From f97fbbcde4946aa02d40f0a8a23510accc3ac334 Mon Sep 17 00:00:00 2001
From: Rob <robsonsjre@gmail.com>
Date: Mon, 13 Dec 2021 21:28:35 -0300
Subject: [PATCH] revert transaction if buyer and seller is paying zero fees
 (#314)

---
 contracts/amm/OptionAMMPool.sol |  1 +
 test/amm/OptionAMMPool.test.js  | 18 ++++++++++++++++++
 2 files changed, 19 insertions(+)

diff --git a/contracts/amm/OptionAMMPool.sol b/contracts/amm/OptionAMMPool.sol
index 1e8cb496..521b0d82 100644
--- a/contracts/amm/OptionAMMPool.sol
+++ b/contracts/amm/OptionAMMPool.sol
@@ -929,6 +929,7 @@ contract OptionAMMPool is AMM, IOptionAMMPool, CappedPool, CombinedActionsGuard,
 
     function _onTrade(TradeDetails memory tradeDetails) internal override {
         uint256 newIV = abi.decode(tradeDetails.params, (uint256));
+        require(tradeDetails.feesTokenA > 0 && tradeDetails.feesTokenB > 0, "Pool: zero fees");
         priceProperties.currentIV = newIV;
 
         IERC20(tokenB()).safeTransfer(address(feePoolA), tradeDetails.feesTokenA);
diff --git a/test/amm/OptionAMMPool.test.js b/test/amm/OptionAMMPool.test.js
index 85f9f0ae..b3e5cc8b 100644
--- a/test/amm/OptionAMMPool.test.js
+++ b/test/amm/OptionAMMPool.test.js
@@ -1170,6 +1170,24 @@ scenarios.forEach(scenario => {
 
         expect(bsPriceWithOracleIV).to.be.gte(bsPriceWithoutOracleIV)
       })
+      it('Should revert if caller is going to pay 0 fees due to a small trade', async () => {
+        const stableLiquidityToAdd = toBigNumber(60000).mul(toBigNumber(10).pow(scenario.strikeAssetDecimals))
+        const optionLiquidityToAdd = toBigNumber(100).mul(toBigNumber(10).pow(toBigNumber(scenario.underlyingAssetDecimals)))
+        const optionLiquidityToBuy = toBigNumber(1)
+
+        await addLiquidity(optionAMMPool, optionLiquidityToAdd, stableLiquidityToAdd, lp)
+
+        await mintOptions(option, optionLiquidityToBuy, buyer)
+        await mockStrikeAsset.connect(buyer).mint(stableLiquidityToAdd.mul(2))
+
+        await option.connect(buyer).approve(optionAMMPool.address, ethers.constants.MaxUint256)
+        await mockStrikeAsset.connect(buyer).approve(optionAMMPool.address, ethers.constants.MaxUint256)
+
+        const tradeDetails = await optionAMMPool.getOptionTradeDetailsExactAInput(optionLiquidityToBuy)
+
+        await expect(optionAMMPool.connect(buyer)
+          .tradeExactAInput(optionLiquidityToBuy, 0, buyerAddress, tradeDetails.newIV)).to.be.revertedWith('Pool: zero fees')
+      })
     })
 
     describe('Withdraw Amount > TotalBalance case', () => {