#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define LEN(arr) ((int) (sizeof(arr) / sizeof(arr)[0]))
#define MAX 80
#define MAX_ENTRIES 2

struct passwd {
	char user[MAX];
	char password[MAX];
};

typedef struct passwd Passwd;

static Passwd entries[MAX_ENTRIES];
static int slot;

void has_slot()
{
	if (slot == -1 ) {
		puts("No empty slot.");
		exit(1);
	}
}

void exists(char *user)
{
	slot = -1;

	for (int i = LEN(entries) - 1; i >= 0; i--) {
		if (strcmp(entries[i].user, user) == 0) {
			puts("A password for user has already been created.");
			exit(1);
		}
		if (strlen(entries[i].user) == 0)
			slot = i;
	}
}

char * decrypt(char *password)
{
	int l = strlen(password);

	while (*password != '\0') {
		*password -= 1;
		password++;
	}

	return password - l;
}

char * encrypt(char *password)
{
	int l = strlen(password);

	while (*password != '\0') {
		*password += 1;
		password++;
	}

	return password - l;
}

char * fill(char *password, int len)
{
	int l = strlen(password);

	if (len >= l) {
		for (password += l; l < len; l++, password++)
			*password = '?';
	} else {
		l = 0;
	}

	*password = '\0';

	return password - l;
}

void create(char *user, char *password)
{
	exists(user);
	has_slot();

	strcpy(entries[slot].user, user);
	strcpy(entries[slot].password, encrypt(password));
}

void get(char *user, char *password)
{
	char password2[MAX];

	printf("user: ");
	scanf("%s", user);

	printf("password: ");
	scanf("%s", password);

	printf("retype password: ");
	scanf("%s", password2);

	if (strcmp(password, password2) != 0) {
		puts("Passwords are not equal.");
		exit(1);
	}
}

void find_password(char *password)
{
	int i;
	for (i = 0; i < LEN(entries); i++) {
		if (strcmp(entries[i].password, password) == 0) {
			printf("user: %s password: %s\n",
			       entries[i].user,
			       entries[i].password);
			break;
		}
	}
}

int main()
{
	// char user[MAX];
	// char password[MAX];

	// get(user, password);
	// printf("scanned: %s\n", password);
	// create(user, password);
	// printf("encrypted: %s\n", entries[0].password);
	// printf("decrypted: %s\n", decrypt(entries[0].password));

	// strcpy(user, "u");
	// strcpy(password, "abc");
	// create(user, password);

	// printf("find %s …\n", password);
	// find_password(password);

	// strcpy(user, "u");
	// strcpy(password, "abc");
	// create(user, password);

	// strcpy(user, "user");
	// strcpy(password, "123456");
	// printf("<%s>\n", fill(password,10));
	// printf("<%s>\n", fill(password,-1));
	// printf("<%s>\n", fill(password,6));

	return 0;
}

// vim: set ft=c :