package consensus

import "source.quilibrium.com/quilibrium/monorepo/consensus/models"

// Finalizer is used by the consensus algorithm to inform other components for
// (such as the protocol state) about finalization of states.
//
// Since we have two different protocol states: one for the main consensus,
// the other for the collection cluster consensus, the Finalizer interface
// allows the two different protocol states to provide different implementations
// for updating its state when a state has been finalized.
//
// Updating the protocol state should always succeed when the data is
// consistent. However, in case the protocol state is corrupted, error should be
// returned and the consensus algorithm should halt. So the error returned from
// MakeFinal is for the protocol state to report exceptions.
type Finalizer interface {

	// MakeFinal will declare a state and all of its ancestors as finalized, which
	// makes it an immutable part of the time reel. Returning an error indicates
	// some fatal condition and will cause the finalization logic to terminate.
	MakeFinal(stateID models.Identity) error
}