using System;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using MediatR;
using Microsoft.Extensions.Logging;
using X1.Domain.Entities;
using X1.Domain.Repositories.Identity;
using X1.Domain.Common;
using System.Collections.Generic;

namespace X1.Application.Features.Permissions.Queries;

/// <summary>
/// 获取所有权限查询处理器
/// </summary>
public sealed class GetAllPermissionsQueryHandler : IRequestHandler<GetAllPermissionsQuery, OperationResult<GetAllPermissionsResponse>>
{
    private readonly IPermissionRepository _permissionRepository;
    private readonly ILogger<GetAllPermissionsQueryHandler> _logger;

    /// <summary>
    /// 初始化处理器
    /// </summary>
    public GetAllPermissionsQueryHandler(
        IPermissionRepository permissionRepository,
        ILogger<GetAllPermissionsQueryHandler> logger)
    {
        _permissionRepository = permissionRepository;
        _logger = logger;
    }

    /// <summary>
    /// 处理获取所有权限查询
    /// </summary>
    public async Task<OperationResult<GetAllPermissionsResponse>> Handle(
        GetAllPermissionsQuery request,
        CancellationToken cancellationToken)
    {
        try
        {
            _logger.LogInformation("开始获取权限列表，页码: {PageNumber}, 页大小: {PageSize}", request.PageNumber, request.PageSize);

            var permissions = await _permissionRepository.GetAllAsync();
            
            if (!permissions.Any())
            {
                _logger.LogWarning("未找到任何权限");
                return OperationResult<GetAllPermissionsResponse>.CreateSuccess(
                    new GetAllPermissionsResponse(
                        new List<PermissionListItemDto>(),
                        0,
                        request.PageNumber,
                        request.PageSize
                    ));
            }

            // 应用筛选条件
            var filteredPermissions = permissions.AsQueryable();

            // 关键词搜索
            if (!string.IsNullOrWhiteSpace(request.Keyword))
            {
                filteredPermissions = filteredPermissions.Where(p =>
                    p.Name.Contains(request.Keyword) ||
                    p.Code.Contains(request.Keyword) ||
                    (p.Description != null && p.Description.Contains(request.Keyword))
                );
            }

            // 启用状态筛选
            if (request.IsEnabled.HasValue)
            {
                filteredPermissions = filteredPermissions.Where(p => p.IsEnabled == request.IsEnabled.Value);
            }

            // 系统权限筛选
            if (request.IsSystem.HasValue)
            {
                filteredPermissions = filteredPermissions.Where(p => p.IsSystem == request.IsSystem.Value);
            }

            // 获取总数
            var totalCount = filteredPermissions.Count();

            // 分页
            var pagedPermissions = filteredPermissions
                .Skip((request.PageNumber - 1) * request.PageSize)
                .Take(request.PageSize)
                .ToList();

            // 转换为DTO
            var permissionDtos = pagedPermissions.Select(p => new PermissionListItemDto(
                p.Id,
                p.Name,
                p.Code,
                p.Description,
                p.IsEnabled,
                p.IsSystem
            )).ToList();

            var response = new GetAllPermissionsResponse(
                permissionDtos,
                totalCount,
                request.PageNumber,
                request.PageSize
            );

            _logger.LogInformation("权限列表获取成功，共 {TotalCount} 条记录，当前页 {PageNumber}/{TotalPages}", 
                totalCount, request.PageNumber, response.TotalPages);

            return OperationResult<GetAllPermissionsResponse>.CreateSuccess(response);
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "获取权限列表时发生错误");
            return OperationResult<GetAllPermissionsResponse>.CreateFailure(
                new List<string> { "获取权限列表失败" });
        }
    }
}