From 2fd2c30325e6b717c68ba4d11fb92f6760aea470 Mon Sep 17 00:00:00 2001
From: Daniel Karzel <daniel@comit.network>
Date: Mon, 27 Sep 2021 15:38:24 +1000
Subject: [PATCH] move refund transaction signing onto cfd

---
 daemon/src/maker_cfd.rs | 28 ++++------------------------
 daemon/src/model/cfd.rs | 32 +++++++++++++++++++++++++++++++-
 2 files changed, 35 insertions(+), 25 deletions(-)

diff --git a/daemon/src/maker_cfd.rs b/daemon/src/maker_cfd.rs
index 9a88d54..08d2e50 100644
--- a/daemon/src/maker_cfd.rs
+++ b/daemon/src/maker_cfd.rs
@@ -13,9 +13,6 @@ use crate::{maker_inc_connections, monitor, setup_contract_actor};
 use anyhow::Result;
 use async_trait::async_trait;
 use bdk::bitcoin::secp256k1::schnorrsig;
-use bdk::bitcoin::{Amount, PublicKey};
-use cfd_protocol::secp256k1_zkp::SECP256K1;
-use cfd_protocol::{finalize_spend_transaction, spending_tx_sighash};
 use std::time::SystemTime;
 use tokio::sync::{mpsc, watch};
 use xtra::prelude::*;
@@ -421,27 +418,10 @@ impl Actor {
 
         insert_new_cfd_state_by_order_id(order_id, new_state.clone(), &mut conn).await?;
 
-        // TODO: Consider sending a message to ourselves to trigger broadcasting refund?
-        if let CfdState::MustRefund { dlc, .. } = new_state {
-            let sig_hash = spending_tx_sighash(
-                &dlc.refund.0,
-                &dlc.commit.2,
-                Amount::from_sat(dlc.commit.0.output[0].value),
-            );
-            let our_sig = SECP256K1.sign(&sig_hash, &dlc.identity);
-            let our_pubkey = PublicKey::new(bdk::bitcoin::secp256k1::PublicKey::from_secret_key(
-                SECP256K1,
-                &dlc.identity,
-            ));
-            let counterparty_sig = dlc.refund.1;
-            let counterparty_pubkey = dlc.identity_counterparty;
-            let signed_refund_tx = finalize_spend_transaction(
-                dlc.refund.0,
-                &dlc.commit.2,
-                (our_pubkey, our_sig),
-                (counterparty_pubkey, counterparty_sig),
-            )?;
-
+        // TODO: Not sure that should be done here...
+        //  Consider sending a message to ourselves to trigger broadcasting refund?
+        if let CfdState::MustRefund { .. } = new_state {
+            let signed_refund_tx = cfd.refund_tx()?;
             let txid = self
                 .wallet
                 .try_broadcast_transaction(signed_refund_tx)
diff --git a/daemon/src/model/cfd.rs b/daemon/src/model/cfd.rs
index c399dde..f8cf1cd 100644
--- a/daemon/src/model/cfd.rs
+++ b/daemon/src/model/cfd.rs
@@ -4,7 +4,8 @@ use anyhow::{bail, Result};
 use bdk::bitcoin::secp256k1::{SecretKey, Signature};
 use bdk::bitcoin::{Address, Amount, PublicKey, Transaction};
 use bdk::descriptor::Descriptor;
-use cfd_protocol::secp256k1_zkp::EcdsaAdaptorSignature;
+use cfd_protocol::secp256k1_zkp::{EcdsaAdaptorSignature, SECP256K1};
+use cfd_protocol::{finalize_spend_transaction, spending_tx_sighash};
 use rust_decimal::Decimal;
 use rust_decimal_macros::dec;
 use serde::{Deserialize, Serialize};
@@ -543,6 +544,35 @@ impl Cfd {
 
         Ok(new_state)
     }
+
+    pub fn refund_tx(&self) -> Result<Transaction> {
+        let dlc = if let CfdState::MustRefund { dlc, .. } = self.state.clone() {
+            dlc
+        } else {
+            bail!("Refund transaction can only be constructed when in state MustRefund, but we are currently in {}", self.state.clone())
+        };
+
+        let sig_hash = spending_tx_sighash(
+            &dlc.refund.0,
+            &dlc.commit.2,
+            Amount::from_sat(dlc.commit.0.output[0].value),
+        );
+        let our_sig = SECP256K1.sign(&sig_hash, &dlc.identity);
+        let our_pubkey = PublicKey::new(bdk::bitcoin::secp256k1::PublicKey::from_secret_key(
+            SECP256K1,
+            &dlc.identity,
+        ));
+        let counterparty_sig = dlc.refund.1;
+        let counterparty_pubkey = dlc.identity_counterparty;
+        let signed_refund_tx = finalize_spend_transaction(
+            dlc.refund.0,
+            &dlc.commit.2,
+            (our_pubkey, our_sig),
+            (counterparty_pubkey, counterparty_sig),
+        )?;
+
+        Ok(signed_refund_tx)
+    }
 }
 
 #[derive(Debug, Clone)]