src/chess/rook.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 "rules.h"
#include "rook.h"

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

_Bool rook_isblocked(GameState *gamestate, Move *move) {
    
    if (move->torow == move->fromrow) {
        int d = move->tofile > move->fromfile ? 1 : -1;
        uint8_t f = move->fromfile;
        while (f != move->tofile-d) {
            f += d;
            if (gamestate->board[move->fromrow][f]) {
                return 1;
            }
        }
    } else {
        int d = move->torow > move->fromrow ? 1 : -1;
        uint8_t r = move->fromrow;
        while (r != move->torow - d) {
            r += d;
            if (gamestate->board[r][move->fromfile]) {
                return 1;
            }
        }
    }
    
    return 0;
}

static int rook_getloc_fixedrow(GameState *gamestate, Move *move) {
    uint8_t file = POS_UNSPECIFIED;
    for (uint8_t f = 0 ; f < 8 ; f++) {
        if (gamestate->board[move->fromrow][f] == move->piece) {
            if (file == POS_UNSPECIFIED) {
                file = f;
            } else {
                return AMBIGUOUS_MOVE;
            }
        }
    }
    if (file == POS_UNSPECIFIED) {
        return INVALID_POSITION;
    } else {
        move->fromfile = file;
        return VALID_MOVE_SYNTAX;
    }
}

static int rook_getloc_fixedfile(GameState *gamestate, Move *move) {
    uint8_t row = POS_UNSPECIFIED;
    for (uint8_t r = 0 ; r < 8 ; r++) {
        if (gamestate->board[r][move->fromfile] == move->piece) {
            if (row == POS_UNSPECIFIED) {
                row = r;
            } else {
                return AMBIGUOUS_MOVE;
            }
        }   
    }
    if (row == POS_UNSPECIFIED) {
        return INVALID_POSITION;
    } else {
        move->fromrow = row;
        return VALID_MOVE_SYNTAX;
    }
}

int rook_getlocation(GameState *gamestate, Move *move) {
    
    if (move->fromfile != POS_UNSPECIFIED) {
        if (move->fromfile == move->tofile) {
            return rook_getloc_fixedfile(gamestate, move);
        } else {
            if (gamestate->board[move->torow][move->fromfile] == move->piece) {
                move->fromrow = move->torow;
                return VALID_MOVE_SYNTAX;
            } else {
                return INVALID_POSITION;
            }
        }
    }
    
    if (move->fromrow != POS_UNSPECIFIED) {
        if (move->fromrow == move->torow) {
            return rook_getloc_fixedrow(gamestate, move);
        } else {
            if (gamestate->board[move->fromrow][move->tofile] == move->piece) {
                move->fromfile = move->tofile;
                return VALID_MOVE_SYNTAX;
            } else {
                return INVALID_POSITION;
            }
        }
    }
    
    Move chkrowmove = *move, chkfilemove = *move;
    
    chkrowmove.fromrow = move->torow;
    int chkrow = rook_getloc_fixedrow(gamestate, &chkrowmove);
    
    chkfilemove.fromfile = move->tofile;
    int chkfile = rook_getloc_fixedfile(gamestate, &chkfilemove);
    
    if ((chkrow == VALID_MOVE_SYNTAX && chkfile == VALID_MOVE_SYNTAX) ||
        chkrow == AMBIGUOUS_MOVE || chkfile == AMBIGUOUS_MOVE) {
        return AMBIGUOUS_MOVE;
    }
    
    if (chkrow == VALID_MOVE_SYNTAX) {
        *move = chkrowmove;
        return VALID_MOVE_SYNTAX;
    }
    
    if (chkfile == VALID_MOVE_SYNTAX) {
        *move = chkfilemove;
        return VALID_MOVE_SYNTAX;
    }
    
    return INVALID_POSITION;
}