/*
	This file is part of ctak.

	This program is free software: you can redistribute it and/or modify
	it under the terms of the GNU 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
	General Public License for more details.

	You should have received a copy of the GNU General Public License
	along with Takwrap.  If not, see <https://www.gnu.org/licenses/>.
*/

#include "zobrist.h"

// ===================================================================
// Variables
// ===================================================================

static uint64_t *zobrist;

// ===================================================================
// Exported method implementations
// ===================================================================

int zobrist_init(void) {
	if (zobrist != NULL) return EXIT_FAILURE;

	zobrist = malloc(sizeof(uint64_t)*board_size*board_size*(15*2*3));
	// TODO: trap errno

	for (int k=0; k<board_size*board_size*(15*2*3); k++) {
		XORSHIFT64;
		zobrist[k] = RANDOM64;
	}

	return EXIT_SUCCESS;
}

void zobrist_free(void) {
	if (zobrist != NULL) {
		free(zobrist);
		zobrist = NULL;
	}
}

uint64_t zobrist_compute(void) {
	uint64_t hash = 0;
	for (uint8_t l=0; l<board_size*board_size; l++) {
		colour_stack_t c = colours[l];
		const uint8_t count = COUNT_AT(l);
		enum STONE_VARIANT s = STONE_AT(l);
		for (uint8_t h=0; h<count; h++, c >>= 1)
			hash ^= zobrist[l*(15*2*3)+h*2*3+(c&1)*3+s];
	}
	return hash;
}