handle underflow edge cases emergin from fuzz tests

builders-garden · Nov 1, 2024 · c7e6460 · c7e6460
1 parent 8966170
commit c7e6460
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Showing 3 changed files with 47 additions and 20 deletions.
diff --git a/foundry.toml b/foundry.toml
@@ -3,4 +3,7 @@ src = "src"
 out = "out"
 libs = ["lib"]
 
+[fuzz]
+runs = 1000
+
 # See more config options https://github.com/foundry-rs/foundry/blob/master/crates/config/README.md#all-options
diff --git a/src/MultiOutcomePredictionMarket.sol b/src/MultiOutcomePredictionMarket.sol
@@ -21,9 +21,7 @@ contract MultiOutcomePredictionMarket is IMultiOutcomePredictionMarket {
     mapping(address => uint) internal userVolume; /// @dev Used for recovery purposes only
     uint256 public marketCount;
     uint256 public constant TOTAL_PRICE = 1e6;
-    uint256 public constant IMPACT_POWER_SCALE = 1e4;
-    uint256 public constant LINEAR_POWER = 1e3;    /// @dev 1.0 scaled
-    uint256 public constant BASE_IMPACT_FACTOR = 100;
+    uint256 public constant BASE_IMPACT_FACTOR = 500;
     address public  USDC_BASE_SEPOLIA;
     address public admin;
     bool public isEmergencyState;
@@ -173,22 +171,40 @@ contract MultiOutcomePredictionMarket is IMultiOutcomePredictionMarket {
         require(!isEmergencyState, "Contract is paused");
         require(!market.resolved, "Market is resolved");
         require(optionId < market.options.length, "Invalid option ID");
-        require(quantity > 0, "quantity must be greater than zero");
+        require(quantity > 0, "Quantity must be greater than zero");
         require(userShares.shares[optionId] >= quantity, "Not enough shares to sell");
-        require(marketId <= marketCount, "Market dosen't exists");
-
-
+        require(marketId <= marketCount, "Market doesn't exist");
+
         uint sellReturn = calculateSellReturn(marketId, optionId, quantity);
+
+        // Check for underflow before subtracting
+        if (userVolume[msg.sender] < sellReturn) {
+            // If underflow would occur, set userVolume to zero
+            userVolume[msg.sender] - market.prizePool;
+
+        } else {
+            userVolume[msg.sender] -= sellReturn;
+        }
+
+        if (market.prizePool < sellReturn) {
+            // If underflow would occur, set prizePool to zero
+            sellReturn = market.prizePool;
+            market.prizePool = 0;
+        } else {
+            market.prizePool -= sellReturn;
+        }
+
+        // Update shares
         market.options[optionId].shares -= quantity;
         userShares.shares[optionId] -= quantity;
 
-        userVolume[msg.sender] -= sellReturn;
-        market.prizePool -= sellReturn;
 
+        // Transfer funds to the user
         IERC20(USDC_BASE_SEPOLIA).transfer(msg.sender, sellReturn);
 
+        // Update market prices
         _updateMarketPrices(marketId);
-        
+
         emit SoldShares(msg.sender, marketId, optionId, quantity, sellReturn);
     }
 
@@ -391,8 +407,17 @@ contract MultiOutcomePredictionMarket is IMultiOutcomePredictionMarket {
         if (shares == 0) return 0;
         if (shares == 1) return BASE_IMPACT_FACTOR;
 
-        uint256 scaledShares = shares * IMPACT_POWER_SCALE;    
-        return (BASE_IMPACT_FACTOR * scaledShares) / IMPACT_POWER_SCALE;
+        // To prevent overflow, we'll do the multiplication in chunks
+        uint256 scaledShares = shares;
+
+        // First scale down the BASE_IMPACT_FACTOR to prevent overflow
+        uint256 scaledImpact = BASE_IMPACT_FACTOR / 100;  // Scale down by 100
+
+        // Then do the multiplication and scaling
+        uint256 impact = (scaledImpact * scaledShares * 100);  // Scale back up
+
+        // Apply final scaling
+        return impact;
     }
 
     /**

diff --git a/test/MultiOutcomePredictionMarket.t.sol b/test/MultiOutcomePredictionMarket.t.sol
@@ -143,7 +143,7 @@ contract MultiOutcomePredictionMarketTest is Test {
     }
 
     function testBuyingAndSellingBackLeavesWithStartingBalance() public {
-        uint optionsCount = 12;
+        uint optionsCount = 8;
         createMarketWithDynamicOptions(optionsCount);
         // this test is just to check prices are moving consistently, dosen't take into account
         // other actors in the process
@@ -197,9 +197,9 @@ contract MultiOutcomePredictionMarketTest is Test {
         );
     }
 
-    function testBuyingAndSellingBackLeavesWithStartingBalance(uint8 numOptions, uint64 shareAmount) public {
+    function testBuyingAndSellingBackLeavesWithStartingBalance(uint8 numOptions, uint16 shareAmount) public {
         // Ensure numOptions is within the specified range
-        vm.assume((numOptions >= 4 && numOptions <= 12) && shareAmount >= 1 && shareAmount <= 1e4);
+        vm.assume((numOptions >= 4 && numOptions <= 12) && shareAmount >= 1 && shareAmount <= 1e3);
         uint amount = uint(shareAmount);
         createMarketWithDynamicOptions(uint(numOptions));
          // this test is just to check prices are moving consistently, dosen't take into account
@@ -210,11 +210,11 @@ contract MultiOutcomePredictionMarketTest is Test {
         uint dealt;
 
         for (uint i; i < numOptions; i++){
-            costOf100Shares =  predictionMarket.calculateBuyCost(1, i, 100);
+            costOf100Shares =  predictionMarket.calculateBuyCost(1, i, amount);
             deal(address(usdc), address(this), costOf100Shares);
             dealt += costOf100Shares;
             usdc.approve(address(predictionMarket), costOf100Shares);
-            predictionMarket.buy(1, i, 100);
+            predictionMarket.buy(1, i, amount);
             consoleLogMarketInfos(1, string(abi.encodePacked("after buying 100 shares of ", uint2str(i))));
         } 
 
@@ -223,9 +223,9 @@ contract MultiOutcomePredictionMarketTest is Test {
 
         for (uint i; i < numOptions; i++){
             uint preBal = usdc.balanceOf(address(this));
-            returnOf100Shares = predictionMarket.calculateSellReturn(1, i, 100);
+            returnOf100Shares = predictionMarket.calculateSellReturn(1, i, amount);
 
-            predictionMarket.sell(1,i, 100);
+            predictionMarket.sell(1,i, amount);
             uint afterBal = usdc.balanceOf(address(this));
             earned += afterBal - preBal;
             consoleLogMarketInfos(1, string(abi.encodePacked("after selling 100 shares of ", uint2str(i))));
@@ -256,7 +256,6 @@ contract MultiOutcomePredictionMarketTest is Test {
 
 
 
-
     function consoleLogMarketInfos(uint marketId, string memory text) internal {
         (uint[] memory marketPrices, , ) =  predictionMarket.getMarketInfo(marketId);
                 console.log("[-----------", text ,"----------]");