using System.Linq.Expressions;
using System.Security.Cryptography;
using SPMS.Application.DTOs.Service;
using SPMS.Application.Interfaces;
using SPMS.Domain.Common;
using SPMS.Domain.Entities;
using SPMS.Domain.Enums;
using SPMS.Domain.Exceptions;
using SPMS.Domain.Interfaces;

namespace SPMS.Application.Services;

public class ServiceManagementService : IServiceManagementService
{
    private readonly IServiceRepository _serviceRepository;
    private readonly IUnitOfWork _unitOfWork;

    public ServiceManagementService(IServiceRepository serviceRepository, IUnitOfWork unitOfWork)
    {
        _serviceRepository = serviceRepository;
        _unitOfWork = unitOfWork;
    }

    public async Task<ServiceListResponseDto> GetListAsync(ServiceListRequestDto request)
    {
        Expression<Func<Service, bool>>? predicate = null;

        // 검색어 필터
        if (!string.IsNullOrWhiteSpace(request.SearchKeyword))
        {
            var keyword = request.SearchKeyword;
            predicate = s => s.ServiceName.Contains(keyword) || s.ServiceCode.Contains(keyword);
        }

        // Status 필터
        if (request.Status.HasValue)
        {
            var status = (ServiceStatus)request.Status.Value;
            if (predicate != null)
            {
                var basePredicate = predicate;
                predicate = s => basePredicate.Compile()(s) && s.Status == status;
            }
            else
            {
                predicate = s => s.Status == status;
            }
        }

        var (items, totalCount) = await _serviceRepository.GetPagedAsync(
            request.Page,
            request.PageSize,
            predicate,
            s => s.CreatedAt,
            descending: true);

        return new ServiceListResponseDto
        {
            Items = items.Select(MapToSummaryDto).ToList(),
            TotalCount = totalCount,
            Page = request.Page,
            PageSize = request.PageSize
        };
    }

    public async Task<ServiceResponseDto> GetByServiceCodeAsync(string serviceCode)
    {
        var service = await _serviceRepository.GetByServiceCodeAsync(serviceCode);
        if (service is null)
        {
            throw new SpmsException(
                ErrorCodes.NotFound,
                "서비스를 찾을 수 없습니다.",
                404);
        }

        // IP 목록 포함해서 다시 조회
        var serviceWithIps = await _serviceRepository.GetByIdWithIpsAsync(service.Id);

        return MapToDto(serviceWithIps ?? service);
    }

    public async Task<ServiceResponseDto> ChangeStatusAsync(string serviceCode, ChangeServiceStatusRequestDto request)
    {
        var service = await _serviceRepository.GetByServiceCodeAsync(serviceCode);
        if (service is null)
        {
            throw new SpmsException(
                ErrorCodes.NotFound,
                "서비스를 찾을 수 없습니다.",
                404);
        }

        var newStatus = (ServiceStatus)request.Status;

        // 이미 같은 상태면 변경 없음
        if (service.Status == newStatus)
        {
            throw new SpmsException(
                ErrorCodes.NoChange,
                "이미 해당 상태입니다.",
                400);
        }

        service.Status = newStatus;
        service.UpdatedAt = DateTime.UtcNow;

        _serviceRepository.Update(service);
        await _unitOfWork.SaveChangesAsync();

        return MapToDto(service);
    }

    public async Task<ApiKeyRefreshResponseDto> RefreshApiKeyAsync(string serviceCode)
    {
        var service = await _serviceRepository.GetByServiceCodeAsync(serviceCode);
        if (service is null)
        {
            throw new SpmsException(
                ErrorCodes.NotFound,
                "서비스를 찾을 수 없습니다.",
                404);
        }

        // 32~64자 랜덤 API Key 생성 (48자 = 36바이트 Base64)
        var randomBytes = new byte[36];
        using (var rng = RandomNumberGenerator.Create())
        {
            rng.GetBytes(randomBytes);
        }
        var newApiKey = Convert.ToBase64String(randomBytes);

        service.ApiKey = newApiKey;
        service.ApiKeyCreatedAt = DateTime.UtcNow;
        service.UpdatedAt = DateTime.UtcNow;

        _serviceRepository.Update(service);
        await _unitOfWork.SaveChangesAsync();

        return new ApiKeyRefreshResponseDto
        {
            ServiceCode = service.ServiceCode,
            ApiKey = newApiKey,
            ApiKeyCreatedAt = service.ApiKeyCreatedAt
        };
    }

    private static ServiceSummaryDto MapToSummaryDto(Service service)
    {
        return new ServiceSummaryDto
        {
            ServiceCode = service.ServiceCode,
            ServiceName = service.ServiceName,
            Description = service.Description,
            SubTier = service.SubTier.ToString(),
            Status = service.Status.ToString(),
            CreatedAt = service.CreatedAt,
            DeviceCount = service.Devices?.Count ?? 0
        };
    }

    private static ServiceResponseDto MapToDto(Service service)
    {
        return new ServiceResponseDto
        {
            ServiceCode = service.ServiceCode,
            ServiceName = service.ServiceName,
            Description = service.Description,
            ApiKey = service.ApiKey,
            ApiKeyCreatedAt = service.ApiKeyCreatedAt,
            ApnsBundleId = service.ApnsBundleId,
            ApnsKeyId = service.ApnsKeyId,
            ApnsTeamId = service.ApnsTeamId,
            HasApnsKey = !string.IsNullOrEmpty(service.ApnsPrivateKey),
            HasFcmCredentials = !string.IsNullOrEmpty(service.FcmCredentials),
            WebhookUrl = service.WebhookUrl,
            Tags = service.Tags,
            SubTier = service.SubTier.ToString(),
            SubStartedAt = service.SubStartedAt,
            Status = service.Status.ToString(),
            CreatedAt = service.CreatedAt,
            CreatedByName = service.CreatedByAdmin?.Name ?? string.Empty,
            UpdatedAt = service.UpdatedAt,
            DeviceCount = service.Devices?.Count ?? 0,
            AllowedIps = service.ServiceIps?.Select(ip => ip.IpAddress).ToList() ?? new List<string>()
        };
    }
}