add refund functionality

index.ts

@@ -435,4 +435,64 @@ export default class PortalBtcWallet {
       listener();
     }
   }
+
+  /**
+   * Refunds a payment
+   *
+   * @param payment - The payment to refund
+   */
+  async refundPayment(payment: Payment) {
+    if (!this.breezSDK) throw new Error("Breez SDK not initialized");
+    const prepareAddr = await this.breezSDK.prepareReceivePayment({
+      paymentMethod: "bitcoinAddress",
+    });
+    const receiveRes = await this.breezSDK.receivePayment({
+      prepareResponse: prepareAddr,
+    });
+    const refundAddress = receiveRes.destination as string;
+
+    try {
+      const refundables = await this.breezSDK.listRefundables();
+      let swapAddress: string | undefined;
+      if (refundables.length === 1) {
+        swapAddress = refundables[0]?.swapAddress;
+      } else {
+        swapAddress = refundables.find(
+          (r) =>
+            r.amountSat === payment.amountSat &&
+            Math.abs(r.timestamp - payment.timestamp) < 300,
+        )?.swapAddress;
+      }
+
+      if (!swapAddress) {
+        throw new Error("Could not identify refundable swap for this payment.");
+      }
+
+      const fees = await this.breezSDK.recommendedFees();
+      const feeRateSatPerVbyte = fees.economyFee;
+
+      const refundRequest = {
+        swapAddress,
+        refundAddress,
+        feeRateSatPerVbyte,
+      } as const;
+
+      try {
+        await this.breezSDK.prepareRefund(refundRequest);
+      } catch (err) {
+        console.warn(
+          "prepareRefund failed (may be expected for some swaps)",
+          err,
+        );
+        return;
+      }
+
+      await this.breezSDK.refund(refundRequest);
+    } catch (err) {
+      console.error("Refund failed", err);
+      throw new Error(
+        `Refund failed: ${err instanceof Error ? err.message : err}`,
+      );
+    }
+  }
 }