Interface.sol

// SPDX-License-Identifier: GPL-3.0
pragma solidity >=0.6.2 <0.9.0;

interface Token {
    enum TokenType {
        Fungible,
        NonFungible
    }
    struct Coin {
        string obverse;
        string reverse;
    }

    function transfer(address recipient, uint amount) external;
}