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

#include "lua-bcrypt/compat/include/pwd.h"

#define USER_DATABASE "./user.db"
#define SECURITY_LEVEL 12
#define SEP '|'

static bool
valid_char(int ch)
{
	return isalnum(ch) || ch == '_' || ch == '-' || ch == '.';
}

/**
 * Create a new user/password
 *
 * \param[in] username
 * \param[in] password
 *
 * \return true on success (user was created) or false on error
 */
bool
create_user(const char *username, const char *password)
{
	// check for invalid characters in username
	for ( const char *ptr = username; *ptr; ++ptr ) {
		if ( !valid_char(*ptr) ) {
			return false;
		}
	}

	FILE *db = fopen(USER_DATABASE, "a");
	if ( db == NULL ) {
		return false;
	}

	char hash[_PASSWORD_LEN + 1] = { 0 };

	if ( bcrypt_newhash(password, SECURITY_LEVEL, hash, _PASSWORD_LEN) != 0 ) {
		return false;
	}

	fprintf(db, "%s%c%s\n", username, SEP, hash);
	fclose(db);

	return true;
}

/**
 * Check is a valid username/password exists in the user-database
 *
 * username A username
 * password A strong password
 *
 * @return true, if the user was successfully authenticated, otherwise false
 */
bool
check_user(const char *const username, const char *const password)
{
	FILE *db = fopen(USER_DATABASE, "r");
	if ( db == NULL ) {
		return false;
	}

	const size_t username_length = strlen(username);
	char line[256];

	bool found = false;
	while ( !found && fgets(line, sizeof line, db) ) {
		line[strcspn(line, "\r\n")] = '\0'; // remove newline (if exists)

		if ( strncmp(line, username, username_length) != 0 ) {
			continue;
		}

		if ( line[username_length] != SEP ) {
			continue;
		}

		if ( bcrypt_checkpass(password, &line[username_length+1]) != 0 ) {
			continue;
		}

		// User successfully authenticated!
		found = true;
	}

	fclose(db);

	return found;
}

/**
 * Check if a valid username already exists in the user-database
 *
 * \param[in] username to be checked
 *
 * \return true, if the user was successfully authenticated, otherwise false
 */
bool
check_user_if_exists(const char *username)
{
	FILE *db = fopen(USER_DATABASE, "r");
	if ( db == NULL ) {
		return false;
	}

	const size_t username_length = strlen(username);
	char line[256];

	bool found = false;
	while ( !found && fgets(line, sizeof line, db) ) {
		line[strcspn(line, "\r\n")] = '\0'; // remove newline (if exists)

		if ( strncmp(line, username, username_length) != 0 ) {
			continue;
		}

		if ( line[username_length] != '|' ) {
			continue;
		}

		// User successfully authenticated!
		found = true;
	}

	fclose(db);

	return found;
}

int
main(void)
{
	if ( check_user("Thomas", "Passwort") ) {
		puts("Benutzer erfolgreich überprüft!");
	}

	return EXIT_SUCCESS;
}