- /// Signs a transaction created by build_htlc_transaction. If the transaction is an
- /// HTLC-Success transaction, preimage must be set!
- /// TODO: should be merged with sign_local_commitment as a slice of HTLC transactions to sign
- fn sign_htlc_transaction<T: secp256k1::Signing>(&self, local_commitment_tx: &mut LocalCommitmentTransaction, htlc_index: u32, preimage: Option<PaymentPreimage>, local_csv: u16, secp_ctx: &Secp256k1<T>);
+ /// Create a signature for each HTLC transaction spending a local commitment transaction.
+ ///
+ /// Unlike sign_local_commitment, this may be called multiple times with *different*
+ /// local_commitment_tx values. While this will never be called with a revoked
+ /// local_commitment_tx, it is possible that it is called with the second-latest
+ /// local_commitment_tx (only if we haven't yet revoked it) if some watchtower/secondary
+ /// ChannelMonitor decided to broadcast before it had been updated to the latest.
+ ///
+ /// Either an Err should be returned, or a Vec with one entry for each HTLC which exists in
+ /// local_commitment_tx. For those HTLCs which have transaction_output_index set to None
+ /// (implying they were considered dust at the time the commitment transaction was negotiated),
+ /// a corresponding None should be included in the return value. All other positions in the
+ /// return value must contain a signature.
+ fn sign_local_commitment_htlc_transactions<T: secp256k1::Signing + secp256k1::Verification>(&self, local_commitment_tx: &LocalCommitmentTransaction, local_csv: u16, secp_ctx: &Secp256k1<T>) -> Result<Vec<Option<Signature>>, ()>;
+