DeutschLernen/GermanApp/Domain/Entities/Quiz.cs

namespace GermanApp.Domain.Entities;

/// <summary>
/// Represents a quiz that can be associated with a lesson.
/// A quiz contains multiple questions and has a passing score threshold.
/// </summary>
public class Quiz
{
    public int Id { get; private set; }
    public int LessonId { get; private set; }
    public string Title { get; private set; } = string.Empty;
    public string? Description { get; private set; }
    public int PassingScore { get; private set; } = 80; // Default 80%
    public int TimeLimitMinutes { get; private set; } = 0; // 0 = no limit
    public bool IsActive { get; private set; } = true;
    public bool ShuffleQuestions { 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<QuizQuestion> Questions { get; private set; } = new List<QuizQuestion>();

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

    /// <summary>
    /// Factory method to create a new quiz.
    /// </summary>
    /// <param name="lessonId">ID of the associated lesson</param>
    /// <param name="title">Title of the quiz</param>
    /// <param name="description">Optional description</param>
    /// <param name="passingScore">Passing score percentage (default 80)</param>
    /// <param name="timeLimitMinutes">Time limit in minutes (0 for no limit)</param>
    public static Quiz Create(
        int lessonId,
        string title,
        string? description = null,
        int passingScore = 80,
        int timeLimitMinutes = 0)
    {
        if (string.IsNullOrWhiteSpace(title))
            throw new ArgumentException("Quiz title cannot be empty", nameof(title));
        
        if (passingScore < 0 || passingScore > 100)
            throw new ArgumentOutOfRangeException(nameof(passingScore), "Passing score must be between 0 and 100");
        
        if (timeLimitMinutes < 0)
            throw new ArgumentOutOfRangeException(nameof(timeLimitMinutes), "Time limit cannot be negative");

        return new Quiz
        {
            LessonId = lessonId,
            Title = title,
            Description = description,
            PassingScore = passingScore,
            TimeLimitMinutes = timeLimitMinutes,
            CreatedAt = DateTime.UtcNow
        };
    }

    /// <summary>
    /// Updates the quiz title.
    /// </summary>
    public void UpdateTitle(string newTitle)
    {
        if (string.IsNullOrWhiteSpace(newTitle))
            throw new ArgumentException("Quiz title cannot be empty", nameof(newTitle));

        Title = newTitle;
        UpdatedAt = DateTime.UtcNow;
    }

    /// <summary>
    /// Updates the quiz description.
    /// </summary>
    public void UpdateDescription(string? newDescription)
    {
        Description = newDescription;
        UpdatedAt = DateTime.UtcNow;
    }

    /// <summary>
    /// Updates the passing score.
    /// </summary>
    public void UpdatePassingScore(int newPassingScore)
    {
        if (newPassingScore < 0 || newPassingScore > 100)
            throw new ArgumentOutOfRangeException(nameof(newPassingScore), "Passing score must be between 0 and 100");

        PassingScore = newPassingScore;
        UpdatedAt = DateTime.UtcNow;
    }

    /// <summary>
    /// Updates the time limit.
    /// </summary>
    public void UpdateTimeLimit(int newTimeLimitMinutes)
    {
        if (newTimeLimitMinutes < 0)
            throw new ArgumentOutOfRangeException(nameof(newTimeLimitMinutes), "Time limit cannot be negative");

        TimeLimitMinutes = newTimeLimitMinutes;
        UpdatedAt = DateTime.UtcNow;
    }

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

    /// <summary>
    /// Updates the shuffle questions setting.
    /// </summary>
    public void UpdateShuffleQuestions(bool newShuffleQuestions)
    {
        ShuffleQuestions = newShuffleQuestions;
        UpdatedAt = DateTime.UtcNow;
    }

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

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

    /// <summary>
    /// Adds a question to this quiz.
    /// </summary>
    public void AddQuestion(QuizQuestion question)
    {
        if (question == null)
            throw new ArgumentNullException(nameof(question));
        
        Questions.Add(question);
    }

    /// <summary>
    /// Removes a question from this quiz.
    /// </summary>
    public void RemoveQuestion(QuizQuestion question)
    {
        if (question == null)
            throw new ArgumentNullException(nameof(question));
        
        Questions.Remove(question);
    }

    /// <summary>
    /// Checks if the quiz is passed based on a score percentage.
    /// </summary>
    public bool IsPassed(double scorePercentage) => scorePercentage >= PassingScore;

    /// <summary>
    /// Calculates the score percentage based on correct answers.
    /// </summary>
    public double CalculateScore(int correctAnswers, int totalQuestions)
    {
        if (totalQuestions == 0)
            return 0;
        
        return (double)correctAnswers / totalQuestions * 100;
    }
}