From a2e12ea51ed8326b9b424bca1fc907c28ac37b35 Mon Sep 17 00:00:00 2001
From: CalDescent <>
Date: Sun, 15 May 2022 12:15:16 +0100
Subject: [PATCH] Attempt to redeem P2SH with secret. This is highly
 experimental.

Based on Qortal standard HTLCs. Will need adapting to Pirate specific ones at the very least.
---
 zcash_primitives/src/transaction/builder.rs | 28 ++++++++++++++++++---
 1 file changed, 24 insertions(+), 4 deletions(-)

diff --git a/zcash_primitives/src/transaction/builder.rs b/zcash_primitives/src/transaction/builder.rs
index e30d88f..dc60bd1 100644
--- a/zcash_primitives/src/transaction/builder.rs
+++ b/zcash_primitives/src/transaction/builder.rs
@@ -141,6 +141,7 @@ struct TransparentInputInfo {
     sk: secp256k1::SecretKey,
     pubkey: [u8; secp256k1::constants::PUBLIC_KEY_SIZE],
     coin: TxOut,
+    secret: Vec<u8>,
 }
 
 #[cfg(feature = "transparent-inputs")]
@@ -171,6 +172,7 @@ impl TransparentInputs {
         sk: secp256k1::SecretKey,
         utxo: OutPoint,
         coin: TxOut,
+        secret: Vec<u8>,
     ) -> Result<(), Error> {
         if coin.value.is_negative() {
             return Err(Error::InvalidAmount);
@@ -190,7 +192,7 @@ impl TransparentInputs {
         }
 
         mtx.vin.push(TxIn::new(utxo));
-        self.inputs.push(TransparentInputInfo { sk, pubkey, coin });
+        self.inputs.push(TransparentInputInfo { sk, pubkey, coin, secret });
 
         Ok(())
     }
@@ -232,8 +234,14 @@ impl TransparentInputs {
             let mut sig_bytes: Vec<u8> = sig.serialize_der()[..].to_vec();
             sig_bytes.extend(&[SIGHASH_ALL as u8]);
 
-            // P2PKH scriptSig
-            mtx.vin[i].script_sig = Script::default() << &sig_bytes[..] << &info.pubkey[..];
+            if (&info.secret.len() > 0) {
+                // Include secret and redeem script
+                mtx.vin[i].script_sig = Script::default() << &info.secret[..] << &sig_bytes[..] << &info.pubkey[..] << &info.coin.script_pubkey[..];
+            }
+            else {
+                // P2PKH scriptSig
+                mtx.vin[i].script_sig = Script::default() << &sig_bytes[..] << &info.pubkey[..];
+            }
         }
     }
 
@@ -398,7 +406,19 @@ impl<R: RngCore + CryptoRng> Builder<R> {
         utxo: OutPoint,
         coin: TxOut,
     ) -> Result<(), Error> {
-        self.transparent_inputs.push(&mut self.mtx, sk, utxo, coin)
+        self.transparent_inputs.push(&mut self.mtx, sk, utxo, coin, Vec::new())
+    }
+
+    /// Adds a transparent coin to be spent in this transaction, with HTLC secret.
+    #[cfg(feature = "transparent-inputs")]
+    pub fn add_transparent_input_with_secret(
+        &mut self,
+        sk: secp256k1::SecretKey,
+        utxo: OutPoint,
+        coin: TxOut,
+        secret: Vec<u8>,
+    ) -> Result<(), Error> {
+        self.transparent_inputs.push(&mut self.mtx, sk, utxo, coin, secret)
     }
 
     /// Adds a transparent address to send funds to.