added dr eq range

Author: aalavandhan

spot-contracts/contracts/FeePolicy.sol

@@ -68,6 +68,11 @@ contract FeePolicy is IFeePolicy, OwnableUpgradeable {
     ///      is *different* from button-wood's tranche ratios.
     uint256 public override targetSystemRatio;
 
+    /// @notice The range of deviation ratios which define the equilibrium zone.
+    /// @dev When the system's dr is within the equilibrium zone, no value is transferred
+    ///      during a rebalance operation.
+    Range public equilibriumDR;
+
     //-----------------------------------------------------------------------------
     // Fee parameters
 
@@ -113,6 +118,7 @@ contract FeePolicy is IFeePolicy, OwnableUpgradeable {
         __Ownable_init();
 
         targetSystemRatio = 3 * ONE; // 3.0
+        equilibriumDR = Range({ lower: (ONE * 95) / 100, upper: (ONE * 105) / 100 });
 
         // initializing fees
         feeFnDRDown = Line({
@@ -153,6 +159,15 @@ contract FeePolicy is IFeePolicy, OwnableUpgradeable {
         targetSystemRatio = targetSystemRatio_;
     }
 
+    /// @notice Updates the equilibrium DR range.
+    /// @param equilibriumDR_ The new equilibrium DR range as tuple of a fixed point numbers with {DECIMALS} places.
+    function updateEquilibriumDR(Range memory equilibriumDR_) external onlyOwner {
+        if (equilibriumDR_.lower > equilibriumDR_.upper || equilibriumDR_.lower > ONE || equilibriumDR_.upper < ONE) {
+            revert InvalidRange();
+        }
+        equilibriumDR = equilibriumDR_;
+    }
+
     /// @notice Updates the system fee functions.
     /// @param feeFnDRDown_ The new fee function for operations that decrease DR.
     /// @param feeFnDRUp_ The new fee function for operations that increase DR.
@@ -261,8 +276,7 @@ contract FeePolicy is IFeePolicy, OwnableUpgradeable {
     function computeRebalanceAmount(SystemTVL memory s) external view override returns (int256 underlyingAmtIntoPerp) {
         // We skip rebalancing if dr is close to 1.0
         uint256 dr = computeDeviationRatio(s);
-        Range memory drEq = drEqZone();
-        if (dr >= drEq.lower && dr <= drEq.upper) {
+        if (dr >= equilibriumDR.lower && dr <= equilibriumDR.upper) {
             return 0;
         }
 
@@ -305,11 +319,4 @@ contract FeePolicy is IFeePolicy, OwnableUpgradeable {
         // NOTE: We assume that perp's TVL and vault's TVL values have the same base denomination.
         return s.vaultTVL.mulDiv(ONE, s.perpTVL).mulDiv(ONE, targetSystemRatio);
     }
-
-    /// @return The range of deviation ratios which define the equilibrium zone.
-    /// @dev We infer the equilibrium from the fee function definitions, i.e) the upperDR in `feeFnDRDown`
-    ///      and lowerDR in `feeFnDRUp`.
-    function drEqZone() public view returns (Range memory) {
-        return Range({ lower: feeFnDRDown.x2, upper: feeFnDRUp.x1 });
-    }
 }

spot-contracts/test/FeePolicy.ts

@@ -46,7 +46,7 @@ describe("FeePolicy", function () {
       expect(f2[2]).to.eq(toPerc("1.5"));
       expect(f2[3]).to.eq(toPerc("0.25"));
 
-      const drEq = await feePolicy.drEqZone();
+      const drEq = await feePolicy.equilibriumDR();
       expect(drEq[0]).to.eq(toPerc("0.95"));
       expect(drEq[1]).to.eq(toPerc("1.05"));
 
@@ -91,6 +91,42 @@ describe("FeePolicy", function () {
     });
   });
 
+  describe("#updateEquilibriumDR", function () {
+    describe("when triggered by non-owner", function () {
+      it("should revert", async function () {
+        await expect(
+          feePolicy.connect(otherUser).updateEquilibriumDR([toPerc("0.9"), toPerc("1.1")]),
+        ).to.be.revertedWith("Ownable: caller is not the owner");
+      });
+    });
+
+    describe("when range is invalid", function () {
+      it("should revert", async function () {
+        await expect(feePolicy.updateEquilibriumDR([toPerc("1.2"), toPerc("1.1")])).to.be.revertedWithCustomError(
+          feePolicy,
+          "InvalidRange",
+        );
+        await expect(feePolicy.updateEquilibriumDR([toPerc("1.01"), toPerc("1.1")])).to.be.revertedWithCustomError(
+          feePolicy,
+          "InvalidRange",
+        );
+        await expect(feePolicy.updateEquilibriumDR([toPerc("0.9"), toPerc("0.99")])).to.be.revertedWithCustomError(
+          feePolicy,
+          "InvalidRange",
+        );
+      });
+    });
+
+    describe("when triggered by owner", function () {
+      it("should update the target sr", async function () {
+        await feePolicy.connect(deployer).updateEquilibriumDR([toPerc("0.9"), toPerc("1.1")]);
+        const eq = await feePolicy.equilibriumDR();
+        expect(eq[0]).to.eq(toPerc("0.9"));
+        expect(eq[1]).to.eq(toPerc("1.1"));
+      });
+    });
+  });
+
   describe("#updateFees", function () {
     const VALID_DOWN = toLine("0.0", "1.0", "0.99", "0.0");
     const VALID_UP = toLine("1.01", "0.0", "2.0", "1.0");
@@ -333,7 +369,7 @@ describe("FeePolicy", function () {
 
     describe("when deviation is within eq range", function () {
       it("should compute rebalance data", async function () {
-        await feePolicy.updateFees(toLine("0", "0.5", "0.5", "0"), toLine("2", "0", "10", "0.5"));
+        await feePolicy.updateEquilibriumDR([toPerc("0.5"), toPerc("2")]);
         const r1 = await feePolicy.computeRebalanceAmount({
           perpTVL: toAmt("120"),
           vaultTVL: toAmt("500"),