[skip ci] Implement prepare_refund_failed_swap()

Author: danielgranhao

src/lib.rs

@@ -66,8 +66,8 @@ use breez_sdk_core::{
     parse, parse_invoice, BreezEvent, BreezServices, EventListener, GreenlightCredentials,
     GreenlightNodeConfig, InputType, ListPaymentsRequest, LnUrlPayRequest, LnUrlPayRequestData,
     LnUrlPayResult, LnUrlWithdrawRequest, LnUrlWithdrawResult, NodeConfig, OpenChannelFeeRequest,
-    OpeningFeeParams, PaymentDetails, PaymentStatus, PaymentTypeFilter, ReceiveOnchainRequest,
-    RefundRequest, SendPaymentRequest, SweepRequest,
+    OpeningFeeParams, PaymentDetails, PaymentStatus, PaymentTypeFilter, PrepareRefundRequest,
+    ReceiveOnchainRequest, RefundRequest, SendPaymentRequest, SweepRequest,
 };
 use cipher::generic_array::typenum::U32;
 use crow::{CountryCode, LanguageCode, OfferManager, TopupError, TopupInfo, TopupStatus};
@@ -278,6 +278,14 @@ pub struct FailedSwapInfo {
     pub created_at: SystemTime,
 }
 
+/// Information about a failed swap refund
+pub struct FailedSwapRefundInfo {
+    /// The amount that will be sent (swap amount - onchain fee)
+    pub refund_amount: Amount,
+    /// The amount that will be paid in onchain fees
+    pub onchain_fee: Amount,
+}
+
 #[derive(Clone, PartialEq, Debug)]
 pub(crate) struct UserPreferences {
     fiat_currency: String,
@@ -1404,6 +1412,45 @@ impl LightningNode {
             .collect())
     }
 
+    /// Prepares a failed swap refund in order to know how much will be recovered and how much
+    /// will be paid in onchain fees
+    ///
+    /// Parameters:
+    /// * `failed_swap_info` - the failed swap that will be prepared
+    /// * `to_address` - the destination address to which funds will be sent
+    /// * `onchain_fee_rate` - the fee rate that will be applied. The recommended one can be fetched
+    /// using [`LightningNode::query_onchain_fee_rate`]
+    pub fn prepare_refund_failed_swap(
+        &self,
+        failed_swap_info: FailedSwapInfo,
+        to_address: String,
+        onchain_fee_rate: u32,
+    ) -> Result<FailedSwapRefundInfo> {
+        let response = self
+            .rt
+            .handle()
+            .block_on(self.sdk.prepare_refund(PrepareRefundRequest {
+                swap_address: failed_swap_info.address,
+                to_address,
+                sat_per_vbyte: onchain_fee_rate,
+            }))
+            .map_to_runtime_error(
+                RuntimeErrorCode::NodeUnavailable,
+                "Failed to create and broadcast failed swap refund transaction",
+            )?;
+
+        let rate = self.get_exchange_rate();
+        let onchain_fee = response.refund_tx_fee_sat.as_sats().to_amount_up(&rate);
+        let refund_amount = (failed_swap_info.amount.sats - onchain_fee.sats)
+            .as_sats()
+            .to_amount_down(&rate);
+
+        Ok(FailedSwapRefundInfo {
+            refund_amount,
+            onchain_fee,
+        })
+    }
+
     /// 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`].
     ///

src/lipalightninglib.udl

@@ -85,6 +85,9 @@ interface LightningNode {
     [Throws=LnError]
     sequence<FailedSwapInfo> get_unresolved_failed_swaps();
 
+    [Throws=LnError]
+    FailedSwapRefundInfo prepare_refund_failed_swap(FailedSwapInfo failed_swap_info, string to_address, u32 onchain_fee_rate);
+
     [Throws=LnError]
     string resolve_failed_swap(string failed_swap_address, string to_address, u32 onchain_fee_rate);
 
@@ -347,12 +350,18 @@ enum OfferStatus {
     "SETTLED",
 };
 
+
 dictionary SwapAddressInfo {
     string address;
     Amount min_deposit;
     Amount max_deposit;
 };
 
+dictionary FailedSwapRefundInfo {
+    Amount refund_amount;
+    Amount onchain_fee;
+};
+
 dictionary FailedSwapInfo {
     string address;
     Amount amount;