Update health precision from UFix64 to UInt256 with 18 decimals (#31)

* update health from UFix64 to UInt256 increasing decimal precision from 8 to 18

* update tests for compatibility with increased health precision

* clean up lines commented during refactor

* update test to use global constants

* add funds_required_ tests & fix contract miscalculation

* uncomment bypassed test cases

* fix overflow in TidalProtocolUtils.mul

* add undercollateralized scenarios to funds_required_for_target_health_test.cdc

* fix fundsRequired miscalculation by accounting for collateral/deposit factors

Author: sisyphusSmiling

cadence/contracts/TidalProtocol.cdc

@@ -186,7 +186,26 @@ access(all) contract TidalProtocolUtils {
     /// @param y: Second operand (scaled by 10^18)
     /// @return: Product scaled by 10^18
     access(all) view fun mul(_ x: UInt256, _ y: UInt256): UInt256 {
-        return (x * y) / self.e18
+        // multiply the two values as 18-decimal fixed-point numbers in a manner that avoids overflow in the cases where
+        // the result would be greater than 2^256 but also avoids rounding to 0 in the cases where the result would be
+        // less than 10^18
+        // To avoid overflow, perform the multiplication in two steps if either x or y is large.
+        // If both x and y are less than sqrt(UInt256.max), safe to multiply directly.
+        // Otherwise, rearrange: (x * y) / e18 = x * (y / e18) if y >= e18, or y * (x / e18) if x >= e18.
+        if x == 0 || y == 0 {
+            return 0
+        }
+        // Calculate sqrt(2^256) = 2^128 using a bitshift, using the value as a threshold to avoid overflow
+        let sqrtMax = UInt256(1) << 128
+        if x < sqrtMax && y < sqrtMax {
+            return (x * y) / self.e18
+        }
+        // Prefer to divide the larger value first to avoid loss of precision
+        if x >= y {
+            return x * (y / self.e18)
+        } else {
+            return y * (x / self.e18)
+        }
     }
 
     /// Divides two 18-decimal fixed-point numbers

cadence/contracts/TidalProtocolUtils.cdc

@@ -4,7 +4,7 @@ access(all)
 fun main(
     pid: UInt64,
     withdrawType: String,
-    targetHealth: UFix64,
+    targetHealth: UInt256,
     depositType: String,
     depositAmount: UFix64
 ): UFix64 {

cadence/scripts/tidal-protocol/funds_avail_above_target_health_after_deposit.cdc

@@ -4,7 +4,7 @@ access(all)
 fun main(
     pid: UInt64,
     depositType: String,
-    targetHealth: UFix64,
+    targetHealth: UInt256,
     withdrawType: String,
     withdrawAmount: UFix64
 ): UFix64 {

cadence/scripts/tidal-protocol/funds_req_for_target_health_after_withdraw.cdc

@@ -5,7 +5,7 @@ import "TidalProtocol"
 /// @param pid: The Position ID
 ///
 access(all)
-fun main(pid: UInt64): UFix64 {
+fun main(pid: UInt64): UInt256 {
     let protocolAddress= Type<@TidalProtocol.Pool>().address!
     return getAccount(protocolAddress).capabilities.borrow<&TidalProtocol.Pool>(TidalProtocol.PoolPublicPath)
         ?.positionHealth(pid: pid)

cadence/scripts/tidal-protocol/position_health.cdc

@@ -81,8 +81,8 @@ fun testAutoBorrowBehaviorWithTargetHealth() {
 
     // Verify position health is at target
     let health = getPositionHealth(pid: 0, beFailed: false)
-    Test.assert(health >= 1.29 && health <= 1.31,
-        message: "Expected health to be at target (1.3), but got \(health)")
+    Test.assert(equalWithinVariance(intTargetHealth, health),
+        message: "Expected health to be \(intTargetHealth), but got \(health)")
 
     // Verify the user actually received the borrowed MOET in their Vault (draw-down sink)
     let userMoetBalance = getBalance(address: user.address, vaultPublicPath: MOET.VaultPublicPath)!

cadence/tests/auto_borrow_behavior_test.cdc

@@ -5,6 +5,7 @@ import "test_helpers.cdc"
 
 import "MOET"
 import "TidalProtocol"
+import "TidalProtocolUtils"
 
 access(all) let protocolAccount = Test.getAccount(0x0000000000000007)
 access(all) let userAccount = Test.createAccount()
@@ -14,10 +15,7 @@ access(all) var moetTokenIdentifier = "A.0000000000000007.MOET.Vault"
 access(all) let flowVaultStoragePath = /storage/flowTokenVault
 access(all) let wrapperStoragePath = /storage/tidalProtocolPositionWrapper
 
-access(all) let minHealth = 1.1
-access(all) let targetHealth = 1.3
-access(all) let maxHealth = 1.5
-access(all) let ceilingHealth = UFix64.max      // the maximum health value when health is virtually infinite AKA debt ~0.0
+
 access(all) let flowCollateralFactor = 0.8
 access(all) let flowBorrowFactor = 1.0
 access(all) let flowStartPrice = 1.0            // denominated in MOET
@@ -97,7 +95,7 @@ fun testFundsAvailableAboveTargetHealthAfterDepositingWithPushFromHealthy() {
     // assert expected starting point
     let balanceAfterBorrow = getBalance(address: userAccount.address, vaultPublicPath: MOET.VaultPublicPath)!
     let expectedBorrowAmount = (positionFundingAmount * flowCollateralFactor * flowStartPrice) / targetHealth
-    Test.assert(balanceAfterBorrow >= expectedBorrowAmount - 0.01 && balanceAfterBorrow <= expectedBorrowAmount + 0.01,
+    Test.assert(equalWithinVariance(expectedBorrowAmount, balanceAfterBorrow),
         message: "Expected MOET balance to be ~\(expectedBorrowAmount), but got \(balanceAfterBorrow)")
 
     let evts = Test.eventsOfType(Type<TidalProtocol.Opened>())
@@ -113,8 +111,8 @@ fun testFundsAvailableAboveTargetHealthAfterDepositingWithPushFromHealthy() {
     Test.assertEqual(TidalProtocol.BalanceDirection.Credit, flowPositionBalance.direction)
     Test.assertEqual(TidalProtocol.BalanceDirection.Debit, moetBalance.direction)
 
-    Test.assertEqual(targetHealth, health)
-    // Test.assertEqual(ceilingHealth, health)
+    Test.assert(equalWithinVariance(intTargetHealth, health),
+        message: "Expected health to be \(intTargetHealth), but got \(health)")
 
     log("[TEST] FLOW price set to \(flowStartPrice)")
 
@@ -126,8 +124,8 @@ fun testFundsAvailableAboveTargetHealthAfterDepositingWithPushFromHealthy() {
         runFundsAvailableAboveTargetHealthAfterDepositing(
             pid: positionID,
             existingBorrowed: expectedBorrowAmount,
-            existingFlowCollateral: positionFundingAmount,
-            currentFlowPrice: flowStartPrice,
+            existingFLOWCollateral: positionFundingAmount,
+            currentFLOWPrice: flowStartPrice,
             depositAmount: amount,
             withdrawIdentifier: moetTokenIdentifier,
             depositIdentifier: flowTokenIdentifier
@@ -141,8 +139,8 @@ fun testFundsAvailableAboveTargetHealthAfterDepositingWithPushFromHealthy() {
         runFundsAvailableAboveTargetHealthAfterDepositing(
             pid: positionID,
             existingBorrowed: expectedBorrowAmount,
-            existingFlowCollateral: positionFundingAmount,
-            currentFlowPrice: flowStartPrice,
+            existingFLOWCollateral: positionFundingAmount,
+            currentFLOWPrice: flowStartPrice,
             depositAmount: amount,
             withdrawIdentifier: moetTokenIdentifier,
             depositIdentifier: flowTokenIdentifier
@@ -198,8 +196,8 @@ fun testFundsAvailableAboveTargetHealthAfterDepositingWithoutPushFromHealthy() {
         runFundsAvailableAboveTargetHealthAfterDepositing(
             pid: positionID,
             existingBorrowed: expectedBorrowAmount,
-            existingFlowCollateral: positionFundingAmount,
-            currentFlowPrice: flowStartPrice,
+            existingFLOWCollateral: positionFundingAmount,
+            currentFLOWPrice: flowStartPrice,
             depositAmount: amount,
             withdrawIdentifier: moetTokenIdentifier,
             depositIdentifier: flowTokenIdentifier
@@ -213,8 +211,8 @@ fun testFundsAvailableAboveTargetHealthAfterDepositingWithoutPushFromHealthy() {
         runFundsAvailableAboveTargetHealthAfterDepositing(
             pid: positionID,
             existingBorrowed: expectedBorrowAmount,
-            existingFlowCollateral: positionFundingAmount,
-            currentFlowPrice: flowStartPrice,
+            existingFLOWCollateral: positionFundingAmount,
+            currentFLOWPrice: flowStartPrice,
             depositAmount: amount,
             withdrawIdentifier: moetTokenIdentifier,
             depositIdentifier: flowTokenIdentifier
@@ -282,21 +280,19 @@ fun testFundsAvailableAboveTargetHealthAfterDepositingWithoutPushFromOvercollate
 
     log("..............................")
     var depositAmount = 0.0
-    // var expectedAvailable = expectedAvailableAboveTarget + (depositAmount * flowCollateralFactor / targetHealth * flowBorrowFactor) * newPrice
     var expectedAvailable = (positionFundingAmount + depositAmount) * newPrice * flowCollateralFactor / targetHealth * flowBorrowFactor
     var actualAvailable = fundsAvailableAboveTargetHealthAfterDepositing(
             pid: positionID,
             withdrawType: moetTokenIdentifier,
-            targetHealth: targetHealth,
+            targetHealth: intTargetHealth,
             depositType: flowTokenIdentifier,
             depositAmount: depositAmount,
             beFailed: false
         )
     log("[TEST] Depositing: \(depositAmount)")
     log("[TEST] Expected Available: \(expectedAvailable)")
     log("[TEST] Actual Available: \(actualAvailable)")
-    // getting error here -  expected: 76.92307692, actual: 61.53846153
-    Test.assert(equalWithinVariance(expectedAvailable, actualAvailable, plusMinus: nil),
+    Test.assert(equalWithinVariance(expectedAvailable, actualAvailable),
         message: "Values are not equal within variance - expected: \(expectedAvailable), actual: \(actualAvailable)")
 
     log("..............................")
@@ -306,15 +302,15 @@ fun testFundsAvailableAboveTargetHealthAfterDepositingWithoutPushFromOvercollate
     actualAvailable = fundsAvailableAboveTargetHealthAfterDepositing(
             pid: positionID,
             withdrawType: moetTokenIdentifier,
-            targetHealth: targetHealth,
+            targetHealth: intTargetHealth,
             depositType: flowTokenIdentifier,
             depositAmount: depositAmount,
             beFailed: false
         )
     log("[TEST] Depositing: \(depositAmount)")
     log("[TEST] Expected Available: \(expectedAvailable)")
     log("[TEST] Actual Available: \(actualAvailable)")
-    Test.assert(equalWithinVariance(expectedAvailable, actualAvailable, plusMinus: nil),
+    Test.assert(equalWithinVariance(expectedAvailable, actualAvailable),
         message: "Values are not equal within variance - expected: \(expectedAvailable), actual: \(actualAvailable)")
 
     log("==============================")
@@ -330,20 +326,20 @@ access(all)
 fun runFundsAvailableAboveTargetHealthAfterDepositing(
     pid: UInt64,
     existingBorrowed: UFix64,
-    existingFlowCollateral: UFix64,
-    currentFlowPrice: UFix64,
+    existingFLOWCollateral: UFix64,
+    currentFLOWPrice: UFix64,
     depositAmount: UFix64,
     withdrawIdentifier: String,
     depositIdentifier: String
 ) {
     log("..............................")
-    let expectedTotalBorrowCapacity = (existingFlowCollateral + depositAmount) * currentFlowPrice * flowCollateralFactor / targetHealth * flowBorrowFactor
+    let expectedTotalBorrowCapacity = (existingFLOWCollateral + depositAmount) * currentFLOWPrice * flowCollateralFactor / targetHealth * flowBorrowFactor
     let expectedAvailable = expectedTotalBorrowCapacity - existingBorrowed
 
     let actualAvailable = fundsAvailableAboveTargetHealthAfterDepositing(
             pid: pid,
             withdrawType: withdrawIdentifier,
-            targetHealth: targetHealth,
+            targetHealth: intTargetHealth,
             depositType: depositIdentifier,
             depositAmount: depositAmount,
             beFailed: false
@@ -353,6 +349,6 @@ fun runFundsAvailableAboveTargetHealthAfterDepositing(
     log("[TEST] Depositing: \(depositAmount)")
     log("[TEST] Expected Available: \(expectedAvailable)")
     log("[TEST] Actual Available: \(actualAvailable)")
-    Test.assert(equalWithinVariance(expectedAvailable, actualAvailable, plusMinus: nil),
+    Test.assert(equalWithinVariance(expectedAvailable, actualAvailable),
         message: "Values are not equal within variance - expected: \(expectedAvailable), actual: \(actualAvailable)")
 }