package mls

// MLS secret tree (RFC 9420 §9).
// Type definitions - crypto derivation methods go in secret_tree_crypto.mx.
//
// A ratchet label is a []byte and a secret tree is a [][]byte. Moxie forbids
// named slice types, so the old methods are free functions whose first
// parameter is the value.

var (
	ratchetLabelHandshake   []byte
	ratchetLabelApplication []byte
)

func ratchetLabelFromContentType(ct contentType) (v []byte) {
	switch ct {
	case contentTypeApplication:
		return ratchetLabelApplication
	case contentTypeProposal, contentTypeCommit:
		return ratchetLabelHandshake
	default:
		panic("unreachable")
	}
}

// secretTreeGet returns the secret stored at node ni.
func secretTreeGet(tree [][]byte, ni nodeIndex) (buf []byte) {
	secret := tree[int32(ni)]
	if secret == nil {
		panic("empty node in secret tree")
	}
	return secret
}

// secretTreeSet stores secret at node ni.
func secretTreeSet(tree [][]byte, ni nodeIndex, secret []byte) {
	tree[int32(ni)] = secret
}

type ratchetSecret struct {
	secret     []byte
	generation uint32
}