/* See LICENSE file for copyright and license details. */
#include "common.h"

/* TODO add support for up and down arrows to browse previous entries in the same session */

USAGE("");


struct die {
	intmax_t count;
	intmax_t min;
	intmax_t max;
};


static intmax_t
random_int(intmax_t min, intmax_t max)
{
	uintmax_t res, max0 = (uintmax_t)max - (uintmax_t)min, max1;
	int steps;
	ssize_t r;
	size_t n;

	for (max1 = max0, steps = 0; max1 < UINTMAX_MAX && (max1 & (max1 + 1)); steps++)
		max1 |= max1 >> steps;

	do {
		for (n = 0; n < sizeof(res); n += (size_t)r) {
			r = getrandom(&((char *)&res)[n], sizeof(res) - n, 0);
			if (r < 0)
				eprintf("getrandom <buffer> %zu 0:", sizeof(res) - n);
		}
		res &= max1;
	} while (res > max0);

	return (intmax_t)res + min;
}


static void
roll_dice(const struct die *dice, size_t n)
{
	intmax_t sum = 0, res, j;
	size_t i;
	for (i = 0; i < n; i++) {
		for (j = 0; j < dice[i].count; j++) {
			sum += res = random_int(dice[i].min, dice[i].max);
			printf("Die roll: %ji\n", res);
		}
	}
	if (n > 1 || (n == 1 && dice[0].count > 1)) {
		printf("Sum: %ji\n", sum);
	}
}


static int
parse_dice(const char *s, struct die **dicep, size_t *ndicep)
{
	struct die *dice = NULL, *die;
	size_t ndice = 0;
	intmax_t min_sum = 0, max_sum = 0, num, i;

	ndice = 0;

	for (;;) {
		while (*s == ' ' || *s == '\t')
			s++;

		if (!*s)
			break;

		if (!isdigit(*s) && *s != '-' && *s != 'd' && *s != 'D')
			goto invalid;

		dice = ereallocn(dice, ++ndice, sizeof(*dice), 0);
		die = &dice[ndice - 1];
		die->count = 1;
		die->min = 1;
		num = 1;
		if (*s == 'd' || *s == 'D')
			goto at_d;
		errno = 0;
		num = strtoimax(s, (void *)&s, 0);
		if (errno)
			goto invalid;
		if (*s == 'd' || *s == 'D') {
		at_d:
			s++;
			if (num < 1)
				goto invalid;
			die->count = num;
			if (!isdigit(*s) && *s != '-')
				goto invalid;
			errno = 0;
			num = strtoimax(s, (void *)&s, 0);
			if (errno)
				goto invalid;
		}
		die->max = num;
		if (*s == '-') {
			s++;
			die->min = num;
			errno = 0;
			die->max = strtoimax(s, (void *)&s, 0);
			if (errno)
				goto invalid;
		}
		if (die->min > die->max)
			goto invalid;

		for (i = 0; i < die->count; i++) {
			if (die->min < 0 && min_sum < INTMAX_MIN - die->min) {
				printf("\033[31m%s\033[m\n", "Negative overflow in sum of minimums");
				return -1;
			}
			if (die->min > 0 && min_sum > INTMAX_MAX - die->min) {
				printf("\033[31m%s\033[m\n", "Positive overflow in sum of minimums");
				return -1;
			}
			if (die->max < 0 && max_sum < INTMAX_MIN - die->max) {
				printf("\033[31m%s\033[m\n", "Negative overflow in sum of maximums");
				return -1;
			}
			if (die->max > 0 && max_sum > INTMAX_MAX - die->max) {
				printf("\033[31m%s\033[m\n", "Positive overflow in sum of maximums");
				return -1;
			}
			min_sum += die->min;
			max_sum += die->max;
		}

		if (*s && *s != ',' && *s != ' ' && *s != '\t')
			goto invalid;

		if (*s == ',')
			s++;
	}

	if (*s || !ndice)
		goto invalid;

	free(*dicep);
	*dicep = dice;
	*ndicep = ndice;

	return 0;

invalid:
	printf("\033[31m%s\033[m\n", "Invalid input");
	return -1;
}


int
main(int argc, char *argv[])
{
	struct die *dice = NULL;
	size_t ndice = 0;
	char *line = NULL;
	size_t size = 0;
	ssize_t len;
	int first;

	NOFLAGS(argc);

	for (first = 1;; first = 0) {
	again:
		if (first)
			printf("\033[1m%s: \033[m", "Enter dice to roll");
		else
			printf("\033[1m%s\033[m (%s): ", "Enter dice to roll", "Leave empty to reroll");
		fflush(stdout);
		len = getdelim(&line, &size, '\n', stdin);
		if (len < 0) {
			printf("\n");
			break;
		}
		if (len && line[len - 1] == '\n')
			line[--len] = '\0';
		if (!strcasecmp(line, "q") || !strcasecmp(line, "exit") || !strcasecmp(line, "quit"))
			break;
		if (!*line ? first : parse_dice(line, &dice, &ndice))
			goto again;
		roll_dice(dice, ndice);
	}

	if (ferror(stdin))
		eprintf("getdelim <stdin>:");

	free(dice);
	free(line);
	return 0;
}