Gas Optimisation Fixes

contracts/Staking.sol

@@ -2,13 +2,12 @@
 pragma solidity ^0.8.4;
 
 import "@openzeppelin/contracts/interfaces/IERC721.sol";
-
-import "./Camp.sol";
+import "./interfaces/ICamp.sol";
 
 /* solhint-disable not-rely-on-time */
 contract Staking {
-    Camp public camp;
-    IERC721 public dappCampWarriors;
+    address public campAddress;
+    address public dappCampWarriorsAddress;
 
     struct Stake {
         address owner;
@@ -27,8 +26,8 @@ contract Staking {
     uint256 public rewardPerSecondInWei = 1000000000000000000;
 
     constructor(address _camp, address _dappCampWarriors) {
-        camp = Camp(_camp);
-        dappCampWarriors = IERC721(_dappCampWarriors);
+        campAddress = _camp;
+        dappCampWarriorsAddress = _dappCampWarriors;
     }
 
     function stake(uint256 tokenId) public {
@@ -39,11 +38,11 @@ contract Staking {
          *   - Staking NFTs that are already staked (since the owner is this contract)
          */
         require(
-            dappCampWarriors.ownerOf(tokenId) == msg.sender,
+            IERC721(dappCampWarriorsAddress).ownerOf(tokenId) == msg.sender,
             "Staking: only the owner can stake an NFT"
         );
 
-        dappCampWarriors.transferFrom(msg.sender, address(this), tokenId);
+        IERC721(dappCampWarriorsAddress).transferFrom(msg.sender, address(this), tokenId);
 
         // solhint-disable-next-line not-rely-on-time
         staked[tokenId] = Stake(msg.sender, tokenId, block.timestamp);
@@ -54,24 +53,25 @@ contract Staking {
          * @dev This prevents 3 things:
          *   - Unstaking non-existing NFTs (ERC721 ownerOf validates existence)
          *   - Unstaking if msg.sender is not the owner
-         *   - Unstaking NFTs that are not staked (since staked[tokenId].owner will be the zero address)
+         *   - Unstaking NFTs that are not staked (since staking.owner will be the zero address)
          */
+        Stake memory staking = staked[tokenId];
+
         require(
-            staked[tokenId].owner == msg.sender,
+            staking.owner == msg.sender,
             "Staking: only the owner can unstake an NFT"
         );
         require(
-            staked[tokenId].initTimestamp != block.timestamp,
+            staking.initTimestamp != block.timestamp,
             "Staking: cannot unstake an NFT in the same block it was staked"
         );
 
-        uint256 stakedSeconds = block.timestamp - staked[tokenId].initTimestamp;
-
-        delete staked[tokenId];
+        uint256 stakedSeconds = block.timestamp - staking.initTimestamp;
 
-        dappCampWarriors.transferFrom(address(this), msg.sender, tokenId);
+        delete staking;
 
-        camp.mint(msg.sender, stakedSeconds * rewardPerSecondInWei);
+        IERC721(dappCampWarriorsAddress).transferFrom(address(this), msg.sender, tokenId);
+        ICamp(campAddress).mint(msg.sender, stakedSeconds * rewardPerSecondInWei);
     }
 }
 /* solhint-enable not-rely-on-time */

contracts/interfaces/ICamp.sol

@@ -0,0 +1,6 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.4;
+
+interface ICamp {
+    function mint(address account, uint256 amount) external;
+}

test/Staking.spec.ts

@@ -154,16 +154,39 @@ describe("Camp tests", () => {
         ethers.utils.parseEther("1")
       );
     });
+  });
 
-    it("Should remove the NFT from the `staked` mapping", async () => {
-      await createValidStake();
-      const stakedData1 = await stakingContract.staked(1);
-      expect(stakedData1.tokenId).to.equal(1);
+  describe("gasCheck", () => {
+    it("Should check the gas used for contract creation is below minimum threshold", async () => {
+      const GAS_THRESHOLD = 755_000;
 
-      await stakingContract.unstake(1);
+      const StakingFactory = await ethers.getContractFactory("Staking");
+      const stakingContract = await StakingFactory.deploy(campContract.address, dappCampWarriorsContract.address);
+
+      const gasLimit = stakingContract.deployTransaction.gasLimit;
+
+      expect(gasLimit).lt(GAS_THRESHOLD);
+    });
+
+    it("Should check the gas used for staking is below minimum threshold", async () => {
+      const GAS_THRESHOLD = 142_000;
+
+      await (
+        await dappCampWarriorsContract.approve(stakingContract.address, 1)
+      ).wait();
+
+      const gasUsed = await stakingContract.estimateGas.stake(1);
+
+      expect(gasUsed).lt(GAS_THRESHOLD);
+    });
+
+    it("Should check the gas used for unstake is below minimum threshold", async () => {
+      const GAS_THRESHOLD = 120_000;
+
+      await createValidStake();
+      const gasUsed = await stakingContract.estimateGas.unstake(1);
 
-      const stakedData2 = await stakingContract.staked(1);
-      expect(stakedData2.tokenId).to.equal(0);
+      expect(gasUsed).lt(GAS_THRESHOLD);
     });
   });
 });