dai price

abis/ETHDAIOracle.json

@@ -0,0 +1,17 @@
+[
+    {
+      "constant": true,
+      "inputs": [],
+      "name": "getMedianPrice",
+      "outputs": [
+        {
+          "internalType": "uint256",
+          "name": "",
+          "type": "uint256"
+        }
+      ],
+      "payable": false,
+      "stateMutability": "view",
+      "type": "function"
+    }
+]

config.js

@@ -6,5 +6,6 @@ module.exports = {
   privateKey: process.env.PRIVATE_KEY,
   mixerAddress: process.env.MIXER_ADDRESS,
   defaultGasPrice: 2,
-  gasOracleUrls: ['https://www.etherchain.org/api/gasPriceOracle', 'https://gasprice.poa.network/']
+  gasOracleUrls: ['https://www.etherchain.org/api/gasPriceOracle', 'https://gasprice.poa.network/'],
+  ethdaiAddress: '0x7Ef645705cb7D401C5CD91a395cfcc3Db3C93689'
 }

index.js

@@ -21,16 +21,17 @@ app.use(function(req, res, next) {
 })
 
 const { netId, rpcUrl, privateKey, mixerAddress, defaultGasPrice } = require('./config')
-const { fetchGasPrice, isValidProof } = require('./utils')
+const { fetchGasPrice, isValidProof, fetchDAIprice } = require('./utils')
 
 const web3 = new Web3(rpcUrl, null, { transactionConfirmationBlocks: 1 })
 const account = web3.eth.accounts.privateKeyToAccount('0x' + privateKey)
 web3.eth.accounts.wallet.add('0x' + privateKey)
 web3.eth.defaultAccount = account.address
 
-const mixerABI = require('./mixerABI.json') 
+const mixerABI = require('./abis/mixerABI.json') 
 const mixer = new web3.eth.Contract(mixerABI, mixerAddress)
 const gasPrices = { fast: defaultGasPrice }
+const ethPriceInDai = toWei('200')
 
 app.get('/', function (req, res) {
   // just for testing purposes
@@ -87,5 +88,6 @@ app.listen(8000)
 
 if (Number(netId) === 1) {
   fetchGasPrice({ gasPrices })
+  fetchDAIprice({ ethPriceInDai, web3 })
   console.log('Gas price oracle started.')
 }

utils.js

@@ -1,6 +1,7 @@
 const fetch = require('node-fetch')
-const { isHexStrict } = require('web3-utils')
-const { gasOracleUrls } = require('./config')
+const { isHexStrict, hexToNumberString } = require('web3-utils')
+const { gasOracleUrls, ethdaiAddress } = require('./config')
+const oracleABI = require('./abis/ETHDAIOracle.json')
 
 async function fetchGasPrice({ gasPrices, oracleIndex = 0 }) {
   oracleIndex = (oracleIndex + 1) % gasOracleUrls.length
@@ -30,6 +31,17 @@ async function fetchGasPrice({ gasPrices, oracleIndex = 0 }) {
   }
 }
 
+async function fetchDAIprice({ ethPriceInDai, web3 }) {
+  try {
+    const ethDaiInstance = web3.eth.Contract(oracleABI, ethdaiAddress)
+    const price = await ethDaiInstance.methods.getMedianPrice().call()
+    ethPriceInDai = hexToNumberString(price)
+    setTimeout(() => fetchDAIprice({ ethPriceInDai, web3 }), 1000 * 30)
+  } catch(e) {
+    setTimeout(() => fetchDAIprice({ ethPriceInDai, web3 }), 1000 * 30)
+  }
+}
+
 function isValidProof(proof) {
   // validator expects `websnarkUtils.toSolidityInput(proof)` output
 
@@ -82,4 +94,4 @@ function sleep(ms) {
   return new Promise(resolve => setTimeout(resolve, ms))
 }
 
-module.exports = { fetchGasPrice, isValidProof, sleep }
+module.exports = { fetchGasPrice, isValidProof, sleep, fetchDAIprice }