Display tx fee on lightning pay confirm view

src/action/payment.js

@@ -70,13 +70,31 @@ class PaymentAction {
       });
       payment.amount = toAmount(parseSat(request.num_satoshis), settings.unit);
       payment.note = request.description;
+      await this.estimateLightningFee({
+        destination: request.destination,
+        satAmt: request.num_satoshis,
+      });
       return true;
     } catch (err) {
       log.info(`Decoding payment request failed: ${err.message}`);
       return false;
     }
   }
 
+  async estimateLightningFee({ destination, satAmt }) {
+    try {
+      const { payment, settings } = this._store;
+      const { routes } = await this._grpc.sendCommand('queryRoutes', {
+        pub_key: destination,
+        amt: satAmt,
+        num_routes: 1,
+      });
+      payment.fee = toAmount(parseSat(routes[0].total_fees), settings.unit);
+    } catch (err) {
+      log.error(`Estimating lightning fee failed!`, err);
+    }
+  }
+
   async payBitcoin() {
     try {
       const { payment, settings } = this._store;

test/integration/action/action-integration.spec.js

@@ -344,11 +344,16 @@ describe('Action Integration Tests', function() {
       expect(isValid, 'to be', false);
     });
 
-    it('should decode invoice and return true', async () => {
+    it('should decode invoice, set fee and return true', async () => {
       const isValid = await payments1.decodeInvoice({
         invoice: store2.invoice.uri,
       });
       expect(isValid, 'to be', true);
+      expect(
+        parseFloat(store1.payment.fee),
+        'to be greater than or equal to',
+        0
+      );
     });
 
     it('should send lightning payment from request', async () => {

test/unit/action/payment.spec.js

@@ -139,21 +139,48 @@ describe('Action Payments Unit Tests', () => {
       grpc.sendCommand.withArgs('decodePayReq').resolves({
         num_satoshis: '1700',
         description: 'foo',
+        destination: 'bar',
       });
+      grpc.sendCommand
+        .withArgs('queryRoutes', {
+          pub_key: 'bar',
+          amt: '1700',
+          num_routes: 1,
+        })
+        .resolves({
+          routes: [{ total_fees: '100' }],
+        });
       const isValid = await payment.decodeInvoice({ invoice: 'some-invoice' });
       expect(isValid, 'to be', true);
       expect(store.payment.amount, 'to match', /^0[,.]0{4}1{1}7{1}$/);
       expect(store.payment.note, 'to be', 'foo');
+      expect(store.payment.fee, 'to match', /^0[,.]0{5}1{1}$/);
     });
 
-    it('should set response to null on error', async () => {
+    it('should set nothing on decode error', async () => {
       grpc.sendCommand.withArgs('decodePayReq').rejects(new Error('Boom!'));
       const isValid = await payment.decodeInvoice({ invoice: 'some-invoice' });
       expect(isValid, 'to be', false);
       expect(store.payment.amount, 'to be', '');
       expect(store.payment.note, 'to be', '');
+      expect(store.payment.fee, 'to be', '');
       expect(logger.info, 'was called once');
     });
+
+    it('should set no fee on query route error', async () => {
+      grpc.sendCommand.withArgs('decodePayReq').resolves({
+        num_satoshis: '1700',
+        description: 'foo',
+        destination: 'bar',
+      });
+      grpc.sendCommand.withArgs('queryRoutes').rejects(new Error('Boom!'));
+      const isValid = await payment.decodeInvoice({ invoice: 'some-invoice' });
+      expect(isValid, 'to be', true);
+      expect(store.payment.amount, 'to match', /^0[,.]0{4}1{1}7{1}$/);
+      expect(store.payment.note, 'to be', 'foo');
+      expect(store.payment.fee, 'to be', '');
+      expect(logger.error, 'was called once');
+    });
   });
 
   describe('payBitcoin()', () => {