From 6bfd1e60b37c4873bea0760347eb6f89d711c318 Mon Sep 17 00:00:00 2001
From: conduition <conduition@proton.me>
Date: Sun, 18 Feb 2024 17:11:20 +0000
Subject: [PATCH] add sighash methods for sweep transactions

---
 src/contract/outcome.rs |  6 ----
 src/spend_info/split.rs | 64 +++++++++++++++++++++++++++++++++++++++--
 2 files changed, 61 insertions(+), 9 deletions(-)

diff --git a/src/contract/outcome.rs b/src/contract/outcome.rs
index c7b1034..25a1961 100644
--- a/src/contract/outcome.rs
+++ b/src/contract/outcome.rs
@@ -24,12 +24,6 @@ impl OutcomeTransactionBuildOutput {
     pub fn outcome_txs(&self) -> &[Transaction] {
         &self.outcome_txs
     }
-
-    //     /// Return a slice of the spending info objects needed to spend
-    //     /// from an outcome transaction.
-    //     pub(crate) fn outcome_spend_infos(&self) -> &[OutcomeSpendInfo] {
-    //         &self.outcome_spend_infos
-    //     }
 }
 
 /// Construct a set of unsigned outcome transactions which spend from the funding TX.
diff --git a/src/spend_info/split.rs b/src/spend_info/split.rs
index 5e24f9d..4ca937c 100644
--- a/src/spend_info/split.rs
+++ b/src/spend_info/split.rs
@@ -1,13 +1,16 @@
 use bitcoin::{
     key::constants::SCHNORR_SIGNATURE_SIZE,
     opcodes::all::*,
-    taproot::{LeafVersion, TaprootSpendInfo},
+    sighash::{Prevouts, SighashCache},
+    taproot::{LeafVersion, TapLeafHash, TaprootSpendInfo},
     transaction::InputWeightPrediction,
-    Amount, ScriptBuf,
+    Amount, ScriptBuf, TapSighash, TapSighashType, Transaction, TxOut,
 };
 use musig2::KeyAggContext;
 use secp::Point;
 
+use std::borrow::Borrow;
+
 use crate::{
     errors::Error,
     hashlock::PREIMAGE_SIZE,
@@ -208,5 +211,60 @@ impl SplitSpendInfo {
         )
     }
 
-    // pub(crate) fn sighash_tx_win(&self)
+    /// Derive the signature hash for a win transaction, which spends from
+    /// a split transaction.
+    pub(crate) fn sighash_tx_win<T: Borrow<TxOut>>(
+        &self,
+        win_tx: &Transaction,
+        input_index: usize,
+        prevouts: &Prevouts<T>,
+    ) -> Result<TapSighash, Error> {
+        let leaf_hash = TapLeafHash::from_script(&self.win_script, LeafVersion::TapScript);
+
+        let sighash = SighashCache::new(win_tx).taproot_script_spend_signature_hash(
+            input_index,
+            prevouts,
+            leaf_hash,
+            TapSighashType::Default,
+        )?;
+        Ok(sighash)
+    }
+
+    /// Derive the signature hash for a reclaim transaction, which spends from
+    /// a split transaction.
+    pub(crate) fn sighash_tx_reclaim<T: Borrow<TxOut>>(
+        &self,
+        reclaim_tx: &Transaction,
+        input_index: usize,
+        prevouts: &Prevouts<T>,
+    ) -> Result<TapSighash, Error> {
+        let leaf_hash = TapLeafHash::from_script(&self.reclaim_script, LeafVersion::TapScript);
+
+        let sighash = SighashCache::new(reclaim_tx).taproot_script_spend_signature_hash(
+            input_index,
+            prevouts,
+            leaf_hash,
+            TapSighashType::Default,
+        )?;
+        Ok(sighash)
+    }
+
+    /// Derive the signature hash for a sellback transaction, which spends from
+    /// a split transaction.
+    pub(crate) fn sighash_tx_sellback<T: Borrow<TxOut>>(
+        &self,
+        sellback_tx: &Transaction,
+        input_index: usize,
+        prevouts: &Prevouts<T>,
+    ) -> Result<TapSighash, Error> {
+        let leaf_hash = TapLeafHash::from_script(&self.sellback_script, LeafVersion::TapScript);
+
+        let sighash = SighashCache::new(sellback_tx).taproot_script_spend_signature_hash(
+            input_index,
+            prevouts,
+            leaf_hash,
+            TapSighashType::Default,
+        )?;
+        Ok(sighash)
+    }
 }