perf(ethereum): reduce number of calls by batching all polling node calls (#840)

* initial refactoring

* rebase lint error

* start implementing reducer

* multicall reducer

* working multicall!

* clean up performance, re-fix annoying error

* use multicall everywhere

* use multicall for balances

* fix lint warning

* Use checksummed address

* Fix strict warning

* get it to a working state with the more generic form

* convert useETHBalances

* Remove the eth-scan contract completely

* Remove the eth-scan contract completely more

* Default export

* Put the encoding/decoding in the methods that can do it most efficiently

* Avoid duplicate fetches via debounce

* Reduce delay to something less noticeable

* Return null if pair reserves are undefined to indicate it does not exist

README.md

@@ -43,7 +43,7 @@ change `REACT_APP_NETWORK_ID` to `"{yourNetworkId}"`, and change `REACT_APP_NETW
 
 Note that the front end only works properly on testnets where both 
 [Uniswap V2](https://uniswap.org/docs/v2/smart-contracts/factory/) and 
-[eth-scan](https://github.com/MyCryptoHQ/eth-scan) are deployed.
+[multicall](https://github.com/makerdao/multicall) are deployed.
 The frontend will not work on other networks.
 
 ## Contributions

package.json

@@ -14,7 +14,6 @@
     "@ethersproject/units": "^5.0.0-beta.132",
     "@ethersproject/wallet": "^5.0.0-beta.141",
     "@material-ui/core": "^4.9.5",
-    "@mycrypto/eth-scan": "^2.1.0",
     "@popperjs/core": "^2.4.0",
     "@reach/dialog": "^0.10.3",
     "@reach/portal": "^0.10.3",
@@ -79,7 +78,6 @@
     "serve": "^11.3.0",
     "start-server-and-test": "^1.11.0",
     "styled-components": "^4.2.0",
-    "swr": "0.1.18",
     "typescript": "^3.8.3",
     "use-media": "^1.4.0"
   },

src/components/AccountDetails/Copy.tsx

 import React from 'react'
 import styled from 'styled-components'
-import { useCopyClipboard } from '../../hooks'
+import useCopyClipboard from '../../hooks/useCopyClipboard'
 
 import { Link } from '../../theme'
 import { CheckCircle, Copy } from 'react-feather'

src/components/AddressInputPanel/index.tsx

 import React, { useState, useEffect, useContext } from 'react'
 import styled, { ThemeContext } from 'styled-components'
+import useDebounce from '../../hooks/useDebounce'
 
 import { isAddress } from '../../utils'
-import { useActiveWeb3React, useDebounce } from '../../hooks'
+import { useActiveWeb3React } from '../../hooks'
 import { Link, TYPE } from '../../theme'
 import { AutoColumn } from '../Column'
 import { RowBetween } from '../Row'

src/components/Menu/index.tsx

@@ -2,9 +2,9 @@ import React, { useRef, useEffect } from 'react'
 import { Info, BookOpen, Code, PieChart, MessageCircle } from 'react-feather'
 import styled from 'styled-components'
 import { ReactComponent as MenuIcon } from '../../assets/images/menu.svg'
+import useToggle from '../../hooks/useToggle'
 
 import { Link } from '../../theme'
-import { useToggle } from '../../hooks'
 
 const StyledMenuIcon = styled(MenuIcon)`
   path {

src/components/Modal/index.tsx

@@ -9,9 +9,9 @@ import '@reach/dialog/styles.css'
 import { transparentize } from 'polished'
 import { useGesture } from 'react-use-gesture'
 
-// errors emitted, fix with https://github.com/styled-components/styled-components/pull/3006
 const AnimatedDialogOverlay = animated(DialogOverlay)
-const StyledDialogOverlay = styled(AnimatedDialogOverlay)<{ mobile: boolean }>`
+// eslint-disable-next-line @typescript-eslint/no-unused-vars
+const StyledDialogOverlay = styled(({ mobile, ...rest }) => <AnimatedDialogOverlay {...rest} />)<{ mobile: boolean }>`
   &[data-reach-dialog-overlay] {
     z-index: 2;
     display: flex;
@@ -41,7 +41,9 @@ const StyledDialogOverlay = styled(AnimatedDialogOverlay)<{ mobile: boolean }>`
 
 // destructure to not pass custom props to Dialog DOM element
 // eslint-disable-next-line @typescript-eslint/no-unused-vars
-const StyledDialogContent = styled(({ minHeight, maxHeight, mobile, isOpen, ...rest }) => <DialogContent {...rest} />)`
+const StyledDialogContent = styled(({ minHeight, maxHeight, mobile, isOpen, ...rest }) => (
+  <DialogContent aria-label="content" {...rest} />
+))`
   &[data-reach-dialog-content] {
     margin: 0 0 2rem 0;
     border: 1px solid ${({ theme }) => theme.bg1};
@@ -163,6 +165,7 @@ export default function Modal({
                       }}
                     >
                       <StyledDialogContent
+                        ariaLabel="test"
                         style={props}
                         hidden={true}
                         minHeight={minHeight}

src/components/NavigationTabs/index.tsx

@@ -3,14 +3,13 @@ import styled from 'styled-components'
 import { darken } from 'polished'
 import { useTranslation } from 'react-i18next'
 import { withRouter, NavLink, Link as HistoryLink, RouteComponentProps } from 'react-router-dom'
+import useBodyKeyDown from '../../hooks/useBodyKeyDown'
 
 import { CursorPointer } from '../../theme'
 import { ArrowLeft } from 'react-feather'
 import { RowBetween } from '../Row'
 import QuestionHelper from '../QuestionHelper'
 
-import { useBodyKeyDown } from '../../hooks'
-
 const tabOrder = [
   {
     path: '/swap',

src/components/SearchModal/index.tsx

@@ -57,7 +57,7 @@ function SearchModal({
 
   const allTokens = useAllTokens()
   const allPairs = useAllDummyPairs()
-  const allTokenBalances = useAllTokenBalancesTreatingWETHasETH()[account] ?? {}
+  const allTokenBalances = useAllTokenBalancesTreatingWETHasETH() ?? {}
   const allPairBalances = useTokenBalances(
     account,
     allPairs.map(p => p.liquidityToken)

src/components/SearchModal/sorting.ts

@@ -42,10 +42,10 @@ function getTokenComparator(
 }
 
 export function useTokenComparator(inverted: boolean): (tokenA: Token, tokenB: Token) => number {
-  const { account, chainId } = useActiveWeb3React()
+  const { chainId } = useActiveWeb3React()
   const weth = WETH[chainId]
   const balances = useAllTokenBalancesTreatingWETHasETH()
-  const comparator = useMemo(() => getTokenComparator(weth, balances[account] ?? {}), [account, balances, weth])
+  const comparator = useMemo(() => getTokenComparator(weth, balances ?? {}), [balances, weth])
   return useMemo(() => {
     if (inverted) {
       return (tokenA: Token, tokenB: Token) => comparator(tokenA, tokenB) * -1

src/components/WalletModal/index.tsx

@@ -4,6 +4,7 @@ import styled from 'styled-components'
 import { isMobile } from 'react-device-detect'
 import { UnsupportedChainIdError, useWeb3React } from '@web3-react/core'
 import { URI_AVAILABLE } from '@web3-react/walletconnect-connector'
+import usePrevious from '../../hooks/usePrevious'
 import { useWalletModalOpen, useWalletModalToggle } from '../../state/application/hooks'
 
 import Modal from '../Modal'
@@ -11,7 +12,6 @@ import AccountDetails from '../AccountDetails'
 import PendingView from './PendingView'
 import Option from './Option'
 import { SUPPORTED_WALLETS } from '../../constants'
-import { usePrevious } from '../../hooks'
 import { Link } from '../../theme'
 import MetamaskIcon from '../../assets/images/metamask.png'
 import { ReactComponent as Close } from '../../assets/images/x.svg'

src/components/Web3Status/index.tsx

@@ -4,6 +4,7 @@ import { useTranslation } from 'react-i18next'
 import { useWeb3React, UnsupportedChainIdError } from '@web3-react/core'
 import { darken, lighten } from 'polished'
 import { Activity } from 'react-feather'
+import useENSName from '../../hooks/useENSName'
 import { useWalletModalToggle } from '../../state/application/hooks'
 import { TransactionDetails } from '../../state/transactions/reducer'
 
@@ -19,7 +20,6 @@ import { Spinner } from '../../theme'
 import LightCircle from '../../assets/svg/lightcircle.svg'
 
 import { RowBetween } from '../Row'
-import { useENSName } from '../../hooks'
 import { shortenAddress } from '../../utils'
 import { useAllTransactions } from '../../state/transactions/hooks'
 import { NetworkContextName } from '../../constants'

src/constants/abis/erc20.ts

+import { Interface } from '@ethersproject/abi'
+import ERC20_ABI from './erc20.json'
+
+const ERC20_INTERFACE = new Interface(ERC20_ABI)
+
+export default ERC20_INTERFACE

src/constants/multicall/abi.json

+[
+  {
+    "constant": true,
+    "inputs": [],
+    "name": "getCurrentBlockTimestamp",
+    "outputs": [
+      {
+        "name": "timestamp",
+        "type": "uint256"
+      }
+    ],
+    "payable": false,
+    "stateMutability": "view",
+    "type": "function"
+  },
+  {
+    "constant": true,
+    "inputs": [
+      {
+        "components": [
+          {
+            "name": "target",
+            "type": "address"
+          },
+          {
+            "name": "callData",
+            "type": "bytes"
+          }
+        ],
+        "name": "calls",
+        "type": "tuple[]"
+      }
+    ],
+    "name": "aggregate",
+    "outputs": [
+      {
+        "name": "blockNumber",
+        "type": "uint256"
+      },
+      {
+        "name": "returnData",
+        "type": "bytes[]"
+      }
+    ],
+    "payable": false,
+    "stateMutability": "view",
+    "type": "function"
+  },
+  {
+    "constant": true,
+    "inputs": [],
+    "name": "getLastBlockHash",
+    "outputs": [
+      {
+        "name": "blockHash",
+        "type": "bytes32"
+      }
+    ],
+    "payable": false,
+    "stateMutability": "view",
+    "type": "function"
+  },
+  {
+    "constant": true,
+    "inputs": [
+      {
+        "name": "addr",
+        "type": "address"
+      }
+    ],
+    "name": "getEthBalance",
+    "outputs": [
+      {
+        "name": "balance",
+        "type": "uint256"
+      }
+    ],
+    "payable": false,
+    "stateMutability": "view",
+    "type": "function"
+  },
+  {
+    "constant": true,
+    "inputs": [],
+    "name": "getCurrentBlockDifficulty",
+    "outputs": [
+      {
+        "name": "difficulty",
+        "type": "uint256"
+      }
+    ],
+    "payable": false,
+    "stateMutability": "view",
+    "type": "function"
+  },
+  {
+    "constant": true,
+    "inputs": [],
+    "name": "getCurrentBlockGasLimit",
+    "outputs": [
+      {
+        "name": "gaslimit",
+        "type": "uint256"
+      }
+    ],
+    "payable": false,
+    "stateMutability": "view",
+    "type": "function"
+  },
+  {
+    "constant": true,
+    "inputs": [],
+    "name": "getCurrentBlockCoinbase",
+    "outputs": [
+      {
+        "name": "coinbase",
+        "type": "address"
+      }
+    ],
+    "payable": false,
+    "stateMutability": "view",
+    "type": "function"
+  },
+  {
+    "constant": true,
+    "inputs": [
+      {
+        "name": "blockNumber",
+        "type": "uint256"
+      }
+    ],
+    "name": "getBlockHash",
+    "outputs": [
+      {
+        "name": "blockHash",
+        "type": "bytes32"
+      }
+    ],
+    "payable": false,
+    "stateMutability": "view",
+    "type": "function"
+  }
+]
\ No newline at end of file

src/constants/multicall/index.ts

+import { ChainId } from '@uniswap/sdk'
+import MULTICALL_ABI from './abi.json'
+
+const MULTICALL_NETWORKS: { [chainId in ChainId]: string } = {
+  [ChainId.MAINNET]: '0xeefBa1e63905eF1D7ACbA5a8513c70307C1cE441',
+  [ChainId.ROPSTEN]: '0x53C43764255c17BD724F74c4eF150724AC50a3ed',
+  [ChainId.KOVAN]: '0x2cc8688C5f75E365aaEEb4ea8D6a480405A48D2A',
+  [ChainId.RINKEBY]: '0x42Ad527de7d4e9d9d011aC45B31D8551f8Fe9821',
+  [ChainId.GÖRLI]: '0x77dCa2C955b15e9dE4dbBCf1246B4B85b651e50e'
+}
+
+export { MULTICALL_ABI, MULTICALL_NETWORKS }

src/data/Allowances.ts

-import { Contract } from '@ethersproject/contracts'
 import { Token, TokenAmount } from '@uniswap/sdk'
-import useSWR from 'swr'
+import { useMemo } from 'react'
 
-import { SWRKeys, useKeepSWRDataLiveAsBlocksArrive } from '.'
-import { useTokenContract } from '../hooks'
+import { useTokenContract } from '../hooks/useContract'
+import { useSingleCallResult } from '../state/multicall/hooks'
 
-function getTokenAllowance(contract: Contract, token: Token): (owner: string, spender: string) => Promise<TokenAmount> {
-  return async (owner: string, spender: string): Promise<TokenAmount> =>
-    contract
-      .allowance(owner, spender)
-      .then((balance: { toString: () => string }) => new TokenAmount(token, balance.toString()))
-}
-
-export function useTokenAllowance(token?: Token, owner?: string, spender?: string): TokenAmount {
+export function useTokenAllowance(token?: Token, owner?: string, spender?: string): TokenAmount | undefined {
   const contract = useTokenContract(token?.address, false)
 
-  const shouldFetch = !!contract && typeof owner === 'string' && typeof spender === 'string'
-  const { data, mutate } = useSWR(
-    shouldFetch ? [owner, spender, token.address, token.chainId, SWRKeys.Allowances] : null,
-    getTokenAllowance(contract, token)
-  )
-  useKeepSWRDataLiveAsBlocksArrive(mutate)
+  const inputs = useMemo(() => [owner, spender], [owner, spender])
+  const allowance = useSingleCallResult(contract, 'allowance', inputs)
 
-  return data
+  return useMemo(() => (token && allowance ? new TokenAmount(token, allowance.toString()) : undefined), [
+    token,
+    allowance
+  ])
 }

src/data/Reserves.ts

-import { Contract } from '@ethersproject/contracts'
 import { Token, TokenAmount, Pair } from '@uniswap/sdk'
-import useSWR from 'swr'
+import { useMemo } from 'react'
 
-import { SWRKeys, useKeepSWRDataLiveAsBlocksArrive } from '.'
-import { usePairContract } from '../hooks'
-
-function getReserves(contract: Contract, tokenA: Token, tokenB: Token): () => Promise<Pair | null> {
-  return async (): Promise<Pair | null> =>
-    contract
-      .getReserves()
-      .then(
-        ({ reserve0, reserve1 }: { reserve0: { toString: () => string }; reserve1: { toString: () => string } }) => {
-          const [token0, token1] = tokenA.sortsBefore(tokenB) ? [tokenA, tokenB] : [tokenB, tokenA]
-          return new Pair(new TokenAmount(token0, reserve0.toString()), new TokenAmount(token1, reserve1.toString()))
-        }
-      )
-      .catch(() => {
-        return null
-      })
-}
+import { usePairContract } from '../hooks/useContract'
+import { useSingleCallResult } from '../state/multicall/hooks'
 
 /*
  * if loading, return undefined
@@ -26,13 +10,15 @@ function getReserves(contract: Contract, tokenA: Token, tokenB: Token): () => Pr
  * if pair already created (even if 0 reserves), return pair
  */
 export function usePair(tokenA?: Token, tokenB?: Token): undefined | Pair | null {
-  const pairAddress = !!tokenA && !!tokenB && !tokenA.equals(tokenB) ? Pair.getAddress(tokenA, tokenB) : undefined
+  const pairAddress = tokenA && tokenB && !tokenA.equals(tokenB) ? Pair.getAddress(tokenA, tokenB) : undefined
   const contract = usePairContract(pairAddress, false)
+  const reserves = useSingleCallResult(contract, 'getReserves')
 
-  const shouldFetch = !!contract
-  const key = shouldFetch ? [pairAddress, tokenA.chainId, SWRKeys.Reserves] : null
-  const { data, mutate } = useSWR(key, getReserves(contract, tokenA, tokenB))
-  useKeepSWRDataLiveAsBlocksArrive(mutate)
-
-  return data
+  return useMemo(() => {
+    if (!pairAddress || !contract || !tokenA || !tokenB) return undefined
+    if (!reserves) return null
+    const { reserve0, reserve1 } = reserves
+    const [token0, token1] = tokenA.sortsBefore(tokenB) ? [tokenA, tokenB] : [tokenB, tokenA]
+    return new Pair(new TokenAmount(token0, reserve0.toString()), new TokenAmount(token1, reserve1.toString()))
+  }, [contract, pairAddress, reserves, tokenA, tokenB])
 }

src/data/TotalSupply.ts

-import { Contract } from '@ethersproject/contracts'
+import { BigNumber } from '@ethersproject/bignumber'
 import { Token, TokenAmount } from '@uniswap/sdk'
-import useSWR from 'swr'
+import { useTokenContract } from '../hooks/useContract'
+import { useSingleCallResult } from '../state/multicall/hooks'
 
-import { SWRKeys, useKeepSWRDataLiveAsBlocksArrive } from '.'
-import { useTokenContract } from '../hooks'
-
-function getTotalSupply(contract: Contract, token: Token): () => Promise<TokenAmount> {
-  return async (): Promise<TokenAmount> =>
-    contract
-      .totalSupply()
-      .then((totalSupply: { toString: () => string }) => new TokenAmount(token, totalSupply.toString()))
-}
-
-export function useTotalSupply(token?: Token): TokenAmount {
+// returns undefined if input token is undefined, or fails to get token contract,
+// or contract total supply cannot be fetched
+export function useTotalSupply(token?: Token): TokenAmount | undefined {
   const contract = useTokenContract(token?.address, false)
 
-  const shouldFetch = !!contract
-  const { data, mutate } = useSWR(
-    shouldFetch ? [token.address, token.chainId, SWRKeys.TotalSupply] : null,
-    getTotalSupply(contract, token)
-  )
-  useKeepSWRDataLiveAsBlocksArrive(mutate)
+  const totalSupply: BigNumber = useSingleCallResult(contract, 'totalSupply')?.[0]
 
-  return data
+  return token && totalSupply ? new TokenAmount(token, totalSupply.toString()) : undefined
 }

src/data/V1.ts

-import { Contract } from '@ethersproject/contracts'
-import { Token, TokenAmount, Pair, Trade, ChainId, WETH, Route, TradeType, Percent } from '@uniswap/sdk'
-import useSWR from 'swr'
+import { ChainId, Pair, Percent, Route, Token, TokenAmount, Trade, TradeType, WETH } from '@uniswap/sdk'
+import { useMemo } from 'react'
 import { useActiveWeb3React } from '../hooks'
-import { useV1FactoryContract } from '../hooks'
-import { SWRKeys } from '.'
-import { useETHBalances, useTokenBalances } from '../state/wallet/hooks'
-
-function getV1PairAddress(contract: Contract): (tokenAddress: string) => Promise<string> {
-  return async (tokenAddress: string): Promise<string> => contract.getExchange(tokenAddress)
-}
-
-function useV1PairAddress(tokenAddress: string) {
-  const { chainId } = useActiveWeb3React()
+import { useV1FactoryContract } from '../hooks/useContract'
+import { useSingleCallResult } from '../state/multicall/hooks'
+import { useETHBalances, useTokenBalance } from '../state/wallet/hooks'
 
+function useV1PairAddress(tokenAddress?: string): string | undefined {
   const contract = useV1FactoryContract()
 
-  const shouldFetch = chainId === ChainId.MAINNET && typeof tokenAddress === 'string' && !!contract
-  const { data } = useSWR(shouldFetch ? [tokenAddress, SWRKeys.V1PairAddress] : null, getV1PairAddress(contract), {
-    // don't need to update this data
-    revalidateOnFocus: false,
-    revalidateOnReconnect: false
-  })
-
-  return data
+  const inputs = useMemo(() => [tokenAddress], [tokenAddress])
+  return useSingleCallResult(contract, 'getExchange', inputs)?.[0]
 }
 
 function useMockV1Pair(token?: Token) {
@@ -30,37 +17,35 @@ function useMockV1Pair(token?: Token) {
 
   // will only return an address on mainnet, and not for WETH
   const v1PairAddress = useV1PairAddress(isWETH ? undefined : token?.address)
-  const tokenBalance = useTokenBalances(v1PairAddress, [token])[token?.address]
-  const ETHBalance = useETHBalances([v1PairAddress])[v1PairAddress]
+  const tokenBalance = useTokenBalance(v1PairAddress, token)
+  const ETHBalance = useETHBalances([v1PairAddress])[v1PairAddress ?? '']
 
-  return tokenBalance && ETHBalance
-    ? new Pair(tokenBalance, new TokenAmount(WETH[token?.chainId], ETHBalance.toString()))
+  return tokenBalance && ETHBalance && token
+    ? new Pair(tokenBalance, new TokenAmount(WETH[token.chainId], ETHBalance.toString()))
     : undefined
 }
 
 export function useV1TradeLinkIfBetter(
   isExactIn?: boolean,
-  inputToken?: Token,
-  outputToken?: Token,
+  input?: Token,
+  output?: Token,
   exactAmount?: TokenAmount,
   v2Trade?: Trade,
   minimumDelta: Percent = new Percent('0')
-): string {
+): string | undefined {
   const { chainId } = useActiveWeb3React()
 
-  const input = inputToken
-  const output = outputToken
-  const mainnet = chainId === ChainId.MAINNET
+  const isMainnet: boolean = chainId === ChainId.MAINNET
 
   // get the mock v1 pairs
   const inputPair = useMockV1Pair(input)
   const outputPair = useMockV1Pair(output)
 
-  const inputIsWETH = mainnet && input?.equals(WETH[ChainId.MAINNET])
-  const outputIsWETH = mainnet && output?.equals(WETH[ChainId.MAINNET])
+  const inputIsWETH = isMainnet && input?.equals(WETH[ChainId.MAINNET])
+  const outputIsWETH = isMainnet && output?.equals(WETH[ChainId.MAINNET])
 
   // construct a direct or through ETH v1 route
-  let pairs: Pair[]
+  let pairs: Pair[] = []
   if (inputIsWETH && outputPair) {
     pairs = [outputPair]
   } else if (outputIsWETH && inputPair) {
@@ -71,8 +56,8 @@ export function useV1TradeLinkIfBetter(
     pairs = [inputPair, outputPair]
   }
 
-  const route = pairs && new Route(pairs, input)
-  let v1Trade: Trade
+  const route = input && pairs && pairs.length > 0 && new Route(pairs, input)
+  let v1Trade: Trade | undefined
   try {
     v1Trade =
       route && exactAmount
@@ -86,16 +71,16 @@ export function useV1TradeLinkIfBetter(
       // discount the v1 output amount by minimumDelta
       const discountedV1Output = v1Trade?.outputAmount.multiply(new Percent('1').subtract(minimumDelta))
       // check if the discounted v1 amount is still greater than v2, short-circuiting if no v2 trade exists
-      v1HasBetterTrade = !!!v2Trade || discountedV1Output.greaterThan(v2Trade.outputAmount)
+      v1HasBetterTrade = !v2Trade || discountedV1Output.greaterThan(v2Trade.outputAmount)
     } else {
       // inflate the v1 amount by minimumDelta
       const inflatedV1Input = v1Trade?.inputAmount.multiply(new Percent('1').add(minimumDelta))
       // check if the inflated v1 amount is still less than v2, short-circuiting if no v2 trade exists
-      v1HasBetterTrade = !!!v2Trade || inflatedV1Input.lessThan(v2Trade.inputAmount)
+      v1HasBetterTrade = !v2Trade || inflatedV1Input.lessThan(v2Trade.inputAmount)
     }
   }
 
-  return v1HasBetterTrade
+  return v1HasBetterTrade && input && output
     ? `https://v1.uniswap.exchange/swap?inputCurrency=${inputIsWETH ? 'ETH' : input.address}&outputCurrency=${
         outputIsWETH ? 'ETH' : output.address
       }`

src/data/index.ts

-import { useEffect, useRef } from 'react'
-import { responseInterface } from 'swr'
-
-import { useBlockNumber } from '../state/application/hooks'
-
-export enum SWRKeys {
-  Allowances,
-  Reserves,
-  TotalSupply,
-  V1PairAddress
-}
-
-export function useKeepSWRDataLiveAsBlocksArrive(mutate: responseInterface<any, any>['mutate']) {
-  // because we don't care about the referential identity of mutate, just bind it to a ref
-  const mutateRef = useRef(mutate)
-  useEffect(() => {
-    mutateRef.current = mutate
-  })
-  // then, whenever a new block arrives, trigger a mutation
-  const blockNumber = useBlockNumber()
-  useEffect(() => {
-    mutateRef.current()
-  }, [blockNumber])
-}

src/data/tsconfig.json

+{
+  "extends": "../../tsconfig.strict.json",
+  "include": ["**/*"]
+}
\ No newline at end of file

src/hooks/index.ts

-import { Contract } from '@ethersproject/contracts'
 import { Web3Provider } from '@ethersproject/providers'
-import { useState, useMemo, useCallback, useEffect, useRef } from 'react'
 import { useWeb3React as useWeb3ReactCore } from '@web3-react/core'
+import { useEffect, useState } from 'react'
 import { isMobile } from 'react-device-detect'
-import copy from 'copy-to-clipboard'
-
-import IUniswapV1Factory from '../constants/abis/v1_factory.json'
-import ERC20_ABI from '../constants/abis/erc20.json'
-import { abi as IUniswapV2PairABI } from '@uniswap/v2-core/build/IUniswapV2Pair.json'
 import { injected } from '../connectors'
-import { NetworkContextName, V1_FACTORY_ADDRESS } from '../constants'
-import { getContract, isAddress } from '../utils'
+import { NetworkContextName } from '../constants'
 
 export function useActiveWeb3React() {
   const context = useWeb3ReactCore<Web3Provider>()
@@ -64,7 +57,7 @@ export function useInactiveListener(suppress = false) {
       const handleChainChanged = () => {
         // eat errors
         activate(injected, undefined, true).catch(error => {
-          console.log(error)
+          console.error('Failed to activate after chain changed', error)
         })
       }
 
@@ -72,7 +65,7 @@ export function useInactiveListener(suppress = false) {
         if (accounts.length > 0) {
           // eat errors
           activate(injected, undefined, true).catch(error => {
-            console.log(error)
+            console.error('Failed to activate after accounts changed', error)
           })
         }
       }
@@ -80,7 +73,7 @@ export function useInactiveListener(suppress = false) {
       const handleNetworkChanged = () => {
         // eat errors
         activate(injected, undefined, true).catch(error => {
-          console.log(error)
+          console.error('Failed to activate after networks changed', error)
         })
       }
 
@@ -99,157 +92,3 @@ export function useInactiveListener(suppress = false) {
     return
   }, [active, error, suppress, activate])
 }
-
-// modified from https://usehooks.com/useDebounce/
-export function useDebounce<T>(value: T, delay: number): T {
-  const [debouncedValue, setDebouncedValue] = useState<T>(value)
-
-  useEffect(() => {
-    // Update debounced value after delay
-    const handler = setTimeout(() => {
-      setDebouncedValue(value)
-    }, delay)
-
-    // Cancel the timeout if value changes (also on delay change or unmount)
-    // This is how we prevent debounced value from updating if value is changed ...
-    // .. within the delay period. Timeout gets cleared and restarted.
-    return () => {
-      clearTimeout(handler)
-    }
-  }, [value, delay])
-
-  return debouncedValue
-}
-
-// modified from https://usehooks.com/useKeyPress/
-export function useBodyKeyDown(targetKey: string, onKeyDown: () => void, suppressOnKeyDown = false) {
-  const downHandler = useCallback(
-    event => {
-      const {
-        target: { tagName },
-        key
-      } = event
-      if (key === targetKey && tagName === 'BODY' && !suppressOnKeyDown) {
-        event.preventDefault()
-        onKeyDown()
-      }
-    },
-    [targetKey, onKeyDown, suppressOnKeyDown]
-  )
-
-  useEffect(() => {
-    window.addEventListener('keydown', downHandler)
-    return () => {
-      window.removeEventListener('keydown', downHandler)
-    }
-  }, [downHandler])
-}
-
-export function useENSName(address?: string): string | null {
-  const { library } = useActiveWeb3React()
-
-  const [ENSName, setENSName] = useState<string | null>(null)
-
-  useEffect(() => {
-    if (!library || !address) return
-    if (isAddress(address)) {
-      let stale = false
-      library
-        .lookupAddress(address)
-        .then(name => {
-          if (!stale) {
-            if (name) {
-              setENSName(name)
-            } else {
-              setENSName(null)
-            }
-          }
-        })
-        .catch(() => {
-          if (!stale) {
-            setENSName(null)
-          }
-        })
-
-      return () => {
-        stale = true
-        setENSName(null)
-      }
-    }
-    return
-  }, [library, address])
-
-  return ENSName
-}
-
-// returns null on errors
-function useContract(address?: string, ABI?: any, withSignerIfPossible = true): Contract | null {
-  const { library, account } = useActiveWeb3React()
-
-  return useMemo(() => {
-    if (!address || !ABI || !library) return null
-    try {
-      return getContract(address, ABI, library, withSignerIfPossible && account ? account : undefined)
-    } catch {
-      return null
-    }
-  }, [address, ABI, library, withSignerIfPossible, account])
-}
-
-export function useV1FactoryContract(): Contract | null {
-  return useContract(V1_FACTORY_ADDRESS, IUniswapV1Factory, false)
-}
-
-// returns null on errors
-export function useTokenContract(tokenAddress?: string, withSignerIfPossible = true): Contract | null {
-  return useContract(tokenAddress, ERC20_ABI, withSignerIfPossible)
-}
-
-export function usePairContract(pairAddress?: string, withSignerIfPossible = true): Contract | null {
-  return useContract(pairAddress, IUniswapV2PairABI, withSignerIfPossible)
-}
-
-export function useCopyClipboard(timeout = 500): [boolean, (toCopy: string) => void] {
-  const [isCopied, setIsCopied] = useState(false)
-
-  const staticCopy = useCallback(text => {
-    const didCopy = copy(text)
-    setIsCopied(didCopy)
-  }, [])
-
-  useEffect(() => {
-    if (isCopied) {
-      const hide = setTimeout(() => {
-        setIsCopied(false)
-      }, timeout)
-
-      return () => {
-        clearTimeout(hide)
-      }
-    }
-    return
-  }, [isCopied, setIsCopied, timeout])
-
-  return [isCopied, staticCopy]
-}
-
-// modified from https://usehooks.com/usePrevious/
-export function usePrevious<T>(value: T) {
-  // The ref object is a generic container whose current property is mutable ...
-  // ... and can hold any value, similar to an instance property on a class
-  const ref = useRef<T>()
-
-  // Store current value in ref
-  useEffect(() => {
-    ref.current = value
-  }, [value]) // Only re-run if value changes
-
-  // Return previous value (happens before update in useEffect above)
-  return ref.current
-}
-
-export function useToggle(initialState = false): [boolean, () => void] {
-  const [state, setState] = useState(initialState)
-  const toggle = useCallback(() => setState(state => !state), [])
-  return [state, toggle]
-}

src/hooks/useApproveCallback.ts

@@ -8,7 +8,8 @@ import { Field } from '../state/swap/actions'
 import { useTransactionAdder, useHasPendingApproval } from '../state/transactions/hooks'
 import { computeSlippageAdjustedAmounts } from '../utils/prices'
 import { calculateGasMargin } from '../utils'
-import { useTokenContract, useActiveWeb3React } from './index'
+import { useTokenContract } from './useContract'
+import { useActiveWeb3React } from './index'
 
 export enum ApprovalState {
   UNKNOWN,

src/hooks/useBodyKeyDown.ts

+import { useCallback, useEffect } from 'react'
+
+// modified from https://usehooks.com/useKeyPress/
+export default function useBodyKeyDown(targetKey: string, onKeyDown: () => void, suppressOnKeyDown = false) {
+  const downHandler = useCallback(
+    event => {
+      const {
+        target: { tagName },
+        key
+      } = event
+      if (key === targetKey && tagName === 'BODY' && !suppressOnKeyDown) {
+        event.preventDefault()
+        onKeyDown()
+      }
+    },
+    [targetKey, onKeyDown, suppressOnKeyDown]
+  )
+
+  useEffect(() => {
+    window.addEventListener('keydown', downHandler)
+    return () => {
+      window.removeEventListener('keydown', downHandler)
+    }
+  }, [downHandler])
+}

src/hooks/useContract.ts

+import { Contract } from '@ethersproject/contracts'
+import { ChainId } from '@uniswap/sdk'
+import { abi as IUniswapV2PairABI } from '@uniswap/v2-core/build/IUniswapV2Pair.json'
+import { useMemo } from 'react'
+import { V1_FACTORY_ADDRESS } from '../constants'
+import ERC20_ABI from '../constants/abis/erc20.json'
+import IUniswapV1Factory from '../constants/abis/v1_factory.json'
+import { MULTICALL_ABI, MULTICALL_NETWORKS } from '../constants/multicall'
+import { getContract } from '../utils'
+import { useActiveWeb3React } from './index'
+
+// returns null on errors
+function useContract(address?: string, ABI?: any, withSignerIfPossible = true): Contract | null {
+  const { library, account } = useActiveWeb3React()
+
+  return useMemo(() => {
+    if (!address || !ABI || !library) return null
+    try {
+      return getContract(address, ABI, library, withSignerIfPossible && account ? account : undefined)
+    } catch (error) {
+      console.error('Failed to get contract', error)
+      return null
+    }
+  }, [address, ABI, library, withSignerIfPossible, account])
+}
+
+export function useV1FactoryContract(): Contract | null {
+  return useContract(V1_FACTORY_ADDRESS, IUniswapV1Factory, false)
+}
+
+export function useTokenContract(tokenAddress?: string, withSignerIfPossible = true): Contract | null {
+  return useContract(tokenAddress, ERC20_ABI, withSignerIfPossible)
+}
+
+export function usePairContract(pairAddress?: string, withSignerIfPossible = true): Contract | null {
+  return useContract(pairAddress, IUniswapV2PairABI, withSignerIfPossible)
+}
+
+export function useMulticallContract(): Contract | null {
+  const { chainId } = useActiveWeb3React()
+  return useContract(MULTICALL_NETWORKS[chainId as ChainId], MULTICALL_ABI, false)
+}

src/hooks/useCopyClipboard.ts

+import copy from 'copy-to-clipboard'
+import { useCallback, useEffect, useState } from 'react'
+
+export default function useCopyClipboard(timeout = 500): [boolean, (toCopy: string) => void] {
+  const [isCopied, setIsCopied] = useState(false)
+
+  const staticCopy = useCallback(text => {
+    const didCopy = copy(text)
+    setIsCopied(didCopy)
+  }, [])
+
+  useEffect(() => {
+    if (isCopied) {
+      const hide = setTimeout(() => {
+        setIsCopied(false)
+      }, timeout)
+
+      return () => {
+        clearTimeout(hide)
+      }
+    }
+    return
+  }, [isCopied, setIsCopied, timeout])
+
+  return [isCopied, staticCopy]
+}

src/hooks/useDebounce.ts

+import { useEffect, useState } from 'react'
+
+// modified from https://usehooks.com/useDebounce/
+export default function useDebounce<T>(value: T, delay: number): T {
+  const [debouncedValue, setDebouncedValue] = useState<T>(value)
+
+  useEffect(() => {
+    // Update debounced value after delay
+    const handler = setTimeout(() => {
+      setDebouncedValue(value)
+    }, delay)
+
+    // Cancel the timeout if value changes (also on delay change or unmount)
+    // This is how we prevent debounced value from updating if value is changed ...
+    // .. within the delay period. Timeout gets cleared and restarted.
+    return () => {
+      clearTimeout(handler)
+    }
+  }, [value, delay])
+
+  return debouncedValue
+}

src/hooks/useENSName.ts

+import { useEffect, useState } from 'react'
+import { isAddress } from '../utils'
+import { useActiveWeb3React } from './index'
+
+/**
+ * Does a reverse lookup for an address to find its ENS name.
+ * Note this is not the same as looking up an ENS name to find an address.
+ */
+export default function useENSName(address?: string): string | null {
+  const { library } = useActiveWeb3React()
+
+  const [ENSName, setENSName] = useState<string | null>(null)
+
+  useEffect(() => {
+    if (!library || !address) return
+    const validated = isAddress(address)
+    if (validated) {
+      let stale = false
+      library
+        .lookupAddress(validated)
+        .then(name => {
+          if (!stale) {
+            if (name) {
+              setENSName(name)
+            } else {
+              setENSName(null)
+            }
+          }
+        })
+        .catch(() => {
+          if (!stale) {
+            setENSName(null)
+          }
+        })
+
+      return () => {
+        stale = true
+        setENSName(null)
+      }
+    }
+    return
+  }, [library, address])
+
+  return ENSName
+}

src/hooks/usePrevious.ts

+import { useEffect, useRef } from 'react'
+
+// modified from https://usehooks.com/usePrevious/
+export default function usePrevious<T>(value: T) {
+  // The ref object is a generic container whose current property is mutable ...
+  // ... and can hold any value, similar to an instance property on a class
+  const ref = useRef<T>()
+
+  // Store current value in ref
+  useEffect(() => {
+    ref.current = value
+  }, [value]) // Only re-run if value changes
+
+  // Return previous value (happens before update in useEffect above)
+  return ref.current
+}

src/hooks/useSendCallback.ts

@@ -6,7 +6,9 @@ import { useTransactionAdder } from '../state/transactions/hooks'
 import { useTokenBalanceTreatingWETHasETH } from '../state/wallet/hooks'
 
 import { calculateGasMargin, getSigner, isAddress } from '../utils'
-import { useENSName, useTokenContract, useActiveWeb3React } from './index'
+import { useTokenContract } from './useContract'
+import { useActiveWeb3React } from './index'
+import useENSName from './useENSName'
 
 // returns a callback for sending a token amount, treating WETH as ETH
 // returns null with invalid arguments

src/hooks/useSwapCallback.ts

@@ -8,7 +8,8 @@ import { Field } from '../state/swap/actions'
 import { useTransactionAdder } from '../state/transactions/hooks'
 import { computeSlippageAdjustedAmounts } from '../utils/prices'
 import { calculateGasMargin, getRouterContract, isAddress } from '../utils'
-import { useENSName, useActiveWeb3React } from './index'
+import { useActiveWeb3React } from './index'
+import useENSName from './useENSName'
 
 enum SwapType {
   EXACT_TOKENS_FOR_TOKENS,

src/hooks/useToggle.ts

+import { useCallback, useState } from 'react'
+
+export default function useToggle(initialState = false): [boolean, () => void] {
+  const [state, setState] = useState(initialState)
+  const toggle = useCallback(() => setState(state => !state), [])
+  return [state, toggle]
+}

src/index.tsx

@@ -12,7 +12,7 @@ import store from './state'
 import ApplicationUpdater from './state/application/updater'
 import TransactionUpdater from './state/transactions/updater'
 import UserUpdater from './state/user/updater'
-import WalletUpdater from './state/wallet/updater'
+import MulticallUpdater from './state/multicall/updater'
 import ThemeProvider, { FixedGlobalStyle, ThemedGlobalStyle } from './theme'
 
 const Web3ProviderNetwork = createWeb3ReactRoot(NetworkContextName)
@@ -37,7 +37,7 @@ function Updaters() {
       <UserUpdater />
       <ApplicationUpdater />
       <TransactionUpdater />
-      <WalletUpdater />
+      <MulticallUpdater />
     </>
   )
 }

src/pages/RemoveLiquidity/index.tsx

@@ -19,7 +19,8 @@ import Row, { RowBetween, RowFixed } from '../../components/Row'
 import Slider from '../../components/Slider'
 import TokenLogo from '../../components/TokenLogo'
 import { ROUTER_ADDRESS, DEFAULT_DEADLINE_FROM_NOW, INITIAL_ALLOWED_SLIPPAGE } from '../../constants'
-import { usePairContract, useActiveWeb3React } from '../../hooks'
+import { useActiveWeb3React } from '../../hooks'
+import { usePairContract } from '../../hooks/useContract'
 
 import { useTransactionAdder } from '../../state/transactions/hooks'
 import { TYPE } from '../../theme'

src/pages/Send/index.tsx

@@ -251,7 +251,7 @@ export default function Send({ location: { search } }: RouteComponentProps) {
   const swapState = useSwapState()
   function _onTokenSelect(address: string) {
     // if no user balance - switch view to a send with swap
-    const hasBalance = allBalances?.[account]?.[address]?.greaterThan('0') ?? false
+    const hasBalance = allBalances?.[address]?.greaterThan('0') ?? false
     if (!hasBalance) {
       onTokenSelection(
         Field.INPUT,

src/state/application/updater.ts

 import { useEffect, useState } from 'react'
-import { useDebounce, useActiveWeb3React } from '../../hooks'
+import { useActiveWeb3React } from '../../hooks'
+import useDebounce from '../../hooks/useDebounce'
 import useIsWindowVisible from '../../hooks/useIsWindowVisible'
 import { updateBlockNumber } from './actions'
 import { useDispatch } from 'react-redux'

src/state/index.ts

@@ -4,10 +4,10 @@ import { save, load } from 'redux-localstorage-simple'
 import application from './application/reducer'
 import user from './user/reducer'
 import transactions from './transactions/reducer'
-import wallet from './wallet/reducer'
 import swap from './swap/reducer'
 import mint from './mint/reducer'
 import burn from './burn/reducer'
+import multicall from './multicall/reducer'
 
 import { updateVersion } from './user/actions'
 
@@ -18,10 +18,10 @@ const store = configureStore({
     application,
     user,
     transactions,
-    wallet,
     swap,
     mint,
-    burn
+    burn,
+    multicall
   },
   middleware: [...getDefaultMiddleware(), save({ states: PERSISTED_KEYS })],
   preloadedState: load({ states: PERSISTED_KEYS })

src/state/multicall/actions.ts

+import { createAction } from '@reduxjs/toolkit'
+import { isAddress } from '../../utils'
+
+export interface Call {
+  address: string
+  callData: string
+}
+
+export function toCallKey(call: Call): string {
+  return `${call.address}-${call.callData}`
+}
+
+export function parseCallKey(callKey: string): Call {
+  const pcs = callKey.split('-')
+  if (pcs.length !== 2) {
+    throw new Error(`Invalid call key: ${callKey}`)
+  }
+  const addr = isAddress(pcs[0])
+  if (!addr) {
+    throw new Error(`Invalid address: ${pcs[0]}`)
+  }
+
+  if (!pcs[1].match(/^0x[a-fA-F0-9]*$/)) {
+    throw new Error(`Invalid hex: ${pcs[1]}`)
+  }
+
+  return {
+    address: pcs[0],
+    callData: pcs[1]
+  }
+}
+
+export const addMulticallListeners = createAction<{ chainId: number; calls: Call[] }>('addMulticallListeners')
+export const removeMulticallListeners = createAction<{ chainId: number; calls: Call[] }>('removeMulticallListeners')
+export const updateMulticallResults = createAction<{
+  chainId: number
+  blockNumber: number
+  results: {
+    [callKey: string]: string | null
+  }
+}>('updateMulticallResults')

src/state/multicall/hooks.ts

+import { Interface } from '@ethersproject/abi'
+import { BigNumber } from '@ethersproject/bignumber'
+import { Contract } from '@ethersproject/contracts'
+import { useEffect, useMemo } from 'react'
+import { useDispatch, useSelector } from 'react-redux'
+import { useActiveWeb3React } from '../../hooks'
+import useDebounce from '../../hooks/useDebounce'
+import { AppDispatch, AppState } from '../index'
+import { addMulticallListeners, Call, removeMulticallListeners, parseCallKey, toCallKey } from './actions'
+
+export interface Result extends ReadonlyArray<any> {
+  readonly [key: string]: any
+}
+
+type MethodArg = string | number | BigNumber
+type MethodArgs = Array<MethodArg | MethodArg[]>
+
+type OptionalMethodInputs = Array<MethodArg | MethodArg[] | undefined> | undefined
+
+function isMethodArg(x: unknown): x is MethodArg {
+  return ['string', 'number'].indexOf(typeof x) !== -1
+}
+
+function isValidMethodArgs(x: unknown): x is MethodArgs | undefined {
+  return (
+    x === undefined || (Array.isArray(x) && x.every(y => isMethodArg(y) || (Array.isArray(y) && y.every(isMethodArg))))
+  )
+}
+
+// the lowest level call for subscribing to contract data
+function useCallsData(calls: (Call | undefined)[]): (string | undefined)[] {
+  const { chainId } = useActiveWeb3React()
+  const callResults = useSelector<AppState, AppState['multicall']['callResults']>(state => state.multicall.callResults)
+  const dispatch = useDispatch<AppDispatch>()
+
+  const serializedCallKeys: string = useMemo(
+    () =>
+      JSON.stringify(
+        calls
+          ?.filter((c): c is Call => Boolean(c))
+          ?.map(toCallKey)
+          ?.sort() ?? []
+      ),
+    [calls]
+  )
+
+  const debouncedSerializedCallKeys = useDebounce(serializedCallKeys, 20)
+
+  // update listeners when there is an actual change that persists for at least 100ms
+  useEffect(() => {
+    const callKeys: string[] = JSON.parse(debouncedSerializedCallKeys)
+    if (!chainId || callKeys.length === 0) return
+    const calls = callKeys.map(key => parseCallKey(key))
+    dispatch(
+      addMulticallListeners({
+        chainId,
+        calls
+      })
+    )
+
+    return () => {
+      dispatch(
+        removeMulticallListeners({
+          chainId,
+          calls
+        })
+      )
+    }
+  }, [chainId, dispatch, debouncedSerializedCallKeys])
+
+  return useMemo(() => {
+    return calls.map<string | undefined>(call => {
+      if (!chainId || !call) return undefined
+
+      const result = callResults[chainId]?.[toCallKey(call)]
+      if (!result || !result.data || result.data === '0x') {
+        return undefined
+      }
+
+      return result.data
+    })
+  }, [callResults, calls, chainId])
+}
+
+export function useSingleContractMultipleData(
+  contract: Contract | null | undefined,
+  methodName: string,
+  callInputs: OptionalMethodInputs[]
+): (Result | undefined)[] {
+  const fragment = useMemo(() => contract?.interface?.getFunction(methodName), [contract, methodName])
+
+  const calls = useMemo(
+    () =>
+      contract && fragment && callInputs && callInputs.length > 0
+        ? callInputs.map<Call>(inputs => {
+            return {
+              address: contract.address,
+              callData: contract.interface.encodeFunctionData(fragment, inputs)
+            }
+          })
+        : [],
+    [callInputs, contract, fragment]
+  )
+
+  const data = useCallsData(calls)
+
+  return useMemo(() => {
+    if (!fragment || !contract) return []
+    return data.map(data => (data ? contract.interface.decodeFunctionResult(fragment, data) : undefined))
+  }, [contract, data, fragment])
+}
+
+export function useMultipleContractSingleData(
+  addresses: (string | undefined)[],
+  contractInterface: Interface,
+  methodName: string,
+  callInputs?: OptionalMethodInputs
+): (Result | undefined)[] {
+  const fragment = useMemo(() => contractInterface.getFunction(methodName), [contractInterface, methodName])
+  const callData: string | undefined = useMemo(
+    () =>
+      fragment && isValidMethodArgs(callInputs)
+        ? contractInterface.encodeFunctionData(fragment, callInputs)
+        : undefined,
+    [callInputs, contractInterface, fragment]
+  )
+
+  const calls = useMemo(
+    () =>
+      fragment && addresses && addresses.length > 0 && callData
+        ? addresses.map<Call | undefined>(address => {
+            return address && callData
+              ? {
+                  address,
+                  callData
+                }
+              : undefined
+          })
+        : [],
+    [addresses, callData, fragment]
+  )
+
+  const data = useCallsData(calls)
+
+  return useMemo(() => {
+    if (!fragment) return []
+    return data.map(data => (data ? contractInterface.decodeFunctionResult(fragment, data) : undefined))
+  }, [contractInterface, data, fragment])
+}
+
+export function useSingleCallResult(
+  contract: Contract | null | undefined,
+  methodName: string,
+  inputs?: OptionalMethodInputs
+): Result | undefined {
+  const fragment = useMemo(() => contract?.interface?.getFunction(methodName), [contract, methodName])
+
+  const calls = useMemo<Call[]>(() => {
+    return contract && fragment && isValidMethodArgs(inputs)
+      ? [
+          {
+            address: contract.address,
+            callData: contract.interface.encodeFunctionData(fragment, inputs)
+          }
+        ]
+      : []
+  }, [contract, fragment, inputs])
+
+  const data = useCallsData(calls)[0]
+  return useMemo(() => {
+    if (!contract || !fragment || !data) return undefined
+    return contract.interface.decodeFunctionResult(fragment, data)
+  }, [data, fragment, contract])
+}

src/state/multicall/reducer.ts

+import { createReducer } from '@reduxjs/toolkit'
+import { addMulticallListeners, removeMulticallListeners, toCallKey, updateMulticallResults } from './actions'
+
+interface MulticallState {
+  callListeners: {
+    [chainId: number]: {
+      [callKey: string]: number
+    }
+  }
+
+  callResults: {
+    [chainId: number]: {
+      [callKey: string]: {
+        data: string | null
+        blockNumber: number
+      }
+    }
+  }
+}
+
+const initialState: MulticallState = {
+  callListeners: {},
+  callResults: {}
+}
+
+export default createReducer(initialState, builder =>
+  builder
+    .addCase(addMulticallListeners, (state, { payload: { calls, chainId } }) => {
+      state.callListeners[chainId] = state.callListeners[chainId] ?? {}
+      calls.forEach(call => {
+        const callKey = toCallKey(call)
+        state.callListeners[chainId][callKey] = (state.callListeners[chainId][callKey] ?? 0) + 1
+      })
+    })
+    .addCase(removeMulticallListeners, (state, { payload: { chainId, calls } }) => {
+      if (!state.callListeners[chainId]) return
+      calls.forEach(call => {
+        const callKey = toCallKey(call)
+        if (state.callListeners[chainId][callKey] === 1) {
+          delete state.callListeners[chainId][callKey]
+        } else {
+          state.callListeners[chainId][callKey]--
+        }
+      })
+    })
+    .addCase(updateMulticallResults, (state, { payload: { chainId, results, blockNumber } }) => {
+      state.callResults[chainId] = state.callResults[chainId] ?? {}
+      Object.keys(results).forEach(callKey => {
+        const current = state.callResults[chainId][callKey]
+        if (current && current.blockNumber > blockNumber) return
+        state.callResults[chainId][callKey] = {
+          data: results[callKey],
+          blockNumber
+        }
+      })
+    })
+)

src/state/multicall/updater.tsx

+import { BigNumber } from '@ethersproject/bignumber'
+import { useEffect, useMemo } from 'react'
+import { useDispatch, useSelector } from 'react-redux'
+import { useActiveWeb3React } from '../../hooks'
+import { useMulticallContract } from '../../hooks/useContract'
+import useDebounce from '../../hooks/useDebounce'
+import chunkArray from '../../utils/chunkArray'
+import { useBlockNumber } from '../application/hooks'
+import { AppDispatch, AppState } from '../index'
+import { parseCallKey, updateMulticallResults } from './actions'
+
+// chunk calls so we do not exceed the gas limit
+const CALL_CHUNK_SIZE = 250
+
+export default function Updater() {
+  const dispatch = useDispatch<AppDispatch>()
+  const state = useSelector<AppState, AppState['multicall']>(state => state.multicall)
+  const latestBlockNumber = useBlockNumber()
+  const { chainId } = useActiveWeb3React()
+  const multicallContract = useMulticallContract()
+
+  const listeningKeys = useMemo(() => {
+    if (!chainId || !state.callListeners[chainId]) return []
+    return Object.keys(state.callListeners[chainId]).filter(callKey => state.callListeners[chainId][callKey] > 0)
+  }, [state.callListeners, chainId])
+
+  const debouncedResults = useDebounce(state.callResults, 20)
+  const debouncedListeningKeys = useDebounce(listeningKeys, 20)
+
+  const unserializedOutdatedCallKeys = useMemo(() => {
+    if (!chainId || !debouncedResults[chainId]) return debouncedListeningKeys
+    if (!latestBlockNumber) return []
+
+    return debouncedListeningKeys.filter(key => {
+      const data = debouncedResults[chainId][key]
+      return !data || data.blockNumber < latestBlockNumber
+    })
+  }, [chainId, debouncedResults, debouncedListeningKeys, latestBlockNumber])
+
+  const serializedOutdatedCallKeys = useMemo(() => JSON.stringify(unserializedOutdatedCallKeys.sort()), [
+    unserializedOutdatedCallKeys
+  ])
+
+  useEffect(() => {
+    const outdatedCallKeys: string[] = JSON.parse(serializedOutdatedCallKeys)
+    if (!multicallContract || !chainId || outdatedCallKeys.length === 0) return
+    const calls = outdatedCallKeys.map(key => parseCallKey(key))
+
+    const chunkedCalls = chunkArray(calls, CALL_CHUNK_SIZE)
+
+    console.debug('Firing off chunked calls', chunkedCalls)
+
+    chunkedCalls.forEach((chunk, index) =>
+      multicallContract
+        .aggregate(chunk.map(obj => [obj.address, obj.callData]))
+        .then(([resultsBlockNumber, returnData]: [BigNumber, string[]]) => {
+          // accumulates the length of all previous indices
+          const firstCallKeyIndex = chunkedCalls.slice(0, index).reduce<number>((memo, curr) => memo + curr.length, 0)
+          const lastCallKeyIndex = firstCallKeyIndex + returnData.length
+
+          dispatch(
+            updateMulticallResults({
+              chainId,
+              results: outdatedCallKeys
+                .slice(firstCallKeyIndex, lastCallKeyIndex)
+                .reduce<{ [callKey: string]: string | null }>((memo, callKey, i) => {
+                  memo[callKey] = returnData[i] ?? null
+                  return memo
+                }, {}),
+              blockNumber: resultsBlockNumber.toNumber()
+            })
+          )
+        })
+        .catch((error: any) => {
+          console.error('Failed to fetch multicall chunk', chunk, chainId, error)
+        })
+    )
+  }, [chainId, multicallContract, dispatch, serializedOutdatedCallKeys])
+
+  return null
+}

src/state/wallet/actions.ts

-import { createAction } from '@reduxjs/toolkit'
-
-export interface TokenBalanceListenerKey {
-  address: string
-  tokenAddress: string
-}
-
-// used by components that care about balances of given tokens and accounts
-// being kept up to date
-export const startListeningForTokenBalances = createAction<TokenBalanceListenerKey[]>('startListeningForTokenBalances')
-export const stopListeningForTokenBalances = createAction<TokenBalanceListenerKey[]>('stopListeningForTokenBalances')
-export const startListeningForBalance = createAction<{ addresses: string[] }>('startListeningForBalance')
-export const stopListeningForBalance = createAction<{ addresses: string[] }>('stopListeningForBalance')
-
-// these are used by the updater to update balances, and can also be used
-// for optimistic updates, e.g. when a transaction is confirmed that changes the
-// user's balances or allowances
-export const updateTokenBalances = createAction<{
-  chainId: number
-  blockNumber: number
-  address: string
-  tokenBalances: {
-    [address: string]: string
-  }
-}>('updateTokenBalances')
-
-export const updateEtherBalances = createAction<{
-  chainId: number
-  blockNumber: number
-  etherBalances: {
-    [address: string]: string
-  }
-}>('updateEtherBalances')

src/state/wallet/hooks.ts

-import { getAddress } from '@ethersproject/address'
 import { ChainId, JSBI, Token, TokenAmount, WETH } from '@uniswap/sdk'
-import { useEffect, useMemo } from 'react'
-import { useDispatch, useSelector } from 'react-redux'
+import { useMemo } from 'react'
+import ERC20_INTERFACE from '../../constants/abis/erc20'
 import { useAllTokens } from '../../hooks/Tokens'
 import { useActiveWeb3React } from '../../hooks'
+import { useMulticallContract } from '../../hooks/useContract'
 import { isAddress } from '../../utils'
-import { AppDispatch, AppState } from '../index'
-import {
-  startListeningForBalance,
-  startListeningForTokenBalances,
-  stopListeningForBalance,
-  stopListeningForTokenBalances,
-  TokenBalanceListenerKey
-} from './actions'
-import { balanceKey } from './reducer'
+import { useSingleContractMultipleData, useMultipleContractSingleData } from '../multicall/hooks'
 
 /**
  * Returns a map of the given addresses to their eventually consistent ETH balances.
  */
 export function useETHBalances(uncheckedAddresses?: (string | undefined)[]): { [address: string]: JSBI | undefined } {
-  const dispatch = useDispatch<AppDispatch>()
-  const { chainId } = useActiveWeb3React()
+  const multicallContract = useMulticallContract()
 
   const addresses: string[] = useMemo(
     () =>
       uncheckedAddresses
         ? uncheckedAddresses
-            .filter((a): a is string => isAddress(a) !== false)
-            .map(getAddress)
+            .map(isAddress)
+            .filter((a): a is string => a !== false)
             .sort()
         : [],
     [uncheckedAddresses]
   )
 
-  // used so that we do a deep comparison in `useEffect`
-  const serializedAddresses = JSON.stringify(addresses)
-
-  // add the listeners on mount, remove them on dismount
-  useEffect(() => {
-    const addresses = JSON.parse(serializedAddresses)
-    if (addresses.length === 0) return
-
-    dispatch(startListeningForBalance({ addresses }))
-    return () => {
-      dispatch(stopListeningForBalance({ addresses }))
-    }
-  }, [serializedAddresses, dispatch])
-
-  const rawBalanceMap = useSelector<AppState, AppState['wallet']['balances']>(({ wallet: { balances } }) => balances)
+  const results = useSingleContractMultipleData(
+    multicallContract,
+    'getEthBalance',
+    addresses.map(address => [address])
+  )
 
-  return useMemo(() => {
-    if (!chainId) return {}
-    return addresses.reduce<{ [address: string]: JSBI }>((map, address) => {
-      const key = balanceKey({ address, chainId })
-      const { value } = rawBalanceMap[key] ?? {}
-      if (value) {
-        map[address] = JSBI.BigInt(value)
-      }
-      return map
-    }, {})
-  }, [chainId, addresses, rawBalanceMap])
+  return useMemo(
+    () =>
+      addresses.reduce<{ [address: string]: JSBI | undefined }>((memo, address, i) => {
+        const value = results?.[i]?.[0]
+        if (value) memo[address] = JSBI.BigInt(value.toString())
+        return memo
+      }, {}),
+    [addresses, results]
+  )
 }
 
 /**
@@ -69,54 +48,29 @@ export function useTokenBalances(
   address?: string,
   tokens?: (Token | undefined)[]
 ): { [tokenAddress: string]: TokenAmount | undefined } {
-  const dispatch = useDispatch<AppDispatch>()
-  const { chainId } = useActiveWeb3React()
-
-  const validTokens: Token[] = useMemo(
+  const validatedTokens: Token[] = useMemo(
     () => tokens?.filter((t?: Token): t is Token => isAddress(t?.address) !== false) ?? [],
     [tokens]
   )
 
-  // used so that we do a deep comparison in `useEffect`
-  const serializedCombos: string = useMemo(() => {
-    return JSON.stringify(
-      !address || validTokens.length === 0
-        ? []
-        : validTokens
-            .map(t => t.address)
-            .sort()
-            .map(tokenAddress => ({ address, tokenAddress }))
-    )
-  }, [address, validTokens])
-
-  // keep the listeners up to date
-  useEffect(() => {
-    const combos: TokenBalanceListenerKey[] = JSON.parse(serializedCombos)
-    if (combos.length === 0) return
-
-    dispatch(startListeningForTokenBalances(combos))
-    return () => {
-      dispatch(stopListeningForTokenBalances(combos))
-    }
-  }, [address, serializedCombos, dispatch])
+  const validatedTokenAddresses = useMemo(() => validatedTokens.map(vt => vt.address), [validatedTokens])
 
-  const rawBalanceMap = useSelector<AppState, AppState['wallet']['balances']>(({ wallet: { balances } }) => balances)
+  const balances = useMultipleContractSingleData(validatedTokenAddresses, ERC20_INTERFACE, 'balanceOf', [address])
 
-  return useMemo(() => {
-    if (!address || validTokens.length === 0 || !chainId) {
-      return {}
-    }
-    return (
-      validTokens.reduce<{ [address: string]: TokenAmount }>((map, token) => {
-        const key = balanceKey({ address, chainId, tokenAddress: token.address })
-        const { value } = rawBalanceMap[key] ?? {}
-        if (value) {
-          map[token.address] = new TokenAmount(token, JSBI.BigInt(value))
-        }
-        return map
-      }, {}) ?? {}
-    )
-  }, [address, validTokens, chainId, rawBalanceMap])
+  return useMemo(
+    () =>
+      address && validatedTokens.length > 0
+        ? validatedTokens.reduce<{ [tokenAddress: string]: TokenAmount | undefined }>((memo, token, i) => {
+            const value = balances?.[i]?.[0]
+            const amount = value ? JSBI.BigInt(value.toString()) : undefined
+            if (amount) {
+              memo[token.address] = new TokenAmount(token, amount)
+            }
+            return memo
+          }, {})
+        : {},
+    [address, validatedTokens, balances]
+  )
 }
 
 // contains the hacky logic to treat the WETH token input as if it's ETH to
@@ -173,12 +127,10 @@ export function useTokenBalanceTreatingWETHasETH(account?: string, token?: Token
 }
 
 // mimics useAllBalances
-export function useAllTokenBalancesTreatingWETHasETH(): {
-  [account: string]: { [tokenAddress: string]: TokenAmount | undefined }
-} {
+export function useAllTokenBalancesTreatingWETHasETH(): { [tokenAddress: string]: TokenAmount | undefined } {
   const { account } = useActiveWeb3React()
   const allTokens = useAllTokens()
   const allTokensArray = useMemo(() => Object.values(allTokens ?? {}), [allTokens])
   const balances = useTokenBalancesTreatWETHAsETH(account ?? undefined, allTokensArray)
-  return account ? { [account]: balances } : {}
+  return balances ?? {}
 }

src/state/wallet/reducer.tsx

-import { createReducer } from '@reduxjs/toolkit'
-import { isAddress } from '../../utils'
-import {
-  startListeningForBalance,
-  startListeningForTokenBalances,
-  stopListeningForBalance,
-  stopListeningForTokenBalances,
-  updateEtherBalances,
-  updateTokenBalances
-} from './actions'
-
-// all address keys are checksummed and valid addresses starting with 0x
-interface WalletState {
-  readonly tokenBalanceListeners: {
-    readonly [address: string]: {
-      // the number of listeners for each address/token combo
-      readonly [tokenAddress: string]: number
-    }
-  }
-
-  readonly balanceListeners: {
-    // the number of ether balance listeners for each address
-    readonly [address: string]: number
-  }
-
-  readonly balances: {
-    readonly [balanceKey: string]: {
-      readonly value: string
-      readonly blockNumber: number | undefined
-    }
-  }
-}
-
-export function balanceKey({
-  chainId,
-  address,
-  tokenAddress
-}: {
-  chainId: number
-  address: string
-  tokenAddress?: string // undefined for ETH
-}): string {
-  return `${chainId}-${address}-${tokenAddress ?? 'ETH'}`
-}
-
-const initialState: WalletState = {
-  balanceListeners: {},
-  tokenBalanceListeners: {},
-  balances: {}
-}
-
-export default createReducer(initialState, builder =>
-  builder
-    .addCase(startListeningForTokenBalances, (state, { payload: combos }) => {
-      combos.forEach(combo => {
-        const [checksummedTokenAddress, checksummedAddress] = [isAddress(combo.tokenAddress), isAddress(combo.address)]
-        if (!checksummedAddress || !checksummedTokenAddress) {
-          console.error('invalid combo', combo)
-          return
-        }
-        state.tokenBalanceListeners[checksummedAddress] = state.tokenBalanceListeners[checksummedAddress] ?? {}
-        state.tokenBalanceListeners[checksummedAddress][checksummedTokenAddress] =
-          (state.tokenBalanceListeners[checksummedAddress][checksummedTokenAddress] ?? 0) + 1
-      })
-    })
-    .addCase(stopListeningForTokenBalances, (state, { payload: combos }) => {
-      combos.forEach(combo => {
-        const [checksummedTokenAddress, checksummedAddress] = [isAddress(combo.tokenAddress), isAddress(combo.address)]
-        if (!checksummedAddress || !checksummedTokenAddress) {
-          console.error('invalid combo', combo)
-          return
-        }
-        if (!state.tokenBalanceListeners[checksummedAddress]) return
-        if (!state.tokenBalanceListeners[checksummedAddress][checksummedTokenAddress]) return
-        if (state.tokenBalanceListeners[checksummedAddress][checksummedTokenAddress] === 1) {
-          delete state.tokenBalanceListeners[checksummedAddress][checksummedTokenAddress]
-        } else {
-          state.tokenBalanceListeners[checksummedAddress][checksummedTokenAddress]--
-        }
-      })
-    })
-    .addCase(startListeningForBalance, (state, { payload: { addresses } }) => {
-      addresses.forEach(address => {
-        const checksummedAddress = isAddress(address)
-        if (!checksummedAddress) {
-          console.error('invalid address', address)
-          return
-        }
-        state.balanceListeners[checksummedAddress] = (state.balanceListeners[checksummedAddress] ?? 0) + 1
-      })
-    })
-    .addCase(stopListeningForBalance, (state, { payload: { addresses } }) => {
-      addresses.forEach(address => {
-        const checksummedAddress = isAddress(address)
-        if (!checksummedAddress) {
-          console.error('invalid address', address)
-          return
-        }
-        if (!state.balanceListeners[checksummedAddress]) return
-        if (state.balanceListeners[checksummedAddress] === 1) {
-          delete state.balanceListeners[checksummedAddress]
-        } else {
-          state.balanceListeners[checksummedAddress]--
-        }
-      })
-    })
-    .addCase(updateTokenBalances, (state, { payload: { chainId, address, blockNumber, tokenBalances } }) => {
-      const checksummedAddress = isAddress(address)
-      if (!checksummedAddress) return
-      Object.keys(tokenBalances).forEach(tokenAddress => {
-        const checksummedTokenAddress = isAddress(tokenAddress)
-        if (!checksummedTokenAddress) return
-        const balance = tokenBalances[checksummedTokenAddress]
-        const key = balanceKey({ chainId, address: checksummedAddress, tokenAddress: checksummedTokenAddress })
-        const data = state.balances[key]
-        if (!data || data.blockNumber === undefined || data.blockNumber <= blockNumber) {
-          state.balances[key] = { value: balance, blockNumber }
-        }
-      })
-    })
-    .addCase(updateEtherBalances, (state, { payload: { etherBalances, chainId, blockNumber } }) => {
-      Object.keys(etherBalances).forEach(address => {
-        const checksummedAddress = isAddress(address)
-        if (!checksummedAddress) return
-
-        const balance = etherBalances[checksummedAddress]
-        const key = balanceKey({ chainId, address: checksummedAddress })
-        const data = state.balances[key]
-        if (!data || data.blockNumber === undefined || data.blockNumber <= blockNumber) {
-          state.balances[key] = { value: balance, blockNumber }
-        }
-      })
-    })
-)

src/state/wallet/updater.tsx

-import { BalanceMap, getEtherBalances, getTokensBalance } from '@mycrypto/eth-scan'
-import { useEffect, useMemo } from 'react'
-import { useDispatch, useSelector } from 'react-redux'
-import { useActiveWeb3React } from '../../hooks'
-import { useBlockNumber } from '../application/hooks'
-import { AppDispatch, AppState } from '../index'
-import { updateEtherBalances, updateTokenBalances } from './actions'
-import { balanceKey } from './reducer'
-
-function convertBalanceMapValuesToString(balanceMap: BalanceMap): { [key: string]: string } {
-  return Object.keys(balanceMap).reduce<{ [key: string]: string }>((map, key) => {
-    map[key] = balanceMap[key].toString()
-    return map
-  }, {})
-}
-
-export default function Updater() {
-  const { chainId, library } = useActiveWeb3React()
-  const lastBlockNumber = useBlockNumber()
-  const dispatch = useDispatch<AppDispatch>()
-  const ethBalanceListeners = useSelector<AppState, AppState['wallet']['balanceListeners']>(state => {
-    return state.wallet.balanceListeners
-  })
-  const tokenBalanceListeners = useSelector<AppState, AppState['wallet']['tokenBalanceListeners']>(state => {
-    return state.wallet.tokenBalanceListeners
-  })
-  const allBalances = useSelector<AppState, AppState['wallet']['balances']>(state => state.wallet.balances)
-
-  const activeETHListeners: string[] = useMemo(() => {
-    return Object.keys(ethBalanceListeners).filter(address => ethBalanceListeners[address] > 0) // redundant check
-  }, [ethBalanceListeners])
-
-  const activeTokenBalanceListeners: { [address: string]: string[] } = useMemo(() => {
-    return Object.keys(tokenBalanceListeners).reduce<{ [address: string]: string[] }>((map, address) => {
-      const tokenAddresses = Object.keys(tokenBalanceListeners[address]).filter(
-        tokenAddress => tokenBalanceListeners[address][tokenAddress] > 0 // redundant check
-      )
-      map[address] = tokenAddresses
-      return map
-    }, {})
-  }, [tokenBalanceListeners])
-
-  const ethBalancesNeedUpdate: string[] = useMemo(() => {
-    if (!chainId || !lastBlockNumber) return []
-    return activeETHListeners.filter(address => {
-      const data = allBalances[balanceKey({ chainId, address })]
-      if (!data || !data.blockNumber) return true
-      return data.blockNumber < lastBlockNumber
-    })
-  }, [activeETHListeners, allBalances, chainId, lastBlockNumber])
-
-  const tokenBalancesNeedUpdate: { [address: string]: string[] } = useMemo(() => {
-    if (!chainId || !lastBlockNumber) return {}
-    return Object.keys(activeTokenBalanceListeners).reduce<{ [address: string]: string[] }>((map, address) => {
-      const needsUpdate =
-        activeTokenBalanceListeners[address]?.filter(tokenAddress => {
-          const data = allBalances[balanceKey({ chainId, tokenAddress, address })]
-          if (!data || !data.blockNumber) return true
-          return data.blockNumber < lastBlockNumber
-        }) ?? []
-      if (needsUpdate.length > 0) {
-        map[address] = needsUpdate
-      }
-      return map
-    }, {})
-  }, [activeTokenBalanceListeners, allBalances, chainId, lastBlockNumber])
-
-  useEffect(() => {
-    if (!library || !chainId || !lastBlockNumber || ethBalancesNeedUpdate.length === 0) return
-    getEtherBalances(library, ethBalancesNeedUpdate)
-      .then(balanceMap => {
-        dispatch(
-          updateEtherBalances({
-            blockNumber: lastBlockNumber,
-            chainId,
-            etherBalances: convertBalanceMapValuesToString(balanceMap)
-          })
-        )
-      })
-      .catch(error => {
-        console.error('balance fetch failed', ethBalancesNeedUpdate, error)
-      })
-  }, [library, ethBalancesNeedUpdate, dispatch, lastBlockNumber, chainId])
-
-  useEffect(() => {
-    if (!library || !chainId || !lastBlockNumber) return
-    Object.keys(tokenBalancesNeedUpdate).forEach(address => {
-      if (tokenBalancesNeedUpdate[address].length === 0) return
-      getTokensBalance(library, address, tokenBalancesNeedUpdate[address])
-        .then(tokenBalanceMap => {
-          dispatch(
-            updateTokenBalances({
-              address,
-              chainId,
-              blockNumber: lastBlockNumber,
-              tokenBalances: convertBalanceMapValuesToString(tokenBalanceMap)
-            })
-          )
-        })
-        .catch(error => {
-          console.error(`failed to get token balances`, address, tokenBalancesNeedUpdate[address], error)
-        })
-    })
-  }, [library, tokenBalancesNeedUpdate, dispatch, lastBlockNumber, chainId])
-
-  return null
-}

src/utils/chunkArray.test.ts

+import chunkArray from './chunkArray'
+
+describe('#chunkArray', () => {
+  it('size 1', () => {
+    expect(chunkArray([1, 2, 3], 1)).toEqual([[1], [2], [3]])
+  })
+  it('size 0 throws', () => {
+    expect(() => chunkArray([1, 2, 3], 0)).toThrow('maxChunkSize must be gte 1')
+  })
+  it('size gte items', () => {
+    expect(chunkArray([1, 2, 3], 3)).toEqual([[1, 2, 3]])
+    expect(chunkArray([1, 2, 3], 4)).toEqual([[1, 2, 3]])
+  })
+  it('size exact half', () => {
+    expect(chunkArray([1, 2, 3, 4], 2)).toEqual([
+      [1, 2],
+      [3, 4]
+    ])
+  })
+  it('evenly distributes', () => {
+    const chunked = chunkArray([...Array(100).keys()], 40)
+
+    expect(chunked).toEqual([
+      [...Array(34).keys()],
+      [...Array(34).keys()].map(i => i + 34),
+      [...Array(32).keys()].map(i => i + 68)
+    ])
+
+    expect(chunked[0][0]).toEqual(0)
+    expect(chunked[2][31]).toEqual(99)
+  })
+})

src/utils/chunkArray.ts

+// chunks array into chunks of maximum size
+// evenly distributes items among the chunks
+export default function chunkArray<T>(items: T[], maxChunkSize: number): T[][] {
+  if (maxChunkSize < 1) throw new Error('maxChunkSize must be gte 1')
+  if (items.length <= maxChunkSize) return [items]
+
+  const numChunks: number = Math.ceil(items.length / maxChunkSize)
+  const chunkSize = Math.ceil(items.length / numChunks)
+
+  return [...Array(numChunks).keys()].map(ix => items.slice(ix * chunkSize, ix * chunkSize + chunkSize))
+}

tsconfig.strict.json

@@ -7,6 +7,7 @@
     "strictNullChecks": true,
     "noImplicitReturns": true,
     "noImplicitThis": true,
-    "noImplicitUseStrict": true
+    "noUnusedLocals": true,
+    "noFallthroughCasesInSwitch": true
   }
 }
\ No newline at end of file

yarn.lock

@@ -1349,21 +1349,6 @@
     "@ethersproject/properties" ">=5.0.0-beta.140"
     "@ethersproject/strings" ">=5.0.0-beta.136"
 
-"@ethersproject/abi@^5.0.0-beta.146":
-  version "5.0.0-beta.155"
-  resolved "https://registry.yarnpkg.com/@ethersproject/abi/-/abi-5.0.0-beta.155.tgz#b02cc0d54a44fd499be9778be53ed112220e3ecd"
-  integrity sha512-Oy00vZtb/Yr6gL9SJdKj7lmcL3e/04K5Dpd20ej52rXuRDYddCn9yHSkYWRM8/ZFFepFqeXmZ3XVN0ixLOJwcA==
-  dependencies:
-    "@ethersproject/address" ">=5.0.0-beta.134"
-    "@ethersproject/bignumber" ">=5.0.0-beta.138"
-    "@ethersproject/bytes" ">=5.0.0-beta.137"
-    "@ethersproject/constants" ">=5.0.0-beta.133"
-    "@ethersproject/hash" ">=5.0.0-beta.133"
-    "@ethersproject/keccak256" ">=5.0.0-beta.131"
-    "@ethersproject/logger" ">=5.0.0-beta.137"
-    "@ethersproject/properties" ">=5.0.0-beta.140"
-    "@ethersproject/strings" ">=5.0.0-beta.136"
-
 "@ethersproject/abstract-provider@>=5.0.0-beta.131":
   version "5.0.0-beta.139"
   resolved "https://registry.yarnpkg.com/@ethersproject/abstract-provider/-/abstract-provider-5.0.0-beta.139.tgz#a3b52c5494dcf67d277e2c0443813d9de746f8b4"
@@ -1468,7 +1453,7 @@
     "@ethersproject/properties" ">=5.0.0-beta.131"
     bn.js "^4.4.0"
 
-"@ethersproject/bignumber@>=5.0.0-beta.138", "@ethersproject/bignumber@^5.0.0-beta.135":
+"@ethersproject/bignumber@>=5.0.0-beta.138":
   version "5.0.0-beta.139"
   resolved "https://registry.yarnpkg.com/@ethersproject/bignumber/-/bignumber-5.0.0-beta.139.tgz#12a4fa5a76ee90f77932326311caf04e1de1cae0"
   integrity sha512-h1C1okCmPK3UVWwMGUbuCZykplJmD/TdknPQQHJWL/chK5MqBhyQ5o1Cay7mHXKCBnjWrR9BtwjfkAh76pYtFA==
@@ -2308,15 +2293,6 @@
     call-me-maybe "^1.0.1"
     glob-to-regexp "^0.3.0"
 
-"@mycrypto/eth-scan@^2.1.0":
-  version "2.1.0"
-  resolved "https://registry.yarnpkg.com/@mycrypto/eth-scan/-/eth-scan-2.1.0.tgz#9248b00000bff0b4ac9acda093d98eae0c84b93c"
-  integrity sha512-ncbWZDz6lL/8iFklGYt5MG2iTtTzJ6V6P10ht6PoOMHFG/2HiAm9AbKzwP0twYRh/oa/p/nSg3SrZer0Zuk7ZA==
-  dependencies:
-    "@ethersproject/abi" "^5.0.0-beta.146"
-    "@ethersproject/bignumber" "^5.0.0-beta.135"
-    isomorphic-unfetch "^3.0.0"
-
 "@nodelib/fs.stat@^1.1.2":
   version "1.1.3"
   resolved "https://registry.yarnpkg.com/@nodelib/fs.stat/-/fs.stat-1.1.3.tgz#2b5a3ab3f918cca48a8c754c08168e3f03eba61b"
@@ -8323,7 +8299,7 @@ fancy-log@^1.3.2:
     parse-node-version "^1.0.0"
     time-stamp "^1.0.0"
 
-fast-deep-equal@2.0.1, fast-deep-equal@^2.0.1:
+fast-deep-equal@^2.0.1:
   version "2.0.1"
   resolved "https://registry.yarnpkg.com/fast-deep-equal/-/fast-deep-equal-2.0.1.tgz#7b05218ddf9667bf7f370bf7fdb2cb15fdd0aa49"
   integrity sha1-ewUhjd+WZ79/Nwv3/bLLFf3Qqkk=
@@ -10351,14 +10327,6 @@ isomorphic-fetch@2.2.1:
     node-fetch "^1.0.1"
     whatwg-fetch ">=0.10.0"
 
-isomorphic-unfetch@^3.0.0:
-  version "3.0.0"
-  resolved "https://registry.yarnpkg.com/isomorphic-unfetch/-/isomorphic-unfetch-3.0.0.tgz#de6d80abde487b17de2c400a7ef9e5ecc2efb362"
-  integrity sha512-V0tmJSYfkKokZ5mgl0cmfQMTb7MLHsBMngTkbLY0eXvKqiVRRoZP04Ly+KhKrJfKtzC9E6Pp15Jo+bwh7Vi2XQ==
-  dependencies:
-    node-fetch "^2.2.0"
-    unfetch "^4.0.0"
-
 isstream@~0.1.2:
   version "0.1.2"
   resolved "https://registry.yarnpkg.com/isstream/-/isstream-0.1.2.tgz#47e63f7af55afa6f92e1500e690eb8b8529c099a"
@@ -12341,11 +12309,6 @@ node-fetch@^1.0.1, node-fetch@~1.7.1:
     encoding "^0.1.11"
     is-stream "^1.0.1"
 
-node-fetch@^2.2.0:
-  version "2.6.0"
-  resolved "https://registry.yarnpkg.com/node-fetch/-/node-fetch-2.6.0.tgz#e633456386d4aa55863f676a7ab0daa8fdecb0fd"
-  integrity sha512-8dG4H5ujfvFiqDmVu9fQ5bOHUC15JMjMY/Zumv26oOvvVJjM67KF8koCWIabKQ1GJIa9r2mMZscBq/TbdOcmNA==
-
 node-forge@0.9.0:
   version "0.9.0"
   resolved "https://registry.yarnpkg.com/node-forge/-/node-forge-0.9.0.tgz#d624050edbb44874adca12bb9a52ec63cb782579"
@@ -16532,13 +16495,6 @@ swarm-js@0.1.39:
     tar "^4.0.2"
     xhr-request-promise "^0.1.2"
 
-swr@0.1.18:
-  version "0.1.18"
-  resolved "https://registry.yarnpkg.com/swr/-/swr-0.1.18.tgz#be62df4cb8d188dc092305b35ecda1f3be8e61c1"
-  integrity sha512-lD31JxsD0bXdT7dyGVIB7MHcwgFp+HbBBOLt075hJT0sEgW01E3+EuCeB6fsavxZ2UjUZ3f+SbNMo9c8pv9uiA==
-  dependencies:
-    fast-deep-equal "2.0.1"
-
 symbol-observable@^1.1.0, symbol-observable@^1.2.0:
   version "1.2.0"
   resolved "https://registry.yarnpkg.com/symbol-observable/-/symbol-observable-1.2.0.tgz#c22688aed4eab3cdc2dfeacbb561660560a00804"
@@ -17063,11 +17019,6 @@ undertaker@^1.2.1:
     object.reduce "^1.0.0"
     undertaker-registry "^1.0.0"
 
-unfetch@^4.0.0:
-  version "4.1.0"
-  resolved "https://registry.yarnpkg.com/unfetch/-/unfetch-4.1.0.tgz#6ec2dd0de887e58a4dee83a050ded80ffc4137db"
-  integrity sha512-crP/n3eAPUJxZXM9T80/yv0YhkTEx2K1D3h7D1AJM6fzsWZrxdyRuLN0JH/dkZh1LNH8LxCnBzoPFCPbb2iGpg==
-
 unicode-canonical-property-names-ecmascript@^1.0.4:
   version "1.0.4"
   resolved "https://registry.yarnpkg.com/unicode-canonical-property-names-ecmascript/-/unicode-canonical-property-names-ecmascript-1.0.4.tgz#2619800c4c825800efdd8343af7dd9933cbe2818"