using SPMS.Application.DTOs.Notice;
using SPMS.Application.DTOs.Notification;
using SPMS.Application.Interfaces;
using SPMS.Domain.Common;
using SPMS.Domain.Enums;
using SPMS.Domain.Exceptions;
using SPMS.Domain.Interfaces;

namespace SPMS.Application.Services;

public class NotificationService : INotificationService
{
    private readonly INotificationRepository _notificationRepository;
    private readonly IUnitOfWork _unitOfWork;

    public NotificationService(
        INotificationRepository notificationRepository,
        IUnitOfWork unitOfWork)
    {
        _notificationRepository = notificationRepository;
        _unitOfWork = unitOfWork;
    }

    public async Task<NotificationSummaryResponseDto> GetSummaryAsync(long adminId, NotificationSummaryRequestDto request)
    {
        var limit = request.Limit > 0 ? request.Limit : 5;
        var recentItems = await _notificationRepository.GetRecentAsync(adminId, limit);
        var unreadCount = await _notificationRepository.GetUnreadCountAsync(adminId);

        return new NotificationSummaryResponseDto
        {
            RecentItems = recentItems.Select(MapToItemDto).ToList(),
            UnreadCount = unreadCount
        };
    }

    public async Task<NotificationListResponseDto> GetListAsync(long adminId, NotificationListRequestDto request)
    {
        // category 문자열 → enum 파싱
        NotificationCategory? category = null;
        if (!string.IsNullOrWhiteSpace(request.Category))
        {
            if (!Enum.TryParse<NotificationCategory>(request.Category, true, out var parsed))
                throw new SpmsException(ErrorCodes.BadRequest, $"유효하지 않은 카테고리: {request.Category}");
            category = parsed;
        }

        var (items, totalCount) = await _notificationRepository.GetPagedAsync(
            adminId, category, request.From, request.To, request.IsRead, request.Page, request.Size);

        var unreadCount = await _notificationRepository.GetUnreadCountAsync(adminId);
        var totalPages = (int)Math.Ceiling((double)totalCount / request.Size);

        return new NotificationListResponseDto
        {
            Items = items.Select(MapToItemDto).ToList(),
            Pagination = new PaginationDto
            {
                Page = request.Page,
                Size = request.Size,
                TotalCount = totalCount,
                TotalPages = totalPages
            },
            UnreadCount = unreadCount
        };
    }

    public async Task<NotificationReadResponseDto> MarkAsReadAsync(long adminId, NotificationReadRequestDto request)
    {
        var notification = await _notificationRepository.GetByIdAndAdminAsync(request.NotificationId, adminId);
        if (notification == null)
            throw new SpmsException(ErrorCodes.NotFound, "알림을 찾을 수 없습니다.", 404);

        // 멱등성: 이미 읽은 알림은 스킵
        if (!notification.IsRead)
        {
            notification.IsRead = true;
            notification.ReadAt = DateTime.UtcNow;
            _notificationRepository.Update(notification);
            await _unitOfWork.SaveChangesAsync();
        }

        var unreadCount = await _notificationRepository.GetUnreadCountAsync(adminId);
        return new NotificationReadResponseDto { UnreadCount = unreadCount };
    }

    public async Task<NotificationReadResponseDto> MarkAllAsReadAsync(long adminId)
    {
        await _notificationRepository.MarkAllAsReadAsync(adminId);
        return new NotificationReadResponseDto { UnreadCount = 0 };
    }

    private static NotificationItemDto MapToItemDto(Domain.Entities.Notification n) => new()
    {
        NotificationId = n.Id,
        Category = n.Category.ToString().ToLower(),
        Title = n.Title,
        Content = n.Content,
        LinkUrl = n.LinkUrl,
        IsRead = n.IsRead,
        ReadAt = n.ReadAt,
        CreatedAt = n.CreatedAt
    };
}