src/chess/bishop.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:
 *
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 *      notice, this list of conditions and the following disclaimer.
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 *   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
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#include "bishop.h"
#include "rules.h"
#include <stdlib.h>

bool bishop_chkrules(const Move* move) {
    return abs(move->torank-move->fromrank) == abs(move->tofile-move->fromfile);
}

bool bishop_isblocked(const GameState *gamestate, const Move *move) {
    int dy = move->torank > move->fromrank ? 1 : -1;
    int dx = move->tofile > move->fromfile ? 1 : -1;
    
    Rank y = move->fromrank;
    File x = move->fromfile;
    
    while (x != move->tofile-dx && y != move->torank-dy) {
        x += dx;
        y += dy;
        if (gamestate->board[y][x]) {
            return true;
        }
    }
    
    return false;
}

size_t bishop_moves(const GameState *gamestate,
        Color c, File f, Rank r, Move *moves) {

    size_t count = 0;
    const int directions[4][2] = {
        { 1,  1},
        { 1, -1},
        {-1,  1},
        {-1, -1}
    };

    for (size_t i = 0 ; i < 4 ; i++) {
        int rank = r + directions[i][0];
        int file = f + directions[i][1];

        while (isidx(rank) && isidx(file)) {
            moves[count] = (Move){0};
            moves[count].piece = mkpiece(BISHOP, c);
            moves[count].fromrank = r;
            moves[count].fromfile = f;
            moves[count].torank = rank;
            moves[count].tofile = file;
            moves[count].capture = piece_at(gamestate, file, rank) != 0;
            count++;

            rank += directions[i][0];
            file += directions[i][1];
        }
    }

    return count;
}