backend/internal/repository/notification_repo.go

package repository

import (
	"carrot_bbs/internal/model"
	"carrot_bbs/internal/pkg/cursor"
	"context"

	"gorm.io/gorm"
)

// NotificationRepository 通知仓储
type NotificationRepository struct {
	db *gorm.DB
}

// NewNotificationRepository 创建通知仓储
func NewNotificationRepository(db *gorm.DB) *NotificationRepository {
	return &NotificationRepository{db: db}
}

// Create 创建通知
func (r *NotificationRepository) Create(notification *model.Notification) error {
	return r.db.Create(notification).Error
}

// GetByID 根据ID获取通知
func (r *NotificationRepository) GetByID(id string) (*model.Notification, error) {
	var notification model.Notification
	err := r.db.First(&notification, "id = ?", id).Error
	if err != nil {
		return nil, err
	}
	return &notification, nil
}

// GetByUserID 获取用户通知
func (r *NotificationRepository) GetByUserID(userID string, page, pageSize int, unreadOnly bool) ([]*model.Notification, int64, error) {
	var notifications []*model.Notification
	var total int64

	query := r.db.Model(&model.Notification{}).Where("user_id = ?", userID)

	if unreadOnly {
		query = query.Where("is_read = ?", false)
	}

	query.Count(&total)

	offset := (page - 1) * pageSize
	err := query.Offset(offset).Limit(pageSize).Order("created_at DESC").Find(&notifications).Error

	return notifications, total, err
}

// MarkAsRead 标记为已读
func (r *NotificationRepository) MarkAsRead(id string) error {
	return r.db.Model(&model.Notification{}).Where("id = ?", id).Update("is_read", true).Error
}

// MarkAllAsRead 标记所有为已读
func (r *NotificationRepository) MarkAllAsRead(userID string) error {
	return r.db.Model(&model.Notification{}).Where("user_id = ?", userID).Update("is_read", true).Error
}

// Delete 删除通知
func (r *NotificationRepository) Delete(id string) error {
	return r.db.Delete(&model.Notification{}, "id = ?", id).Error
}

// GetUnreadCount 获取未读数量
func (r *NotificationRepository) GetUnreadCount(userID string) (int64, error) {
	var count int64
	err := r.db.Model(&model.Notification{}).Where("user_id = ? AND is_read = ?", userID, false).Count(&count).Error
	return count, err
}

// DeleteAllByUserID 删除用户所有通知
func (r *NotificationRepository) DeleteAllByUserID(userID string) error {
	return r.db.Where("user_id = ?", userID).Delete(&model.Notification{}).Error
}

// ========== Cursor Pagination Methods ==========

// GetNotificationsByCursor 游标分页获取用户通知
// 排序方式：created_at DESC
func (r *NotificationRepository) GetNotificationsByCursor(ctx context.Context, userID string, unreadOnly bool, req *cursor.PageRequest) (*cursor.CursorPageResult[*model.Notification], error) {
	// 构建基础查询
	query := r.db.WithContext(ctx).Model(&model.Notification{}).Where("user_id = ?", userID)

	if unreadOnly {
		query = query.Where("is_read = ?", false)
	}

	// 使用游标构建器
	builder := cursor.NewBuilder(query, cursor.SortByCreatedAtDesc).
		WithCursor(req.Cursor, req.Direction).
		WithPageSize(req.PageSize)

	if builder.Error() != nil {
		// 无效游标，返回空列表
		return cursor.NewCursorPageResult[*model.Notification]([]*model.Notification{}, "", "", false), nil
	}

	// 执行查询
	var notifications []*model.Notification
	query = builder.Build()
	if err := query.Find(&notifications).Error; err != nil {
		return nil, err
	}

	// 构建响应
	pageSize := builder.GetPageSize()
	hasMore := cursor.HasMore(len(notifications), pageSize)
	if hasMore {
		notifications = notifications[:pageSize]
	}

	// 生成游标
	var nextCursor, prevCursor string
	if len(notifications) > 0 {
		// 下一页游标
		if hasMore {
			lastNotification := notifications[len(notifications)-1]
			nextCursor = cursor.NewCursor(
				cursor.FormatTime(lastNotification.CreatedAt),
				lastNotification.ID,
				cursor.SortByCreatedAtDesc,
			).Encode()
		}
		// 上一页游标
		firstNotification := notifications[0]
		prevCursor = cursor.NewCursor(
			cursor.FormatTime(firstNotification.CreatedAt),
			firstNotification.ID,
			cursor.SortByCreatedAtDesc,
		).Encode()
	}

	return cursor.NewCursorPageResult(notifications, nextCursor, prevCursor, hasMore), nil
}