Enable ERC20Permit by default about contracts-wizard HOT 7 CLOSED

const { ethers, network } = require(`hardhat`)

async function main() {
  const [ownerWallet, spenderWallet] = await ethers.getSigners()
  console.log(`Using network: ${network.name} (${network.config.chainId}), RPC url: ${network.config.url}`)

  const tokenContractName = `TESTERC20`
  const contractAddress = `0xc45Eb76AB6A29B64FD17A0F49e214a1f0a20A59D` // localhost

  const contractOfOwner = await ethers.getContractAt(tokenContractName, contractAddress, ownerWallet)
  const contractOfSpender = await ethers.getContractAt(tokenContractName, contractAddress, spenderWallet)

  let txRec

  const totalSupply = ethers.formatUnits(await contractOfOwner.totalSupply())

  console.log(`Initially:`)
  console.log(`owner has ${ethers.formatUnits(await contractOfOwner.balanceOf(ownerWallet.address))} of ${totalSupply} tokens`)
  console.log(`spender has ${ethers.formatUnits(await contractOfOwner.balanceOf(spenderWallet.address))} of ${totalSupply} tokens`)

  console.log(`owner has allowed spender to spend ${ethers.formatUnits(await contractOfOwner.allowance(ownerWallet.address, spenderWallet.address))} tokens`)

  console.log(`owner has ${ethers.formatUnits(await ethers.provider.getBalance(ownerWallet.address), `ether`)} of native currency`)
  console.log(`spender has ${ethers.formatUnits(await ethers.provider.getBalance(spenderWallet.address), `ether`)} of native currency`)

  const amountAllowedToSpend = ethers.parseUnits(`2`, `ether`)

  if (tokenHasPermit(await contractOfOwner.getDeployedCode())) {
    const deadline = Math.floor(Date.now() / 1000 + 3600)
    const splitSigAsArray = await getPermitSignature(contractOfOwner, ownerWallet, spenderWallet, amountAllowedToSpend, deadline) // ownerWallet does the signing in here to permit spender to spend his tokens
    console.log(`Owner has given his signature`)
    console.log(`Spender is now calling token's permit function with owner's signature so that she can spend his tokens...`)
    txRec = await contractOfSpender.permit( // any account can call the permit function, as long as there's a signature (values in splitSigAsArray) that proves that owner has permitted his tokens to be spent by spender. Gas is paid by permit function caller, so approval process is free for owner if he didn't call permit.
      ownerWallet.address,
      spenderWallet.address,
      amountAllowedToSpend,
      deadline,
      ...splitSigAsArray
    )
  } else {
    console.log(`Owner is calling token's approve function...`)
    txRec = await contractOfOwner.approve(spenderWallet.address, amountAllowedToSpend) // only owner can call approve to let spender spend his tokens. contractOfSpender.approve doesn't work.
  }
  await txRec.wait()

  console.log(`After permit / approve:`)
  console.log(`owner has allowed spender to spend ${ethers.formatUnits(await contractOfOwner.allowance(ownerWallet.address, spenderWallet.address))} tokens`)

  console.log(`owner has ${ethers.formatUnits(await ethers.provider.getBalance(ownerWallet.address), `ether`)} of native currency`)
  console.log(`spender has ${ethers.formatUnits(await ethers.provider.getBalance(spenderWallet.address), `ether`)} of native currency`)


  txRec = await contractOfSpender.transferFrom(ownerWallet.address, spenderWallet.address, amountAllowedToSpend) // spender calls transferFrom to transfer tokens from owner
  await txRec.wait()
  console.log(`After transferFrom:`)

  console.log(`spender took ${ethers.formatUnits(amountAllowedToSpend)} tokens from owner`)

  console.log(`owner has ${ethers.formatUnits(await contractOfOwner.balanceOf(ownerWallet.address))} of ${totalSupply} tokens`)
  console.log(`spender has ${ethers.formatUnits(await contractOfOwner.balanceOf(spenderWallet.address))} of ${totalSupply} tokens`)

}


const getPermitSignature = async (tokenContract, ownerWallet, spenderWallet, value, deadline) => { // owner allows spender to spend value wei tokens before deadline
  const [name, nonce] = await Promise.all([
    tokenContract.name(),
    tokenContract.nonces(ownerWallet.address),
  ])

  const domain = {
    name,
    version: `1`,
    chainId: network.config.chainId,
    verifyingContract: tokenContract.target
  }
  // console.log(`domain: ${JSON.stringify(domain)}`)

  const permitTypes = {
    Permit: [{
      name: `owner`,
      type: `address`
    },
    {
      name: `spender`,
      type: `address`
    },
    {
      name: `value`,
      type: `uint256`
    },
    {
      name: `nonce`,
      type: `uint256`
    },
    {
      name: `deadline`,
      type: `uint256`
    },
    ],
  }
  const permitValues = {
    owner: ownerWallet.address,
    spender: spenderWallet.address,
    value,
    nonce,
    deadline,
  }
  // console.log(`permitValues: ${JSON.stringify(permitValues)}`)

  const signature = await ownerWallet.signTypedData(domain, permitTypes, permitValues) // owner signs the data
  const { v, r, s } = ethers.Signature.from(signature)

  // const recoveredAddress = ethers.verifyTypedData(
  //   domain,
  //   permitTypes,
  //   permitValues,
  //   { v, r, s }
  // )
  // console.log(`recoveredAddress: ${recoveredAddress}. Verification ${recoveredAddress === ownerWallet.address ? "passed" : "failed"}.`)

  return [v, r, s]
}

const tokenHasPermit = bytecode => bytecode.includes(`d505accf`) && bytecode.includes(`7ecebe00`) // permit & nonces selectors


main().catch(error => {
  console.error(error)
  process.exitCode = 1
})