fix: Remove checkMinAmount

If minAmountOut == 0, then skip the check

--- don't change below this line ---
ENG-4041 Took 35 minutes

foundry/src/TychoRouter.sol

@@ -97,13 +97,12 @@ contract TychoRouter is
      * - For ERC20 tokens, Permit2 is used to approve and transfer tokens from the caller to the router.
      * - Swaps are executed sequentially using the `_splitSwap` function.
      * - A fee is deducted from the output token if `fee > 0`, and the remaining amount is sent to the receiver.
-     * - Reverts with `TychoRouter__NegativeSlippage` if the output amount is less than `minAmountOut` and `checkMinAmount` is true.
+     * - Reverts with `TychoRouter__NegativeSlippage` if the output amount is less than `minAmountOut` and `minAmountOut` is bigger than 0.
      *
      * @param amountIn The input token amount to be swapped.
      * @param tokenIn The address of the input token. Use `address(0)` for native ETH when `wrapEth` is true.
      * @param tokenOut The address of the output token. Use `address(0)` for native ETH when `unwrapEth` is true.
-     * @param checkMinAmount A boolean indicating whether to enforce the `minAmountOut` check.
+     * @param minAmountOut The minimum acceptable amount of the output token. Reverts if this condition is not met. If it's 0, no check is performed.
-     * @param minAmountOut The minimum acceptable amount of the output token. Reverts if this condition is not met.
      * @param wrapEth If true, treats the input token as native ETH and wraps it into WETH.
      * @param unwrapEth If true, unwraps the resulting WETH into native ETH and sends it to the receiver.
      * @param nTokens The total number of tokens involved in the swap graph (used to initialize arrays for internal calculations).
@@ -118,7 +117,6 @@ contract TychoRouter is
         uint256 amountIn,
         address tokenIn,
         address tokenOut,
-        bool checkMinAmount,
         uint256 minAmountOut,
         bool wrapEth,
         bool unwrapEth,
@@ -131,8 +129,7 @@ contract TychoRouter is
         // For native ETH, assume funds already in our router. Else, transfer and handle approval.
         if (wrapEth) {
             _wrapETH(amountIn);
-        } else {
+        } else if (tokenIn != address(0)) {
-            if (tokenIn != address(0)) {
                 permit2.permit(msg.sender, permitSingle, signature);
                 permit2.transferFrom(
                     msg.sender,
@@ -140,7 +137,6 @@ contract TychoRouter is
                     uint160(amountIn),
                     permitSingle.details.token
                 );
-            }
         }
 
         amountOut = _splitSwap(amountIn, nTokens, swaps);
@@ -154,7 +150,7 @@ contract TychoRouter is
             }
         }
 
-        if (checkMinAmount && amountOut < minAmountOut) {
+        if (minAmountOut > 0 && amountOut < minAmountOut) {
             revert TychoRouter__NegativeSlippage(amountOut, minAmountOut);
         }
 

foundry/test/TychoRouter.t.sol

@@ -351,7 +351,6 @@ contract TychoRouterTest is TychoRouterTestSetup {
             amount_in,
             WETH_ADDR,
             DAI_ADDR,
-            true,
             minAmountOut,
             false,
             false,
@@ -403,7 +402,6 @@ contract TychoRouterTest is TychoRouterTestSetup {
             amount_in,
             WETH_ADDR,
             DAI_ADDR,
-            true,
             minAmountOut,
             false,
             false,
@@ -449,7 +447,6 @@ contract TychoRouterTest is TychoRouterTestSetup {
             amount_in,
             WETH_ADDR,
             DAI_ADDR,
-            false,
             0,
             false,
             false,
@@ -498,7 +495,6 @@ contract TychoRouterTest is TychoRouterTestSetup {
             amount_in,
             address(0),
             DAI_ADDR,
-            false,
             0,
             true,
             false,
@@ -542,7 +538,6 @@ contract TychoRouterTest is TychoRouterTestSetup {
             amount_in,
             DAI_ADDR,
             address(0),
-            false,
             0,
             false,
             true,