Make multiplier non-linear

Snowfork · Mar 21, 2024 · c5d8db3 · c5d8db3
1 parent 1ae5ef5
commit c5d8db3
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Showing 2 changed files with 12 additions and 14 deletions.
diff --git a/contracts/src/Gateway.sol b/contracts/src/Gateway.sol
@@ -463,24 +463,22 @@ contract Gateway is IGateway, IInitializable {
     }
 
     // Convert foreign currency to native currency (ROC/KSM/DOT -> ETH)
-    function _convertToNative(UD60x18 exchangeRate, UD60x18 amount) internal view returns (uint256) {
+    function _convertToNative(UD60x18 exchangeRate, UD60x18 multiplier, UD60x18 amount)
+        internal
+        view
+        returns (uint256)
+    {
         UD60x18 ethDecimals = convert(1e18);
         UD60x18 foreignDecimals = convert(10).pow(convert(uint256(FOREIGN_TOKEN_DECIMALS)));
-        UD60x18 nativeAmount = amount.mul(exchangeRate).div(foreignDecimals).mul(ethDecimals);
+        UD60x18 nativeAmount = multiplier.mul(amount).mul(exchangeRate).div(foreignDecimals).mul(ethDecimals);
         return convert(nativeAmount);
     }
 
     // Calculate the fee for accepting an outbound message
     function _calculateFee(Costs memory costs) internal view returns (uint256) {
         PricingStorage.Layout storage pricing = PricingStorage.layout();
-
-        // The exchange rate and amount are both multiplied by `multiplier` to add a safety margin
-        // * `exchangeRate` is subject to real-world fluctuations
-        // * `amount` includes XCM execution fees in Polkadot that are also subject to fluctuations
-        UD60x18 exchangeRate = pricing.multiplier.mul(pricing.exchangeRate);
-        UD60x18 amount = pricing.multiplier.mul(convert(pricing.deliveryCost + costs.foreign));
-
-        return costs.native + _convertToNative(exchangeRate, amount);
+        UD60x18 amount = convert(pricing.deliveryCost + costs.foreign);
+        return costs.native + _convertToNative(pricing.exchangeRate, pricing.multiplier, amount);
     }
 
     // Submit an outbound message to Polkadot, after taking fees

diff --git a/contracts/test/Gateway.t.sol b/contracts/test/Gateway.t.sol
@@ -519,7 +519,7 @@ contract GatewayTest is Test {
 
         testSetPricingParameters();
         uint256 fee = IGateway(address(gateway)).quoteRegisterTokenFee();
-        assertEq(fee, 40000000000000003);
+        assertEq(fee, 20000000000000001);
 
         testCreateAgent();
         assertNotEq(GatewayMock(address(gateway)).agentOf(agentID), address(0));
@@ -541,7 +541,7 @@ contract GatewayTest is Test {
 
         // Verify that storage was not overwritten
         fee = IGateway(address(gateway)).quoteRegisterTokenFee();
-        assertEq(fee, 40000000000000003);
+        assertEq(fee, 20000000000000001);
         assertNotEq(GatewayMock(address(gateway)).agentOf(agentID), address(0));
     }
 
@@ -878,7 +878,7 @@ contract GatewayTest is Test {
     function testSetPricingParameters() public {
         uint256 fee = IGateway(address(gateway)).quoteRegisterTokenFee();
         assertEq(fee, 5000000000000000);
-        // Double both the exchangeRate and multiplier. Should lead to an 8x fee increase
+        // Double both the exchangeRate and multiplier. Should lead to an 4x fee increase
         GatewayMock(address(gateway)).setPricingParametersPublic(
             abi.encode(
                 SetPricingParametersParams({
@@ -890,7 +890,7 @@ contract GatewayTest is Test {
         );
         // Should expect 4x fee increase
         fee = IGateway(address(gateway)).quoteRegisterTokenFee();
-        assertEq(fee, 40000000000000003);
+        assertEq(fee, 20000000000000001);
     }
 
     function testSendTokenToForeignDestWithInvalidFee() public {