using Microsoft.AspNetCore.Identity;
using Microsoft.Extensions.Logging;
using MediatR;
using CellularManagement.Domain.Entities;
using CellularManagement.Domain.Repositories;
using CellularManagement.Domain.Common;
using System.Threading.Tasks;
using System.Threading;
using System;
using System.Linq;

namespace CellularManagement.Application.Features.Users.Commands.CreateUser;

/// <summary>
/// 创建用户命令处理器
/// 处理创建新用户的业务逻辑
/// </summary>
public sealed class CreateUserCommandHandler : IRequestHandler<CreateUserCommand, OperationResult<CreateUserResponse>>
{
    private readonly UserManager<AppUser> _userManager;
    private readonly ILogger<CreateUserCommandHandler> _logger;
    private readonly IUnitOfWork _unitOfWork;

    /// <summary>
    /// 构造函数
    /// </summary>
    /// <param name="userManager">用户管理器，用于管理用户身份</param>
    /// <param name="logger">日志记录器</param>
    /// <param name="unitOfWork">工作单元，用于事务管理</param>
    public CreateUserCommandHandler(
        UserManager<AppUser> userManager,
        ILogger<CreateUserCommandHandler> logger,
        IUnitOfWork unitOfWork)
    {
        _userManager = userManager;
        _logger = logger;
        _unitOfWork = unitOfWork;
    }

    /// <summary>
    /// 处理创建用户命令
    /// </summary>
    /// <param name="request">创建用户命令</param>
    /// <param name="cancellationToken">取消令牌</param>
    /// <returns>操作结果，包含创建的用户ID</returns>
    public async Task<OperationResult<CreateUserResponse>> Handle(
        CreateUserCommand request,
        CancellationToken cancellationToken)
    {
        try
        {
            // 检查用户是否已存在
            var existingUser = await _userManager.FindByEmailAsync(request.Email);
            if (existingUser != null)
            {
                _logger.LogWarning("用户邮箱 {Email} 已存在", request.Email);
                return OperationResult<CreateUserResponse>.CreateFailure("用户已存在");
            }

            // 创建新用户
            var user = new AppUser
            {
                UserName = request.UserName,
                Email = request.Email,
                PhoneNumber = request.PhoneNumber
            };

            // 在事务中创建用户
            await _unitOfWork.ExecuteTransactionAsync(async () =>
            {
                var result = await _userManager.CreateAsync(user, request.Password);
                if (!result.Succeeded)
                {
                    var errors = result.Errors.Select(e => e.Description).ToList();
                    _logger.LogWarning("创建用户失败: {Errors}", string.Join(", ", errors));
                    throw new InvalidOperationException(string.Join(", ", errors));
                }
            }, cancellationToken: cancellationToken);

            _logger.LogInformation("用户 {UserId} 创建成功", user.Id);

            return OperationResult<CreateUserResponse>.CreateSuccess(
                new CreateUserResponse(user.Id));
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "创建用户时发生错误");
            _logger.LogError(ex, "Error creating user");
            return OperationResult<CreateUserResponse>.CreateFailure("Failed to create user");
        }
    }
}