Add a constraint for the amount of pools to TCA (trusttoken#993)

* Introduce maxPools

* Add maxPools setter

* Add event emission on changing max pools

* Restrict the amount of pools supported by TCA

* Rename test

Author: MiksuJak

contracts/truefi2/TrueCreditAgency.sol

@@ -117,6 +117,9 @@ contract TrueCreditAgency is UpgradeableClaimable, ITrueCreditAgency {
     /// @dev minimum credit score required to use lines of credit
     uint256 public minCreditScore;
 
+    // maximum amount of pools credit agency can handle at once
+    uint256 public maxPools;
+
     // ======= STORAGE DECLARATION END ============
 
     /// @dev emit `newRateAdjuster` when rate adjuster changed
@@ -140,11 +143,15 @@ contract TrueCreditAgency is UpgradeableClaimable, ITrueCreditAgency {
     /// @dev emit `newValue` when minimum credit score is changed
     event MinCreditScoreChanged(uint256 newValue);
 
+    /// @dev emit `maxPools` when maximum pools amount is changed
+    event MaxPoolsChanged(uint256 maxPools);
+
     /// @dev initialize
     function initialize(ITrueFiCreditOracle _creditOracle, ITrueRateAdjuster _rateAdjuster) public initializer {
         UpgradeableClaimable.initialize(msg.sender);
         creditOracle = _creditOracle;
         rateAdjuster = _rateAdjuster;
+        maxPools = 10;
         interestRepaymentPeriod = 31 days;
     }
 
@@ -173,6 +180,12 @@ contract TrueCreditAgency is UpgradeableClaimable, ITrueCreditAgency {
         emit MinCreditScoreChanged(newValue);
     }
 
+    /// @dev set maxPools to `_maxPools`
+    function setMaxPools(uint256 _maxPools) external onlyOwner {
+        maxPools = _maxPools;
+        emit MaxPoolsChanged(_maxPools);
+    }
+
     /// @dev set borrower `who` to whitelist status `isAllowed`
     function allowBorrower(address who, bool isAllowed) external onlyOwner {
         isBorrowerAllowed[who] = isAllowed;
@@ -184,6 +197,7 @@ contract TrueCreditAgency is UpgradeableClaimable, ITrueCreditAgency {
      * Loop through
      */
     function allowPool(ITrueFiPool2 pool, bool isAllowed) external onlyOwner {
+        require(pools.length < maxPools, "TrueRatingAgency: Pools number has reached the limit");
         // if allowing new pool, push to pools array
         if (!isPoolAllowed[pool] && isAllowed) {
             pools.push(pool);

test/truefi2/lines-of-credit/TrueCreditAgency.test.ts

@@ -67,7 +67,7 @@ describe('TrueCreditAgency', () => {
     timeTravel = (time: number) => _timeTravel(_provider, time)
     provider = _provider
 
-    ;({
+    ; ({
       standardToken: tusd,
       standardPool: tusdPool,
       feeToken: usdc,
@@ -101,9 +101,17 @@ describe('TrueCreditAgency', () => {
       expect(await creditAgency.creditOracle()).to.equal(creditOracle.address)
     })
 
+    it('sets rateAdjuster', async () => {
+      expect(await creditAgency.rateAdjuster()).to.equal(rateAdjuster.address)
+    })
+
     it('sets interestRepaymentPeriod', async () => {
       expect(await creditAgency.interestRepaymentPeriod()).to.equal(MONTH)
     })
+
+    it('sets maxPools to 10', async () => {
+      expect(await creditAgency.maxPools()).to.equal(10)
+    })
   })
 
   describe('Ownership', () => {
@@ -157,6 +165,24 @@ describe('TrueCreditAgency', () => {
     })
   })
 
+  describe('setMaxPools', () => {
+    it('reverts if not called by the owner', async () => {
+      await expect(creditAgency.connect(borrower).setMaxPools(1))
+        .to.be.revertedWith('Ownable: caller is not the owner')
+    })
+
+    it('changes maximum pools capacity', async () => {
+      await creditAgency.setMaxPools(1)
+      expect(await creditAgency.maxPools()).to.eq(1)
+    })
+
+    it('emits event', async () => {
+      await expect(creditAgency.setMaxPools(1))
+        .to.emit(creditAgency, 'MaxPoolsChanged')
+        .withArgs(1)
+    })
+  })
+
   describe('Borrower allowance', () => {
     it('only owner can set allowance', async () => {
       await expect(creditAgency.connect(borrower).allowBorrower(borrower.address, true))
@@ -185,7 +211,14 @@ describe('TrueCreditAgency', () => {
       }
     }
     it('can only be called by the owner', async () => {
-      await expect(creditAgency.connect(borrower).allowPool(tusdPool.address, true)).to.be.revertedWith('Ownable: caller is not the owner')
+      await expect(creditAgency.connect(borrower).allowPool(tusdPool.address, true))
+        .to.be.revertedWith('Ownable: caller is not the owner')
+    })
+
+    it('reverts if there are too many pools', async () => {
+      await creditAgency.setMaxPools(1)
+      await expect(creditAgency.allowPool(usdcPool.address, true))
+        .to.be.revertedWith('TrueRatingAgency: Pools number has reached the limit')
     })
 
     it('changes pool allowance status', async () => {