Describe a market.
Get a hook.

pragma solidity ^0.8.26;

import {BaseHook} from "v4-periphery/BaseHook.sol";
import {IPoolManager} from "v4-core/interfaces/IPoolManager.sol";
import {PoolKey} from "v4-core/types/PoolKey.sol";
import {VolatilityOracle} from "./oracles/VolOracle.sol";

/// @title VolatilityPunish
/// @notice Scales sell tax by realized volatility
contract VolatilityPunish is BaseHook {
    uint256 constant VOL_THRESHOLD = 6e16;  // 6%
    uint256 constant BASE_TAX      = 5e15;  // 0.5%
    uint256 constant MAX_TAX       = 8e16;  // 8.0%
    uint256 constant COOLDOWN      = 12;    // blocks

    VolatilityOracle public oracle;

    event VolatilityPunish(address indexed seller, uint256 tax);

    function beforeSwap(
        address sender,
        PoolKey calldata key,
        IPoolManager.SwapParams calldata params,
        bytes calldata
    ) external override returns (bytes4, BeforeSwapDelta, uint24) {
        uint256 vol = oracle.realized(key.toId());

        if (vol > VOL_THRESHOLD && params.zeroForOne) {
            uint256 scale = ((vol - VOL_THRESHOLD) * MAX_TAX) /
                            (18e16 - VOL_THRESHOLD);
            uint256 tax = BASE_TAX + scale;

            _collectTax(sender, tax);
            _route(tax, 4000, 3000, 3000); // burn / lp / holders
            emit VolatilityPunish(sender, tax);
        }

        return (
            IHooks.beforeSwap.selector,
            BeforeSwapDeltaLibrary.ZERO_DELTA,
            0
        );
    }
}