Borrower (Base Contract)

constructor(IFlashLoanRouter _router) {
    router = _router;
    settlementContract = _router.settlementContract();
}

function flashLoanAndCallBack(
    address lender,
    IERC20 token,
    uint256 amount,
    bytes calldata callBackData
) external onlyRouter

function approve(
    IERC20 token,
    address target,
    uint256 amount
) external onlySettlementContract

function triggerFlashLoan(
    address lender,
    IERC20 token,
    uint256 amount,
    bytes calldata callBackData
) internal virtual;

function flashLoanCallBack(bytes calldata callBackData) internal {
    router.borrowerCallBack(callBackData);
}

modifier onlyRouter() {
    require(msg.sender == address(router), "Not the router");
    _;
}

modifier onlySettlementContract() {
    require(
        msg.sender == address(settlementContract),
        "Only callable in a settlement"
    );
    _;
}

contract NewProviderBorrower is Borrower, IProviderCallback {
    constructor(IFlashLoanRouter _router) Borrower(_router) {}

    function triggerFlashLoan(
        address lender,
        IERC20 token,
        uint256 amount,
        bytes calldata callBackData
    ) internal override {
        // Call provider-specific flash loan function
        IProvider(lender).requestFlashLoan(
            address(token),
            amount,
            callBackData
        );
    }

    // Implement provider's callback
    function providerCallback(bytes calldata data) external {
        flashLoanCallBack(data);
    }
}