import std/options, chronos, web3, stew/byteutils, stint, results, chronicles import waku/incentivization/rpc const SimpleTransferGasUsed = Quantity(21000) const TxReceiptQueryTimeout = 3.seconds proc getTransactionByHash( txHash: TxHash, web3: Web3 ): Future[TransactionObject] {.async.} = await web3.provider.eth_getTransactionByHash(txHash) proc getMinedTransactionReceipt( txHash: TxHash, web3: Web3 ): Future[Result[ReceiptObject, string]] {.async.} = let txReceipt = web3.getMinedTransactionReceipt(txHash) if (await txReceipt.withTimeout(TxReceiptQueryTimeout)): return ok(txReceipt.value()) else: return err("Timeout on tx receipt query") proc getTxAndTxReceipt( txHash: TxHash, web3: Web3 ): Future[Result[(TransactionObject, ReceiptObject), string]] {.async.} = let txFuture = getTransactionByHash(txHash, web3) let receiptFuture = getMinedTransactionReceipt(txHash, web3) await allFutures(txFuture, receiptFuture) let tx = txFuture.read() let txReceipt = receiptFuture.read() if txReceipt.isErr: return err("Cannot get tx receipt") return ok((tx, txReceipt.get())) proc isEligibleTxId*( eligibilityProof: EligibilityProof, expectedToAddress: Address, expectedValue: UInt256, ethClient: string, ): Future[Result[void, string]] {.async.} = ## We consider a tx eligible, ## in the context of service incentivization PoC, ## if it is confirmed and pays the expected amount to the server's address. ## See spec: https://github.com/waku-org/specs/blob/master/standards/core/incentivization.md if eligibilityProof.proofOfPayment.isNone: return err("Eligibility proof is empty") var web3: Web3 try: web3 = await newWeb3(ethClient) except ValueError: let errorMsg = "Failed to set up a web3 provider connection: " & getCurrentExceptionMsg() error "exception in isEligibleTxId", error = $errorMsg return err($errorMsg) var tx: TransactionObject var txReceipt: ReceiptObject let txHash = TxHash.fromHex(byteutils.toHex(eligibilityProof.proofOfPayment.get())) try: let txAndTxReceipt = await getTxAndTxReceipt(txHash, web3) txAndTxReceipt.isOkOr: return err("Failed to fetch tx or tx receipt") (tx, txReceipt) = txAndTxReceipt.value() except ValueError: let errorMsg = "Failed to fetch tx or tx receipt: " & getCurrentExceptionMsg() error "exception in isEligibleTxId", error = $errorMsg return err($errorMsg) # check that it is not a contract creation tx let toAddressOption = txReceipt.to if toAddressOption.isNone: # this is a contract creation tx return err("A contract creation tx is not eligible") # 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 err("A contract call tx is not eligible") # check that the to address is "as expected" let toAddress = toAddressOption.get() if toAddress != expectedToAddress: return err("Wrong destination address: " & $toAddress) # check that the amount is "as expected" let txValue = tx.value if txValue != expectedValue: return err("Wrong tx value: got " & $txValue & ", expected " & $expectedValue) defer: await web3.close() return ok()