refactor unlock percentage

contracts/CunaFinanceBsc.sol

@@ -302,35 +302,20 @@ contract CunaFinanceBsc is Initializable, ReentrancyGuardUpgradeable {
 
     // Epoch-based Staking Functions
     
-    /// @notice Internal function to calculate unlock percentage based on TVL/liability ratio improvement
-    /// @dev Formula: (current_tvl / current_liability) - (last_tvl / last_liability) * payback_percent
+    /// @notice Internal function to calculate unlock percentage based on ratio improvement vs historical high
+    /// @dev Formula: (current_ratio - highest_ratio) * payback_percent
     function calculateUnlockPercentage(
-        uint256 currentTvl,
-        uint256 currentLiability,
-        uint256 lastTvl,
-        uint256 lastLiability,
+        uint256 currentRatio,
         uint256 paybackPercent
     ) internal view returns (uint256) {
 
-        if (lastLiability == 0 || currentLiability == 0) {
-            return 0; // Safety check
-        }
-
-        // Calculate ratios (scaled by 10000 for precision)
-        uint256 currentRatio = (currentTvl * 10000) / currentLiability;
-        uint256 lastRatio = (lastTvl * 10000) / lastLiability;
-
         // Check if current ratio is below the highest ratio ever achieved
-        if (currentRatio < highestRatio) {
+        if (currentRatio <= highestRatio) {
             return 0; // No unlock if we're below historical high
         }
 
-        if (currentRatio <= lastRatio) {
-            return 0; // No unlock if ratio didn't improve
-        }
-
         // Ratio improvement * payback percentage
-        uint256 ratioImprovement = currentRatio - lastRatio;
+        uint256 ratioImprovement = currentRatio - highestRatio;
         uint256 unlockPercentage = (ratioImprovement * paybackPercent) / 10000;
 
         return unlockPercentage;
@@ -349,19 +334,10 @@ contract CunaFinanceBsc is Initializable, ReentrancyGuardUpgradeable {
             if (currentRatio > highestRatio) {
                 highestRatio = currentRatio;
             }
-        }
 
-        if (currentEpochId > 0) {
-            // Get previous epoch data
-            Epoch storage lastEpoch = epochs[currentEpochId - 1];
-
-            unlockPercentage = calculateUnlockPercentage(
-                currentTreasuryTvl,
-                _currentLiability,
-                lastEpoch.currentTreasuryTvl,
-                lastEpoch.totalLiability,
-                _paybackPercent
-            );
+            if (currentEpochId > 0) {
+                unlockPercentage = calculateUnlockPercentage(currentRatio, _paybackPercent);
+            }
         }
 
         // Check that unlock percentage doesn't exceed maximum