using GermanApp.Domain.Entities;

namespace GermanApp.Domain.Interfaces;

/// <summary>
/// Generic repository interface for domain entities.
/// All repositories should implement this interface.
/// </summary>
/// <typeparam name="TEntity">The entity type</typeparam>
/// <typeparam name="TId">The identifier type (usually int or Guid)</typeparam>
public interface IRepository<TEntity, TId> where TEntity : class
{
    /// <summary>
    /// Gets an entity by its identifier.
    /// </summary>
    Task<TEntity?> GetByIdAsync(TId id, CancellationToken cancellationToken = default);

    /// <summary>
    /// Gets all entities.
    /// </summary>
    Task<IReadOnlyList<TEntity>> GetAllAsync(CancellationToken cancellationToken = default);

    /// <summary>
    /// Adds a new entity.
    /// </summary>
    Task<TEntity> AddAsync(TEntity entity, CancellationToken cancellationToken = default);

    /// <summary>
    /// Updates an existing entity.
    /// </summary>
    Task UpdateAsync(TEntity entity, CancellationToken cancellationToken = default);

    /// <summary>
    /// Deletes an entity.
    /// </summary>
    Task DeleteAsync(TEntity entity, CancellationToken cancellationToken = default);

    /// <summary>
    /// Checks if an entity with the given identifier exists.
    /// </summary>
    Task<bool> ExistsAsync(TId id, CancellationToken cancellationToken = default);
}

/// <summary>
/// Repository interface for Level entities.
/// </summary>
public interface ILevelRepository : IRepository<Level, int>
{
    /// <summary>
    /// Gets a level by its code (e.g., "A1", "B2").
    /// </summary>
    Task<Level?> GetByCodeAsync(string code, CancellationToken cancellationToken = default);

    /// <summary>
    /// Gets all levels ordered by their sort order.
    /// </summary>
    Task<IReadOnlyList<Level>> GetAllOrderedAsync(CancellationToken cancellationToken = default);

    /// <summary>
    /// Gets the first level (lowest order number).
    /// </summary>
    Task<Level?> GetFirstLevelAsync(CancellationToken cancellationToken = default);

    /// <summary>
    /// Gets the next level after the specified one.
    /// </summary>
    Task<Level?> GetNextLevelAsync(int currentLevelId, CancellationToken cancellationToken = default);
}

/// <summary>
/// Repository interface for Lesson entities.
/// </summary>
public interface ILessonRepository : IRepository<Lesson, int>
{
    /// <summary>
    /// Gets lessons by level.
    /// </summary>
    Task<IReadOnlyList<Lesson>> GetByLevelAsync(int levelId, CancellationToken cancellationToken = default);

    /// <summary>
    /// Gets all lessons ordered by level and lesson order.
    /// </summary>
    Task<IReadOnlyList<Lesson>> GetAllOrderedAsync(CancellationToken cancellationToken = default);

    /// <summary>
    /// Gets the first lesson in a level.
    /// </summary>
    Task<Lesson?> GetFirstLessonInLevelAsync(int levelId, CancellationToken cancellationToken = default);

    /// <summary>
    /// Gets the next lesson after the specified one (in the same level).
    /// </summary>
    Task<Lesson?> GetNextLessonAsync(int currentLessonId, CancellationToken cancellationToken = default);

    /// <summary>
    /// Gets lessons that the user can access (completed previous lessons or first in level).
    /// </summary>
    Task<IReadOnlyList<Lesson>> GetAccessibleLessonsAsync(int userId, CancellationToken cancellationToken = default);
}

/// <summary>
/// Repository interface for UserProgress entities.
/// </summary>
public interface IUserProgressRepository : IRepository<UserProgress, int>
{
    /// <summary>
    /// Gets user progress for a specific user and lesson.
    /// </summary>
    Task<UserProgress?> GetByUserAndLessonAsync(int userId, int lessonId, CancellationToken cancellationToken = default);

    /// <summary>
    /// Gets all progress records for a user.
    /// </summary>
    Task<IReadOnlyList<UserProgress>> GetByUserAsync(int userId, CancellationToken cancellationToken = default);

    /// <summary>
    /// Gets progress for all lessons in a specific level for a user.
    /// </summary>
    Task<IReadOnlyList<UserProgress>> GetByUserAndLevelAsync(int userId, int levelId, CancellationToken cancellationToken = default);

    /// <summary>
    /// Checks if a user has completed a lesson (with 80% or higher score).
    /// </summary>
    Task<bool> HasUserCompletedLessonAsync(int userId, int lessonId, CancellationToken cancellationToken = default);

    /// <summary>
    /// Gets the user's average score for a level.
    /// </summary>
    Task<double> GetAverageScoreForLevelAsync(int userId, int levelId, CancellationToken cancellationToken = default);

    /// <summary>
    /// Gets the percentage of lessons completed in a level.
    /// </summary>
    Task<double> GetLevelCompletionPercentageAsync(int userId, int levelId, CancellationToken cancellationToken = default);
}