backend/internal/service/notification_service.go

package service

import (
	"context"
	"time"

	"carrot_bbs/internal/cache"
	"carrot_bbs/internal/model"
	"carrot_bbs/internal/repository"
)

// 缓存TTL常量
const (
	NotificationUnreadCountTTL = 30 * time.Second // 通知未读数缓存30秒
	NotificationNullTTL        = 5 * time.Second
	NotificationCacheJitter    = 0.1
)

// NotificationService 通知服务
type NotificationService struct {
	notificationRepo *repository.NotificationRepository
	cache            cache.Cache
}

// NewNotificationService 创建通知服务
func NewNotificationService(notificationRepo *repository.NotificationRepository) *NotificationService {
	return &NotificationService{
		notificationRepo: notificationRepo,
		cache:            cache.GetCache(),
	}
}

// Create 创建通知
func (s *NotificationService) Create(ctx context.Context, userID string, notificationType model.NotificationType, title, content string) (*model.Notification, error) {
	notification := &model.Notification{
		UserID:  userID,
		Type:    notificationType,
		Title:   title,
		Content: content,
		IsRead:  false,
	}

	err := s.notificationRepo.Create(notification)
	if err != nil {
		return nil, err
	}

	// 失效未读数缓存
	cache.InvalidateUnreadSystem(s.cache, userID)

	return notification, nil
}

// GetByUserID 获取用户通知
func (s *NotificationService) GetByUserID(ctx context.Context, userID string, page, pageSize int, unreadOnly bool) ([]*model.Notification, int64, error) {
	return s.notificationRepo.GetByUserID(userID, page, pageSize, unreadOnly)
}

// MarkAsRead 标记为已读
func (s *NotificationService) MarkAsRead(ctx context.Context, id string) error {
	err := s.notificationRepo.MarkAsRead(id)
	if err != nil {
		return err
	}

	// 注意：这里无法获取userID，所以不在缓存中失效
	// 调用方应该使用MarkAsReadWithUserID方法

	return nil
}

// MarkAsReadWithUserID 标记为已读（带用户ID，用于缓存失效）
func (s *NotificationService) MarkAsReadWithUserID(ctx context.Context, id, userID string) error {
	err := s.notificationRepo.MarkAsRead(id)
	if err != nil {
		return err
	}

	// 失效未读数缓存
	cache.InvalidateUnreadSystem(s.cache, userID)

	return nil
}

// MarkAllAsRead 标记所有为已读
func (s *NotificationService) MarkAllAsRead(ctx context.Context, userID string) error {
	err := s.notificationRepo.MarkAllAsRead(userID)
	if err != nil {
		return err
	}

	// 失效未读数缓存
	cache.InvalidateUnreadSystem(s.cache, userID)

	return nil
}

// Delete 删除通知
func (s *NotificationService) Delete(ctx context.Context, id string) error {
	return s.notificationRepo.Delete(id)
}

// GetUnreadCount 获取未读数量（带缓存）
func (s *NotificationService) GetUnreadCount(ctx context.Context, userID string) (int64, error) {
	cacheSettings := cache.GetSettings()
	unreadTTL := cacheSettings.UnreadCountTTL
	if unreadTTL <= 0 {
		unreadTTL = NotificationUnreadCountTTL
	}
	nullTTL := cacheSettings.NullTTL
	if nullTTL <= 0 {
		nullTTL = NotificationNullTTL
	}
	jitter := cacheSettings.JitterRatio
	if jitter <= 0 {
		jitter = NotificationCacheJitter
	}

	// 生成缓存键
	cacheKey := cache.UnreadSystemKey(userID)
	return cache.GetOrLoadTyped[int64](
		s.cache,
		cacheKey,
		unreadTTL,
		jitter,
		nullTTL,
		func() (int64, error) {
			return s.notificationRepo.GetUnreadCount(userID)
		},
	)
}

// DeleteNotification 删除通知（带用户验证）
func (s *NotificationService) DeleteNotification(ctx context.Context, id, userID string) error {
	// 先检查通知是否属于该用户
	notification, err := s.notificationRepo.GetByID(id)
	if err != nil {
		return err
	}
	if notification.UserID != userID {
		return ErrUnauthorizedNotification
	}

	err = s.notificationRepo.Delete(id)
	if err != nil {
		return err
	}

	// 失效未读数缓存
	cache.InvalidateUnreadSystem(s.cache, userID)

	return nil
}

// ClearAllNotifications 清空所有通知
func (s *NotificationService) ClearAllNotifications(ctx context.Context, userID string) error {
	err := s.notificationRepo.DeleteAllByUserID(userID)
	if err != nil {
		return err
	}

	// 失效未读数缓存
	cache.InvalidateUnreadSystem(s.cache, userID)

	return nil
}

// 错误定义
var ErrUnauthorizedNotification = &ServiceError{Code: 403, Message: "unauthorized to delete this notification"}