feat: flag to enable/disable flash loans

src/core/KatanaV3Factory.sol

@@ -19,6 +19,8 @@ contract KatanaV3Factory is IKatanaV3Factory, KatanaV3PoolDeployer {
   address public override owner;
   /// @inheritdoc IKatanaV3Factory
   address public override treasury;
+  /// @inheritdoc IKatanaV3Factory
+  bool public override flashLoanEnabled;
 
   /// @inheritdoc IKatanaV3Factory
   mapping(uint24 => int24) public override feeAmountTickSpacing;
@@ -83,6 +85,11 @@ contract KatanaV3Factory is IKatanaV3Factory, KatanaV3PoolDeployer {
     treasury = _treasury;
   }
 
+  function toggleFlashLoanPermission() external override {
+    require(msg.sender == owner);
+    flashLoanEnabled = !flashLoanEnabled;
+  }
+
   /// @inheritdoc IKatanaV3Factory
   function enableFeeAmount(uint24 fee, int24 tickSpacing, uint16 feeProtocol) public override {
     require(msg.sender == owner);

src/core/KatanaV3Pool.sol

@@ -82,9 +82,11 @@ contract KatanaV3Pool is IKatanaV3Pool {
   /// @inheritdoc IKatanaV3PoolState
   Oracle.Observation[65535] public override observations;
 
-  // These immutable constants are set when deploy the beacon proxy of the pool and cannot be changed unless upgrading.
   /// @inheritdoc IKatanaV3PoolImmutables
-  address public override factory;
+  address public immutable override factory;
+
+  // These below immutable constants are set when deploying the beacon proxy of the pool and
+  // cannot be changed unless upgraded.
   /// @inheritdoc IKatanaV3PoolImmutables
   address public override token0;
   /// @inheritdoc IKatanaV3PoolImmutables
@@ -118,6 +120,7 @@ contract KatanaV3Pool is IKatanaV3Pool {
   }
 
   constructor() {
+    factory = msg.sender;
     // disable immutables initialization
     _immutablesInitialized = true;
   }
@@ -127,7 +130,9 @@ contract KatanaV3Pool is IKatanaV3Pool {
   {
     require(!_immutablesInitialized);
 
-    (factory, token0, token1, fee, tickSpacing) = (factory_, token0_, token1_, fee_, tickSpacing_);
+    require(factory_ == factory, "IF");
+
+    (token0, token1, fee, tickSpacing) = (token0_, token1_, fee_, tickSpacing_);
 
     maxLiquidityPerTick = Tick.tickSpacingToMaxLiquidityPerTick(tickSpacing_);
 
@@ -349,7 +354,7 @@ contract KatanaV3Pool is IKatanaV3Pool {
     uint256 _feeGrowthGlobal0X128 = feeGrowthGlobal0X128; // SLOAD for gas optimization
     uint256 _feeGrowthGlobal1X128 = feeGrowthGlobal1X128; // SLOAD for gas optimization
     uint128 _maxLiquidityPerTick = maxLiquidityPerTick; // SLOAD for gas optimization
-    
+
     // if we need to update the ticks, do it
     bool flippedLower;
     bool flippedUpper;
@@ -736,6 +741,8 @@ contract KatanaV3Pool is IKatanaV3Pool {
 
   /// @inheritdoc IKatanaV3PoolActions
   function flash(address recipient, uint256 amount0, uint256 amount1, bytes calldata data) external override lock {
+    require(IKatanaV3Factory(factory).flashLoanEnabled(), "FD");
+
     uint128 _liquidity = liquidity;
     require(_liquidity > 0, "L");
 

src/core/interfaces/IKatanaV3Factory.sol

@@ -44,6 +44,11 @@ interface IKatanaV3Factory {
   /// @return The address of the treasury
   function treasury() external view returns (address);
 
+  /// @notice Returns whether flash loans are enabled
+  /// @dev Can be changed by the current owner via toggleFlashLoanPermission
+  /// @return Whether flash loans are enabled
+  function flashLoanEnabled() external view returns (bool);
+
   /// @notice Returns the tick spacing for a given fee amount, if enabled, or 0 if not enabled
   /// @dev A fee amount can never be removed, so this value should be hard coded or cached in the calling context
   /// @param fee The enabled fee, denominated in hundredths of a bip. Returns 0 in case of unenabled fee
@@ -84,6 +89,10 @@ interface IKatanaV3Factory {
   /// @param _treasury The new treasury address
   function setTreasury(address _treasury) external;
 
+  /// @notice Toggles the ability to call the `flash` function on KatanaV3Pool
+  /// @dev Must be called by the current owner
+  function toggleFlashLoanPermission() external;
+
   /// @notice Enables a fee amount with the given tickSpacing
   /// @dev Fee amounts may never be removed once enabled
   /// @param fee The fee amount to enable, denominated in hundredths of a bip (i.e. 1e-6)

src/core/interfaces/pool/IKatanaV3PoolEvents.sol

@@ -102,7 +102,12 @@ interface IKatanaV3PoolEvents {
   /// @param feeProtocolDenominatorOld The denominator of the previous value of protocol fee
   /// @param feeProtocolNumeratorNew The numerator of the updated value of protocol fee
   /// @param feeProtocolDenominatorNew The denominator of the oupdated value of protocol fee
-  event SetFeeProtocol(uint8 feeProtocolNumeratorOld, uint8 feeProtocolDenominatorOld, uint8 feeProtocolNumeratorNew, uint8 feeProtocolDenominatorNew);
+  event SetFeeProtocol(
+    uint8 feeProtocolNumeratorOld,
+    uint8 feeProtocolDenominatorOld,
+    uint8 feeProtocolNumeratorNew,
+    uint8 feeProtocolDenominatorNew
+  );
 
   /// @notice Emitted when the collected protocol fees are withdrawn by the factory owner
   /// @param sender The address that collects the protocol fees