class Forum {
    users;
    questions;
    #id;
    logged;


    set users(value) {
        this._users = value;
    }

    set questions(value) {
        this._questions = value;
    }

    set logged(value) {
        this._logged = value;
    }

    get users() {
        return this._users;
    }

    get questions() {
        return this._questions;
    }

    constructor() {
        this._users = [];
        this._questions = [];
        this.#id = 1;
        this._logged = [];
    }

    register(username, password, repeatPassword, email) {
        if (username === "" || password === "" || repeatPassword === "" || email === "") {
            throw new Error("Input can not be empty");
        }
        if (password !== repeatPassword) {
            throw new Error("Passwords do not match");
        }
        let isRegistered = this._users.filter(el => el.username === username)[0];
        let isRegisteredEmail = this._users.filter(el => el.email === email)[0];
        if (isRegistered !== undefined || isRegisteredEmail !== undefined) {
            throw new Error("This user already exists!");
        }
        let obj = {
            username: username,
            email: email,
            password: password
        };
        this._users.push(obj);
        return `${username} with ${email} was registered successfully!`;
    }

    login(username, password) {
        let user = this._users.filter(el => el.username === username)[0];
        if (user === undefined) {
            throw new Error("There is no such user");
        }
        if (user.username === username && user.password === password) {
            this._logged.push(user);
            return "Hello! You have logged in successfully";
        }
    }

    logout(username, password) {
        let user = this._users.filter(el => el.username === username)[0];
        if (user === undefined) {
            throw new Error("There is no such user");
        }
        if (user.username === username && user.password === password) {
            let indexOf = this._logged.indexOf(user);
            this._logged.splice(indexOf, 1);
            return "You have logged out successfully";
        }
    }

    postQuestion(username, question) {
        let user = this._users.filter(el => el.username === username)[0];
        let isLogged = this._logged.filter(el => el.username === username)[0];
        if (user === undefined || isLogged === undefined) {
            throw new Error("You should be logged in to post questions");
        }
        if (question === "") {
            throw new Error("Invalid question");
        }
        let obj = {
            id: this.#id,
            question: question,
            username: username,
            answers: []
        };
        this._questions.push(obj);
        this.#id++;
        return "Your question has been posted successfully";
    }

    postAnswer(username, id, answer) {
        let user = this._users.filter(el => el.username === username)[0];
        let isLogged = this._logged.filter(el => el.username === username)[0];
        if (user === undefined || isLogged === undefined) {
            throw new Error("You should be logged in to post answers");
        }
        if (answer === "") {
            throw new Error("Invalid answer");
        }
        let question = this._questions.filter(el => el.id === id)[0];
        if (question === undefined) {
            throw new Error("There is no such question");
        }
        let obj = {
            username: username,
            answer: answer
        };
        question.answers.push(obj);
        return "Your answer has been posted successfully";
    }

    showQuestions() {
        let output = "";
        this._questions.forEach(el => {
            output += `Question ${el.id} by ${el.username}: ${el.question}\n`;
            let answers = "";
            el.answers.forEach(answer => {
                answers += `---${answer.username}: ${answer.answer}\n`;
            });
            output += answers;
        });
        return output.trim();
    }

}