如何批准令牌，然后从后端发送

Question

我创建了这样的简单合同：

pragma solidity ^0.8.0;

import '@openzeppelin/contracts/token/ERC20/IERC20.sol';

contract PaymentProcessor {
    address public admin;
    IERC20 public dai;

    event PaymentDone (
        address payer,
        uint amount,
        uint paymentId,
        uint date
    );

    constructor(address adminAdress, address daiAddress) public {
        admin = adminAdress;
        dai = IERC20(daiAddress);
    }

    function pay(uint amount, uint paymentId) external {
        dai.transferFrom(msg.sender, admin, amount);
        emit PaymentDone(msg.sender, amount, paymentId, block.timestamp);
    }
}

我现在可以从前端应用程序发送带有元掩码的交易

// approve send of token
const tx1 = await dai.approve(proc.address, ethers.utils.parseEther('100'));
await tx1.wait();
console.log(tx1);
// call cotnract to send token to main address
const tx2 = await proc.pay(ethers.utils.parseEther('100'), '1111');
await tx2.wait();
console.log(tx2)

我想要完成的是从前端批准支出令牌，然后从后端批准将这些批准的令牌发送到不同的地址。如果是的话，你能告诉我连接和交易发送应该是什么样子吗？我正在使用以太币连接到网络。