DeutschLernen/GermanApp/Domain/Entities/QuizQuestion.cs

namespace GermanApp.Domain.Entities;

/// <summary>
/// Represents a quiz question for a lesson.
/// Each question has a type (multiple choice, true/false, fill-in-the-blank, etc.)
/// and is associated with a specific lesson.
/// </summary>
public class QuizQuestion
{
    public int Id { get; private set; }
    public int LessonId { get; private set; }
    public string QuestionText { get; private set; } = string.Empty;
    public QuestionType Type { get; private set; }
    public string? CorrectAnswer { get; private set; }
    public int Difficulty { get; private set; } // 1-5 scale
    public int Order { get; private set; }
    public bool IsActive { get; private set; } = true;
    public DateTime CreatedAt { get; private set; }
    public DateTime? UpdatedAt { get; private set; }

    // Navigation property
    public virtual Lesson? Lesson { get; private set; }
    public virtual ICollection<QuizOption> Options { get; private set; } = new List<QuizOption>();

    /// <summary>
    /// Constructor for EF Core deserialization.
    /// </summary>
    private QuizQuestion() { }

    /// <summary>
    /// Factory method to create a new quiz question.
    /// </summary>
    /// <param name="lessonId">ID of the parent lesson</param>
    /// <param name="questionText">The question text</param>
    /// <param name="type">The question type</param>
    /// <param name="correctAnswer">The correct answer</param>
    /// <param name="difficulty">Difficulty level (1-5)</param>
    /// <param name="order">Sort order within the lesson</param>
    public static QuizQuestion Create(
        int lessonId,
        string questionText,
        QuestionType type,
        string correctAnswer,
        int difficulty = 3,
        int order = 1)
    {
        if (difficulty < 1 || difficulty > 5)
            throw new ArgumentOutOfRangeException(nameof(difficulty), "Difficulty must be between 1 and 5");
        
        if (string.IsNullOrWhiteSpace(questionText))
            throw new ArgumentException("Question text cannot be empty", nameof(questionText));

        return new QuizQuestion
        {
            LessonId = lessonId,
            QuestionText = questionText,
            Type = type,
            CorrectAnswer = correctAnswer,
            Difficulty = difficulty,
            Order = order,
            CreatedAt = DateTime.UtcNow
        };
    }

    /// <summary>
    /// Updates the question text.
    /// </summary>
    public void UpdateQuestionText(string newQuestionText)
    {
        if (string.IsNullOrWhiteSpace(newQuestionText))
            throw new ArgumentException("Question text cannot be empty", nameof(newQuestionText));

        QuestionText = newQuestionText;
        UpdatedAt = DateTime.UtcNow;
    }

    /// <summary>
    /// Updates the correct answer.
    /// </summary>
    public void UpdateCorrectAnswer(string newCorrectAnswer)
    {
        CorrectAnswer = newCorrectAnswer;
        UpdatedAt = DateTime.UtcNow;
    }

    /// <summary>
    /// Updates the difficulty level.
    /// </summary>
    public void UpdateDifficulty(int newDifficulty)
    {
        if (newDifficulty < 1 || newDifficulty > 5)
            throw new ArgumentOutOfRangeException(nameof(newDifficulty), "Difficulty must be between 1 and 5");

        Difficulty = newDifficulty;
        UpdatedAt = DateTime.UtcNow;
    }

    /// <summary>
    /// Updates the sort order.
    /// </summary>
    public void UpdateOrder(int newOrder)
    {
        Order = newOrder;
        UpdatedAt = DateTime.UtcNow;
    }

    /// <summary>
    /// Updates the question type.
    /// </summary>
    public void UpdateType(QuestionType newType)
    {
        Type = newType;
        UpdatedAt = DateTime.UtcNow;
    }

    /// <summary>
    /// Updates the associated lesson.
    /// </summary>
    public void UpdateLesson(int newLessonId)
    {
        LessonId = newLessonId;
        UpdatedAt = DateTime.UtcNow;
    }

    /// <summary>
    /// Activates the quiz question.
    /// </summary>
    public void Activate()
    {
        IsActive = true;
        UpdatedAt = DateTime.UtcNow;
    }

    /// <summary>
    /// Deactivates the quiz question.
    /// </summary>
    public void Deactivate()
    {
        IsActive = false;
        UpdatedAt = DateTime.UtcNow;
    }

    /// <summary>
    /// Adds an option to this question.
    /// </summary>
    public void AddOption(QuizOption option)
    {
        Options.Add(option);
    }

    /// <summary>
    /// Removes an option from this question.
    /// </summary>
    public void RemoveOption(QuizOption option)
    {
        Options.Remove(option);
    }
}

/// <summary>
/// Represents an option for a multiple-choice quiz question.
/// </summary>
public class QuizOption
{
    public int Id { get; private set; }
    public int QuizQuestionId { get; private set; }
    public string Text { get; private set; } = string.Empty;
    public bool IsCorrect { get; private set; }
    public int Order { get; private set; }

    // Navigation property
    public virtual QuizQuestion? QuizQuestion { get; private set; }

    /// <summary>
    /// Constructor for EF Core deserialization.
    /// </summary>
    private QuizOption() { }

    /// <summary>
    /// Factory method to create a new quiz option.
    /// </summary>
    /// <param name="quizQuestionId">ID of the parent quiz question</param>
    /// <param name="text">The option text</param>
    /// <param name="isCorrect">Whether this is the correct answer</param>
    /// <param name="order">Sort order within the question's options</param>
    public static QuizOption Create(
        int quizQuestionId,
        string text,
        bool isCorrect = false,
        int order = 1)
    {
        if (string.IsNullOrWhiteSpace(text))
            throw new ArgumentException("Option text cannot be empty", nameof(text));

        return new QuizOption
        {
            QuizQuestionId = quizQuestionId,
            Text = text,
            IsCorrect = isCorrect,
            Order = order
        };
    }

    /// <summary>
    /// Updates the option text.
    /// </summary>
    public void UpdateText(string newText)
    {
        if (string.IsNullOrWhiteSpace(newText))
            throw new ArgumentException("Option text cannot be empty", nameof(newText));

        Text = newText;
    }

    /// <summary>
    /// Updates whether this option is correct.
    /// </summary>
    public void UpdateIsCorrect(bool newIsCorrect)
    {
        IsCorrect = newIsCorrect;
    }

    /// <summary>
    /// Updates the sort order.
    /// </summary>
    public void UpdateOrder(int newOrder)
    {
        Order = newOrder;
    }
}

/// <summary>
/// Enum representing the types of quiz questions.
/// </summary>
public enum QuestionType
{
    /// <summary>
    /// Multiple choice with single correct answer
    /// </summary>
    MultipleChoice = 0,
    
    /// <summary>
    /// Multiple choice with multiple correct answers
    /// </summary>
    MultipleSelect = 1,
    
    /// <summary>
    /// True or false question
    /// </summary>
    TrueFalse = 2,
    
    /// <summary>
    /// Fill-in-the-blank question
    /// </summary>
    FillInTheBlank = 3,
    
    /// <summary>
    /// Matching question
    /// </summary>
    Matching = 4,
    
    /// <summary>
    /// Short answer question
    /// </summary>
    ShortAnswer = 5
}