fee check

.env.example

@@ -2,3 +2,5 @@ NET_ID=42
 RPC_URL=https://kovan.infura.io/v3/a3f4d001c1fc4a359ea70dd27fd9cb51
 PRIVATE_KEY=
 MIXER_ADDRESS=0x30AF2e92263C5387A8A689322BbfE60b6B0855C4
+# in wei
+DESIRED_FEE=10000000000000000

config.js

@@ -4,7 +4,8 @@ module.exports = {
   netId: process.env.NET_ID || 42,
   rpcUrl: process.env.RPC_URL || 'https://kovan.infura.io/v3/a3f4d001c1fc4a359ea70dd27fd9cb51',
   privateKey: process.env.PRIVATE_KEY,
-  mixerAddress: process.env.MIXER_ADDRESS || '0x30AF2e92263C5387A8A689322BbfE60b6B0855C4',
+  mixerAddress: process.env.MIXER_ADDRESS,
+  desiredFee: process.env.DESIRED_FEE || 10000000000000000, // 0.01 ETH
   defaultGasPrice: 1,
   gasOracleUrls: ['https://www.etherchain.org/api/gasPriceOracle', 'https://gasprice.poa.network/']
 }

index.js

@@ -1,16 +1,16 @@
-const { numberToHex, toWei, toHex } = require('web3-utils')
+const { numberToHex, toWei, toHex, toBN } = require('web3-utils')
 const Web3 = require('web3')
 const express = require('express')
 
 const app = express()
 app.use(express.json())
 app.use(function(req, res, next) {
-  res.header('Access-Control-Allow-Origin', '*') // update to match the domain you will make the request from
+  res.header('Access-Control-Allow-Origin', '*')
   res.header('Access-Control-Allow-Headers', 'Origin, X-Requested-With, Content-Type, Accept')
   next()
 })
 
-const { netId, rpcUrl, privateKey, mixerAddress, defaultGasPrice } = require('./config')
+const { netId, rpcUrl, privateKey, mixerAddress, defaultGasPrice, desiredFee } = require('./config')
 const { fetchGasPrice, isValidProof } = require('./utils')
 
 const web3 = new Web3(rpcUrl, null, { transactionConfirmationBlocks: 1 })
@@ -36,10 +36,11 @@ app.post('/relay', async (req, resp) => {
 
   let { pi_a, pi_b, pi_c, publicSignals } = req.body
 
-  // TODO
-  // if (bigInt(proof.publicSignals[3]) < getMinimumFee()) {
-  //   resp.status(403).send('Fee is too low')
-  // }
+  const fee = toBN(publicSignals[3])
+  if (fee.lt(toBN(desiredFee))) {
+    console.log('Fee is too low')
+    return resp.status(400).send('Fee is too low')
+  }
 
   try {
     const nullifier = publicSignals[1]