#include "zobrist.h"

// ===================================================================
// Globals
// ===================================================================

static uint64_t *zobrist[15];

// ===================================================================
// Helpers
// ===================================================================


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

int
zobrist_init(void) {
	for (int k=0; k<15; k++) {
		if (zobrist[k] != NULL) return EXIT_FAILURE;
	}

	for (int j=0; j<15; j++) {
		zobrist[j] = malloc(sizeof(uint64_t)*board_size*board_size*(2*3+1));
		for (int k=0; k<board_size*board_size*(2*3+1); k++) {
			XORSHIFT64;
			zobrist[j][k] = RANDOM64;
		}
	}

	return EXIT_SUCCESS;
}

void
zobrist_free(void) {
	for (int k=0; k<15; k++) {
		if (zobrist[k] != NULL) {
			free(zobrist[k]);
			zobrist[k] = 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[h][l*(2*3+1)+(c&1)*3+s];
	}
	return hash;
}

uint64_t
zobrist_apply(const action_t action, uint64_t hash) {
	const enum A_TYPE type = GET_TYPE(action);
	const int8_t loc = GET_LOC(action);
	if (type == A_PLACE) {
		enum COLOUR c = (current_colour == C_BLACK) ? C_WHITE : C_BLACK;
		hash ^= zobrist[0][loc*(2*3+1)
											 +c*3
											 +GET_DATA0(action)];
	} else {
		const uint8_t gaps = GET_DATA0(action) & 0x7F,
			crush = GET_DATA0(action) & 0x80,
			num = GET_DATA1(action) & 0x0F,
			dir = GET_DATA1(action) >> 4;
		const int8_t delta = move_deltas[dir];

		int8_t steps = 1;
		uint8_t gap_bit = 1, num_dropped = 1, total = COUNT_AT(loc);
		for (int8_t d = 1; d < num; d++, num_dropped++, gap_bit <<= 1) {
			if (gaps & gap_bit) {
				const int8_t target = loc+steps*delta, th = COUNT_AT(target);
				// Stash these stones to offset for the height at source
				total += num_dropped;
				// Apply XOR for stones at source and current target
				uint8_t point = 1;
				for (int k = 0, ht = th-1, hs = total-1; k < num_dropped;
						 k++, ht--, hs--, point<<=1) {
					hash ^= zobrist[ht][target*(2*3+1)
														 +(point & colours[target])*3
														 +STONE_FLAT];
					hash ^= zobrist[hs][loc*(2*3+1)
															+(point & colours[target])*3
															+STONE_FLAT];
				}
				// Continue processing gap sequence
				num_dropped = 0;
				steps++;
			}
		}
		total += num_dropped;
		const int8_t target = loc+steps*delta, th = COUNT_AT(target);
		const enum STONE_VARIANT top_stone = STONE_AT(target);
		// Stash these stones to offset for the height at source
		// Apply XOR for stones at source and end target. After this
		// source will be correct, but we must account for crush @ target.
		uint8_t point = 1;
		for (int k = 0, ht = th-1, hs = total-1; k < num_dropped;
				 k++, ht--, hs--, point<<=1) {
			if (k == 0) {
				hash ^= zobrist[ht][target*(2*3+1)
														+(point & colours[target])*3
														+top_stone];
				hash ^= zobrist[hs][loc*(2*3+1)
														+(point & colours[target])*3
														+top_stone];
			} else {
				hash ^= zobrist[ht][target*(2*3+1)
														+(point & colours[target])*3
														+STONE_FLAT];
				hash ^= zobrist[hs][loc*(2*3+1)
														+(point & colours[target])*3
														+STONE_FLAT];
			}
		}
		// Correct for crush
		if (crush) {
			hash ^= zobrist[th-1][target*(2*3+1)
														+(colours[target] & 1)*3
														+STONE_FLAT];
			hash ^= zobrist[th-1][target*(2*3+1)
														+(colours[target] & 1)*3
														+STONE_STANDING];
		}
	}
	return hash;
}