    function prepareLeverage(
        uint256 tokenId,
        uint128 liquidity,
        bool zeroForOne
    )
        internal
        view
        returns (
            address tokenFrom,
            address tokenTo,
            uint256 feeGrowthInside0LastX128,
            uint256 feeGrowthInside1LastX128,
            uint256 collateralFrom,
            uint256 collateralTo
        )
    {
        int24 tickLower;
        int24 tickUpper;
        (
            ,
            ,
            tokenFrom,
            tokenTo,
            ,
            tickLower,
            tickUpper,
            ,
            feeGrowthInside0LastX128,
            feeGrowthInside1LastX128,
            ,

        ) = UNI_POSITION_MANAGER.positions(tokenId);
// prepare data for swap
(
	cache.tokenFrom,
	cache.tokenTo,
	cache.feeGrowthInside0LastX128,
	cache.feeGrowthInside1LastX128,
	cache.collateralFrom,
	collateralTo
) = Base.prepareLeverage(params.tokenId, params.liquidity, params.zeroForOne);
// create a new lien
liens[keccak256(abi.encodePacked(msg.sender, lienId = _nextRecordId++))] = Lien.Info({
	tokenId: uint40(params.tokenId), // @audit
	liquidity: params.liquidity,
	token0PremiumPortion: cache.token0PremiumPortion,
	token1PremiumPortion: cache.token1PremiumPortion,
	startTime: uint32(block.timestamp),
	feeGrowthInside0LastX128: cache.feeGrowthInside0LastX128,
	feeGrowthInside1LastX128: cache.feeGrowthInside1LastX128,
	zeroForOne: params.zeroForOne
});
// obtain the position's latest FeeGrowthInside after increaseLiquidity
(, , , , , , , , cache.feeGrowthInside0LastX128, cache.feeGrowthInside1LastX128, , ) = Base
	.UNI_POSITION_MANAGER
	.positions(lien.tokenId);

// caculate the amounts owed since last fee collection during the borrowing period
(cache.token0Owed, cache.token1Owed) = Base.getOwedFee(
	cache.feeGrowthInside0LastX128,
	cache.feeGrowthInside1LastX128,
	lien.feeGrowthInside0LastX128,
	lien.feeGrowthInside1LastX128,
	lien.liquidity
);
