type BlockmetaDB interface {
	BlockIDAt(ctx context.Context, start time.Time) (id string, err error)
	BlockIDAfter(ctx context.Context, start time.Time, inclusive bool) (id string, foundtime time.Time, err error)
	BlockIDBefore(ctx context.Context, start time.Time, inclusive bool) (id string, foundtime time.Time, err error)

	GetLastWrittenBlockID(ctx context.Context) (blockID string, err error)
	GetIrreversibleIDAtBlockNum(ctx context.Context, num uint64) (ref bstream.BlockRef, err error)
	GetIrreversibleIDAtBlockID(ctx context.Context, id string) (ref bstream.BlockRef, err error)

	
	
	GetForkPreviousBlocks(ctx context.Context, forkTop bstream.BlockRef) ([]bstream.BlockRef, error)
}