/*
 * Copyright (c) Camden Dixie O'Brien
 * SPDX-License-Identifier: AGPL-3.0-only
 */

#include "puzz.h"

#include <assert.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/time.h>

#define NRUNS 1000

enum { UNKNOWN = 0xfe, KILLER = 0xfd };

static void setadj(puzz_t field, int x, int y, uint8_t from, uint8_t to)
{
	for (int yp = y - 1; yp < y + 2; ++yp) {
		for (int xp = x - 1; xp < x + 2; ++xp) {
			if (xp < 0 || xp >= WIDTH || yp < 0 || yp >= HEIGHT
			    || (xp == x && yp == y))
				continue;
			field[xp][yp] = field[xp][yp] == from ? to : field[xp][yp];
		}
	}
}

static void getadj(puzz_t field, int *x, int *y, uint8_t val)
{
	for (int yp = *y - 1; yp < *y + 2; ++yp) {
		for (int xp = *x - 1; xp < *x + 2; ++xp) {
			if (xp < 0 || xp >= WIDTH || yp < 0 || yp >= HEIGHT
			    || (xp == *x && yp == *y))
				continue;
			if (field[xp][yp] == val) {
				*x = xp;
				*y = yp;
				return;
			}
		}
	}
	assert(false);
}

static status_t solve(void)
{
	puzz_t field;
	memset(field, UNKNOWN, sizeof(field));

	status_t status;
	int total_mines = 0, total_unknowns = WIDTH * HEIGHT;
	do {
		int x = rand() % WIDTH;
		int y = rand() % HEIGHT;

	probe:
		if (field[x][y] != MINE && (status = probe(x, y, field)) == DEAD) {
			field[x][y] = KILLER;
			break;
		}

	update:
		total_mines = total_unknowns = 0;
		for (y = 0; y < HEIGHT; ++y) {
			for (x = 0; x < WIDTH; ++x) {
				total_mines += field[x][y] == MINE ? 1 : 0;
				total_unknowns += field[x][y] == UNKNOWN ? 1 : 0;
			}
		}
		for (y = 0; y < HEIGHT; ++y) {
			for (x = 0; x < WIDTH; ++x) {
				if (field[x][y] == UNKNOWN || field[x][y] == MINE)
					continue;

				const int mines = countadj(field, x, y, MINE);
				const int unknowns = countadj(field, x, y, UNKNOWN);
				if (unknowns == 0)
					continue;

				if (mines + unknowns == field[x][y]) {
					setadj(field, x, y, UNKNOWN, MINE);
					goto update;
				}

				if (mines == field[x][y]) {
					getadj(field, &x, &y, UNKNOWN);
					goto probe;
				}
			}
		}
	} while (total_mines < NMINES);

	return status;
}

int main(void)
{
	struct timeval tv;
	if (gettimeofday(&tv, NULL) != 0) {
		perror("Failed to get time");
		exit(1);
	}
	srand(tv.tv_usec);

	int nsolved = 0;
	for (int i = 0; i < NRUNS; ++i) {
		gen();
		nsolved += solve() == OK ? 1 : 0;
	}

	const double prop = (double)nsolved / NRUNS;
	printf("Solved %d/%d (%0.1f%%)\n", nsolved, NRUNS, 100 * prop);

	return 0;
}