package mls

// MLS secret tree (RFC 9420 §9).
// Type definitions — crypto derivation methods go in secret_tree_crypto.mx.

type ratchetLabel []byte

var (
	ratchetLabelHandshake   = ratchetLabel("handshake")
	ratchetLabelApplication = ratchetLabel("application")
)

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

// secretTree holds tree node secrets for encryption key/nonce generation.
type secretTree [][]byte

func (tree secretTree) get(ni nodeIndex) []byte {
	secret := tree[int(ni)]
	if secret == nil {
		panic("empty node in secret tree")
	}
	return secret
}

func (tree secretTree) set(ni nodeIndex, secret []byte) {
	tree[int(ni)] = secret
}

type ratchetSecret struct {
	secret     []byte
	generation uint32
}