Add APY calculation (#436)

script/APYCalc.s.sol

@@ -0,0 +1,39 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity 0.8.10;
+
+import "forge-std/Script.sol";
+import {Addresses} from "contracts/utils/Addresses.sol";
+import {IMintableERC20} from "contracts/interfaces/IMintableERC20.sol";
+import {ExponentialStaking} from "contracts/ExponentialStaking.sol";
+import {FixedRateRewardsSource} from "contracts/FixedRateRewardsSource.sol";
+
+contract APYCalc is Script {
+    uint256 constant BASE_SCALE = 10_000 ether;
+
+    function run() external {
+        IMintableERC20 ogn = IMintableERC20(Addresses.OGN);
+        ExponentialStaking xogn = ExponentialStaking(0x63898b3b6Ef3d39332082178656E9862bee45C57);
+        FixedRateRewardsSource ognRewardsSource = FixedRateRewardsSource(0x7609c88E5880e934dd3A75bCFef44E31b1Badb8b);
+
+        (, uint192 rewardsPerSecond) = ognRewardsSource.rewardConfig();
+        uint256 rewardsPerYear = rewardsPerSecond * 60 * 60 * 24 * 365;
+
+        uint256 xognTotalSupply = xogn.totalSupply();
+
+        /// Global APY
+        uint256 globalApy = (BASE_SCALE * rewardsPerYear / xognTotalSupply) / 1 ether;
+        console.log("Global APY (1e4): %i", globalApy);
+
+        /// User APY
+        address userAddress = address(11);
+        uint256 stakeAmount = 10000 ether;
+        uint256 duration = 365 days;
+
+        (uint256 xognPreview,) = xogn.previewPoints(stakeAmount, duration);
+        uint256 userRewardShare = (BASE_SCALE * xognPreview) / (xognTotalSupply + xognPreview);
+        uint256 userProjectedRewards = (rewardsPerYear * userRewardShare) / 1 ether;
+        uint256 userApy = userProjectedRewards / stakeAmount;
+        console.log("User APY (1e4): %i", userApy);
+    }
+}