feat(sdk-api): pass recipient addresses to v1 billing fee endpoint

Forward recipient addresses from the SDK to the server's
GET /api/v1/wallet/:id/billing/fee endpoint as recipients[]
query params. This allows the server to waive the PayGo fee
when all recipients are v2 PayGo wallets (v1-to-v2 migration
scenario). Backward-compatible: existing calls without
recipients are unchanged.

Ticket: T1-3579
Session-Id: 9bcb0f58-d633-492c-a7a4-70bcd09ce08b
Task-Id: bf7868aa-6a4c-4ee7-8520-1e6b61551a64

Author: davidkaplanbitgo

modules/sdk-api/src/v1/transactionBuilder.ts

@@ -288,13 +288,19 @@ exports.createTransaction = function (params) {
       if (bitgoFeeInfo) {
         return;
       }
-      return params.wallet.getBitGoFee({ amount: totalOutputAmount, instant: params.instant }).then(function (result) {
-        if (result && result.fee > 0) {
-          bitgoFeeInfo = {
-            amount: result.fee,
-          };
-        }
-      });
+      return params.wallet
+        .getBitGoFee({
+          amount: totalOutputAmount,
+          instant: params.instant,
+          recipients: params.recipients?.map((r: any) => r.address).filter(Boolean) ?? [],
+        })
+        .then(function (result) {
+          if (result && result.fee > 0) {
+            bitgoFeeInfo = {
+              amount: result.fee,
+            };
+          }
+        });
     }).then(function () {
       if (bitgoFeeInfo && bitgoFeeInfo.amount > 0) {
         totalAmount += bitgoFeeInfo.amount;

modules/sdk-api/src/v1/wallet.ts

@@ -2555,9 +2555,12 @@ Wallet.prototype.getBitGoFee = function (params, callback) {
   if (params.instant && !_.isBoolean(params.instant)) {
     throw new Error('invalid instant argument');
   }
-  return Promise.resolve(this.bitgo.get(this.url('/billing/fee')).query(params).result())
-    .then(callback)
-    .catch(callback);
+  const { recipients, ...baseParams } = params;
+  let req = this.bitgo.get(this.url('/billing/fee')).query(baseParams);
+  if (Array.isArray(recipients) && recipients.length > 0) {
+    req = req.query({ 'recipients[]': recipients });
+  }
+  return Promise.resolve(req.result()).then(callback).catch(callback);
 };
 
 /*

modules/sdk-api/test/unit/v1/wallet.ts

@@ -1823,4 +1823,71 @@ describe('Wallet Prototype Methods', function () {
       });
     });
   });
+
+  describe('getBitGoFee', function () {
+    let bgUrl: string;
+    let wallet: any;
+
+    before(function () {
+      nock.pendingMocks().should.be.empty();
+      const prodBitgo = new BitGoAPI({ env: 'prod', clientConstants: { constants: {} } });
+      bgUrl = common.Environments[prodBitgo.getEnv()].uri;
+      wallet = new Wallet(prodBitgo, {
+        id: '2NCoSfHH6Ls4CdTS5QahgC9k7x9RfXeSwY4',
+        private: { keychains: [userKeypair, backupKeypair, bitgoKey] },
+      });
+    });
+
+    afterEach(function () {
+      nock.cleanAll();
+    });
+
+    it('sends amount and instant without recipients when recipients array is empty', async function () {
+      const scope = nock(bgUrl)
+        .get(`/api/v1/wallet/${wallet.id()}/billing/fee`)
+        .query({ amount: '100000', instant: 'false' })
+        .reply(200, { fee: 1000 });
+
+      const result = await wallet.getBitGoFee({ amount: 100000, instant: false });
+      result.fee.should.equal(1000);
+      scope.isDone().should.be.true();
+    });
+
+    it('sends recipients[] query params when recipients are provided', async function () {
+      const addr1 = '3J98t1WpEZ73CNmQviecrnyiWrnqRhWNLy';
+      const addr2 = '3FZbgi29cpjq2GjdwV8eyHuJJnkLtktZc5';
+
+      const scope = nock(bgUrl)
+        .get(`/api/v1/wallet/${wallet.id()}/billing/fee`)
+        .query((query) => {
+          const recipientsParam = query['recipients[]'];
+          const recipientsList = Array.isArray(recipientsParam) ? recipientsParam : [recipientsParam];
+          return query.amount === '100000' && recipientsList.includes(addr1) && recipientsList.includes(addr2);
+        })
+        .reply(200, { fee: 0 });
+
+      const result = await wallet.getBitGoFee({ amount: 100000, recipients: [addr1, addr2] });
+      result.fee.should.equal(0);
+      scope.isDone().should.be.true();
+    });
+
+    it('omits recipients[] when recipients array is empty', async function () {
+      const scope = nock(bgUrl)
+        .get(`/api/v1/wallet/${wallet.id()}/billing/fee`)
+        .query((query) => query.amount === '200000' && !('recipients[]' in query))
+        .reply(200, { fee: 500 });
+
+      const result = await wallet.getBitGoFee({ amount: 200000, recipients: [] });
+      result.fee.should.equal(500);
+      scope.isDone().should.be.true();
+    });
+
+    it('throws when amount is not a number', function () {
+      (() => wallet.getBitGoFee({ amount: 'bad' })).should.throw('invalid amount argument');
+    });
+
+    it('throws when instant is not a boolean', function () {
+      (() => wallet.getBitGoFee({ amount: 100, instant: 'yes' })).should.throw('invalid instant argument');
+    });
+  });
 });