Merge pull request #63 from euler-xyz/sauce/initialize-once

Initialize Once Constraint

Author: hoytech

src/UniswapHook.sol

@@ -27,6 +27,7 @@ contract UniswapHook is BaseHook {
 
     PoolKey internal _poolKey;
 
+    error AlreadyInitialized();
     error NativeConcentratedLiquidityUnsupported();
 
     constructor(address evc_, address _poolManager) BaseHook(IPoolManager(_poolManager)) {
@@ -118,6 +119,15 @@ contract UniswapHook is BaseHook {
         return (BaseHook.beforeSwap.selector, returnDelta, 0);
     }
 
+    /// @dev Each deployed hook only services one pair and prevent subsequent initializations
+    function _beforeInitialize(address, PoolKey calldata, uint160) internal view override returns (bytes4) {
+        // when the hook is deployed for the first time, the internal _poolKey is empty
+        // upon activation, the internal _poolKey is initialized and set
+        // once the hook contract is activated, do not allow subsequent initializations
+        require(_poolKey.tickSpacing == 0, AlreadyInitialized());
+        return BaseHook.beforeInitialize.selector;
+    }
+
     function _beforeAddLiquidity(address, PoolKey calldata, IPoolManager.ModifyLiquidityParams calldata, bytes calldata)
         internal
         pure
@@ -129,7 +139,7 @@ contract UniswapHook is BaseHook {
 
     function getHookPermissions() public pure override returns (Hooks.Permissions memory) {
         return Hooks.Permissions({
-            beforeInitialize: false,
+            beforeInitialize: true,
             afterInitialize: false,
             beforeAddLiquidity: true,
             afterAddLiquidity: false,

test/EulerSwapTestBase.t.sol

@@ -41,7 +41,10 @@ contract EulerSwapTestBase is EVaultTestBase {
         // use the canonical miner to find a valid 'implementation' address
         (, bytes32 salt) = v4HookMiner.find(
             address(this),
-            uint160(Hooks.BEFORE_SWAP_FLAG | Hooks.BEFORE_SWAP_RETURNS_DELTA_FLAG | Hooks.BEFORE_ADD_LIQUIDITY_FLAG),
+            uint160(
+                Hooks.BEFORE_INITIALIZE_FLAG | Hooks.BEFORE_SWAP_FLAG | Hooks.BEFORE_SWAP_RETURNS_DELTA_FLAG
+                    | Hooks.BEFORE_ADD_LIQUIDITY_FLAG
+            ),
             type(EulerSwap).creationCode,
             abi.encode(address(evc), poolManager_)
         );
@@ -208,7 +211,10 @@ contract EulerSwapTestBase is EVaultTestBase {
         (address predictedAddr, bytes32 salt) = HookMiner.find(
             address(eulerSwapFactory),
             holder,
-            uint160(Hooks.BEFORE_SWAP_FLAG | Hooks.BEFORE_SWAP_RETURNS_DELTA_FLAG | Hooks.BEFORE_ADD_LIQUIDITY_FLAG),
+            uint160(
+                Hooks.BEFORE_INITIALIZE_FLAG | Hooks.BEFORE_SWAP_FLAG | Hooks.BEFORE_SWAP_RETURNS_DELTA_FLAG
+                    | Hooks.BEFORE_ADD_LIQUIDITY_FLAG
+            ),
             creationCode
         );
 

test/FactoryTest.t.sol

@@ -33,8 +33,10 @@ contract FactoryTest is EulerSwapTestBase {
     }
 
     function mineSalt(IEulerSwap.Params memory poolParams) internal view returns (address hookAddress, bytes32 salt) {
-        uint160 flags =
-            uint160(Hooks.BEFORE_SWAP_FLAG | Hooks.BEFORE_SWAP_RETURNS_DELTA_FLAG | Hooks.BEFORE_ADD_LIQUIDITY_FLAG);
+        uint160 flags = uint160(
+            Hooks.BEFORE_INITIALIZE_FLAG | Hooks.BEFORE_SWAP_FLAG | Hooks.BEFORE_SWAP_RETURNS_DELTA_FLAG
+                | Hooks.BEFORE_ADD_LIQUIDITY_FLAG
+        );
         bytes memory creationCode = MetaProxyDeployer.creationCodeMetaProxy(eulerSwapImpl, abi.encode(poolParams));
         (hookAddress, salt) = HookMiner.find(address(eulerSwapFactory), holder, flags, creationCode);
     }

test/HookSwaps.t.sol

@@ -155,6 +155,25 @@ contract HookSwapsTest is EulerSwapTestBase {
         vm.stopPrank();
     }
 
+    /// @dev initializing a new pool on an existing eulerswap instance will revert
+    function test_revertSubsequentInitialize() public {
+        PoolKey memory poolKey = eulerSwap.poolKey();
+        PoolKey memory newPoolKey = eulerSwap.poolKey();
+        newPoolKey.currency0 = CurrencyLibrary.ADDRESS_ZERO;
+
+        // hook intentionally reverts to prevent subsequent initializations
+        vm.expectRevert(
+            abi.encodeWithSelector(
+                CustomRevert.WrappedError.selector,
+                address(eulerSwap),
+                IHooks.beforeInitialize.selector,
+                abi.encodeWithSelector(UniswapHook.AlreadyInitialized.selector),
+                abi.encodeWithSelector(Hooks.HookCallFailed.selector)
+            )
+        );
+        poolManager.initialize(newPoolKey, 79228162514264337593543950336);
+    }
+
     function _swap(PoolKey memory key, bool zeroForOne, bool exactInput, uint256 amount) internal {
         IPoolManager.SwapParams memory swapParams = IPoolManager.SwapParams({
             zeroForOne: zeroForOne,