nwaku/waku/incentivization/txid_proof.nim

import std/options, chronos, web3, stew/byteutils, stint, strutils

import waku/incentivization/rpc

const SimpleTransferGasUsed = Quantity(21000)

proc checkTxIdIsEligible(txHash: TxHash, ethClient: string): Future[bool] {.async.} =
  let web3 = await newWeb3(ethClient)
  try:
    let tx = await web3.provider.eth_getTransactionByHash(txHash)
    let txReceipt = await web3.getMinedTransactionReceipt(txHash)
    # check that it is not a contract creation tx
    let toAddressOption = txReceipt.to
    if toAddressOption.isNone:
      # this is a contract creation tx
      return false
    # check that it is a simple transfer (not a contract call)
    # a simple transfer uses 21000 gas
    let gasUsed = txReceipt.gasUsed
    let isSimpleTransferTx = (gasUsed == SimpleTransferGasUsed)
    if not isSimpleTransferTx:
      return false
    # check that the amount is "as expected" (hard-coded for now)
    let txValue = tx.value
    let hasExpectedValue = (txValue == 200500000000005063.u256)
    # check that the to address is "as expected" (hard-coded for now)
    let toAddress = toAddressOption.get()
    let hasExpectedToAddress =
      (toAddress == Address.fromHex("0x5e809a85aa182a9921edd10a4163745bb3e36284"))
    defer:
      await web3.close()
    return hasExpectedValue and hasExpectedToAddress
  except ValueError as e:
    return false

proc txidEligiblityCriteriaMet*(
    eligibilityProof: EligibilityProof, ethClient: string
): Future[bool] {.async.} =
  if eligibilityProof.proofOfPayment.isNone():
    return false
  let txHash = TxHash.fromHex(byteutils.toHex(eligibilityProof.proofOfPayment.get()))
  let txExists = await checkTxIdIsEligible(txHash, ethClient)
  return txExists