#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <crypt.h>

void generate_salt(char *salt_buffer)
{
	const char *charset = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789./";
	salt_buffer[0] = '$';
	salt_buffer[1] = '6'; // SHA-512
	salt_buffer[2] = '$';
	
	srand(time(NULL));
	for (int i = 3; i < 19; i++) {
		salt_buffer[i] = charset[rand() % 64];
	}
	salt_buffer[19] = '$';
	salt_buffer[20] = '\0';
}

char* hash_password(const char *password)
{
	struct crypt_data data;
	data.initialized = 0;
	
	char salt[21];
	generate_salt(salt);
	
	char *hash = crypt_r(password, salt, &data);
	return hash ? strdup(hash) : NULL;
}

int verify_password(const char *password, const char *stored_hash)
{
	struct crypt_data data;
	data.initialized = 0;
	
	char *calculated = crypt_r(password, stored_hash, &data);
	
	return (calculated && strcmp(calculated, stored_hash) == 0);
}