static hook fee example

contracts/src/examples/FixedHookFee.sol

@@ -30,7 +30,7 @@ contract FixedHookFee is BaseHook {
             beforeDonate: false,
             afterDonate: false,
             noOp: false,
-            accessLock: true
+            accessLock: true // -- Required to take a fee -- //
         });
     }
 
@@ -60,7 +60,7 @@ contract FixedHookFee is BaseHook {
         );
     }
 
-    /// @dev requires the lock pattern in order to call `poolManager.burn`
+    /// @dev requires the lock pattern in order to call poolManager.burn
     function handleCollectFee(address recipient, Currency currency) external returns (uint256 amount) {
         // convert the fee (Claims) into ERC20 tokens
         amount = poolManager.balanceOf(address(this), currency);

src/keywords.json

@@ -21,6 +21,13 @@
     "swap",
     "skip swap"
   ],
+  "/fees/fixed-hook-fee": [
+    "hook",
+    "hooks",
+    "fee",
+    "static fee",
+    "hook fee"
+  ],
   "/create-liquidity": [
     "liquidity",
     "LP",

src/nav.ts

@@ -32,7 +32,12 @@ export const HOOK_ROUTES: Route[] = [
   }
 ]
 
-const HACK_ROUTES: Route[] = []
+const FEE_ROUTES: Route[] = [
+  {
+    path: "fixed-hook-fee",
+    title: "Static Hook Fee"
+  }
+]
 
 export const TEST_ROUTES: Route[] = []
 
@@ -53,13 +58,13 @@ export const ROUTES_BY_CATEGORY = [
       path: `/hooks/${route.path}`,
     })),
   },
-  // {
-  //   title: "Hacks",
-  //   routes: HACK_ROUTES.map((route) => ({
-  //     ...route,
-  //     path: `/hacks/${route.path}`,
-  //   })),
-  // },
+  {
+    title: "Fees",
+    routes: FEE_ROUTES.map((route) => ({
+      ...route,
+      path: `/fees/${route.path}`,
+    })),
+  },
   // {
   //   title: "Tests",
   //   routes: TEST_ROUTES.map((route) => ({

src/pages/fees/fixed-hook-fee/EnableAccessLock.solsnippet

@@ -0,0 +1,16 @@
+import {Hooks} from "@uniswap/v4-core/contracts/libraries/Hooks.sol";
+
+function getHookPermissions() public pure override returns (Hooks.Permissions memory) {
+    return Hooks.Permissions({
+        beforeInitialize: false,
+        afterInitialize: false,
+        beforeModifyPosition: false,
+        afterModifyPosition: false,
+        beforeSwap: true,
+        afterSwap: false,
+        beforeDonate: false,
+        afterDonate: false,
+        noOp: false,
+        accessLock: true // -- ENABLE ACCESS LOCK --  //
+    });
+}

src/pages/fees/fixed-hook-fee/FixedHookFee.sol

@@ -0,0 +1,64 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.19;
+
+// TODO: update to v4-periphery/BaseHook.sol when its compatible
+import {BaseHook} from "../forks/BaseHook.sol";
+
+import {Hooks} from "@uniswap/v4-core/contracts/libraries/Hooks.sol";
+import {IPoolManager} from "@uniswap/v4-core/contracts/interfaces/IPoolManager.sol";
+import {PoolKey} from "@uniswap/v4-core/contracts/types/PoolKey.sol";
+import {PoolId, PoolIdLibrary} from "@uniswap/v4-core/contracts/types/PoolId.sol";
+import {BalanceDelta} from "@uniswap/v4-core/contracts/types/BalanceDelta.sol";
+import {Currency, CurrencyLibrary} from "@uniswap/v4-core/contracts/types/Currency.sol";
+
+contract FixedHookFee is BaseHook {
+    using PoolIdLibrary for PoolKey;
+    using CurrencyLibrary for Currency;
+
+    uint256 public constant FIXED_HOOK_FEE = 0.0001e18;
+
+    constructor(IPoolManager _poolManager) BaseHook(_poolManager) {}
+
+    function getHookPermissions() public pure override returns (Hooks.Permissions memory) {
+        return Hooks.Permissions({
+            beforeInitialize: false,
+            afterInitialize: false,
+            beforeModifyPosition: false,
+            afterModifyPosition: false,
+            beforeSwap: true,
+            afterSwap: false,
+            beforeDonate: false,
+            afterDonate: false,
+            noOp: false,
+            accessLock: true // -- Required to take a fee -- //
+        });
+    }
+
+    function beforeSwap(address, PoolKey calldata key, IPoolManager.SwapParams calldata params, bytes calldata)
+        external
+        override
+        returns (bytes4)
+    {
+        // take a fixed fee of 0.0001 of the input token
+        params.zeroForOne
+            ? poolManager.mint(key.currency0, address(this), FIXED_HOOK_FEE)
+            : poolManager.mint(key.currency1, address(this), FIXED_HOOK_FEE);
+
+        return BaseHook.beforeSwap.selector;
+    }
+
+    /// @dev Hook fees are kept as PoolManager claims, so collecting ERC20s will require locking
+    function collectFee(address recipient, Currency currency) external returns (uint256 amount) {
+        amount = abi.decode(poolManager.lock(abi.encodeCall(this.handleCollectFee, (recipient, currency))), (uint256));
+    }
+
+    /// @dev requires the lock pattern in order to call poolManager.burn
+    function handleCollectFee(address recipient, Currency currency) external returns (uint256 amount) {
+        // convert the fee (Claims) into ERC20 tokens
+        amount = poolManager.balanceOf(address(this), currency);
+        poolManager.burn(currency, amount);
+
+        // direct claims (the tokens) to the recipient
+        poolManager.take(currency, recipient, amount);
+    }
+}

src/pages/fees/fixed-hook-fee/SetAccessLockPermission.solsnippet

@@ -0,0 +1,7 @@
+// Hook can take a fee via ACCESS_LOCK
+uint160 flags = uint160(Hooks.BEFORE_SWAP_FLAG | Hooks.ACCESS_LOCK_FLAG);
+
+(address hookAddress, bytes32 salt) =
+    HookMiner.find(address(this), flags, type(FixedHookFee).creationCode, abi.encode(address(manager)));
+
+hook = new FixedHookFee{salt: salt}(IPoolManager(address(manager)));