const Repository = require('../repository/repository');
const passwordService = require('./passwordService');

const userRepository = new Repository('users');

class UserService {
    /**
     * Get a user from database by its login.
     * @param {String} login User login.
     * @param {Function} onSuccess Callback function to execute if a user exists with this login.
     * @param {Function} onError Callback function to execute if not any user exists with this login.
     */
    getUser(login, onSuccess, onError) {
        userRepository.find({login: login}, results => onSuccess(results[0]), onError);
    }

    /**
     * Checks if credentials matches to an existing user, that have this password.
     * @param {String} login User login.
     * @param {String} password User password, in plain text.
     * @param {Function} onSuccess Callback function to execute if a user exists with this login.
     * @param {Function} onError Callback function to execute if not any user exists with this login.
     */
    checkCredentials(login, password, onSuccess, onError) {
        this.getUser(
            login,
            dbUser => {
                if (!!dbUser && passwordService.areSamePasswords(password, dbUser.password)) {
                    onSuccess();
                } else {
                    onError();
                }
            },
            // If login is incorrect, the "getUser" function will return "undefined".
            // So if "user" is "undefined", this proofs that login is incorrect
            onError
        );
    }
}

const singleton = new UserService();
module.exports = singleton;