Add optional payload to create_transaction_spend_outpoint

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();
@@ -105,6 +106,14 @@ pub fn create_transaction_spend_outpoint(
     // Take the recipient address
     let address = recipient.address.clone();
 
+    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());
@@ -114,10 +123,13 @@ pub fn create_transaction_spend_outpoint(
         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)?;