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

namespace CellularManagement.Application.Features.RolePermissions.Commands.AddRolePermissions;

/// <summary>
/// 添加角色权限命令处理器
/// </summary>
public class AddRolePermissionsCommandHandler : IRequestHandler<AddRolePermissionsCommand, OperationResult<AddRolePermissionsResponse>>
{
    private readonly IRolePermissionRepository _rolePermissionRepository;
    private readonly ILogger<AddRolePermissionsCommandHandler> _logger;

    public AddRolePermissionsCommandHandler(
        IRolePermissionRepository rolePermissionRepository,
        ILogger<AddRolePermissionsCommandHandler> logger)
    {
        _rolePermissionRepository = rolePermissionRepository;
        _logger = logger;
    }

    public async Task<OperationResult<AddRolePermissionsResponse>> Handle(
        AddRolePermissionsCommand request,
        CancellationToken cancellationToken)
    {
        try
        {
            // 获取角色当前已有的权限
            var existingPermissions = await _rolePermissionRepository.GetPermissionsByRoleIdAsync(request.RoleId, cancellationToken);
            var existingPermissionIds = existingPermissions.Select(p => p.Id).ToList();

            // 过滤出需要新增的权限ID
            var newPermissionIds = request.PermissionIds.Except(existingPermissionIds).ToList();

            if (!newPermissionIds.Any())
            {
                return OperationResult<AddRolePermissionsResponse>.CreateFailure("所有权限已存在，无需添加");
            }

            // 添加新的角色权限
            var addedRolePermissions = await _rolePermissionRepository.AddRolePermissionsAsync(
                request.RoleId,
                newPermissionIds,
                cancellationToken);

            var response = new AddRolePermissionsResponse
            {
                AddedPermissionIds = newPermissionIds,
                FailedPermissionIds = request.PermissionIds.Except(newPermissionIds)
            };

            _logger.LogInformation(
                "成功为角色 {RoleId} 添加 {Count} 个权限",
                request.RoleId,
                newPermissionIds.Count);

            return OperationResult<AddRolePermissionsResponse>.CreateSuccess(response);
        }
        catch (Exception ex)
        {
            _logger.LogError(
                ex,
                "为角色 {RoleId} 添加权限时发生错误",
                request.RoleId);

            return OperationResult<AddRolePermissionsResponse>.CreateFailure(
                "添加角色权限失败，请稍后重试");
        }
    }
}