moo.c

#include <assert.h>
#include <math.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>

#ifdef __WIN32
#ifdef __linux__
#undef __WIN32
#else
#include <windows.h>
#include <Fcntl.h>
#endif
#else
#include <termios.h>

static struct termios orig_termios;
#endif

static void enter_raw_mode(void);

#define NUMBER_LEN   4
#define MAX_TRIES    9
#define DIGITS      "123456789"
#define NUM_DIGITS  (sizeof DIGITS - 1)
#define INDICES_MAX (pow(NUM_DIGITS, NUMBER_LEN) - 1)

static char secret[NUMBER_LEN + 1], guess[NUMBER_LEN + 1];

static void
pick_the_number(void) {
	static char digits[] = DIGITS;
	int indices;
	size_t i, j;
	char tmp;

	indices = rand() / ((RAND_MAX / (INDICES_MAX + 1)) + 1);
	for (i = 0; i < NUMBER_LEN; i++) {
		j = indices % NUM_DIGITS;
		tmp = digits[i];
		digits[i] = digits[j];
		digits[j] = tmp;
		indices /= NUM_DIGITS;
	}

	strncpy(secret, digits, NUMBER_LEN);
}

static int
read_guess(void) {
	size_t i;
	int c;

	i = 0;
	while ((c = getchar()) != EOF)
#ifdef __WIN32
		if (c == VK_BACK) {
#else
		if (c == orig_termios.c_cc[VERASE]) {
#endif
			if (i == 0) {
				fputc('\a', stderr);
			}
			else {
				fputs("\b \b", stderr);
				i--;
			}
		}
		else if (c == '\r') {
			if (i < NUMBER_LEN)
				fputc('\a', stderr);
			else
				return 1;
		}
#ifndef __WIN32
		else if (c == orig_termios.c_cc[VINTR]) {
			killpg(getpgrp(), SIGINT);
		}
		else if (c == orig_termios.c_cc[VEOF] && i == 0) {
			break;
		}
#endif
		else {
			if (i >= NUMBER_LEN) {
				fputc('\a', stderr);
			}
			else if (strchr(DIGITS, c) == NULL) {
				fputc('\a', stderr);
			}
			else if (memchr(guess, c, i) != NULL) {
				fputc('\a', stderr);
			}
			else {
				fputc(c, stderr);
				guess[i] = c;
				i++;
			}
		}

	return 0;
}

static void
print_count(int count, const char *what) {
	if (count > 0) {
		printf("%d %s", count, what);

		if (count > 1)
			putchar('s');
	}
}

static int
evaluate_guess(void) {
	size_t i;
	int bulls, cows;

	bulls = 0;
	cows = 0;

	for (i = 0; i < NUMBER_LEN; i++)
		if (guess[i] == secret[i])
			bulls++;

	for (i = 0; i < NUMBER_LEN; i++)
		if (strchr(secret, guess[i]) != NULL)
			cows++;

	cows -= bulls;

	print_count(bulls, "bull");

	if (bulls > 0 && cows > 0)
		fputs(" and ", stdout);

	print_count(cows, "cow");
	fputs("\r\n", stdout);

	return (bulls == NUMBER_LEN);
}

int
main(void) {
	int tries;

	enter_raw_mode();

	srand(time(NULL));
	pick_the_number();

	fprintf(stderr, "What is my number? \
%d different digits and %d guesses\r\n", NUMBER_LEN, MAX_TRIES);

	for (tries = 1; tries <= MAX_TRIES; tries++) {
		fprintf(stderr, "%d\t", tries);

		if (!read_guess()) {
			assert(!ferror(stdin));
			return 1;
		}

		fputc('\t', stderr);

		if (evaluate_guess())
			break;
	}

	if (tries > MAX_TRIES)
		printf("You lose. It was %s.\r\n", secret);
	else
		fputs("You win!\r\n", stdout);
}

#ifndef __WIN32
static void
exit_raw_mode(void) {
	tcsetattr(2, TCSAFLUSH, &orig_termios);
}
#endif

static void
enter_raw_mode(void) {
#ifdef __WIN32
	HANDLE console;
	DWORD mode;

	console = GetStdHandle(STD_INPUT_HANDLE);
	assert(GetConsoleMode(console, &mode));
	mode &= ~(ENABLE_ECHO_INPUT | ENABLE_LINE_INPUT);
	assert(SetConsoleMode(console, mode));
	_setmode(_fileno(stdin), _O_BINARY);
#else
	struct termios raw;

	assert(tcgetattr(2, &orig_termios) != -1);

	raw = orig_termios;
	raw.c_iflag &= ~(BRKINT | ICRNL | INPCK | ISTRIP | IXON);
	raw.c_oflag &= ~OPOST;
	raw.c_cflag |= CS8;
	raw.c_lflag &= ~(ECHO | ICANON | IEXTEN | ISIG);
	raw.c_cc[VMIN] = 1;
	raw.c_cc[VTIME] = 0;

	atexit(exit_raw_mode);
	assert(tcsetattr(2, TCSAFLUSH, &raw) != -1);
#endif
}