Price logic for tokens usin cryptocompare

gas-relayer/plugins/token-utils.js

@@ -1,15 +1,40 @@
+const axios = require('axios');
+
 class TokenUtils {
-    constructor(tokenConfig){
+    constructor(tokenConfig, gasPrice){
+        this.gasPrice = gasPrice;
         this.name = tokenConfig.name || "";
         this.symbol = tokenConfig.symbol || "";
         this.minRelayFactor = tokenConfig.minRelayFactor || 1;
     }
 
-    getFactor(){
-        // TODO get price from somewhere
-        return 100000;
+    async getRate(){
+        // Using cryptocompare API
+        const doc = await axios.get('https://min-api.cryptocompare.com/data/price?fsym=' + this.symbol + '&tsyms=ETH');
+        return parseFloat(doc.data.ETH);
+    }
+
+    calculateMinGasPrice(estimatedGas, currentPrice){
+        // Example
+        // Cost for a simple ETH transaction: 21000
+        // Rate between SNT & ETH = 0.0001562;
+        //
+        // Total SNT that should be spent for a transaction at the previous price:
+        // 21000 / 0.0001562 = 134443021
+        //
+        // Min Gas Price = Total SNT / Cost for Transaction
+        // 134443021 / 21000 = 6402
+
+        const totalGasCost = parseInt(estimatedGas, 10) * this.gasPrice;
+        const totalTokenCost = totalGasCost / currentPrice;
+        const minGasPrice = Math.ceil(totalTokenCost / totalGasCost);
+
+        return minGasPrice;
     }
 }
 
 
+
+
+
 module.exports = TokenUtils;

gas-relayer/src/contract-settings.js

@@ -35,7 +35,7 @@ class ContractSettings {
         for(let token in this.tokens){
             if(this.tokens[token].pricePlugin !== undefined){
                 let PricePlugin = require(this.tokens[token].pricePlugin);
-                this.tokens[token].pricePlugin = new PricePlugin(this.tokens[token]);
+                this.tokens[token].pricePlugin = new PricePlugin(this.tokens[token], this.config.gasPrice);
             }
         }
     }

gas-relayer/src/service.js

@@ -168,7 +168,10 @@ events.on('server:listen', (shhOptions, settings) => {
                                 reply,
                                 settings.buildStrategy("./strategy/AvailabilityStrategy", message.topic)
                               );
-          if(validationResult.success) reply(validationResult.message);
+          if(validationResult.success && validationResult.message) {
+            messagesCheckSum[inputCheckSum] = (new Date().getTime());
+            reply(validationResult.message);
+          }
   
           break;
         default: 
@@ -188,6 +191,7 @@ const deleteOldChecksums = () => {
     }
   }
 };
+
 setInterval(deleteOldChecksums, 3600000);
 
 // Daemon helper functions

gas-relayer/src/strategy/AvailabilityStrategy.js

@@ -11,23 +11,29 @@ class AvailabilityStrategy extends Strategy {
      * @param {object} input - Object obtained from an 'availability' request. It expects an object with this structure `{contract, address, action, gasToken, gasPrice}`
      * @returns {object} Status of validation, and minimum price
      */
-    execute(input){
+    async execute(input){
         // Verifying if token is allowed
         const token = this.settings.getToken(input.gasToken);
         if(token == undefined) return {success: false, message: "Token not allowed"};
 
-        // TODO: Validate gasPrice, and return the minPrice accepted
-        const minPrice = 0.00;
 
+        // Get Price
+        const tokenRate = await token.pricePlugin.getRate();
+        const minRate = token.minAcceptedRate;
+
+        if(tokenRate >= minRate){ // TODO: verify this
             return {
                 success: true,
                 message: {
                     message: "Available",
                     address: this.config.node.blockchain.account,
-                minAcceptedGasPrice: minPrice,
+                    acceptedRate: tokenRate,
                     gasPriceUsed: this.config.gasPrice
                 }
             };
+        } else {
+            return {success: true};
+        }
     }
 
 }

gas-relayer/src/strategy/IdentityStrategy.js

@@ -86,6 +86,19 @@ class IdentityStrategy extends Strategy {
             }
         }
 
+        // Get Price
+        const tokenRate = await token.pricePlugin.getRate();
+        const minRate = token.minAcceptedRate;
+
+        if(tokenRate < minRate){ // TODO: verify this. Maybe we want to accept a minRate instead of just simply not processing the trx
+            return {success: false, message: "Not accepting " + token.symbol + " at current rate. (Min rate: " + token.minAcceptedRate+ ")"};
+        }
+
+        const minGasPrice = this.web3.utils.toBN(token.pricePlugin.calculateMinGasPrice(estimatedGas.toString(10), tokenRate));
+        if(gasPrice.lt(minGasPrice)){
+            return {success: false, message: "Gas price is less than the required amount (" + minGasPrice.toString(10) + ")"};
+        }
+
         return {
             success: true,
             message: "Valid transaction",

gas-relayer/src/strategy/SNTStrategy.js

@@ -29,6 +29,20 @@ class SNTStrategy extends Strategy {
             to: input.contract
         });
 
+        // Get Price
+        const tokenRate = await token.pricePlugin.getRate();
+        const minRate = token.minAcceptedRate;
+
+        if(tokenRate < minRate){ // TODO: verify this. Maybe we want to accept a minRate instead of just simply not processing the trx
+            return {success: false, message: "Not accepting " + token.symbol + " at current rate. (Min rate: " + token.minAcceptedRate+ ")"};
+        }
+
+        const gasPrice = this.web3.utils.toBN(params('_gasPrice'));
+        const minGasPrice = this.web3.utils.toBN(token.pricePlugin.calculateMinGasPrice(estimatedGas.toString(10), tokenRate));
+        if(gasPrice.lt(minGasPrice)){
+            return {success: false, message: "Gas price is less than the required amount (" + minGasPrice.toString(10) + ")"};
+        }
+
         if(input.functionName == TransferSNT){
             const gas = this.web3.utils.toBN(estimatedGas);
             const value = this.web3.utils.toBN(params('_amount'));