Fee Calculations

// SPDX-License-Identifier: MIT
pragma solidity 0.8.28;


import {Assertion} from "../../lib/credible-std/src/Assertion.sol";

// Aerodrome style interface
interface IPool {
    function fee() external view returns (uint256);
    function stable() external view returns (bool);
}

// Check that fee invariants are maintained
contract AmmFeeVerificationAssertion is Assertion {
    IPool public pool = IPool(address(0xbeef));

    function fnSelectors() external pure override returns (bytes4[] memory assertions) {
        assertions = new bytes4[](1);
        assertions[0] = this.feeVerification.selector;
    }

    // Check that the fee is the same before and after the transaction
    // and that they maintain correct percentage based on stable or not
    // revert if the fee is not the same before and after the transaction
    function feeVerification() external {
        ph.forkPreState();
        uint256 preFee = pool.fee();
        bool preStable = pool.stable(); // check pool is stable or not
        ph.forkPostState();
        uint256 postFee = pool.fee();
        bool postStable = pool.stable(); // check pool is stable or not
        // Fee should be the same before and after the transaction
        require(preFee == postFee, "Fee is not the same before and after the transaction");
        // Pool should be stable before and after the transaction
        require(preStable == postStable, "Pool is not stable before and after the transaction");
        if (postStable) {
            require(postFee == 1, "Fee is not 0.1% for stable pool"); // Should be what the protocol defines
        } else {
            require(postFee == 25, "Fee is not 0.25% for non-stable pool"); // Should be what the protocol defines
        }
    }
}