exports.user_exists(user, callback) {
    query_read({username: user}, db_users, function(val, is_err) {
        if (val != [] || is_err != 0) {
            callback(1);
        } else {
            callback(0);
        }
    }
}

exports.reg_user = function(user, pass, salt, rname, rsurname, bday, language, callback) {
    user_exists(user, function(exist) {
        if (exist == 1) {
            callback(JSON.stringify({error: 1})); // error 1: Existent user
        } else {
            db.query_save({username: user, password: sha512.hex(salt+pass), realname: rname, realsurname: rsurname, "bday": bday, "language": language},
            db_users,
            function(val, is_err) {
                if (is_err) {
                    callback(JSON.stringify({error: 2})); // Internal db error, wrong query (???)
                } else {
                    callback(JSON.stringify({error: 0})); // No error, everything is ok
                }
            }
        }
    }
}