src/chess/bishop.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 "bishop.h"
#include "rules.h"
#include <stdlib.h>

_Bool bishop_chkrules(Move* move) {
    return abs(move->torow-move->fromrow) == abs(move->tofile-move->fromfile);
}

_Bool bishop_isblocked(GameState *gamestate, Move *move) {
    int dy = move->torow > move->fromrow ? 1 : -1;
    int dx = move->tofile > move->fromfile ? 1 : -1;
    
    uint8_t y = move->fromrow;
    uint8_t x = move->fromfile;
    
    while (x != move->tofile-dx && y != move->torow-dy) {
        x += dx;
        y += dy;
        if (gamestate->board[y][x]) {
            return 1;
        }
    }
    
    return 0;
}

static int bishop_getloc_fixedfile(GameState *gamestate, Move *move) {
    uint8_t d = abs(move->fromfile - move->tofile);
    if (gamestate->board[move->torow - d][move->fromfile] == move->piece) {
        move->fromrow = move->torow - d;
    }
    if (gamestate->board[move->torow + d][move->fromfile] == move->piece) {
        if (move->fromrow == POS_UNSPECIFIED) {
            move->fromrow = move->torow + d;
        } else {
            return AMBIGUOUS_MOVE; /* rare situation after promotion */
        }
    }
    return move->fromrow == POS_UNSPECIFIED ?
        INVALID_POSITION : VALID_MOVE_SYNTAX;
}

static int bishop_getloc_fixedrow(GameState *gamestate, Move *move) {
    uint8_t d = abs(move->fromrow - move->torow);
    if (gamestate->board[move->fromrow][move->tofile - d] == move->piece) {
        move->fromfile = move->tofile - d;
    }
    if (gamestate->board[move->fromrow][move->tofile + d] == move->piece) {
        if (move->fromfile == POS_UNSPECIFIED) {
            move->fromfile = move->tofile + d;
        } else {
            return AMBIGUOUS_MOVE; /* rare situation after promotion */
        }
    }
    return move->fromfile == POS_UNSPECIFIED ?
        INVALID_POSITION : VALID_MOVE_SYNTAX;
}

int bishop_getlocation(GameState *gamestate, Move *move) {
    
    if (move->fromfile != POS_UNSPECIFIED) {
        return bishop_getloc_fixedfile(gamestate, move);
    }
    
    if (move->fromrow != POS_UNSPECIFIED) {
        return bishop_getloc_fixedrow(gamestate, move);
    }
    
    _Bool amb = 0;
    for (int d = -7 ; d < 8  ; d++) {
        uint8_t row = move->torow + d;
        if (isidx(row)) {
            uint8_t file = move->tofile + d;
            if (isidx(file) && gamestate->board[row][file] == move->piece) {
                if (amb) {
                    return AMBIGUOUS_MOVE;
                }
                amb = 1;
                move->fromrow = row;
                move->fromfile = file;
            }
            file = move->tofile - d;
            if (isidx(file) && gamestate->board[row][file] == move->piece) {
                if (amb) {
                    return AMBIGUOUS_MOVE;
                }
                amb = 1;
                move->fromrow = row;
                move->fromfile = file;
            }
        }
    }
    
    if (move->fromrow == POS_UNSPECIFIED || move->fromfile == POS_UNSPECIFIED) {
        return INVALID_POSITION;
    } else {
        return VALID_MOVE_SYNTAX;
    }
}