/*
 * Copyright (C) 2022 Camden Dixie O'Brien
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public
 * License along with this program.  If not, see
 * <https://www.gnu.org/licenses/>.
 */

#ifndef SUD_H
#define SUD_H

#include <stdint.h>

#define SEGLEN 3
#define NDIGITS 9
#define NCELLS 81

#define DETMASK 0x8000
#define VALSHIFT 9
#define VALMASK 0x1e00
#define PVALSMASK 0x01ff

#define DET(x) (x & DETMASK)
#define VAL(x) ((x & VALMASK) >> VALSHIFT)

#define IDX(r, c) (NDIGITS * (r) + (c))

struct sudoku {
	uint16_t cells[NCELLS];
};

enum update_res { NOT_ALLOWED, ALREADY_DET, OK };

enum check_res { INCOMPLETE, INCORRECT, SOLVED };

/**
 * Read `NCELLS` values from the given pointer and load them into the
 * sudoku.
 */
int load(struct sudoku *sud, const char *ptr);

/**
 * Write the sudoku to the given pointer (`NCELLS` bytes).
 */
void save(struct sudoku *sud, char *ptr);

/**
 * Attempt to update the cell at index `i` to have the value
 * `val`. Returns `OK`.
 */
enum update_res update(struct sudoku *sud, unsigned i, unsigned val);

/**
 * Print a string representation of the sudoku to stdout.
 */
void print(const struct sudoku *sud);

/**
 * Determine whether the sudoku has been solved correctly, contains
 * invalid choices or is incomplete.
 */
enum check_res check(const struct sudoku *sud);

/**
 * Determine whether all the sudoku's cells have been determined.
 */
int filled(const struct sudoku *sud);

#endif