using MediatR;
using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.Storage;
using MerchantService.Domain.AggregatesModel.MerchantAggregate;
using MerchantService.Domain.AggregatesModel.ShopAggregate;
using MerchantService.Domain.AggregatesModel.MerchantStaffAggregate;
using MerchantService.Domain.AggregatesModel.AttendanceAggregate;
using MerchantService.Domain.AggregatesModel.LeaveRequestAggregate;
using MerchantService.Domain.SeedWork;

namespace MerchantService.Infrastructure;

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

    #region DbSets

    /// <summary>
    /// EN: Merchants table.
    /// VI: Bảng Merchants.
    /// </summary>
    public DbSet<Merchant> Merchants => Set<Merchant>();

    /// <summary>
    /// EN: Shops table.
    /// VI: Bảng Shops.
    /// </summary>
    public DbSet<Shop> Shops => Set<Shop>();

    /// <summary>
    /// EN: Shop branches table.
    /// VI: Bảng chi nhánh Shop.
    /// </summary>
    public DbSet<ShopBranch> ShopBranches => Set<ShopBranch>();

    /// <summary>
    /// EN: Merchant staff table.
    /// VI: Bảng nhân viên Merchant.
    /// </summary>
    public DbSet<MerchantStaff> MerchantStaff => Set<MerchantStaff>();

    /// <summary>
    /// EN: Shop members table (staff-shop assignments).
    /// VI: Bảng shop member (gán nhân viên-shop).
    /// </summary>
    public DbSet<ShopMember> ShopMembers => Set<ShopMember>();

    /// <summary>
    /// EN: Device tokens table.
    /// VI: Bảng device tokens.
    /// </summary>
    public DbSet<DeviceToken> DeviceTokens => Set<DeviceToken>();

    /// <summary>
    /// EN: Attendance records table.
    /// VI: Bang cham cong.
    /// </summary>
    public DbSet<AttendanceRecord> AttendanceRecords => Set<AttendanceRecord>();

    /// <summary>
    /// EN: Leave requests table.
    /// VI: Bang yeu cau nghi phep.
    /// </summary>
    public DbSet<LeaveRequest> LeaveRequests => Set<LeaveRequest>();

    #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 MerchantServiceContext(DbContextOptions<MerchantServiceContext> options) : base(options)
    {
        _mediator = null!;
    }

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

        System.Diagnostics.Debug.WriteLine("MerchantServiceContext::ctor - " + GetHashCode());
    }

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        // EN: Apply entity configurations from this assembly
        // VI: Áp dụng các cấu hình entity từ assembly này
        modelBuilder.ApplyConfigurationsFromAssembly(typeof(MerchantServiceContext).Assembly);

        // EN: Ignore Enumeration types so EF Core does NOT auto-discover FKs.
        //     These are DDD Enumerations resolved in-memory; their tables are seeded by migrations.
        // VI: Ignore Enumeration types để EF Core KHÔNG tự phát hiện FK.
        modelBuilder.Ignore<StaffRole>();
        modelBuilder.Ignore<StaffStatus>();
        modelBuilder.Ignore<ShopRole>();
    }

    /// <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);
        }
    }
}
