Add zero-amount Receive Chain Swap (#538)

Add support for Zero-Amount Receive Chain Swaps

lib/core/src/swapper/boltz/mod.rs

@@ -8,6 +8,7 @@ use boltz_client::{
     elements::secp256k1_zkp::{MusigPartialSignature, MusigPubNonce},
     network::{electrum::ElectrumConfig, Chain},
     util::secrets::Preimage,
+    Amount,
 };
 use log::info;
 use url::Url;
@@ -179,6 +180,23 @@ impl Swapper for BoltzSwapper {
         Ok((pair_outgoing, pair_incoming))
     }
 
+    fn get_zero_amount_chain_swap_quote(&self, swap_id: &str) -> Result<Amount, PaymentError> {
+        self.client
+            .get_quote(swap_id)
+            .map(|r| Amount::from_sat(r.amount))
+            .map_err(Into::into)
+    }
+
+    fn accept_zero_amount_chain_swap_quote(
+        &self,
+        swap_id: &str,
+        server_lockup_sat: u64,
+    ) -> Result<(), PaymentError> {
+        self.client
+            .accept_quote(swap_id, server_lockup_sat)
+            .map_err(Into::into)
+    }
+
     /// Get a submarine pair information
     fn get_submarine_pairs(&self) -> Result<Option<SubmarinePair>, PaymentError> {
         Ok(self.client.get_submarine_pairs()?.get_lbtc_to_btc_pair())

lib/core/src/swapper/mod.rs

@@ -8,6 +8,7 @@ use boltz_client::{
         SubmarineClaimTxResponse, SubmarinePair,
     },
     network::Chain,
+    Amount,
 };
 use tokio::sync::{broadcast, watch};
 
@@ -40,6 +41,19 @@ pub trait Swapper: Send + Sync {
     /// Get the current rate, limits and fees for both swap directions
     fn get_chain_pairs(&self) -> Result<(Option<ChainPair>, Option<ChainPair>), PaymentError>;
 
+    /// Get the quote for a Zero-Amount Receive Chain Swap.
+    ///
+    /// If the user locked-up funds in the valid range this will return that amount. In all other
+    /// cases, this will return an error.
+    fn get_zero_amount_chain_swap_quote(&self, swap_id: &str) -> Result<Amount, PaymentError>;
+
+    /// Accept a specific quote for a Zero-Amount Receive Chain Swap
+    fn accept_zero_amount_chain_swap_quote(
+        &self,
+        swap_id: &str,
+        server_lockup_sat: u64,
+    ) -> Result<(), PaymentError>;
+
     /// Get a submarine pair information
     fn get_submarine_pairs(&self) -> Result<Option<SubmarinePair>, PaymentError>;