x402 Integration Guide

import { config } from "dotenv";
import express from "express";
import { paymentMiddleware, x402ResourceServer } from "@x402/express";
import { ExactEvmScheme } from "@x402/evm/exact/server";
import { HTTPFacilitatorClient } from "@x402/core/server";

config();

const evmAddress = process.env.EVM_ADDRESS as `0x${string}`;

if (!evmAddress) {
  console.error("Missing EVM_ADDRESS environment variable");
  process.exit(1);
}

const facilitatorUrl = process.env.FACILITATOR_URL;
if (!facilitatorUrl) {
  console.error("❌ FACILITATOR_URL environment variable is required");
  process.exit(1);
}

const facilitatorClient = new HTTPFacilitatorClient({ url: facilitatorUrl });
const app = express();

// Apply x402 payment middleware
app.use(
  paymentMiddleware(
    {
      "GET /weather": {
        accepts: [
          {
            scheme: "exact",
            price: "$0.02",                // Your price: $0.01 resource + $0.01 fee
            network: "eip155:8453",         // Base Mainnet
            payTo: evmAddress,              // ✅ YOUR merchant address
          },
        ],
        description: "Weather data",
        mimeType: "application/json",
      },
    },
    new x402ResourceServer(facilitatorClient)
      .register("eip155:8453", new ExactEvmScheme()),
  ),
);

app.get("/weather", (req, res) => {
  res.send({
    report: {
      weather: "sunny",
      temperature: 70,
    },
  });
});

app.listen(4021, () => {
  console.log(`🚀 Server listening at http://localhost:4021`);
  console.log(`💰 Pre-settlement fee collection enabled`);
});

import { config } from "dotenv";
import express from "express";
import { paymentMiddleware, Resource, type SolanaAddress } from "x402-express";

config(); 

const facilitatorUrl = process.env.FACILITATOR_URL as Resource;
const payTo = process.env.EVM_ADDRESS as `0x${string}` | SolanaAddress;

if (!facilitatorUrl || !payTo) {
  console.error("Missing required environment variables");
  process.exit(1);
}

const app = express();

app.use(
  paymentMiddleware(
    payTo,  // ✅ YOUR merchant address
    {
      "GET /weather": {
        price: "$0.02",          // $0.01 resource + $0.01 fee
        network: "base",         // Base Mainnet
      },
      "/premium/*": {
        // Or define atomic amounts
        price: {
          amount: "20000",       // 0.02 USDC (6 decimals)
          asset: {
            address: "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
            decimals: 6,
            eip712: {
              name: "USDC",
              version: "2",
            },
          },
        },
        network: "base",
      },
    },
    {
      url: facilitatorUrl,
    },
  ),
);

app.get("/weather", (req, res) => {
  res.send({
    report: {
      weather: "sunny",
      temperature: 70,
    },
  });
});

app.get("/premium/content", (req, res) => {
  res.send({
    content: "This is premium content",
  });
});

app.listen(4021, () => {
  console.log(`Server listening at http://localhost:4021`);
  console.log(`💰 Pre-settlement fee collection enabled`);
});

import { ethers } from "ethers";
import dotenv from "dotenv";
dotenv.config();

const NETWORKS = {
  sepolia: {
    name: "Base Sepolia",
    rpc: "https://sepolia.base.org",
    chainId: 84532,
    usdc: "0x036CbD53842c5426634e7929541eC2318f3dCF7e",
  },
  mainnet: {
    name: "Base Mainnet",
    rpc: "https://mainnet.base.org",
    chainId: 8453,
    usdc: "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
  },
};

const OXMETA_TREASURY = "0x5D791e3554D0e83f171126905Bda1640Bf6f9A8B";

const USDC_ABI = [
  "function approve(address spender, uint256 amount) external returns (bool)",
  "function allowance(address owner, address spender) external view returns (uint256)",
];

async function approveFacilitator() {
  const networkKey = process.env.NETWORK || "sepolia";
  const network = NETWORKS[networkKey];
  
  const privateKey = process.env.EVM_PRIVATE_KEY;
  if (!privateKey) {
    console.error("❌ EVM_PRIVATE_KEY required in .env");
    process.exit(1);
  }
  
  const provider = new ethers.JsonRpcProvider(network.rpc);
  const merchant = new ethers.Wallet(privateKey, provider);
  
  console.log(`\n📍 ${network.name}`);
  console.log(`   Merchant: ${merchant.address}`);
  console.log(`   Treasury: ${OXMETA_TREASURY}`);
  
  const usdc = new ethers.Contract(network.usdc, USDC_ABI, merchant);
  
  // Approve 100 USDC (10,000 settlements)
  const approvalAmount = ethers.parseUnits("100", 6);
  
  console.log(`\n💰 Approving 100 USDC for pre-settlement fee collection...`);
  console.log(`   ⚠️  Fee will be collected BEFORE each settlement`);
  
  const tx = await usdc.approve(OXMETA_TREASURY, approvalAmount);
  console.log(`   Transaction: ${tx.hash}`);
  
  await tx.wait();
  console.log(`✅ Approval successful!`);
  
  // Verify
  const allowance = await usdc.allowance(merchant.address, OXMETA_TREASURY);
  console.log(`   Allowance: ${ethers.formatUnits(allowance, 6)} USDC`);
  console.log(`   Settlements: ~${Math.floor(Number(ethers.formatUnits(allowance, 6)) / 0.01)}`);
  console.log(`\n   Note: $0.01 collected BEFORE each settlement execution`);
}

approveFacilitator().catch(console.error);

import { ethers } from "ethers";
import dotenv from "dotenv";
dotenv.config();

const NETWORKS = {
  sepolia: {
    name: "Base Sepolia",
    rpc: "https://sepolia.base.org",
    usdc: "0x036CbD53842c5426634e7929541eC2318f3dCF7e",
  },
  mainnet: {
    name: "Base Mainnet",
    rpc: "https://mainnet.base.org",
    usdc: "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
  },
};

const OXMETA_TREASURY = "0x5D791e3554D0e83f171126905Bda1640Bf6f9A8B";

const USDC_ABI = [
  "function allowance(address owner, address spender) external view returns (uint256)",
  "function balanceOf(address account) external view returns (uint256)",
];

async function checkNetwork(networkKey, merchantAddress) {
  const network = NETWORKS[networkKey];
  const provider = new ethers.JsonRpcProvider(network.rpc);
  const usdc = new ethers.Contract(network.usdc, USDC_ABI, provider);
  
  const [allowance, balance] = await Promise.all([
    usdc.allowance(merchantAddress, OXMETA_TREASURY),
    usdc.balanceOf(merchantAddress),
  ]);
  
  const allowanceFormatted = ethers.formatUnits(allowance, 6);
  const balanceFormatted = ethers.formatUnits(balance, 6);
  const settlements = Math.floor(Number(allowanceFormatted) / 0.01);
  
  console.log(`\n📍 ${network.name}`);
  console.log(`   USDC Balance: ${balanceFormatted} USDC`);
  console.log(`   Fee Allowance: ${allowanceFormatted} USDC`);
  console.log(`   Settlements Remaining: ${settlements}`);
  console.log(`   Fee Collection: PRE-SETTLEMENT`);
  
  if (settlements < 10) {
    console.log(`   ⚠️  Low - run: NETWORK=${networkKey} node approve-facilitator.mjs`);
  } else if (settlements < 50) {
    console.log(`   ⚠️  Getting low`);
  } else {
    console.log(`   ✅ Good`);
  }
  
  // Check if balance is sufficient for fees
  if (Number(balanceFormatted) < Number(allowanceFormatted)) {
    console.log(`   ⚠️  Warning: Balance < Allowance (pre-settlement will fail)`);
  }
}

async function main() {
  const merchantAddress = process.env.EVM_ADDRESS;
  
  if (!merchantAddress) {
    console.error("❌ Set EVM_ADDRESS in .env");
    process.exit(1);
  }
  
  console.log("=".repeat(60));
  console.log("0xmeta Facilitator Pre-Settlement Fee Allowance Check");
  console.log("=".repeat(60));
  console.log(`\n👤 Merchant: ${merchantAddress}`);
  console.log(`🏦 Treasury: ${OXMETA_TREASURY}`);
  console.log(`⏰ Fee Timing: PRE-SETTLEMENT (before customer payment)`);
  
  const networkArg = process.argv[2] || "both";
  
  if (networkArg === "both") {
    await checkNetwork("sepolia", merchantAddress);
    await checkNetwork("mainnet", merchantAddress);
  } else {
    await checkNetwork(networkArg, merchantAddress);
  }
  
  console.log("\n" + "=".repeat(60));
}

main().catch(console.error);