Quickstart: Subscribe and Redeem USYC

import "../IERC20.sol";

interface ITeller {
  function buy(uint256 _amount) external returns (uint256);
  function sell(uint256 _amount) external returns (uint256);
}

ITeller teller = ITeller(0x0a5ea26fdd38cf2acb06dc64198374c337879dab);

// Subscribe to USYC
IERC20 pyusd = IERC20(0x6c3ea9036406852006290770BEdFcAbA0e23A0e8);
uint256 paying = 100 * 1e6; // 100.000000 PYUSD
pyusd.approve(address(teller), paying);
uint256 usycPurchased = teller.buy(paying);

// Redeem USYC
IERC20 usyc = IERC20(0x136471a34f6ef19fE571EFFC1CA711fdb8E49f2b);
uint256 selling = 100 * 1e6; // 100.000000 USYC
usyc.approve(address(teller), selling);
uint256 usdcPayout = teller.sell(selling);

import { Address, erc20ABI, writeContract } from '@wagmi/core'

const USYC_TELLER_ABI = [
  {
    inputs: [{ internalType: 'uint256', name: '_amount', type: 'uint256' }],
    name: 'sell',
    outputs: [{ internalType: 'uint256', name: '', type: 'uint256' }],
    stateMutability: 'nonpayable',
    type: 'function',
  },
  {
    inputs: [{ internalType: 'uint256', name: '_amount', type: 'uint256' }],
    name: 'buy',
    outputs: [{ internalType: 'uint256', name: '', type: 'uint256' }],
    stateMutability: 'nonpayable',
    type: 'function',
  },
] as const

// Ethereum mainnet addresses
const USYC_TELLER_ADDRESS: Address =
  '0xAAF405C48e8c73aECedA3E40fE34e5C0ff8f5DE5'
const USDC_ADDRESS: Address = '0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48'
const USYC_ADDRESS: Address = '0x136471a34f6ef19fE571EFFC1CA711fdb8E49f2b'

const ONE_HUNDRED_USDC = BigInt(100_000000) // USDC uses 6 decimals
const ONE_HUNDRED_USYC = BigInt(100_000000) // USYC uses 6 decimals

// Subscribe to USYC
export const approveUSYCTellerToSpendUSDC = () =>
  writeContract({
    chainId: 1,
    address: USDC_ADDRESS,
    abi: erc20ABI,
    functionName: 'approve',
    args: [USYC_TELLER_ADDRESS, ONE_HUNDRED_USDC],
  })

export const buyUSYC = () =>
  writeContract({
    address: USYC_TELLER_ADDRESS,
    chainId: 1,
    abi: USYC_TELLER_ABI,
    functionName: 'buy',
    args: [ONE_HUNDRED_USDC],
  })

// Redeem USYC
export const approveUSYCTellerToSpendUSYC = () =>
  writeContract({
    chainId: 1,
    address: USYC_ADDRESS,
    abi: erc20ABI,
    functionName: 'approve',
    args: [USYC_TELLER_ADDRESS, ONE_HUNDRED_USYC],
  })

export const sellUSYC = () =>
  writeContract({
    address: USYC_TELLER_ADDRESS,
    chainId: 1,
    abi: USYC_TELLER_ABI,
    functionName: 'sell',
    args: [ONE_HUNDRED_USYC],
  })