feat: USV3 verification

foundry/src/TychoRouter.sol

@@ -59,10 +59,13 @@ contract TychoRouter is
     );
     event FeeSet(uint256 indexed oldFee, uint256 indexed newFee);
 
-    constructor(address _permit2, address weth) {
+    address private immutable _usv3Factory;
+
+    constructor(address _permit2, address weth, address usv3Factory) {
         permit2 = IAllowanceTransfer(_permit2);
         _grantRole(DEFAULT_ADMIN_ROLE, msg.sender);
         _weth = IWETH(weth);
+        _usv3Factory = usv3Factory;
     }
 
     /**
@@ -340,4 +343,41 @@ contract TychoRouter is
      * @dev Allows this contract to receive native token
      */
     receive() external payable {}
+
+    /**
+     * @dev Called by UniswapV3 pool when swapping on it.
+     * See in IUniswapV3SwapCallback for documentation.
+     */
+    function uniswapV3SwapCallback(
+        int256 amount0Delta,
+        int256 amount1Delta,
+        bytes calldata msgData
+    ) external {
+        (uint256 amountOwed, address tokenOwed) =
+            _verifyUSV3Callback(amount0Delta, amount1Delta, msgData);
+        IERC20(tokenOwed).safeTransfer(msg.sender, amountOwed);
+    }
+
+    function _verifyUSV3Callback(
+        int256 amount0Delta,
+        int256 amount1Delta,
+        bytes calldata data
+    )
+        internal
+        pure
+        returns (uint256 amountOwed, address tokenOwed)
+    {
+        address tokenIn = address(bytes20(data[0:20]));
+        address tokenOut = address(bytes20(data[20:40]));
+        uint24 fee = uint24(bytes3(data[40:43]));
+
+        CallbackValidationV2.verifyCallback(
+            _usv3Factory, tokenIn, tokenOut, fee
+        );
+
+        amountOwed =
+            amount0Delta > 0 ? uint256(amount0Delta) : uint256(amount1Delta);
+
+        return (amountOwed, tokenOwed);
+    }
 }