromRank + 2 == mt->toRank))) {
    /* Should turn on enpassent flag if possible */
    if (gs->onMove == WHITE) {
      if ((mt->toFile < 7) && gs->board[mt->toFile + 1][3] == B_PAWN) {
	gs->ep_possible[1][mt->toFile + 1] = -1;
      }
      if ((mt->toFile - 1 >= 0) && gs->board[mt->toFile - 1][3] == B_PAWN) {
	gs->ep_possible[1][mt->toFile - 1] = 1;
      }
    } else {
      if ((mt->toFile < 7) && gs->board[mt->toFile + 1][4] == W_PAWN) {
	gs->ep_possible[0][mt->toFile + 1] = -1;
      }
      if ((mt->toFile - 1 >= 0) && gs->board[mt->toFile - 1][4] == W_PAWN) {
	gs->ep_possible[0][mt->toFile - 1] = 1;
      }
    }
  }
  if ((piecetype(movedPiece) == ROOK) && (mt->fromFile == 0)) {
    if ((mt->fromRank == 0) && (gs->onMove == WHITE))
      gs->wqrmoved = 1;
    if ((mt->fromRank == 7) && (gs->onMove == BLACK))
      gs->bqrmoved = 1;
  }
  if ((piecetype(movedPiece) == ROOK) && (mt->fromFile == 7)) {
    if ((mt->fromRank == 0) && (gs->onMove == WHITE))
      gs->wkrmoved = 1;
    if ((mt->fromRank == 7) && (gs->onMove == BLACK))
      gs->bkrmoved = 1;
  }
  if (piecetype(movedPiece) == KING) {
    if (gs->onMove == WHITE)
      gs->wkmoved = 1;
    else
      gs->bkmoved = 1;
  }
  if ((piecetype(movedPiece) == KING) &&
      ((mt->fromFile == 4) && ((mt->toFile == 6)))) {	/* Check for KS castling */
    gs->board[5][mt->toRank] = gs->board[7][mt->toRank];
    gs->board[7][mt->toRank] = NOPIECE;
  }
  if ((piecetype(movedPiece) == KING) &&
      ((mt->fromFile == 4) && ((mt->toFile == 2)))) {	/* Check for QS castling */
    gs->board[3][mt->toRank] = gs->board[0][mt->toRank];
    gs->board[0][mt->toRank] = NOPIECE;
  }
  }
  if (gs->onMove == BLACK)
    gs->moveNum++;

  if (check_game_status) {
    /* Does this move result in check? */
    if (in_check(gs)) {
      /* Check for checkmate */
      gs->onMove = CToggle(gs->onMove);
      if (!has_legal_move(gs))
	return MOVE_CHECKMATE;
    } else {
      /* Check for stalemate */
      gs->onMove = CToggle(gs->onMove);
      if (!has_legal_move(gs))
	return MOVE_STALEMATE;
/* loon: check for insufficient mating material, first try */
      foobar = 0;
      for (i=0; i<8; i++) {
        for (j=0; j<8; j++) {
          switch(piecetype(gs->board[i][j])) {
            case KNIGHT:
            case BISHOP:
              foobar++;
              break;
            case KING:
	    case NOPIECE:
	      break;
            default:
              foobar = 2;
              break;
          }
        }
      }
      if (foobar < 2)
        return MOVE_NOMATERIAL;
    }
  } else {
    gs->onMove = CToggle(gs->onMove);
  }
  return MOVE_OK;
}

PUBLIC int backup_move(int g, int mode)
{
  game_state_t *gs;
  move_t *m, *m1;
  int now, i;

  if (garray[g].link >= 0)	/*IanO: not implemented for bughouse yet */
    return MOVE_ILLEGAL;
  if (garray[g].numHalfMoves < 1)
    return MOVE_ILLEGAL;
  gs = &garray[g].game_state;
  m = (mode==REL_GAME) ? &garray[g].moveList[garray[g].numHalfMoves - 1] :
                         &garray[g].examMoveList[garray[g].numHalfMoves - 1];
  if (m->toFile < 0) {
    return MOVE_ILLEGAL;
  }
  gs->board[m->fromFile][m->fromRank] = gs->board[m->toFile][m->toRank];
  if (m->piecePromotionTo != NOPIECE) {
    gs->board[m->fromFile][m->fromRank] = PAWN |
      colorval(gs->board[m->fromFile][m->fromRank]);
  }
  /******************
     When takeback a _first_ move of rook, the ??rmoved variable
     must be cleared . To check, if the move is first, we should
     scan moveList.
  *******************/
  if (piecetype(gs->board[m->fromFile][m->fromRank]) == ROOK) {
    if (m->color == WHITE) {
      if ((m->fromFile == 0) && (m->fromRank == 0)) {
	for (i = 2; i < garray[g].numHalfMoves - 1; i += 2) {
	  m1 = (mode==REL_GAME) ? &garray[g].moveList[i] : &garray[g].examMoveList[i];
	  if ((m1->fromFile == 0) && (m1->fromRank == 0))
	    break;
	}
	if (i == garray[g].numHalfMoves - 1)
	  gs->wqrmoved = 0;
      }
      if ((m->fromFile == 7) && (m->fromRank == 0)) {
	for (i = 2; i < garray[g].numHalfMoves - 1; i += 2) {
	  m1 = (mode==REL_GAME) ? &garray[g].moveList[i] : &garray[g].examMoveList[i];
	  if ((m1->fromFile == 7) && (m1->fromRank == 0))
	    break;
	}
	if (i == garray[g].numHalfMoves - 1)
	  gs->wkrmoved = 0;
      }
    } else {
      if ((m->fromFile == 0) && (m->fromRank == 7)) {
	for (i = 3; i < garray[g].numHalfMoves - 1; i += 2) {
	  m1 = (mode==REL_GAME) ? &garray[g].moveList[i] : &garray[g].examMoveList[i];
	  if ((m1->fromFile == 0) && (m1->fromRank == 0))
	    break;
	}
	if (i == garray[g].numHalfMoves - 1)
	  gs->bqrmoved = 0;
      }
      if ((m->fromFile == 7) && (m->fromRank == 7)) {
	for (i = 3; i < garray[g].numHalfMoves - 1; i += 2) {
	  m1 = (mode==REL_GAME) ? &garray[g].moveList[i] : &garray[g].examMoveList[i];
	  if ((m1->fromFile == 7) && (m1->fromRank == 0))
	    break;
	}
	if (i == garray[g].numHalfMoves - 1)
	  gs->bkrmoved = 0;
      }
    }
  }
  if (piecetype(gs->board[m->fromFile][m->fromRank]) == KING) {
    gs->board[m->toFile][m->toRank] = m->pieceCaptured;

    if (m->toFile - m->fromFile == 2) {
      gs->board[7][m->fromRank] = ROOK |
	colorval(gs->board[m->fromFile][m->fromRank]);
      gs->board[5][m->fromRank] = NOPIECE;

      /********
         If takeback a castling, the appropriates ??moved variables
         must be cleared
      ********/
      if (m->color == WHITE) {
	gs->wkmoved = 0;
	gs->wkrmoved = 0;
      } else {
	gs->bkmoved = 0;
	gs->bkrmoved = 0;
      }
      goto cleanupMove;
    }
    if (m->fromFile - m->toFile == 2) {
      gs->board[0][m->fromRank] = ROOK |
	colorval(gs->board[m->fromFile][m->fromRank]);
      gs->board[3][m->fromRank] = NOPIECE;

      /**********
         If takeback a castling, the appropriate ??moved variables
         must be cleared
      ***********/
      if (m->color == WHITE) {
	gs->wkmoved = 0;
	gs->wqrmoved = 0;
      } else {
	gs->bkmoved = 0;
	gs->bqrmoved = 0;
      }
      goto cleanupMove;
    }
    /******************
       When takeback a _first_ move of king (not the castling),
       the ?kmoved variable must be cleared . To check, if the move is first,
       we should scan moveList.
    *******************/

    if (m->color == WHITE) {

      if ((m->fromFile == 4) && (m->fromRank == 0)) {
	for (i = 2; i < garray[g].numHalfMoves - 1; i += 2) {
	  m1 = (mode==REL_GAME) ? &garray[g].moveList[i] : &garray[g].examMoveList[i];
	  if ((m1->fromFile == 4) && (m1->fromRank == 0))
	    break;
	}
	if (i == garray[g].numHalfMoves - 1)
	  gs->wkmoved = 0;
      }
    } else {
      if ((m->fromFile == 4) && (m->fromRank == 7)) {
	for (i = 3; i < garray[g].numHalfMoves - 1; i += 2) {
	  m1 = (mode==REL_GAME) ? &garray[g].moveList[i] : &garray[g].examMoveList[i];
	  if ((m1->fromFile == 4) && (m1->fromRank == 7))
	    break;
	}
	if (i == garray[g].numHalfMoves - 1)
	  gs->bkmoved = 0;
      }
    }
  }
  if (m->enPassant) {		/* Do enPassant */
    gs->board[m->toFile][m->fromRank] = PAWN |
      (colorval(gs->board[m->fromFile][m->fromRank]) == WHITE ? BLACK : WHITE);
    gs->board[m->toFile][m->toRank] = NOPIECE;
    /* Should set the enpassant array, but I don't care right now */
    goto cleanupMove;
  }
  gs->board[m->toFile][m->toRank] = m->pieceCaptured;
cleanupMove:
  if (garray[g].status != GAME_EXAMINE) {
    game_update_time(g);
  }
  garray[g].numHalfMoves--;
  if (garray[g].status != GAME_EXAMINE) {
    if (garray[g].wInitTime) {	/* Don't update times in untimed games */
      now = tenth_secs();

#ifdef TIMESEAL

      if (m->color == WHITE) {
        if (con[parray[garray[g].white].socket].timeseal) {  /* white uses timeseal? */
          garray[g].wRealTime += (m->tookTime * 100);
          garray[g].wRealTime -= (garray[g].wIncrement * 100);
          garray[g].wTime = garray[g].wRealTime / 100;
          if (con[parray[garray[g].black].socket].timeseal) { /* opp uses timeseal? */
            garray[g].bTime = garray[g].bRealTime / 100;
	  } else {    /* opp has no timeseal */
            garray[g].bTime += (garray[g].lastDecTime - garray[g].lastMoveTime);
	  }
	} else {  /* white has no timeseal */
          garray[g].wTime += m->tookTime;
          garray[g].wTime -= garray[g].wIncrement;
          if (con[parray[garray[g].black].socket].timeseal) { /* opp uses timeseal? */
            garray[g].bTime = garray[g].bRealTime / 100;
	  } else {    /* opp has no timeseal */
            garray[g].bTime += (garray[g].lastDecTime - garray[g].lastMoveTime);
	  }
	}
      } else {
        if (con[parray[garray[g].black].socket].timeseal) {  /* black uses timeseal? */
          garray[g].bRealTime += (m->tookTime * 100);
          garray[g].bRealTime -= (garray[g].wIncrement * 100);
          garray[g].bTime = garray[g].bRealTime / 100;
          if (con[parray[garray[g].white].socket].timeseal) { /* opp uses timeseal? */
            garray[g].wTime = garray[g].wRealTime / 100;
	  } else {    /* opp has no timeseal */
            garray[g].wTime += (garray[g].lastDecTime - garray[g].lastMoveTime);
	  }
	} else {  /* black has no timeseal */
          garray[g].bTime += m->tookTime;
          if (!garray[g].bIncrement)
            garray[g].bTime -= garray[g].wIncrement;
          else
  	    garray[g].bTime -= garray[g].bIncrement;
          if (con[parray[garray[g].white].socket].timeseal) { /* opp uses timeseal? */
            garray[g].wTime = garray[g].wRealTime / 100;
	  } else {    /* opp has no timeseal */
            garray[g].wTime += (garray[g].lastDecTime - garray[g].lastMoveTime);
	  }
	}
      }

#else

      if (m->color == WHITE) {
        garray[g].wTime += m->tookTime;
        garray[g].wTime = garray[g].wTime - garray[g].wIncrement;
        garray[g].bTime += (garray[g].lastDecTime - garray[g].lastMoveTime);
      } else {
        garray[g].bTime += m->tookTime;
        if (!garray[g].bIncrement)
          garray[g].bTime = garray[g].bTime - garray[g].wIncrement;
        else
	  garray[g].bTime = garray[g].bTime - garray[g].bIncrement;
        garray[g].wTime += (garray[g].lastDecTime - garray[g].lastMoveTime);
      }

#endif

      if (garray[g].numHalfMoves == 0)
        garray[g].timeOfStart = now;
      garray[g].lastMoveTime = now;
      garray[g].lastDecTime = now;
    }
  }
  if (gs->onMove == BLACK)
    gs->onMove = WHITE;
  else {
    gs->onMove = BLACK;
    gs->moveNum--;
  }

  /******* Here begins the patch : ********************************
     Takeback of last move is done already, it's time to update enpassant
     array.  (patch from Soso, added by Sparky 3/17/95)
  ********/

  if (garray[g].numHalfMoves > 0) {
    m1 = (mode==REL_GAME) ? &garray[g].moveList[garray[g].numHalfMoves - 1] :
                            &garray[g].examMoveList[garray[g].numHalfMoves - 1];
    if (piecetype(gs->board[m1->toFile][m1->toRank]) == PAWN) {
      if ((m1->toRank - m1->fromRank) == 2) {
	if ((m1->toFile < 7) && gs->board[m1->toFile + 1][3] == B_PAWN) {
	  gs->ep_possible[1][m1->toFile + 1] = -1;
	}
	if ((m1->toFile - 1 >= 0) && gs->board[m1->toFile - 1][3] == B_PAWN) {
	  gs->ep_possible[1][m1->toFile - 1] = 1;
	}
      }
      if ((m1->toRank - m1->fromRank) == -2) {
	if ((m1->toFile < 7) && gs->board[m1->toFile + 1][4] == W_PAWN) {
	  gs->ep_possible[0][m1->toFile + 1] = -1;
	}
	if ((m1->toFile - 1 >= 0) && gs->board[m1->toFile - 1][4] == W_PAWN) {
	  gs->ep_possible[0][m1->toFile - 1] = 1;
	}
      }
    }
  }
  /************** and here's the end **************/
  return MOVE_OK;
}