using MediatR;
using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.Storage;
using MissionService.Domain.AggregatesModel.MissionAggregate;
using MissionService.Domain.AggregatesModel.TaskAggregate;
using MissionService.Domain.AggregatesModel.CheckInAggregate;
using MissionService.Domain.AggregatesModel.RewardAggregate;
using MissionService.Domain.SeedWork;
using MissionService.Infrastructure.EntityConfigurations;

namespace MissionService.Infrastructure;

/// <summary>
/// EN: EF Core DbContext for MissionService.
/// VI: EF Core DbContext cho MissionService.
/// </summary>
public class MissionDbContext : DbContext, IUnitOfWork
{
    private readonly IMediator _mediator;
    private IDbContextTransaction? _currentTransaction;

    #region DbSets
    
    /// <summary>EN: Missions table / VI: Bảng Missions</summary>
    public DbSet<Mission> Missions => Set<Mission>();
    
    /// <summary>EN: Mission rules table / VI: Bảng quy tắc mission</summary>
    public DbSet<MissionRule> MissionRules => Set<MissionRule>();
    
    /// <summary>EN: User tasks table / VI: Bảng tasks của user</summary>
    public DbSet<UserTask> UserTasks => Set<UserTask>();
    
    /// <summary>EN: User check-ins table / VI: Bảng check-in của user</summary>
    public DbSet<UserCheckIn> UserCheckIns => Set<UserCheckIn>();
    
    /// <summary>EN: Check-in days table / VI: Bảng ngày check-in</summary>
    public DbSet<CheckInDay> CheckInDays => Set<CheckInDay>();
    
    /// <summary>EN: User rewards table / VI: Bảng phần thưởng user</summary>
    public DbSet<UserReward> UserRewards => Set<UserReward>();
    
    #endregion

    /// <summary>
    /// EN: Read-only access to current transaction.
    /// VI: Truy cập chỉ đọc đến transaction hiện tại.
    /// </summary>
    public IDbContextTransaction? CurrentTransaction => _currentTransaction;

    /// <summary>
    /// EN: Check if there is an active transaction.
    /// VI: Kiểm tra xem có transaction đang hoạt động không.
    /// </summary>
    public bool HasActiveTransaction => _currentTransaction != null;

    public MissionDbContext(DbContextOptions<MissionDbContext> options) : base(options)
    {
        _mediator = null!;
    }

    public MissionDbContext(DbContextOptions<MissionDbContext> options, IMediator mediator) : base(options)
    {
        _mediator = mediator ?? throw new ArgumentNullException(nameof(mediator));
    }

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        // EN: Apply entity configurations
        // VI: Áp dụng các cấu hình entity
        modelBuilder.ApplyConfiguration(new MissionEntityTypeConfiguration());
        modelBuilder.ApplyConfiguration(new MissionRuleEntityTypeConfiguration());
        modelBuilder.ApplyConfiguration(new UserTaskEntityTypeConfiguration());
        modelBuilder.ApplyConfiguration(new UserCheckInEntityTypeConfiguration());
        modelBuilder.ApplyConfiguration(new CheckInDayEntityTypeConfiguration());
        modelBuilder.ApplyConfiguration(new UserRewardEntityTypeConfiguration());
        
        // EN: Apply Enumeration configurations
        // VI: Áp dụng cấu hình cho Enumerations
        modelBuilder.ApplyConfiguration(new MissionTypeEntityTypeConfiguration());
        modelBuilder.ApplyConfiguration(new MissionCategoryEntityTypeConfiguration());
        modelBuilder.ApplyConfiguration(new MissionStatusEntityTypeConfiguration());
        modelBuilder.ApplyConfiguration(new FrequencyTypeEntityTypeConfiguration());
        modelBuilder.ApplyConfiguration(new TaskStatusEntityTypeConfiguration());
    }

    /// <summary>
    /// EN: Save entities and dispatch domain events.
    /// VI: Lưu entities và dispatch domain events.
    /// </summary>
    public async Task<bool> SaveEntitiesAsync(CancellationToken cancellationToken = default)
    {
        // EN: Dispatch domain events before saving (side effects)
        // VI: Dispatch domain events trước khi lưu (side effects)
        await DispatchDomainEventsAsync();

        // EN: Save changes to database
        // VI: Lưu thay đổi vào database
        await base.SaveChangesAsync(cancellationToken);

        return true;
    }

    /// <summary>
    /// EN: Begin a new transaction if none is active.
    /// VI: Bắt đầu một transaction mới nếu không có transaction nào đang hoạt động.
    /// </summary>
    public async Task<IDbContextTransaction?> BeginTransactionAsync()
    {
        if (_currentTransaction != null) return null;

        _currentTransaction = await Database.BeginTransactionAsync(System.Data.IsolationLevel.ReadCommitted);

        return _currentTransaction;
    }

    /// <summary>
    /// EN: Commit the current transaction.
    /// VI: Commit transaction hiện tại.
    /// </summary>
    public async Task CommitTransactionAsync(IDbContextTransaction transaction)
    {
        ArgumentNullException.ThrowIfNull(transaction);

        if (transaction != _currentTransaction)
            throw new InvalidOperationException($"Transaction {transaction.TransactionId} is not current");

        try
        {
            await SaveChangesAsync();
            await transaction.CommitAsync();
        }
        catch
        {
            RollbackTransaction();
            throw;
        }
        finally
        {
            if (_currentTransaction != null)
            {
                _currentTransaction.Dispose();
                _currentTransaction = null;
            }
        }
    }

    /// <summary>
    /// EN: Rollback the current transaction.
    /// VI: Rollback transaction hiện tại.
    /// </summary>
    public void RollbackTransaction()
    {
        try
        {
            _currentTransaction?.Rollback();
        }
        finally
        {
            if (_currentTransaction != null)
            {
                _currentTransaction.Dispose();
                _currentTransaction = null;
            }
        }
    }

    /// <summary>
    /// EN: Dispatch all domain events from tracked entities.
    /// VI: Dispatch tất cả domain events từ các entities đang được track.
    /// </summary>
    private async Task DispatchDomainEventsAsync()
    {
        var domainEntities = ChangeTracker
            .Entries<Entity>()
            .Where(x => x.Entity.DomainEvents.Any())
            .ToList();

        var domainEvents = domainEntities
            .SelectMany(x => x.Entity.DomainEvents)
            .ToList();

        domainEntities.ForEach(entity => entity.Entity.ClearDomainEvents());

        foreach (var domainEvent in domainEvents)
        {
            await _mediator.Publish(domainEvent);
        }
    }
}
