package service

import (
	"context"
	"time"

	"with_you/internal/cache"
	apperrors "with_you/internal/errors"
	"with_you/internal/model"
	"with_you/internal/pkg/cursor"
	"with_you/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 通知服务接口
type NotificationService interface {
	Create(ctx context.Context, userID string, notificationType model.NotificationType, title, content string) (*model.Notification, error)
	GetByUserID(ctx context.Context, userID string, page, pageSize int, unreadOnly bool) ([]*model.Notification, int64, error)
	MarkAsReadWithUserID(ctx context.Context, id, userID string) error
	MarkAllAsRead(ctx context.Context, userID string) error
	GetUnreadCount(ctx context.Context, userID string) (int64, error)
	DeleteNotification(ctx context.Context, id, userID string) error
	ClearAllNotifications(ctx context.Context, userID string) error
	GetNotificationsByCursor(ctx context.Context, userID string, unreadOnly bool, req *cursor.PageRequest) (*cursor.CursorPageResult[*model.Notification], error)
}

// notificationService 通知服务实现
type notificationService struct {
	notificationRepo repository.NotificationRepository
	cache            cache.Cache
}

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

// 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)
}

// MarkAsReadWithUserID 标记为已读（带用户ID，验证所有权）
func (s *notificationService) MarkAsReadWithUserID(ctx context.Context, id, userID string) error {
	notification, err := s.notificationRepo.GetByID(id)
	if err != nil {
		return err
	}
	if notification.UserID != userID {
		return apperrors.ErrForbidden
	}

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

	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
}

// 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
}

// GetNotificationsByCursor 游标分页获取用户通知
func (s *notificationService) GetNotificationsByCursor(ctx context.Context, userID string, unreadOnly bool, req *cursor.PageRequest) (*cursor.CursorPageResult[*model.Notification], error) {
	return s.notificationRepo.GetNotificationsByCursor(ctx, userID, unreadOnly, req)
}

// 错误定义
var ErrUnauthorizedNotification = apperrors.ErrUnauthorizedNotification