Implement failed swap resolving methods

Author: danielgranhao

src/lib.rs

@@ -246,6 +246,14 @@ pub struct OfferInfo {
     pub status: OfferStatus,
 }
 
+/// Information about a failed swap
+pub struct FailedSwapInfo {
+    pub address: String,
+    /// The amount that is available to be refunded. The refund will involve paying some
+    /// onchain fees so it isn't possible to recover the entire amount.
+    pub amount: Amount,
+}
+
 #[derive(Clone, PartialEq, Debug)]
 pub(crate) struct UserPreferences {
     fiat_currency: String,
@@ -1064,6 +1072,53 @@ impl LightningNode {
             .to_hex())
     }
 
+    /// Lists all unresolved failed swaps. Each individual failed swap can be refunded
+    /// using [`LightningNode::refund_failed_swap`].
+    pub fn get_unresolved_failed_swaps(&self) -> Result<Vec<FailedSwapInfo>> {
+        Ok(self
+            .rt
+            .handle()
+            .block_on(self.sdk.list_refundables())
+            .map_to_runtime_error(
+                RuntimeErrorCode::NodeUnavailable,
+                "Failed to list refundable failed swaps",
+            )?
+            .iter()
+            .map(|s| FailedSwapInfo {
+                address: s.bitcoin_address.clone(),
+                amount: (s.confirmed_sats * 1000).to_amount_down(&self.get_exchange_rate()),
+            })
+            .collect())
+    }
+
+    /// Creates and broadcasts a refund transaction to recover funds from a failed swap. Existing
+    /// failed swaps can be listed using [`LightningNode::get_unresolved_failed_swaps`].
+    ///
+    /// Parameters:
+    /// * `failed_swap_address` - the address of the failed swap (can be obtained from [`FailedSwapInfo`])
+    /// * `to_address` - the destination address to which funds will be sent
+    /// * `onchain_fee_rate` - the fee rate that will be applied. The recommeded one can be fetched
+    /// using [`LightningNode::query_onchain_fee`]
+    ///
+    /// Returns the txid of the refund transaction.
+    pub fn refund_failed_swap(
+        &self,
+        failed_swap_address: String,
+        to_address: String,
+        onchain_fee_rate: u32,
+    ) -> Result<String> {
+        self.rt
+            .handle()
+            .block_on(
+                self.sdk
+                    .refund(failed_swap_address, to_address, onchain_fee_rate),
+            )
+            .map_to_runtime_error(
+                RuntimeErrorCode::NodeUnavailable,
+                "Failed to create and broadcast failed swap refund transaction",
+            )
+    }
+
     /// Prints additional debug information to the logs.
     ///
     /// Throws an error in case that the necessary information can't be retrieved.

src/lipalightninglib.udl

@@ -76,6 +76,12 @@ interface LightningNode {
     [Throws=LnError]
     string sweep(string address, u32 onchain_fee);
 
+    [Throws=LnError]
+    sequence<FailedSwapInfo> get_unresolved_failed_swaps();
+
+    [Throws=LnError]
+    string refund_failed_swap(string failed_swap_address, string to_address, u32 onchain_fee_rate);
+
     [Throws=LnError]
     void hide_topup(string id);
 
@@ -315,6 +321,11 @@ enum OfferStatus {
     "SETTLED",
 };
 
+dictionary FailedSwapInfo {
+    string address;
+    Amount amount;
+};
+
 //
 // ----------------------------- TOP LEVEL FUNCTIONS + RELATED DEFINITIONS -----------------------------
 //