payload.go

package cluster

import (
	"github.com/onflow/flow-go/model/fingerprint"
	"github.com/onflow/flow-go/model/flow"
)

// Payload is the payload for blocks in collection node cluster consensus.
// It contains only a single collection.
type Payload struct {

	// Collection is the collection being created.
	Collection flow.Collection

	// ReferenceBlockID is the ID of a reference block on the main chain. It
	// is defined as the ID of the reference block with the lowest height
	// from all transactions within the collection. If the collection is empty,
	// the proposer may choose any reference block, so long as it is finalized
	// and within the epoch the cluster is associated with. If a cluster was
	// assigned for epoch E, then all of its reference blocks must have a view
	// in the range [E.FirstView, E.FinalView]. However, if epoch fallback is
	// triggered in epoch E, then any reference block with view ≥ E.FirstView
	// may be used.
	//
	// This determines when the collection expires, using the same expiry rules
	// as transactions. It is also used as the reference point for committee
	// state (staking, etc.) when validating the containing block.
	//
	// The root block of a cluster chain has an empty reference block ID, as it
	// is created in advance of its members (necessarily) being authorized network
	// members. It is invalid for any non-root block to have an empty reference
	// block ID.
	ReferenceBlockID flow.Identifier
}

// EmptyPayload returns a payload with an empty collection and the given
// reference block ID.
func EmptyPayload(refID flow.Identifier) Payload {
	return PayloadFromTransactions(refID)
}

// PayloadFromTransactions creates a payload given a reference block ID and a
// list of transaction hashes.
func PayloadFromTransactions(refID flow.Identifier, transactions ...*flow.TransactionBody) Payload {
	// avoid a nil transaction list
	if len(transactions) == 0 {
		transactions = []*flow.TransactionBody{}
	}
	return Payload{
		Collection: flow.Collection{
			Transactions: transactions,
		},
		ReferenceBlockID: refID,
	}
}

// Hash returns the hash of the payload.
func (p Payload) Hash() flow.Identifier {
	return flow.MakeID(p)
}

func (p Payload) Fingerprint() []byte {
	return fingerprint.Fingerprint(struct {
		Collection       []byte
		ReferenceBlockID flow.Identifier
	}{
		Collection:       p.Collection.Fingerprint(),
		ReferenceBlockID: p.ReferenceBlockID,
	})
}