func()

in internal/repo/activity_common/follow.go [164:265]
85 lines of code
14 McCabe index (conditional complexity)

func (ar *FollowRepo) MigrateFollowers(ctx context.Context, sourceObjectID, targetObjectID, action string) error {
	// if source object id and target object id are same type
	sourceObjectTypeStr, err := obj.GetObjectTypeStrByObjectID(sourceObjectID)
	if err != nil {
		return errors.InternalServer(reason.DatabaseError).WithError(err).WithStack()
	}
	targetObjectTypeStr, err := obj.GetObjectTypeStrByObjectID(targetObjectID)
	if err != nil {
		return errors.InternalServer(reason.DatabaseError).WithError(err).WithStack()
	}
	if sourceObjectTypeStr != targetObjectTypeStr {
		return errors.InternalServer(reason.DisallowFollow).WithMsg("not same object type")
	}
	activityType, err := ar.activityRepo.GetActivityTypeByObjectType(ctx, sourceObjectTypeStr, action)
	if err != nil {
		return err
	}

	// 1. get all user ids who follow the source object
	userIDs, err := ar.GetFollowUserIDs(ctx, sourceObjectID)
	if err != nil {
		log.Errorf("MigrateFollowers: failed to get user ids who follow %s: %v", sourceObjectID, err)
		return err
	}

	_, err = ar.data.DB.Transaction(func(session *xorm.Session) (result any, err error) {
		session = session.Context(ctx)
		// 1. delete all follows of the source object
		_, err = session.Table(entity.Activity{}.TableName()).
			Where(builder.Eq{
				"object_id":     sourceObjectID,
				"activity_type": activityType,
			}).
			Delete(&entity.Activity{})
		if err != nil {
			return nil, errors.InternalServer(reason.DatabaseError).WithError(err).WithStack()
		}

		// 2. update cancel status to active for target tag if source tag followers is active
		_, err = session.Table(entity.Activity{}.TableName()).
			Where(builder.Eq{
				"object_id":     targetObjectID,
				"activity_type": activityType,
			}).
			And(builder.In("user_id", userIDs)).
			Cols("cancelled").
			Update(&entity.Activity{
				Cancelled: entity.ActivityAvailable,
			})
		if err != nil {
			return nil, errors.InternalServer(reason.DatabaseError).WithError(err).WithStack()
		}

		// 3. get existing follows of the target object
		targetFollowers := make([]string, 0)
		err = session.Table(entity.Activity{}.TableName()).
			Where(builder.Eq{
				"object_id":     targetObjectID,
				"activity_type": activityType,
				"cancelled":     entity.ActivityAvailable,
			}).
			Cols("user_id").
			Find(&targetFollowers)
		if err != nil {
			return nil, errors.InternalServer(reason.DatabaseError).WithError(err).WithStack()
		}

		// 4. filter out user ids that already follow the target object and create new activity
		// Create a map for faster lookup of existing followers
		existingFollowers := make(map[string]bool)
		for _, uid := range targetFollowers {
			existingFollowers[uid] = true
		}

		// Filter out users who already follow the target
		newFollowers := make([]string, 0)
		for _, uid := range userIDs {
			if !existingFollowers[uid] {
				newFollowers = append(newFollowers, uid)
			}
		}

		// Create new activities for the filtered users
		for _, uid := range newFollowers {
			activity := &entity.Activity{
				UserID:           uid,
				ObjectID:         targetObjectID,
				OriginalObjectID: targetObjectID,
				ActivityType:     activityType,
				CreatedAt:        time.Now(),
				UpdatedAt:        time.Now(),
				Cancelled:        entity.ActivityAvailable,
			}
			if _, err = session.Insert(activity); err != nil {
				return nil, errors.InternalServer(reason.DatabaseError).WithError(err).WithStack()
			}
		}
		return nil, nil
	})

	return err
}