feature: expose isWithinMarketCapacity view function

markets/perps-market/contracts/interfaces/IGlobalPerpsMarketModule.sol

@@ -236,4 +236,17 @@ interface IGlobalPerpsMarketModule {
      * @dev InterestRateUpdated event is emitted
      */
     function updateInterestRate() external;
+
+    /**
+     * @notice Checks if a market is solvent within its capacity when considering a position change.
+     * @param marketId The ID of the market to check.
+     * @param accountId The ID of the account involved in the market.
+     * @param sizeDelta The change in position size to be considered.
+     * @return isMarketSolvent A boolean indicating whether the market is solvent after the position change.
+     */
+    function isWithinMarketCapacity(
+        uint128 marketId,
+        uint128 accountId,
+        int256 sizeDelta
+    ) external view returns (bool isMarketSolvent);
 }

markets/perps-market/contracts/modules/GlobalPerpsMarketModule.sol

@@ -15,6 +15,8 @@ import {OwnableStorage} from "@synthetixio/core-contracts/contracts/ownership/Ow
 import {AddressError} from "@synthetixio/core-contracts/contracts/errors/AddressError.sol";
 import {ParameterError} from "@synthetixio/core-contracts/contracts/errors/ParameterError.sol";
 import {KeeperCosts} from "../storage/KeeperCosts.sol";
+import {PerpsMarket} from "../storage/PerpsMarket.sol";
+import {MathUtil} from "../utils/MathUtil.sol";
 
 /**
  * @title Module for global Perps Market settings.
@@ -25,6 +27,7 @@ contract GlobalPerpsMarketModule is IGlobalPerpsMarketModule {
     using GlobalPerpsMarket for GlobalPerpsMarket.Data;
     using SetUtil for SetUtil.UintSet;
     using KeeperCosts for KeeperCosts.Data;
+    using PerpsMarket for PerpsMarket.Data;
 
     /**
      * @inheritdoc IGlobalPerpsMarketModule
@@ -271,4 +274,25 @@ contract GlobalPerpsMarketModule is IGlobalPerpsMarketModule {
 
         emit InterestRateUpdated(PerpsMarketFactory.load().perpsMarketId, interestRate);
     }
+
+    /**
+     * @inheritdoc IGlobalPerpsMarketModule
+     */
+    function isWithinMarketCapacity(uint128 marketId, uint128 accountId, int256 sizeDelta) external view override returns (bool isMarketSolvent) {
+        int128 oldPositionSize = PerpsMarket.accountPosition(marketId, accountId);
+        int128 newPositionSize = oldPositionSize + sizeDelta;
+
+        uint256 newMagnitude = MathUtil.abs(runtime.newPositionSize);
+        uint256 oldMagnitude = MathUtil.abs(oldPositionSize);
+
+        bool sameSide = newPositionSize > 0 == oldPositionSize > 0;
+
+        if (newMagnitude > oldMagnitude || !sameSide) {
+            int256 lockedCreditDelta = PerpsMarket.requiredCreditForSize(sizeDelta, PerpsPrice.Tolerance.DEFAULT);
+            (bool isMarketSolvent, , ) = GlobalPerpsMarket.isMarketSolventForCreditDelta(sizeDelta);
+            return isMarketSolvent;
+        }
+
+        return true;
+    }
 }