BaseV4Hook

// SPDX-License-Identifier: MIT
// cairoeth/base-v4-hook — excerpt. Full file: source.url
abstract contract BaseV4Hook is BaseHook, ProtocolFees, NoDelegateCall, ERC6909Claims, Extsload, Exttload {
    using PoolIdLibrary for PoolKey;
    using Pool for *;
    using Position for mapping(bytes32 => Position.Info);
    using CurrencyDelta for Currency;
    using CurrencyReserves for Currency;
    using LPFeeLibrary for uint24;

/// @return BeforeSwapDelta The hook's delta in specified and unspecified currencies.
///         Positive: the hook is owed/took currency, negative: the hook owes/sent currency
/// @return uint24 Optionally override the lp fee, only used if three conditions are met:
///         1. the Pool has a dynamic fee, 2. the value's 2nd highest bit is set
///         (23rd bit, 0x400000), and 3. the value is less than or equal to the maximum fee (1 million)
function beforeSwap(address sender, PoolKey calldata key, IPoolManager.SwapParams calldata params, bytes calldata)
    external virtual override onlyByPoolManager returns (bytes4, BeforeSwapDelta, uint24)
{
    return _beforeSwap(
        sender,
        key,
        Pool.SwapParams({
            tickSpacing: key.tickSpacing,
            zeroForOne: params.zeroForOne,
            amountSpecified: params.amountSpecified,
            sqrtPriceLimitX96: params.sqrtPriceLimitX96,
            lpFeeOverride: 0
        })
    );
}

/// @dev Execute swap with custom logic — implement this in your subclass
function _beforeSwap(address sender, PoolKey calldata key, Pool.SwapParams memory params)
    internal virtual returns (bytes4, BeforeSwapDelta, uint24);

function getHookPermissions() public pure virtual override returns (Hooks.Permissions memory) {
    return Hooks.Permissions({
        beforeInitialize: false,
        afterInitialize: false,
        beforeAddLiquidity: true, // -- liquidity must be deposited here directly -- //
        afterAddLiquidity: false,
        beforeRemoveLiquidity: false,
        afterRemoveLiquidity: false,
        beforeSwap: true, // -- custom curve handler -- //
        afterSwap: false,
        beforeDonate: false,
        afterDonate: false,
        beforeSwapReturnDelta: true, // -- enable custom curve by skipping poolmanager swap -- //
        afterSwapReturnDelta: false,
        afterAddLiquidityReturnDelta: false,
        afterRemoveLiquidityReturnDelta: false
    });
}