Add transaction-related helpers to AnchorDescriptor

This provides a similar interface as `HTLCDescriptor` for users which
choose to implement their own bump transaction event handler.

diff --git a/lightning/src/events/bump_transaction.rs b/lightning/src/events/bump_transaction.rs
index 5ea9bdb8e292fa4e4a6d1756a5d6c1a4df782e03..9d086a26d274749d9589aa2a4e814a3d71c7cc04 100644 (file)
--- a/lightning/src/events/bump_transaction.rs
+++ b/lightning/src/events/bump_transaction.rs
@@ -76,6 +76,30 @@ pub struct AnchorDescriptor {
 }
 
 impl AnchorDescriptor {
+       /// Returns the unsigned transaction input spending the anchor output in the commitment
+       /// transaction.
+       pub fn unsigned_tx_input(&self) -> TxIn {
+               TxIn {
+                       previous_output: self.outpoint.clone(),
+                       script_sig: Script::new(),
+                       sequence: Sequence::ENABLE_RBF_NO_LOCKTIME,
+                       witness: Witness::new(),
+               }
+       }
+
+       /// Returns the witness script of the anchor output in the commitment transaction.
+       pub fn witness_script(&self) -> Script {
+               let channel_params = self.channel_derivation_parameters.transaction_parameters.as_holder_broadcastable();
+               chan_utils::get_anchor_redeemscript(&channel_params.broadcaster_pubkeys().funding_pubkey)
+       }
+
+       /// Returns the fully signed witness required to spend the anchor output in the commitment
+       /// transaction.
+       pub fn tx_input_witness(&self, signature: &Signature) -> Witness {
+               let channel_params = self.channel_derivation_parameters.transaction_parameters.as_holder_broadcastable();
+               chan_utils::build_anchor_input_witness(&channel_params.broadcaster_pubkeys().funding_pubkey, signature)
+       }
+
        /// Derives the channel signer required to sign the anchor input.
        pub fn derive_channel_signer<SP: Deref>(&self, signer_provider: &SP) -> <SP::Target as SignerProvider>::Signer
        where
@@ -649,12 +673,7 @@ where
                let mut tx = Transaction {
                        version: 2,
                        lock_time: PackedLockTime::ZERO, // TODO: Use next best height.
-                       input: vec![TxIn {
-                               previous_output: anchor_descriptor.outpoint,
-                               script_sig: Script::new(),
-                               sequence: Sequence::ZERO,
-                               witness: Witness::new(),
-                       }],
+                       input: vec![anchor_descriptor.unsigned_tx_input()],
                        output: vec![],
                };
                self.process_coin_selection(&mut tx, coin_selection);
@@ -688,8 +707,7 @@ where
                self.utxo_source.sign_tx(&mut anchor_tx)?;
                let signer = anchor_descriptor.derive_channel_signer(&self.signer_provider);
                let anchor_sig = signer.sign_holder_anchor_input(&anchor_tx, 0, &self.secp)?;
-               anchor_tx.input[0].witness =
-                       chan_utils::build_anchor_input_witness(&signer.pubkeys().funding_pubkey, &anchor_sig);
+               anchor_tx.input[0].witness = anchor_descriptor.tx_input_witness(&anchor_sig);
 
                self.broadcaster.broadcast_transactions(&[&commitment_tx, &anchor_tx]);
                Ok(())