Enhance Hardhat etherscan configuration for multi-network support with ES6 syntax

hardhat.config.js

@@ -1,34 +1,93 @@
-require("@nomicfoundation/hardhat-toolbox");
+/**
+ * Environment Variables Required:
+ * 
+ * Network RPC URLs:
+ * - SEPOLIA_RPC_URL: Sepolia testnet RPC URL
+ * - MAINNET_RPC_URL: Ethereum mainnet RPC URL  
+ * - POLYGON_RPC_URL: Polygon mainnet RPC URL
+ * - ARBITRUM_RPC_URL: Arbitrum One mainnet RPC URL
+ * - BSC_RPC_URL: BSC mainnet RPC URL
+ * - INFURA_API_KEY: Infura project ID (fallback for RPC URLs)
+ * 
+ * Account Configuration:
+ * - PRIVATE_KEY: Private key for deployment account
+ * 
+ * Block Explorer API Keys:
+ * - ETHERSCAN_API_KEY: API key for Etherscan (Ethereum networks)
+ * - POLYGONSCAN_API_KEY: API key for PolygonScan
+ * - ARBISCAN_API_KEY: API key for Arbiscan (Arbitrum networks)
+ * - BSCSCAN_API_KEY: API key for BscScan
+ * 
+ * Optional:
+ * - REPORT_GAS: Set to any value to enable gas reporting
+ */
+
+import "@nomicfoundation/hardhat-toolbox";
 
 /** @type import('hardhat/config').HardhatUserConfig */
 const config = {
   solidity: "0.8.24",
   networks: {
+    // Local development network
     hardhat: {},
+
+    // Ethereum Sepolia testnet
     sepolia: {
       url: process.env.SEPOLIA_RPC_URL || `https://sepolia.infura.io/v3/${process.env.INFURA_API_KEY}`,
       accounts: process.env.PRIVATE_KEY ? [process.env.PRIVATE_KEY] : [],
     },
+
+    // Ethereum mainnet
     mainnet: {
       url: process.env.MAINNET_RPC_URL || `https://mainnet.infura.io/v3/${process.env.INFURA_API_KEY}`,
       accounts: process.env.PRIVATE_KEY ? [process.env.PRIVATE_KEY] : [],
     },
+
+    // Polygon mainnet
     polygon: {
       url: process.env.POLYGON_RPC_URL || `https://polygon-mainnet.infura.io/v3/${process.env.INFURA_API_KEY}`,
       accounts: process.env.PRIVATE_KEY ? [process.env.PRIVATE_KEY] : [],
     },
+
+    // Arbitrum One mainnet
+    arbitrum: {
+      url: process.env.ARBITRUM_RPC_URL || "https://arb1.arbitrum.io/rpc",
+      accounts: process.env.PRIVATE_KEY ? [process.env.PRIVATE_KEY] : [],
+    },
+
+    // BSC mainnet
     bsc: {
       url: process.env.BSC_RPC_URL || "https://bsc-dataseed1.binance.org",
       accounts: process.env.PRIVATE_KEY ? [process.env.PRIVATE_KEY] : [],
     },
   },
+
+  // Gas usage reporting configuration
   gasReporter: {
     enabled: process.env.REPORT_GAS !== undefined,
     currency: "USD",
   },
+
+  // Block explorer verification configuration
   etherscan: {
-    apiKey: process.env.ETHERSCAN_API_KEY,
+    apiKey: {
+      // Ethereum networks (mainnet, sepolia, etc.)
+      mainnet: process.env.ETHERSCAN_API_KEY,
+      sepolia: process.env.ETHERSCAN_API_KEY,
+
+      // Polygon networks
+      polygon: process.env.POLYGONSCAN_API_KEY,
+      polygonMumbai: process.env.POLYGONSCAN_API_KEY,
+
+      // Arbitrum networks
+      arbitrumOne: process.env.ARBISCAN_API_KEY,
+      arbitrumSepolia: process.env.ARBISCAN_API_KEY,
+
+      // BSC networks
+      bsc: process.env.BSCSCAN_API_KEY,
+      bscTestnet: process.env.BSCSCAN_API_KEY,
+    },
   },
 };
 
-module.exports = config;
+export default config;