src/chess/king.c

/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 *
 * Copyright 2016 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 "rules.h"
#include "king.h"

#include <string.h>

static bool king_castling_chkmoved(
        const GameState *gamestate, Row row, File file) {

    for (unsigned i = 0; i < gamestate->movecount; i++) {
        if (gamestate->moves[i].fromfile == file
            && gamestate->moves[i].fromrow == row) {
            return true;
        }
    }
    
    return false;
}

bool king_chkrules(const GameState *gamestate, const Move* move) {
    if (abs(move->torow - move->fromrow) <= 1 &&
        abs(move->tofile - move->fromfile) <= 1) {
        return true;
    } else {
        /* castling */
        if (move->fromrow == move->torow &&
            move->fromrow == (piece_color(move->piece) == WHITE ? 0 : 7) &&
            move->fromfile == fileidx('e') &&
            (move->tofile == fileidx('c') || move->tofile == fileidx('g'))) {
            
            return !king_castling_chkmoved(gamestate,
                move->fromrow, move->fromfile) &&
                !king_castling_chkmoved(gamestate, move->fromrow,
                move->tofile == fileidx('c') ? 0 : 7);
        } else {
            return false;
        }
    }
}

bool king_isblocked(const GameState *gamestate, const Move *move) {
    
    uint8_t opponent_color = opponent_color(piece_color(move->piece));
    
    /* being in check does not "block" the king, so don't test it here */
    bool blocked = false;
    
    /* just test, if castling move is blocked */
    if (abs(move->tofile - move->fromfile) == 2) {
        if (move->tofile == fileidx('c')) {
            blocked |= gamestate->board[move->torow][fileidx('b')];
        }
        uint8_t midfile = (move->tofile+move->fromfile)/2;
        bool incheck = false;
        if (gamestate->movecount > 0) {
            incheck = is_check_position(gamestate);
        }
        blocked |= incheck || gamestate->board[move->torow][midfile] ||
            is_covered(gamestate, move->torow, midfile, opponent_color);
    }
    
    return blocked;
}