ancestor

type Tree interface {
	// Add a mapping from blkID to parentID.
	//
	// Invariant: blkID must not be equal to parentID
	// Invariant: a given blkID must only ever have one parentID
	Add(blkID ids.ID, parentID ids.ID)

	// Has returns if blkID's parentID is known by the tree.
	Has(blkID ids.ID) bool

	// GetAncestor returns the oldest known ancestor of blkID. If there is no
	// known parentID of blkID, blkID will be returned.
	GetAncestor(blkID ids.ID) ids.ID

	// Remove the mapping from blkID to its parentID from the tree.
	Remove(blkID ids.ID)

	// RemoveDescendants removes blkID from the tree along with all of its known
	// descendants.
	RemoveDescendants(blkID ids.ID)

	// Len returns the total number of blkID to parentID mappings that are
	// currently tracked by the tree.
	Len() int
}