DeutschLernen/GermanApp/Domain/Entities/Lesson.cs

namespace GermanApp.Domain.Entities;

/// <summary>
/// Represents a German language lesson in the system.
/// </summary>
public class Lesson
{
    // Private setter for domain behavior, but internal for EF Core
    public int Id { get; private set; }
    public string Title { get; private set; } = string.Empty;
    public string Description { get; private set; } = string.Empty;
    public int Level { get; private set; }
    public DateTime CreatedAt { get; private set; }
    public DateTime? UpdatedAt { get; private set; }

    // Navigation properties would go here in EF Core
    // public ICollection<VocabularyWord> Words { get; private set; }

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

    /// <summary>
    /// Factory method to create a new lesson.
    /// </summary>
    public static Lesson Create(string title, string description, int level)
    {
        return new Lesson
        {
            Title = title,
            Description = description,
            Level = level,
            CreatedAt = DateTime.UtcNow
        };
    }

    /// <summary>
    /// Updates the lesson details.
    /// </summary>
    public void Update(string title, string description, int level)
    {
        Title = title;
        Description = description;
        Level = level;
        UpdatedAt = DateTime.UtcNow;
    }

    /// <summary>
    /// Domain behavior: Check if lesson is at beginner level.
    /// </summary>
    public bool IsBeginnerLevel() => Level <= 2;

    /// <summary>
    /// Domain behavior: Check if lesson is at advanced level.
    /// </summary>
    public bool IsAdvancedLevel() => Level >= 4;
}