feat: balance utils with conversion and formatting

src/balance/Balance.chain.ts

@@ -90,12 +90,12 @@ export async function listenToBalanceChanges(
 
 /**
  * Transfer Kilt [amount] tokens to [toAccountAddress] using the given [[Identity]].
- * <B>Note that balance amount is in Femto-Kilt (1e-15) and must be translated to Kilt-Coin</B>.
+ * <B>Note that the value of the transferred currency and the balance amount reported by the chain is in Femto-Kilt (1e-15), and must be translated to Kilt-Coin</B>.
  *
  * @param identity Identity to use for token transfer.
  * @param accountAddressTo Address of the receiver account.
  * @param amount Amount of Units to transfer.
- * @param exponent Magnitude of the amount.
+ * @param exponent Magnitude of the amount. Default magnitude of Femto-Kilt.
  * @returns Promise containing the transaction status.
  *
  * @example
@@ -123,12 +123,13 @@ export async function makeTransfer(
   exponent = -15
 ): Promise<SubmittableResult> {
   const blockchain = await getCached()
+  const cleanExponent =
+    (exponent >= 0 ? 1 : -1) * Math.floor(Math.abs(exponent))
   const transfer = blockchain.api.tx.balances.transfer(
     accountAddressTo,
-    BalanceUtils.convertToTxUnit(
-      amount,
-      (exponent >= 0 ? 1 : -1) * Math.floor(Math.abs(exponent))
-    )
+    cleanExponent === -15
+      ? amount
+      : BalanceUtils.convertToTxUnit(amount, cleanExponent)
   )
   return blockchain.submitTx(identity, transfer)
 }

src/balance/Balance.spec.ts

@@ -9,6 +9,7 @@ import {
   makeTransfer,
 } from './Balance.chain'
 import TYPE_REGISTRY from '../blockchainApiConnection/__mocks__/BlockchainQuery'
+import BalanceUtils from './Balance.utils'
 
 jest.mock('../blockchainApiConnection/BlockchainApiConnection')
 
@@ -65,4 +66,21 @@ describe('Balance', () => {
     expect(status).toBeInstanceOf(SubmittableResult)
     expect(status.isFinalized).toBeTruthy()
   })
+  it('should make transfer of amount with arbitrary exponent', async () => {
+    const alice = await Identity.buildFromURI('//Alice')
+    const bob = await Identity.buildFromURI('//Bob')
+    const amount = new BN(10)
+    const exponent = -6
+    const expectedAmount = BalanceUtils.convertToTxUnit(
+      amount,
+      (exponent >= 0 ? 1 : -1) * Math.floor(Math.abs(exponent))
+    )
+    const status = await makeTransfer(alice, bob.address, amount, exponent)
+    expect(blockchainApi.tx.balances.transfer).toHaveBeenCalledWith(
+      bob.address,
+      expectedAmount
+    )
+    expect(status).toBeInstanceOf(SubmittableResult)
+    expect(status.isFinalized).toBeTruthy()
+  })
 })

src/balance/Balance.utils.ts

@@ -8,13 +8,6 @@ import BN from 'bn.js'
 import { formatBalance } from '@polkadot/util'
 
 export const KILT_COIN = new BN(1)
-export const KILT_FEMTO_COIN = new BN('1000000000000000')
-
-export const TRANSACTION_FEE = KILT_COIN.divn(1000000000).muln(125)
-
-export const MIN_BALANCE = KILT_COIN.muln(1)
-
-export const ENDOWMENT = KILT_COIN.muln(30)
 
 export function formatKiltBalance(amount: BN): string {
   return formatBalance(
@@ -27,20 +20,19 @@ export function formatKiltBalance(amount: BN): string {
   )
 }
 
-export function asFemtoKilt(balance: BN): BN {
-  return new BN(balance).mul(KILT_FEMTO_COIN)
-}
-
 export function convertToTxUnit(balance: BN, power: number): BN {
   return new BN(balance).mul(new BN(10).pow(new BN(15 + power)))
 }
 
+export function asFemtoKilt(balance: BN): BN {
+  return convertToTxUnit(balance, 0)
+}
+
+export const TRANSACTION_FEE = convertToTxUnit(new BN(125), -9)
+
 export default {
   KILT_COIN,
-  KILT_FEMTO_COIN,
   TRANSACTION_FEE,
-  MIN_BALANCE,
-  ENDOWMENT,
   formatKiltBalance,
   asFemtoKilt,
   convertToTxUnit,