src/chess/pawn.c

/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 *
 * Copyright 2014 Mike Becker. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *   1. Redistributions of source code must retain the above copyright
 *      notice, this list of conditions and the following disclaimer.
 *
 *   2. Redistributions in binary form must reproduce the above copyright
 *      notice, this list of conditions and the following disclaimer in the
 *      documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 */

#include "pawn.h"
#include "rules.h"

_Bool pawn_chkrules(GameState *gamestate, Move *move) {
    int8_t d = ((move->piece & COLOR_MASK) == WHITE ? -1 : 1);
    
    if (move->torow == (d < 0 ? 7 : 0)) {
        if (move->promotion) {
            uint8_t promopiece = move->promotion & PIECE_MASK;
            if (!promopiece || promopiece == PAWN || promopiece == KING) {
                return 0;
            }
        } else {
            return 0;
        }
    } else {
        if (move->promotion) {
            return 0;
        }
    }
    
    if (move->capture) {
        if (move->fromrow == move->torow + d && (
            move->fromfile == move->tofile + 1 ||
            move->fromfile == move->tofile - 1)) {

            return mdst(gamestate->board, move) ||
                (gamestate->board[move->fromrow][move->tofile]
                & ENPASSANT_THREAT);
        } else {
            return 0;
        }
    } else {
        if (move->fromfile == move->tofile) {
            return (move->fromrow == move->torow + d) ||
                (move->fromrow == (d < 0 ? 1 : 6) && /* advanced first move */
                move->fromrow == move->torow + d*2);
        } else {
            return 0;
        }
    }
}

_Bool pawn_isblocked(GameState *gamestate, Move *move) {
    return mdst(gamestate->board, move) && !move->capture;
}

int pawn_getlocation(GameState *gamestate, Move *move) {
    int8_t d = ((move->piece & COLOR_MASK) == WHITE ? -1 : 1);
    
    if (move->fromfile == POS_UNSPECIFIED) {
        move->fromfile = move->tofile;
    }
    move->fromrow = move->torow + d;
    if (move->fromrow > 6) {
        return INVALID_POSITION;
    } else {
        /* advanced first move */
        if (move->fromrow == (d < 0 ? 2 : 5) &&
            msrc(gamestate->board,move) != move->piece) {

            move->fromrow += d;
            if (move->fromrow > 6) {
                return INVALID_POSITION;
            }
        }
    }
    return VALID_MOVE_SYNTAX;
}