From e4e8298fcde7e87798f250c32514386e7b563fba Mon Sep 17 00:00:00 2001
From: Dave Hrycyszyn <futurechimp@users.noreply.github.com>
Date: Thu, 25 Jul 2024 19:12:39 +0100
Subject: [PATCH] Adding an htlc model file

---
 side-node/src/bitcoin/htlc.rs | 80 +++++++++++++++++++++++++++++++++++
 side-node/src/bitcoin/mod.rs  |  1 +
 2 files changed, 81 insertions(+)
 create mode 100644 side-node/src/bitcoin/htlc.rs

diff --git a/side-node/src/bitcoin/htlc.rs b/side-node/src/bitcoin/htlc.rs
new file mode 100644
index 0000000..8feece7
--- /dev/null
+++ b/side-node/src/bitcoin/htlc.rs
@@ -0,0 +1,80 @@
+use std::str::FromStr;
+
+use bdk_wallet::miniscript::descriptor::Wsh;
+use bdk_wallet::miniscript::policy::{self, Concrete, Liftable};
+use bitcoin::Address;
+
+/// A hash time locked contract between two parties.
+///
+/// If the hash preimage of the hashlock is revealed, the value is sent to the redeem_identity.
+///
+/// Alternately, if the refund timelock expires, the value can be refunded to the refund_identity.
+pub(crate) struct Htlc {
+    value: u64,
+    redeem_identity: Address,
+    hashlock: String,
+    refund_timelock: u64,
+    refund_indentiy: Address,
+}
+
+impl Htlc {
+    /// Create a new HTLC.
+    pub(crate) fn new(
+        value: u64,
+        redeem_identity: Address,
+        hashlock: String,
+        refund_timelock: u64,
+        refund_indentiy: Address,
+    ) -> Self {
+        Self {
+            value,
+            redeem_identity,
+            hashlock,
+            refund_timelock,
+            refund_indentiy,
+        }
+    }
+
+    pub(crate) fn to_miniscript_policy(&self) -> policy::Concrete<bitcoin::PublicKey> {
+        Concrete::<bitcoin::PublicKey>::from_str(&format!(
+            "or(10@and(sha256({secret_hash}),pk({redeem_identity})),1@and(older({expiry}),pk({refund_identity})))",
+            secret_hash = self.hashlock,
+            redeem_identity = self.redeem_identity,
+            refund_identity = self.refund_indentiy,
+            expiry = self.refund_timelock
+        )).expect("Policy compilation only fails on resource limits or mixed timelocks")
+    }
+
+    pub(crate) fn to_miniscript_descriptor(&self) -> Wsh<bitcoin::PublicKey> {
+        Wsh::new(
+            self.to_miniscript_policy()
+                .compile()
+                .expect("Policy compilation only fails on resource limits or mixed timelocks"),
+        )
+        .expect("Resource limits")
+    }
+
+    /// Translate the HTLC to Bitcoin op_codes.
+    pub(crate) fn to_script(&self) -> String {
+        format!(
+            "OP_IF
+                OP_SHA256
+                {}
+                OP_EQUALVERIFY
+                OP_DUP
+                OP_HASH160
+                {}
+                OP_ELSE
+                {}
+                OP_CHECKLOCKTIMEVERIFY
+                OP_DROP
+                OP_DUP
+                OP_HASH160
+                {}
+                OP_ENDIF
+                OP_EQUALVERIFY
+                OP_CHECKSIG",
+            self.hashlock, self.redeem_identity, self.refund_timelock, self.refund_indentiy
+        )
+    }
+}
diff --git a/side-node/src/bitcoin/mod.rs b/side-node/src/bitcoin/mod.rs
index 784440b..50092fa 100644
--- a/side-node/src/bitcoin/mod.rs
+++ b/side-node/src/bitcoin/mod.rs
@@ -1,3 +1,4 @@
 pub mod clients;
 pub mod driver;
+pub mod htlc;
 pub mod keys;