459 lines
16 KiB
C
459 lines
16 KiB
C
// vim: set ts=4 sw=4 et tw=80:
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#include <stdio.h>
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#include <string.h>
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#include <stdbool.h>
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#include <stdlib.h>
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#include "./chessboard.h"
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#define DEBUG_BUILD
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#ifdef DEBUG_BUILD
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#define DEBUG(...) fprintf(stderr, __VA_ARGS__);
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#else
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#define DEBUG(...) (void) 0;
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#endif
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static inline enum pieces cb_move(struct chessboard* cb,
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int from_row, int from_col, int to_row, int to_col);
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static inline void cb_move_restore(struct chessboard* cb, enum pieces piece,
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int ex_from_row, int ex_from_col, int ex_to_row, int ex_to_col);
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static inline int sign(int n);
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static inline enum player player(struct chessboard* cb, int row, int col);
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static inline bool is_empty(struct chessboard* cb, int row, int col);
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static bool check_empty_paths(struct chessboard* cb,
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int from_row, int from_col, int to_row, int to_col);
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static bool can_move_pawn(struct chessboard* cb, enum player p,
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int from_row, int from_col, int to_row, int to_col);
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static bool can_move_rook(struct chessboard* cb,
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int from_row, int from_col, int to_row, int to_col);
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static bool can_move_knight(struct chessboard* cb,
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int from_row, int from_col, int to_row, int to_col);
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static bool can_move_bishop(struct chessboard* cb,
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int from_row, int from_col, int to_row, int to_col);
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static bool can_move_queen(struct chessboard* cb,
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int from_row, int from_col, int to_row, int to_col);
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static bool can_move_king(struct chessboard* cb,
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int from_row, int from_col, int to_row, int to_col);
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void init_chessboard(struct chessboard * cb) {
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int i;
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for (i = 0; i < 8; i++) {
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cb->position[1][i] = WHITE_PAWN;
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cb->position[6][i] = BLACK_PAWN;
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}
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cb->position[0][0] = WHITE_ROOK;
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cb->position[0][1] = WHITE_KNIGHT;
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cb->position[0][2] = WHITE_BISHOP;
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cb->position[0][3] = WHITE_QUEEN;
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cb->position[0][4] = WHITE_KING;
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cb->position[0][5] = WHITE_BISHOP;
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cb->position[0][6] = WHITE_KNIGHT;
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cb->position[0][7] = WHITE_ROOK;
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cb->position[7][0] = BLACK_ROOK;
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cb->position[7][1] = BLACK_KNIGHT;
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cb->position[7][2] = BLACK_BISHOP;
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cb->position[7][3] = BLACK_QUEEN;
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cb->position[7][4] = BLACK_KING;
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cb->position[7][5] = BLACK_BISHOP;
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cb->position[7][6] = BLACK_KNIGHT;
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cb->position[7][7] = BLACK_ROOK;
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int j;
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for (i = 0; i < 8; i++) {
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for (j = 2; j < 6; j++) {
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cb->position[j][i] = EMPTY;
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}
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}
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}
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void print_chessboard(struct chessboard * cb) {
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printf(" a b c d e f g h\n"
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" ┌───┬───┬───┬───┬───┬───┬───┬───┐\n");
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int i;
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for (i = 7; i >= 0; i--) {
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printf("%d │", i + 1);
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int j;
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for (j = 0; j < 8; j++) {
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printf(" %s │", utf_8_pieces[cb->position[i][j]]);
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}
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putchar('\n');
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if (i != 0) {
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printf(" ├───┼───┼───┼───┼───┼───┼───┼───┤\n");
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}
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}
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printf(" └───┴───┴───┴───┴───┴───┴───┴───┘\n"
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" a b c d e f g h\n");
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}
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inline enum pieces cb_move(struct chessboard* cb,
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int from_row, int from_col, int to_row, int to_col) {
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enum pieces tmp = cb->position[to_row][to_col];
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cb->position[to_row][to_col] = cb->position[from_row][from_col];
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cb->position[from_row][from_col] = EMPTY;
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return tmp;
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}
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inline void cb_move_restore(struct chessboard* cb, enum pieces piece,
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int ex_from_row, int ex_from_col, int ex_to_row, int ex_to_col) {
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cb->position[ex_from_row][ex_from_col] =
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cb->position[ex_to_row][ex_to_col];
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cb->position[ex_to_row][ex_to_col] = piece;
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}
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inline bool is_empty(struct chessboard* cb, int row, int col) {
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return cb->position[row][col] == EMPTY;
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}
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inline enum player player(struct chessboard* cb, int row, int col) {
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return cb->position[row][col] < 7 ? WHITE : BLACK;
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}
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inline int sign(int n) {
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return n == 0 ? 0 : (n > 0 ? 1 : -1);
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}
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bool can_move_pawn(struct chessboard* cb, enum player p,
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int from_row, int from_col, int to_row, int to_col) {
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DEBUG("can_move_pawn: from: row %d col %d to: row %d col %d\n",
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from_row, from_col, to_row, to_col);
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// two forward if in the starting position, no capture is valid
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if (((p == WHITE && from_row == 1 && to_row == 3 &&
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is_empty(cb, 2, from_col)) ||
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(p == BLACK && from_row == 6 && to_row == 4 &&
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is_empty(cb, 5, from_col))) &&
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from_col == to_col &&
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is_empty(cb, to_row, to_col)) {
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DEBUG("can_move_pawn: two forward, valid\n");
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return true;
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// one forward, no capture is valid
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} else if (((p == WHITE && to_row - from_row == 1) ||
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(p == BLACK && from_row - to_row == 1)) &&
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from_col == to_col &&
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is_empty(cb, to_row, to_col)) {
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DEBUG("can_move_pawn: one forward no capture, valid\n");
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return true;
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// one forward, one left or right, with capture, is valid
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} else if (to_row == from_row + (p == WHITE ? 1 : -1) &&
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abs(from_col - to_col) == 1 &&
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!is_empty(cb, to_row, to_col)) {
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DEBUG("can_move_pawn: one forward diagonal capture, valid\n");
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return true;
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} else {
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DEBUG("can_move_pawn: move pawn not valid\n");
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return false;
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}
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}
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bool check_empty_paths(struct chessboard* cb,
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int from_row, int from_col, int to_row, int to_col) {
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int ii = sign(to_row - from_row), jj = sign(to_col - from_col);
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int i = from_row + ii, j = from_col + jj;
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DEBUG("check_empty_paths: from: row %d col %d, to: row %d col %d, ii: %d,"
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" jj: %d\n", from_row, from_col, to_row, to_col, ii, jj);
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for (; !(i == to_row && j == to_col); i += ii, j += jj) {
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if (!is_empty(cb, i, j)) {
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DEBUG("check_empty_paths: position row %d col %d"
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" is occupied\n", i, j);
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return false;
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}
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}
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return true;
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}
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bool can_move_rook(struct chessboard* cb,
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int from_row, int from_col, int to_row, int to_col) {
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if (to_row != from_row && to_col != from_col) {
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return false;
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}
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return check_empty_paths(cb, from_row, from_col, to_row, to_col);
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}
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bool can_move_bishop(struct chessboard* cb,
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int from_row, int from_col, int to_row, int to_col) {
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if (abs(from_row - to_row) != abs(from_col - to_col)) {
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return false;
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}
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return check_empty_paths(cb, from_row, from_col, to_row, to_col);
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}
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bool can_move_queen(struct chessboard* cb,
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int from_row, int from_col, int to_row, int to_col) {
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return can_move_bishop(cb, from_row, from_col, to_row, to_col) ||
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can_move_rook(cb, from_row, from_col, to_row, to_col);
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}
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bool can_move_knight(struct chessboard* cb,
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int from_row, int from_col, int to_row, int to_col) {
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return (to_row == from_row + 2 && to_col == from_col + 1) ||
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(to_row == from_row + 2 && to_col == from_col - 1) ||
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(to_row == from_row - 2 && to_col == from_col + 1) ||
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(to_row == from_row - 2 && to_col == from_col - 1) ||
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(to_row == from_row + 1 && to_col == from_col + 2) ||
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(to_row == from_row - 1 && to_col == from_col + 2) ||
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(to_row == from_row + 1 && to_col == from_col - 2) ||
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(to_row == from_row - 1 && to_col == from_col + 2);
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}
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bool can_move_king(struct chessboard* cb,
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int from_row, int from_col, int to_row, int to_col) {
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if (abs(to_row - from_row) > 1) {
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DEBUG("can_move_king: row movement too big (from %d to %d)\n", from_row,
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to_row);
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return false;
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}
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if (abs(to_col - from_col) > 1) {
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DEBUG("can_move_king: column movement too big (from %d to %d)\n",
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from_col, to_col);
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return false;
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}
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return true;
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}
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bool can_move(struct chessboard* cb, enum player p,
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int from_row, int from_col, int to_row, int to_col) {
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// try to understand which piece we are moving
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switch (cb->position[from_row][from_col]) {
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case WHITE_PAWN:
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case BLACK_PAWN:
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DEBUG("can_move: moving a pawn\n");
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return can_move_pawn(cb, p, from_row, from_col, to_row, to_col);
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case WHITE_ROOK:
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case BLACK_ROOK:
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DEBUG("can_move: moving a rook\n");
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return can_move_rook(cb, from_row, from_col, to_row, to_col);
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case WHITE_BISHOP:
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case BLACK_BISHOP:
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DEBUG("can_move: moving a bishop\n");
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return can_move_bishop(cb, from_row, from_col, to_row, to_col);
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case WHITE_QUEEN:
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case BLACK_QUEEN:
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DEBUG("can_move: moving a queen\n");
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return can_move_queen(cb, from_row, from_col, to_row, to_col);
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case WHITE_KNIGHT:
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case BLACK_KNIGHT:
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DEBUG("can_move: moving a knight\n");
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return can_move_knight(cb, from_row, from_col, to_row, to_col);
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case WHITE_KING:
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case BLACK_KING:
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DEBUG("can_move: moving a king\n");
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return can_move_king(cb, from_row, from_col, to_row, to_col);
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default:
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DEBUG("can_move: piece not implemented\n");
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return false;
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}
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}
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void find_other_king(struct chessboard *cb, enum player p,
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int* k_row, int* k_col) {
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for (*k_row = 0; *k_row < 8; (*k_row)++) {
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for (*k_col = 0; *k_col < 8; (*k_col)++) {
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if ((p == BLACK && cb->position[*k_row][*k_col] == WHITE_KING) ||
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(p == WHITE && cb->position[*k_row][*k_col] == BLACK_KING))
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{
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DEBUG("find_other_king: %s king in position row %d col %d\n",
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p == WHITE ? "black" : "white", *k_row, *k_col);
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return;
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}
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}
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}
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DEBUG("find_king: king not found");
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}
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bool player_checks(struct chessboard *cb, enum player p) {
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int k_row, k_col;
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find_other_king(cb, p, &k_row, &k_col);
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int i, j;
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for (i = 0; i < 8; i++) {
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for (j = 0; j < 8; j++) {
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if (!is_empty(cb, i, j) && player(cb, i, j) == p) {
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DEBUG("player_checks: checking row %d col %d to attack king\n",
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i, j);
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if (can_move(cb, p, i, j, k_row, k_col)) {
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DEBUG("player_checks: row %d col %d can attack %s king\n",
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i, j, p == WHITE ? "black" : "white");
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return true;
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}
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}
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}
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}
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return false;
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}
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bool player_checkmates(struct chessboard *cb, enum player p) {
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int i, j;
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// for every opponent's piece
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for (i = 0; i < 8; i++) {
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for (j = 0; j < 8; j++) {
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if (is_empty(cb, i, j) || player(cb, i, j) == p) {
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continue;
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}
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int k, l;
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// for every possible position not equal to the current position of
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// that piece, which is empty or occupied by our pieces (implying
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// capture)
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for (k = 0; k < 8; k++) {
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for (l = 0; l < 8; l++) {
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if ((k == i && l == j) ||
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is_empty(cb, k, l) ||
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player(cb, k, l) != p) {
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continue;
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}
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// check if the move is valid
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bool can = can_move(cb, p == BLACK ? WHITE : BLACK,
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i, j, k, l);
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// if not, carry on
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if (!can) {
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continue;
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}
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// if valid, perform the move and check for check.
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enum pieces tmp = cb_move(cb, i, j, k, l);
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bool check = player_checks(cb, p);
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cb_move_restore(cb, tmp, i, j, k, l);
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// if check is no longer there, then this is not a checkmate
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if (!check) {
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return false;
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}
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}
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}
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}
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}
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// if no such move exists, then this is checkmate
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return true;
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}
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enum mstatus move(
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struct chessboard * cb, enum player p,
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const char * from, const char * to) {
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// if you are giving us garbage, we behave like Rome's municipal services
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if (strlen(from) != 2 || from[0] < 'a' || from[0] > 'h' || from[1] < '1'
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|| from[1] > '8') {
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DEBUG("move: 'from' input '%s' is invalid\n", from);
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return INVALID;
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}
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if (to[0] < 'a' || to[0] > 'h' || to[1] < '1' || to[1] > '8'
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|| strlen(to) != 2) {
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DEBUG("move: 'to' input '%s' is invalid\n", to);
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return INVALID;
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}
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int from_col = from[0] - 'a', to_col = to[0] - 'a';
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int from_row = from[1] - '1', to_row = to[1] - '1';
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// if you are moving thin air, EH VOLEVIH
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if (is_empty(cb, from_row, from_col)) {
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DEBUG("move: from is empty\n");
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return INVALID;
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}
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// if you are moving someone else's pieces, "thou shall not steal"
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if (player(cb, from_row, from_col) != p) {
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DEBUG("move: moving piece of opponent\n");
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return INVALID;
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}
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// if you are trying to suicide (capture your piecies), sorry but assisted
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// suicide is not legal in italy
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if (cb->position[to_row][to_col] != EMPTY &&
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cb->position[from_row][from_col] / 7 ==
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cb->position[to_row][to_col] / 7) {
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DEBUG("move: capturing piece from moving player\n");
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return INVALID;
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}
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// if you try to move on the same spot, don't do it you buffoon
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if (from_row == to_row && from_col == to_col) {
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DEBUG("move: moving to same position\n");
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return INVALID;
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}
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// check if we are currently in check state
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bool check_before = player_checks(cb, p == WHITE ? BLACK : WHITE);
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// determine if move is valid
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bool can = can_move(cb, p, from_row, from_col, to_row, to_col);
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if (!can) {
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return INVALID;
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} else {
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// try to move, and revert if invalid due to check in progress
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enum pieces tmp = cb_move(cb, from_row, from_col, to_row, to_col);
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if (player_checks(cb, p == WHITE ? BLACK : WHITE) && check_before) {
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DEBUG("move: move does not end check state, invalid");
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cb_move_restore(cb, tmp, from_row, from_col, to_row, to_col);
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return INVALID;
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} else if (player_checks(cb, p)) {
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if (player_checkmates(cb, p)) {
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return CHECK_MATE;
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} else {
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return CHECK;
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}
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} else {
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return VALID;
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}
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}
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}
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int main() {
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struct chessboard cb;
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init_chessboard(&cb);
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enum player p = WHITE;
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char from[5], to[5];
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while (true) {
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print_chessboard(&cb);
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printf("%s moves.\n", p == WHITE ? "White" : "Black");
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printf("From: ");
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fgets(from, 5, stdin);
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// remove trailing \n: https://stackoverflow.com/q/2693776
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strtok(from, "\n");
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if (strcmp(from, "exit") == 0) {
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printf("Exiting...\n");
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return 0;
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}
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printf("To: ");
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fgets(to, 5, stdin);
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strtok(to, "\n");
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enum mstatus s = move(&cb, p, from, to);
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switch (s) {
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case INVALID:
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printf("Invalid move.\n");
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break;
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case VALID:
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printf("No check/checkmate.\n");
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break;
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case CHECK:
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printf("Check.\n");
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break;
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case CHECK_MATE:
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printf("Checkmate, %s wins.\n", p == WHITE ? "white" : "black");
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}
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if (s != INVALID) {
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p = !p; // switch player: this works since WHITE = 0 and BLACK = 1
|
|
}
|
|
}
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|
}
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