state

type Chain interface {
	ReadOnlyChain
	avax.UTXOAdder
	avax.UTXODeleter

	AddTx(tx *txs.Tx)
	AddBlock(block block.Block)
	SetLastAccepted(blkID ids.ID)
	SetTimestamp(t time.Time)
}

type Diff interface {
	Chain

	Apply(Chain)
}

type ReadOnlyChain interface {
	avax.UTXOGetter

	GetTx(txID ids.ID) (*txs.Tx, error)
	GetBlockIDAtHeight(height uint64) (ids.ID, error)
	GetBlock(blkID ids.ID) (block.Block, error)
	GetLastAccepted() ids.ID
	GetTimestamp() time.Time
}

type State interface {
	Chain
	avax.UTXOReader

	IsInitialized() (bool, error)
	SetInitialized() error

	// InitializeChainState is called after the VM has been linearized. Calling
	// [GetLastAccepted] or [GetTimestamp] before calling this function will
	// return uninitialized data.
	//
	// Invariant: After the chain is linearized, this function is expected to be
	// called during startup.
	InitializeChainState(stopVertexID ids.ID, genesisTimestamp time.Time) error

	// Discard uncommitted changes to the database.
	Abort()

	// Commit changes to the base database.
	Commit() error

	// Returns a batch of unwritten changes that, when written, will commit all
	// pending changes to the base database.
	CommitBatch() (database.Batch, error)

	// Checksums returns the current TxChecksum and UTXOChecksum.
	Checksums() (txChecksum ids.ID, utxoChecksum ids.ID)

	Close() error
}

type Versions interface {
	// GetState returns the state of the chain after [blkID] has been accepted.
	// If the state is not known, `false` will be returned.
	GetState(blkID ids.ID) (Chain, bool)
}