board->moves = 0;
}
+dvonn_bool_t
+dvonn_board_cell_occupied (dvonn_board_t *board,
+ int x, int y)
+{
+ if (x < 0 || x >= DVONN_BOARD_X_SIZE ||
+ y < 0 || y >= DVONN_BOARD_Y_SIZE)
+ {
+ return FALSE;
+ }
+
+ if (board->cells[x][y].type == DVONN_CELL_INVALID ||
+ board->cells[x][y].type == DVONN_CELL_EMPTY)
+ {
+ return FALSE;
+ }
+
+ return TRUE;
+}
+
+dvonn_bool_t
+dvonn_board_cell_surrounded (dvonn_board_t *board,
+ int x, int y)
+{
+ int surround_count;
+
+ surround_count =
+ dvonn_board_cell_occupied (board, x - 1, y) +
+ dvonn_board_cell_occupied (board, x + 1, y) +
+ dvonn_board_cell_occupied (board, x, y - 1) +
+ dvonn_board_cell_occupied (board, x, y + 1) +
+ dvonn_board_cell_occupied (board, x + 1, y - 1) +
+ dvonn_board_cell_occupied (board, x - 1, y + 1);
+
+ return (surround_count == 6);
+}
+
static dvonn_bool_t
dvonn_board_move_legal (dvonn_board_t *board,
int x1, int y1,
int x2, int y2,
char **error)
{
+ int distance;
+
if (x1 < 0 || x1 >= DVONN_BOARD_X_SIZE ||
y1 < 0 || y1 >= DVONN_BOARD_Y_SIZE ||
x2 < 0 || x2 >= DVONN_BOARD_X_SIZE ||
return FALSE;
}
- if (board->cells[x1][y1].type == DVONN_CELL_INVALID) {
+ if (board->cells[x1][y1].type == DVONN_CELL_INVALID ||
+ board->cells[x2][y2].type == DVONN_CELL_INVALID)
+ {
*error = "Not a valid board space";
return FALSE;
}
if (board->cells[x1][y1].type == DVONN_CELL_EMPTY) {
- *error = "There is no piece there to move";
+ *error = "There are no pieces there to move";
+ return FALSE;
+ }
+
+ if (dvonn_board_cell_surrounded (board, x1, y1)) {
+ *error = "You cannot move a piece that is surrounded";
return FALSE;
}
if (board->cells[x1][y1].type != board->player) {
- *error = "You cannot move your opponent's piece";
+ *error = "You cannot move your opponent's stack";
return FALSE;
}
- /* XXX: Need to code up DVONN-legal move calculation here. */
+ if (board->cells[x2][y2].type == DVONN_CELL_EMPTY) {
+ *error = "You cannot move to an empty space";
+ return FALSE;
+ }
+
+ /* Move must be in a straight line, which in our array is
+ * horizontal, vertical, or one of the diagonals. */
+ if (x2 == x1)
+ distance = abs (y2 - y1);
+ else if (y2 == y1)
+ distance = abs (x2 - x1);
+ else if ((x2 - x1) == - (y2 - y1))
+ distance = abs (x2 - x1);
+ else {
+ *error = "Move is not in a straight line";
+ return FALSE;
+ }
+
+ if (distance != board->cells[x1][y1].height) {
+ *error = "Move distance is not the same as stack height";
+ return FALSE;
+ }
return TRUE;
}