Extract decimal manipulation helpers to it own module

src/helpers/decimal.ts

@@ -0,0 +1,12 @@
+import { BigDecimal } from '@graphprotocol/graph-ts'
+import { BigInt } from '@graphprotocol/graph-ts/index'
+
+export let ZERO = BigDecimal.fromString('0')
+
+export function toDecimal(value: BigInt, decimals: u32): BigDecimal {
+  let precision = BigInt.fromI32(10)
+    .pow(<u8>decimals)
+    .toBigDecimal()
+
+  return value.divDecimal(precision)
+}

src/mappings/account.ts

@@ -1,7 +1,9 @@
-import { BigDecimal, BigInt, Bytes, EthereumEvent } from '@graphprotocol/graph-ts'
+import { BigDecimal, Bytes, EthereumEvent } from '@graphprotocol/graph-ts'
 
 import { Account, AccountBalance, AccountBalanceSnapshot, Token } from '../../generated/schema'
 
+import { ZERO } from '../helpers/decimal'
+
 export function getOrCreateAccount(accountAddress: Bytes): Account {
   let accountId = accountAddress.toHex()
   let existingAccount = Account.load(accountId)
@@ -27,7 +29,7 @@ function getOrCreateAccountBalance(account: Account, token: Token): AccountBalan
   let newBalance = new AccountBalance(balanceId)
   newBalance.account = account.id
   newBalance.token = token.id
-  newBalance.amount = BigInt.fromI32(0).toBigDecimal()
+  newBalance.amount = ZERO
 
   return newBalance
 }

src/mappings/registry.ts

@@ -5,7 +5,7 @@ import { Unknown } from '../../generated/TokenRegistry/TokenRegistry'
 import { BurnableToken, MintableToken, StandardToken } from '../../generated/templates'
 
 import { REGISTRY_HASH } from '../config'
-import { decodeFlags, DEFAULT_DECIMALS, isBurnable, isMintable } from '../helpers/tokens'
+import { decodeFlags, DEFAULT_DECIMALS, isBurnable, isMintable } from '../helpers/token'
 
 export function initRegistry(event: Unknown): void {
   log.debug('Initializing token registry, block={}', [event.block.number.toString()])

src/mappings/token.ts

@@ -1,4 +1,4 @@
-import { BigInt, BigDecimal, Bytes, EthereumEvent } from '@graphprotocol/graph-ts'
+import { BigDecimal, Bytes, EthereumEvent } from '@graphprotocol/graph-ts'
 
 import { Transfer } from '../../generated/templates/StandardToken/ERC20'
 import { Burn } from '../../generated/templates/BurnableToken/Burnable'
@@ -6,11 +6,13 @@ import { Mint } from '../../generated/templates/MintableToken/Mintable'
 
 import { BurnEvent, MintEvent, Token, TransferEvent } from '../../generated/schema'
 
+import { toDecimal } from '../helpers/decimal'
+
 import {
   decreaseAccountBalance,
   getOrCreateAccount,
   increaseAccountBalance,
-  saveAccountBalanceSnapshot
+  saveAccountBalanceSnapshot,
 } from './account'
 
 const GENESIS_ADDRESS = '0x0000000000000000000000000000000000000000'
@@ -163,7 +165,7 @@ function createTransferEvent(
   event: EthereumEvent,
   amount: BigDecimal,
   source: Bytes,
-  destination: Bytes
+  destination: Bytes,
 ): TransferEvent {
   let eventEntity = new TransferEvent(event.transaction.hash.toHex() + '-' + event.logIndex.toString())
   eventEntity.token = event.address.toHex()
@@ -178,11 +180,3 @@ function createTransferEvent(
 
   return eventEntity
 }
-
-function toDecimal(value: BigInt, decimals: u32): BigDecimal {
-  let precision = BigInt.fromI32(10)
-    .pow(<u8>decimals)
-    .toBigDecimal()
-
-  return value.divDecimal(precision)
-}