We do a lil OTC, inspired by https://twitter.com/0xngmi/status/1638537074318909442?s=20

LilOTC.sol

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.4;

import "https://github.com/transmissions11/solmate/blob/main/src/tokens/ERC721.sol";
import "https://github.com/transmissions11/solmate/blob/main/src/utils/SafeTransferLib.sol";

struct OTC {
    address to;
    ERC20 tkn0;
    uint256 tkn0amt;
    ERC20 tkn1;
    uint256 tkn1amt;
    uint256 deadline;
}

contract LilOTC is ERC721("OTC", "OTC") {
    using SafeTransferLib for ERC20;

    event Created(OTC otc);

    event Settled(uint256 indexed id);

    uint256 public count;

    mapping(uint256 => OTC) public otcs;

    // CREATE

    function create(OTC calldata otc) public payable virtual returns (uint256 id) {
        unchecked {
            otcs[id = ++count] = otc;
        }

        _mint(msg.sender, id);

        otc.tkn0.safeTransferFrom(msg.sender, address(this), otc.tkn0amt);

        emit Created(otc);
    }

    // SETTLE

    function settle(uint256 id) public payable virtual {
        OTC storage otc = otcs[id];

        if (block.timestamp < otc.deadline) {
            otc.tkn1.safeTransferFrom(ownerOf(id), otc.to, otc.tkn1amt);
        } else {
            otc.tkn0.safeTransfer(otc.to, otc.tkn0amt);
        }

        delete otcs[id];

        emit Settled(id);
    }

    // METADATA

    function tokenURI(uint256) public view override virtual returns (string memory) {
        return ""; // placeholder
    }
}