From 066410ec6355a70410b90d9f423cc2fd4f31ab58 Mon Sep 17 00:00:00 2001
From: Sosthene <contact@sosthene.net>
Date: Thu, 27 Jun 2024 17:19:04 +0200
Subject: [PATCH] Add optional payload to create_transaction_spend_outpoint

---
 src/silentpayments.rs | 30 +++++++++++++++++++++---------
 1 file changed, 21 insertions(+), 9 deletions(-)

diff --git a/src/silentpayments.rs b/src/silentpayments.rs
index c2b58e5..ff9301f 100644
--- a/src/silentpayments.rs
+++ b/src/silentpayments.rs
@@ -77,6 +77,7 @@ pub fn create_transaction_spend_outpoint(
     sp_wallet: &SpWallet,
     mut recipient: Recipient,
     commited_in_txid: &Txid,
+    payload: Option<Vec<u8>>,
     fee_rate: Amount
 ) -> Result<Psbt> {
     let available_outpoints = sp_wallet.get_outputs().to_spendable_list();
@@ -105,19 +106,30 @@ pub fn create_transaction_spend_outpoint(
     // Take the recipient address
     let address = recipient.address.clone();
 
-    // create a dummy commitment that is H(b_scan | commited_in txid)
-    let mut buf = [0u8;64];
-    buf[..32].copy_from_slice(commited_in_txid.as_raw_hash().as_byte_array());
-    buf[32..].copy_from_slice(&sp_wallet.get_client().get_scan_key().secret_bytes());
- 
-    let mut engine = sha256::HashEngine::default();
-    engine.write_all(&buf)?;
-    let hash = sha256::Hash::from_engine(engine);
+    let mut commitment = [0u8;32];
+    if let Some(p) = payload {
+        let mut engine = sha256::HashEngine::default();
+        engine.write_all(&p)?;
+        let hash = sha256::Hash::from_engine(engine);
+
+        commitment.copy_from_slice(hash.as_byte_array());
+    } else {
+        // create a dummy commitment that is H(b_scan | commited_in txid)
+        let mut buf = [0u8;64];
+        buf[..32].copy_from_slice(commited_in_txid.as_raw_hash().as_byte_array());
+        buf[32..].copy_from_slice(&sp_wallet.get_client().get_scan_key().secret_bytes());
+    
+        let mut engine = sha256::HashEngine::default();
+        engine.write_all(&buf)?;
+        let hash = sha256::Hash::from_engine(engine);
+
+        commitment.copy_from_slice(hash.as_byte_array());
+    }
 
     let mut new_psbt = sp_wallet.get_client().create_new_psbt(
         inputs,
         vec![recipient],
-        Some(hash.as_byte_array()),
+        Some(&commitment),
     )?;
 
     SpClient::set_fees(&mut new_psbt, fee_rate, address)?;