feat: add sidechain-specific RPCs/sugar (#1940)

* federator_info responses/requests

* edit docstring

* make strings narrower

* export federator_info

* implement createXchainPayment

* add tests

* fix dependency cycle

* fix linter errors

* rename xchain -> crosschain

* rename more

* edit HISTORY

* fix docstrings

* add another test

packages/xrpl/test/utils/createCrossChainPayment.ts

@@ -0,0 +1,127 @@
+import { assert } from 'chai'
+import {
+  createCrossChainPayment,
+  convertStringToHex,
+  Payment,
+} from 'xrpl-local'
+
+describe('createCrossChainPayment', function () {
+  it('successful xchain payment creation', function () {
+    const payment: Payment = {
+      TransactionType: 'Payment',
+      Account: 'rRandom',
+      Destination: 'rRandom2',
+      Amount: '3489303',
+    }
+    const sidechainAccount = 'rSidechain'
+
+    const expectedPayment = {
+      ...payment,
+      Memos: [
+        {
+          Memo: {
+            MemoData: convertStringToHex(sidechainAccount),
+          },
+        },
+      ],
+    }
+
+    const resultPayment = createCrossChainPayment(payment, sidechainAccount)
+    assert.deepEqual(resultPayment, expectedPayment)
+
+    // ensure that the original object wasn't modified
+    assert.notDeepEqual(resultPayment, payment)
+  })
+
+  it('successful xchain payment creation with memo', function () {
+    const memo = {
+      Memo: {
+        MemoData: 'deadbeef',
+      },
+    }
+    const payment: Payment = {
+      TransactionType: 'Payment',
+      Account: 'rRandom',
+      Destination: 'rRandom2',
+      Amount: '3489303',
+      Memos: [memo],
+    }
+    const sidechainAccount = 'rSidechain'
+
+    const expectedPayment = {
+      ...payment,
+      Memos: [
+        {
+          Memo: {
+            MemoData: convertStringToHex(sidechainAccount),
+          },
+        },
+        memo,
+      ],
+    }
+
+    const resultPayment = createCrossChainPayment(payment, sidechainAccount)
+    assert.deepEqual(resultPayment, expectedPayment)
+
+    // ensure that the original object wasn't modified
+    assert.notDeepEqual(resultPayment, payment)
+  })
+
+  it('removes TxnSignature', function () {
+    const payment: Payment = {
+      TransactionType: 'Payment',
+      Account: 'rRandom',
+      Destination: 'rRandom2',
+      Amount: '3489303',
+      TxnSignature: 'asodfiuaosdfuaosd',
+    }
+    const sidechainAccount = 'rSidechain'
+
+    const expectedPayment = {
+      ...payment,
+      Memos: [
+        {
+          Memo: {
+            MemoData: convertStringToHex(sidechainAccount),
+          },
+        },
+      ],
+    }
+    delete expectedPayment.TxnSignature
+
+    const resultPayment = createCrossChainPayment(payment, sidechainAccount)
+    assert.deepEqual(resultPayment, expectedPayment)
+
+    // ensure that the original object wasn't modified
+    assert.notDeepEqual(resultPayment, payment)
+  })
+
+  it('fails with 3 memos', function () {
+    const payment: Payment = {
+      TransactionType: 'Payment',
+      Account: 'rRandom',
+      Destination: 'rRandom2',
+      Amount: '3489303',
+      Memos: [
+        {
+          Memo: {
+            MemoData: '2934723843ace',
+          },
+        },
+        {
+          Memo: {
+            MemoData: '2934723843ace',
+          },
+        },
+        {
+          Memo: {
+            MemoData: '2934723843ace',
+          },
+        },
+      ],
+    }
+    assert.throws(() => {
+      createCrossChainPayment(payment, 'rSidechain')
+    }, /Cannot have more than 2 memos/u)
+  })
+})