From 9557d2d9df2769f0bd1cabd56ffe8f3f86815c3d Mon Sep 17 00:00:00 2001
From: Raj Ranjan <rranjan01234@gmail.com>
Date: Thu, 14 Dec 2023 22:03:57 +0530
Subject: [PATCH] mainnet balance checks

---
 config.json                  |  1 +
 server.ts                    | 26 +++++++++++++++++++++++---
 types.ts                     |  2 ++
 utils/mainnetBalanceCheck.ts | 19 +++++++++++++++++++
 4 files changed, 45 insertions(+), 3 deletions(-)
 create mode 100644 utils/mainnetBalanceCheck.ts

diff --git a/config.json b/config.json
index 772468f..0208946 100644
--- a/config.json
+++ b/config.json
@@ -30,6 +30,7 @@
             "DECIMALS": 18,
             "RECALIBRATE": 30,
             "COUPON_REQUIRED": true,
+            "MAINNET_BALANCE_CHECK_RPC": "https://api.avax.network/ext/C/rpc",
             "RATELIMIT": {
                 "MAX_LIMIT": 1,
                 "WINDOW_SIZE": 1440
diff --git a/server.ts b/server.ts
index 9aa3631..4b3034c 100644
--- a/server.ts
+++ b/server.ts
@@ -22,6 +22,7 @@ import {
     DEBUG,
 } from './config.json'
 import { CouponService } from './CouponService/couponService'
+import { checkMainnetBalance } from './utils/mainnetBalanceCheck'
 
 dotenv.config()
 
@@ -128,13 +129,32 @@ router.post('/sendToken', captcha.middleware, async (req: any, res: any) => {
     // drip amount (native or erc20 token) for this request as per config
     const dripAmount = erc20Instance?.config.DRIP_AMOUNT ?? evm.config.DRIP_AMOUNT
 
+    /**
+     * MAINNET BALANCE OR COUPON VALIDATION checks
+     * 1. If mainnet balance check is enabled, users would be required to have mainnet balance
+     * 2. If coupon validation is enabled, users would need a specific coupon id to get tokens
+     * 3. If both are enabled, then any one would be sufficient
+     */
+
+    // mainnet balance checks
+    const mainnetCheckEnabledRPC = erc20Instance?.config.MAINNET_BALANCE_CHECK_RPC ?? evm.config.MAINNET_BALANCE_CHECK_RPC ?? false
+    let mainnetCheckPassed = false
+    if (mainnetCheckEnabledRPC && (await checkMainnetBalance(mainnetCheckEnabledRPC, address))) {
+        mainnetCheckPassed = true
+    }
+
     // validate coupon
     let couponValidity: CouponValidity = {isValid: false, amount: dripAmount}
-
     if (
+        // check coupon validation only if mainnet check failed (either no-balance or check not enabled)
+        !mainnetCheckPassed &&
+
+        // coupon checks
         couponConfig.IS_ENABLED &&
-        (erc20Instance && erc20Instance.config.COUPON_REQUIRED) ||
-        (erc20Instance === undefined && evm.config.COUPON_REQUIRED)
+        // if request is for erc20 tokens
+        ((erc20Instance && erc20Instance.config.COUPON_REQUIRED) ||
+        // if request is for evm native token
+        (erc20Instance === undefined && evm.config.COUPON_REQUIRED))
     ) {
         // if coupon is required but not passed in request
         if (coupon === undefined) {
diff --git a/types.ts b/types.ts
index 1817e1b..71bba96 100644
--- a/types.ts
+++ b/types.ts
@@ -37,6 +37,7 @@ export type ChainType = {
     DRIP_AMOUNT: number,
     RECALIBRATE?: number,
     COUPON_REQUIRED?: boolean,
+    MAINNET_BALANCE_CHECK_RPC?: string,
     RATELIMIT: {
         WINDOW_SIZE: number,
         MAX_LIMIT: number
@@ -64,6 +65,7 @@ export type ERC20Type = {
     MAX_PRIORITY_FEE?: string,
     MAX_FEE?: string,
     COUPON_REQUIRED?: boolean,
+    MAINNET_BALANCE_CHECK_RPC?: string,
 }
 
 export type CouponValidity = {
diff --git a/utils/mainnetBalanceCheck.ts b/utils/mainnetBalanceCheck.ts
new file mode 100644
index 0000000..22ae23d
--- /dev/null
+++ b/utils/mainnetBalanceCheck.ts
@@ -0,0 +1,19 @@
+import axios from "axios"
+
+export async function checkMainnetBalance(rpc: string, address: string, threshold = 0): Promise<boolean> {
+    try {
+        const response = await axios.post<any, any>(rpc, {
+            jsonrpc: "2.0",
+            method: "eth_getBalance",
+            params: [address, "latest"],
+            id: 1,
+        })
+        if (parseInt(response.data.result) > threshold) {
+            return true
+        }
+    } catch(err) {
+        console.error('ERROR: checkMainnetBalance', err)
+        return false
+    }
+    return false
+}