feat(AE): Allow to spend % of balance. (#371)

#336

Author: nduchak

es/ae/index.js

@@ -26,7 +26,9 @@ import stampit from '@stamp/it'
 import Tx from '../tx'
 import Chain from '../chain'
 import Account from '../account'
+import TxBuilder from '../tx/builder'
 import * as R from 'ramda'
+import { BigNumber } from 'bignumber.js'
 
 /**
  * Sign and post a transaction to the chain
@@ -60,6 +62,38 @@ async function spend (amount, recipientId, options = {}) {
   return this.send(spendTx, opt)
 }
 
+/**
+ * Send a percentage of funds to another account
+ * @instance
+ * @category async
+ * @rtype (percentage: Number|String, recipientId: String, options?: Object) => Promise[String]
+ * @param {Number|String} percentage - Percentage of amount to spend
+ * @param {String} recipientId - Address of recipient account
+ * @param {Object} options - Options
+ * @return {String|String} Transaction or transaction hash
+ */
+async function transferFunds (percentage, recipientId, options = { excludeFee: false }) {
+  if (percentage < 0 || percentage > 1) throw new Error(`Percentage should be a number between 0 and 1, got ${percentage}`)
+  const opt = R.merge(this.Ae.defaults, options)
+
+  const requestTransferAmount = BigNumber(await this.balance(await this.address())).times(percentage)
+  let spendTx = await this.spendTx(R.merge(opt, { senderId: await this.address(), recipientId, amount: requestTransferAmount }))
+
+  const { tx: txObject } = TxBuilder.unpackTx(spendTx)
+  // If the requestTransferAmount should include the fee keep calculating the fee
+  let amount = requestTransferAmount
+  if (!options.excludeFee) {
+    while (amount.plus(txObject.fee).gt(requestTransferAmount)) {
+      amount = requestTransferAmount.minus(txObject.fee)
+    }
+  }
+
+  // Rebuild tx
+  spendTx = await this.spendTx(R.merge(opt, { senderId: await this.address(), recipientId, amount }))
+
+  return this.send(spendTx, opt)
+}
+
 /**
  * Remove all listeners for RPC
  * @instance
@@ -90,7 +124,7 @@ function destroyInstance () {
  * @return {Object} Ae instance
  */
 const Ae = stampit(Tx, Account, Chain, {
-  methods: { send, spend, destroyInstance }
+  methods: { send, spend, transferFunds, destroyInstance }
 })
 
 export default Ae

test/integration/accounts.js

@@ -52,6 +52,14 @@ describe('Accounts', function () {
     return wallet.balance(await wallet.address()).should.eventually.be.a('string')
   })
 
+  it('Spend 50% of balance', async () => {
+    const balance = await wallet.balance(await wallet.address())
+
+    await wallet.transferFunds(0.5, 'ak_DMNCzsVoZnpV5fe8FTQnNsTfQ48YM5C3WbHPsJyHjAuTXebFi')
+    const balanceAfter = await wallet.balance(await wallet.address())
+    BigNumber(balance).div(balanceAfter).toNumber().should.be.equal(2)
+  })
+
   it('spends tokens', async () => {
     const ret = await wallet.spend(1, receiver)
     ret.should.have.property('tx')