using Microsoft.AspNetCore.Identity;
using Microsoft.Extensions.Logging;
using MediatR;
using CellularManagement.Domain.Entities;
using CellularManagement.Application.Features.Users.Queries.Dtos;
using Microsoft.EntityFrameworkCore;
using CellularManagement.Domain.Common;
using System.Threading.Tasks;
using System.Threading;
using System.Linq;
using System;

namespace CellularManagement.Application.Features.Users.Queries.GetAllUsers;

/// <summary>
/// 获取所有用户查询处理器
/// 处理获取系统中所有用户信息的业务逻辑
/// </summary>
public sealed class GetAllUsersQueryHandler : IRequestHandler<GetAllUsersQuery, OperationResult<GetAllUsersResponse>>
{
    private readonly UserManager<AppUser> _userManager;
    private readonly ILogger<GetAllUsersQueryHandler> _logger;

    /// <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>
    public GetAllUsersQueryHandler(
        UserManager<AppUser> userManager,
        ILogger<GetAllUsersQueryHandler> logger)
    {
        _userManager = userManager;
        _logger = logger;
    }

    /// <summary>
    /// 处理获取所有用户命令
    /// </summary>
    /// <param name="request">查询命令</param>
    /// <param name="cancellationToken">取消令牌</param>
    /// <returns>操作结果，包含所有用户信息列表</returns>
    public async Task<OperationResult<GetAllUsersResponse>> Handle(
        GetAllUsersQuery request,
        CancellationToken cancellationToken)
    {
        try
        {
            // 构建基础查询
            var query = _userManager.Users.AsQueryable();

            // 应用条件过滤
            if (!string.IsNullOrWhiteSpace(request.UserName))
            {
                query = query.Where(u => u.UserName.Contains(request.UserName));
            }

            if (!string.IsNullOrWhiteSpace(request.Email))
            {
                query = query.Where(u => u.Email.Contains(request.Email));
            }

            if (!string.IsNullOrWhiteSpace(request.PhoneNumber))
            {
                query = query.Where(u => u.PhoneNumber.Contains(request.PhoneNumber));
            }

            // 获取总记录数
            var totalCount = await query.CountAsync(cancellationToken);

            // 应用分页
            var users = await query
                .Skip((request.PageNumber - 1) * request.PageSize)
                .Take(request.PageSize)
                .ToListAsync(cancellationToken);
            
            // 转换为DTO对象
            var userDtos = users.Select(user => new UserDto(
                user.Id,
                user.UserName,
                user.Email,
                user.PhoneNumber)).ToList();

            // 构建响应对象
            var response = new GetAllUsersResponse(
                userDtos,
                totalCount,
                request.PageNumber,
                request.PageSize);

            return OperationResult<GetAllUsersResponse>.CreateSuccess(response);
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "获取所有用户时发生错误");
            return OperationResult<GetAllUsersResponse>.CreateFailure("获取用户列表失败");
        }
    }
}