refactor: sd as 18 decimals

test: update tests accordingly

benchmark/results/SablierFlow.md

@@ -2,15 +2,15 @@
 
 | Function | Gas Usage |
 | ----------------------------- | --------- |
-| `adjustRatePerSecond` | 43628 |
+| `adjustRatePerSecond` | 44149 |
 | `create` | 113659 |
 | `deposit` | 30035 |
 | `depositViaBroker` | 21953 |
-| `pause` | 8983 |
-| `refund` | 11534 |
-| `restart` | 7031 |
-| `void (solvent stream)` | 9517  |
-| `void (insolvent stream)` | 36241 |
-| `withdraw (insolvent stream)` | 57034 |
-| `withdraw (solvent stream)` | 39502 |
-| `withdrawMax` | 51379 |
+| `pause` | 9522 |
+| `refund` | 11894 |
+| `restart` | 7013 |
+| `void (solvent stream)` | 10038 |
+| `void (insolvent stream)` | 37438 |
+| `withdraw (insolvent stream)` | 57688 |
+| `withdraw (solvent stream)` | 40156 |
+| `withdrawMax` | 51966 |

src/SablierFlow.sol

@@ -69,35 +69,35 @@ contract SablierFlow is
  return 0;
  }
 
+ uint8 tokenDecimals = _streams[streamId].tokenDecimals;
+ uint256 scaledBalance = Helpers.scaleAmount({ amount: balance, decimals: tokenDecimals });
+
  uint256 snapshotDebt = _streams[streamId].snapshotDebt;
 
  // If the stream has uncovered debt, return zero.
- if (snapshotDebt + _ongoingDebtOf(streamId) > balance) {
+ if (snapshotDebt + _scaledOngoingDebtOf(streamId) > scaledBalance) {
  return 0;
  }
 
- uint256 tokenDecimals = _streams[streamId].tokenDecimals;
- uint256 solvencyAmount;
-
  // Depletion time is defined as the UNIX timestamp beyond which the total debt exceeds stream balance.
  // So we calculate it by solving: debt at depletion time = stream balance + 1. This ensures that we find the
  // lowest timestamp at which the debt exceeds the balance.
  // Safe to use unchecked because the calculations cannot overflow or underflow.
  unchecked {
- if (tokenDecimals == 18) {
- solvencyAmount = (balance - snapshotDebt + 1);
- } else {
- uint256 scaleFactor = (10 ** (18 - tokenDecimals));
- solvencyAmount = (balance - snapshotDebt + 1) * scaleFactor;
- }
+ uint256 solvencyAmount =
+ scaledBalance - snapshotDebt + Helpers.scaleAmount({ amount: 1, decimals: tokenDecimals });
  uint256 solvencyPeriod = solvencyAmount / _streams[streamId].ratePerSecond.unwrap();
- return _streams[streamId].snapshotTime + solvencyPeriod;
+
+ depletionTime = _streams[streamId].snapshotTime + solvencyPeriod;
  }
  }
 
  /// @inheritdoc ISablierFlow
  function ongoingDebtOf(uint256 streamId) external view override notNull(streamId) returns (uint256 ongoingDebt) {
- ongoingDebt = _ongoingDebtOf(streamId);
+ ongoingDebt = Helpers.descaleAmount({
+ amount: _scaledOngoingDebtOf(streamId),
+ decimals: _streams[streamId].tokenDecimals
+ });
  }
 
  /// @inheritdoc ISablierFlow
@@ -192,7 +192,7 @@ contract SablierFlow is
  // Log the adjustment.
  emit ISablierFlow.AdjustFlowStream({
  streamId: streamId,
- totalDebt: _streams[streamId].snapshotDebt,
+ totalDebt: _totalDebtOf(streamId),
  oldRatePerSecond: oldRatePerSecond,
  newRatePerSecond: newRatePerSecond
  });
@@ -449,11 +449,11 @@ contract SablierFlow is
  return totalDebt.toUint128();
  }
 
- /// @dev Calculates the ongoing debt accrued since last snapshot. Return 0 if the stream is paused or
- /// `block.timestamp` is less than or equal to snapshot time.
- function _ongoingDebtOf(uint256 streamId) internal view returns (uint256 ongoingDebt) {
- uint40 blockTimestamp = uint40(block.timestamp);
- uint40 snapshotTime = _streams[streamId].snapshotTime;
+ /// @dev Calculates the ongoing debt, as a 18-decimals fixed point number, accrued since last snapshot. Return 0 if
+ /// the stream is paused or `block.timestamp` is less than or equal to snapshot time.
+ function _scaledOngoingDebtOf(uint256 streamId) internal view returns (uint256) {
+ uint256 blockTimestamp = block.timestamp;
+ uint256 snapshotTime = _streams[streamId].snapshotTime;
 
  uint256 ratePerSecond = _streams[streamId].ratePerSecond.unwrap();
 
@@ -470,22 +470,8 @@ contract SablierFlow is
  elapsedTime = blockTimestamp - snapshotTime;
  }
 
- // Calculate the ongoing debt accrued by multiplying the elapsed time by the rate per second.
- uint256 scaledOngoingDebt = elapsedTime * ratePerSecond;
-
- uint8 tokenDecimals = _streams[streamId].tokenDecimals;
-
- // If the token decimals are 18, return the scaled ongoing debt and the `block.timestamp`.
- if (tokenDecimals == 18) {
- return scaledOngoingDebt;
- }
-
- // Safe to use unchecked because we use {SafeCast}.
- unchecked {
- uint256 scaleFactor = 10 ** (18 - tokenDecimals);
- // Since debt is denoted in token decimals, descale the amount.
- ongoingDebt = scaledOngoingDebt / scaleFactor;
- }
+ // Calculate the scaled ongoing debt accrued by multiplying the elapsed time by the rate per second.
+ return elapsedTime * ratePerSecond;
  }
 
  /// @dev Calculates the refundable amount.
@@ -497,8 +483,8 @@ contract SablierFlow is
  /// @dev The total debt is the sum of the snapshot debt and the ongoing debt. This value is independent of the
  /// stream's balance.
  function _totalDebtOf(uint256 streamId) internal view returns (uint256) {
- // Calculate the total debt.
- return _streams[streamId].snapshotDebt + _ongoingDebtOf(streamId);
+ uint256 scaledTotalDebt = _scaledOngoingDebtOf(streamId) + _streams[streamId].snapshotDebt;
+ return Helpers.descaleAmount({ amount: scaledTotalDebt, decimals: _streams[streamId].tokenDecimals });
  }
 
  /// @dev Calculates the uncovered debt.
@@ -525,12 +511,12 @@ contract SablierFlow is
  revert Errors.SablierFlow_RatePerSecondNotDifferent(streamId, newRatePerSecond);
  }
 
- uint256 ongoingDebt = _ongoingDebtOf(streamId);
+ uint256 scaledOngoingDebt = _scaledOngoingDebtOf(streamId);
 
  // Update the snapshot debt only if the stream has ongoing debt.
- if (ongoingDebt > 0) {
+ if (scaledOngoingDebt > 0) {
  // Effect: update the snapshot debt.
- _streams[streamId].snapshotDebt += ongoingDebt;
+ _streams[streamId].snapshotDebt += scaledOngoingDebt;
  }
 
  // Effect: update the snapshot time.
@@ -646,7 +632,7 @@ contract SablierFlow is
  streamId: streamId,
  sender: _streams[streamId].sender,
  recipient: _ownerOf(streamId),
- totalDebt: _streams[streamId].snapshotDebt
+ totalDebt: _totalDebtOf(streamId)
  });
  }
 
@@ -715,16 +701,17 @@ contract SablierFlow is
 
  // If the stream is solvent, update the total debt normally.
  if (debtToWriteOff == 0) {
- uint256 ongoingDebt = _ongoingDebtOf(streamId);
- if (ongoingDebt > 0) {
+ uint256 scaledOngoingDebt = _scaledOngoingDebtOf(streamId);
+ if (scaledOngoingDebt > 0) {
  // Effect: Update the snapshot debt by adding the ongoing debt.
- _streams[streamId].snapshotDebt += ongoingDebt;
+ _streams[streamId].snapshotDebt += scaledOngoingDebt;
  }
  }
  // If the stream is insolvent, write off the uncovered debt.
  else {
  // Effect: update the total debt by setting snapshot debt to the stream balance.
- _streams[streamId].snapshotDebt = _streams[streamId].balance;
+ _streams[streamId].snapshotDebt =
+ Helpers.scaleAmount({ amount: _streams[streamId].balance, decimals: _streams[streamId].tokenDecimals });
  }
 
  // Effect: update the snapshot time.
@@ -742,7 +729,7 @@ contract SablierFlow is
  sender: _streams[streamId].sender,
  recipient: _ownerOf(streamId),
  caller: msg.sender,
- newTotalDebt: _streams[streamId].snapshotDebt,
+ newTotalDebt: _totalDebtOf(streamId),
  writtenOffDebt: debtToWriteOff
  });
  }
@@ -772,8 +759,11 @@ contract SablierFlow is
  revert Errors.SablierFlow_WithdrawalAddressNotRecipient({ streamId: streamId, caller: msg.sender, to: to });
  }
 
+ uint8 tokenDecimals = _streams[streamId].tokenDecimals;
+
  // Calculate the total debt.
- uint256 totalDebt = _totalDebtOf(streamId);
+ uint256 scaledTotalDebt = _scaledOngoingDebtOf(streamId) + _streams[streamId].snapshotDebt;
+ uint256 totalDebt = Helpers.descaleAmount(scaledTotalDebt, tokenDecimals);
 
  // Calculate the withdrawable amount.
  uint128 balance = _streams[streamId].balance;
@@ -792,17 +782,20 @@ contract SablierFlow is
  revert Errors.SablierFlow_Overdraw(streamId, amount, withdrawableAmount);
  }
 
+ // Calculate the amount scaled.
+ uint256 scaledAmount = Helpers.scaleAmount(amount, tokenDecimals);
+
  // Safe to use unchecked, `amount` cannot be greater than the balance or total debt at this point.
  unchecked {
  // If the amount is less than the snapshot debt, reduce it from the snapshot debt and leave the snapshot
  // time unchanged.
- if (amount <= _streams[streamId].snapshotDebt) {
- _streams[streamId].snapshotDebt -= amount;
+ if (scaledAmount <= _streams[streamId].snapshotDebt) {
+ _streams[streamId].snapshotDebt -= scaledAmount;
  }
  // Else reduce the amount from the ongoing debt by setting snapshot time to `block.timestamp` and set the
  // snapshot debt to the remaining total debt.
  else {
- _streams[streamId].snapshotDebt = totalDebt - amount;
+ _streams[streamId].snapshotDebt = scaledTotalDebt - scaledAmount;
 
  // Effect: update the stream time.
  _streams[streamId].snapshotTime = uint40(block.timestamp);

src/interfaces/ISablierFlowBase.sol

@@ -84,7 +84,7 @@ interface ISablierFlowBase is
  /// @param streamId The stream ID for the query.
  function getSender(uint256 streamId) external view returns (address sender);
 
- /// @notice Retrieves the snapshot debt of the stream, denoted in token's decimals.
+ /// @notice Retrieves the snapshot debt of the stream, denoted as a fixed-point number where 1e18 is 1 token.
  /// @dev Reverts if `streamId` references a null stream.
  /// @param streamId The stream ID for the query.
  function getSnapshotDebt(uint256 streamId) external view returns (uint256 snapshotDebt);

src/libraries/Helpers.sol

@@ -49,4 +49,34 @@ library Helpers {
  // Calculate the broker fee amount that is going to be transferred to the `broker.account`.
  (brokerFeeAmount, depositAmount) = calculateAmountsFromFee(totalAmount, broker.fee);
  }
+
+ /// @notice Descales the provided `amount` to be denoted in the token's decimals.
+ /// @dev The following logic is used to denormalize the amount:
+ /// - If the token has exactly 18 decimals, the amount is returned as is.
+ /// - if the token has fewer than 18 decimals, the amount is divided by $10^(18 - tokenDecimals)$.
+ function descaleAmount(uint256 amount, uint8 decimals) internal pure returns (uint256) {
+ if (decimals > 18) {
+ return amount;
+ }
+
+ unchecked {
+ uint256 scaleFactor = 10 ** (18 - decimals);
+ return amount / scaleFactor;
+ }
+ }
+
+ /// @notice Scales the provided `amount` to be denoted in 18 decimals.
+ /// @dev The following logic is used to normalize the amount:
+ /// - If the token has exactly 18 decimals, the amount is returned as is.
+ /// - If the token has fewer than 18 decimals, the amount is multiplied by $10^(18 - tokenDecimals)$.
+ function scaleAmount(uint256 amount, uint8 decimals) internal pure returns (uint256) {
+ if (decimals > 18) {
+ return amount;
+ }
+
+ unchecked {
+ uint256 scaleFactor = 10 ** (18 - decimals);
+ return amount * scaleFactor;
+ }
+ }
 }

src/types/DataTypes.sol

@@ -55,9 +55,9 @@ library Flow {
  /// be restarted. Voiding an insolvent stream sets its uncovered debt to zero.
  /// @param token The contract address of the ERC-20 token to stream.
  /// @param tokenDecimals The decimals of the ERC-20 token to stream.
- /// @param snapshotDebt The amount of tokens that the sender owed to the recipient at snapshot time, denoted in
- /// token's decimals. This, along with the ongoing debt, can be used to calculate the total debt at any given point
- /// in time.
+ /// @param snapshotDebt The amount of tokens that the sender owed to the recipient at snapshot time, denoted as a
+ /// 18-decimals fixed-point number. This, along with the ongoing debt, can be used to calculate the total debt at
+ /// any given point in time.
  struct Stream {
  // slot 0
  uint128 balance;

tests/fork/Flow.t.sol

@@ -229,7 +229,6 @@ contract Flow_Fork_Test is Fork_Test {
 
  uint256 beforeSnapshotAmount = flow.getSnapshotDebt(streamId);
  uint256 totalDebt = flow.totalDebtOf(streamId);
- uint256 ongoingDebt = flow.ongoingDebtOf(streamId);
 
  // Compute the snapshot time that will be stored post withdraw.
  vars.expectedSnapshotTime = getBlockTimestamp();
@@ -250,7 +249,9 @@ contract Flow_Fork_Test is Fork_Test {
 
  // It should update snapshot debt.
  vars.actualSnapshotDebt = flow.getSnapshotDebt(streamId);
- vars.expectedSnapshotDebt = ongoingDebt + beforeSnapshotAmount;
+ vars.expectedSnapshotDebt = calculateScaledOngoingDebt(
+ flow.getRatePerSecond(streamId).unwrap(), flow.getSnapshotTime(streamId)
+ ) + beforeSnapshotAmount;
  assertEq(vars.actualSnapshotDebt, vars.expectedSnapshotDebt, "AdjustRatePerSecond: snapshot debt");
 
  // It should set the new rate per second
@@ -561,8 +562,10 @@ contract Flow_Fork_Test is Fork_Test {
  uint256 initialTokenBalance = token.balanceOf(address(flow));
  uint256 totalDebt = flow.totalDebtOf(streamId);
 
- vars.expectedSnapshotTime =
- withdrawAmount <= flow.getSnapshotDebt(streamId) ? flow.getSnapshotTime(streamId) : getBlockTimestamp();
+ vars.expectedSnapshotTime = withdrawAmount
+ <= getDescaledAmount(flow.getSnapshotDebt(streamId), flow.getTokenDecimals(streamId))
+ ? flow.getSnapshotTime(streamId)
+  : getBlockTimestamp();
 
  (, address caller,) = vm.readCallers();
  address recipient = flow.getRecipient(streamId);

tests/integration/concrete/adjust-rate-per-second/adjustRatePerSecond.t.sol

@@ -119,7 +119,7 @@ contract AdjustRatePerSecond_Integration_Concrete_Test is Integration_Test {
 
  // It should update snapshot debt.
  actualSnapshotDebt = flow.getSnapshotDebt(defaultStreamId);
- expectedSnapshotDebt = ONE_MONTH_DEBT_6D;
+ expectedSnapshotDebt = ONE_MONTH_DEBT_18D;
  assertEq(actualSnapshotDebt, expectedSnapshotDebt, "snapshot debt");
 
  // It should set the new rate per second

tests/integration/concrete/deposit-and-pause/depositAndPause.t.sol

@@ -56,7 +56,8 @@ contract DepositAndPause_Integration_Concrete_Test is Integration_Test {
 
  function test_WhenCallerSender() external whenNoDelegateCall givenNotNull givenNotPaused {
  uint128 previousStreamBalance = flow.getBalance(defaultStreamId);
- uint256 previousTotalDebt = flow.totalDebtOf(defaultStreamId);
+ uint256 expectedSnapshotDebt =
+ calculateScaledOngoingDebt(RATE_PER_SECOND_U128, flow.getSnapshotTime(defaultStreamId));
 
  // It should emit 1 {Transfer}, 1 {DepositFlowStream}, 1 {PauseFlowStream}, 1 {MetadataUpdate} events
  vm.expectEmit({ emitter: address(usdc) });
@@ -74,7 +75,7 @@ contract DepositAndPause_Integration_Concrete_Test is Integration_Test {
  streamId: defaultStreamId,
  sender: users.sender,
  recipient: users.recipient,
- totalDebt: previousTotalDebt
+ totalDebt: flow.totalDebtOf(defaultStreamId)
  });
 
  vm.expectEmit({ emitter: address(flow) });
@@ -99,6 +100,6 @@ contract DepositAndPause_Integration_Concrete_Test is Integration_Test {
 
  // It should update the snapshot debt
  uint256 actualSnapshotDebt = flow.getSnapshotDebt(defaultStreamId);
- assertEq(actualSnapshotDebt, previousTotalDebt, "snapshot debt");
+ assertEq(actualSnapshotDebt, expectedSnapshotDebt, "snapshot debt");
  }
 }

tests/integration/concrete/pause/pause.t.sol

@@ -51,7 +51,7 @@ contract Pause_Integration_Concrete_Test is Integration_Test {
  assertGt(flow.uncoveredDebtOf(defaultStreamId), 0, "uncovered debt");
 
  // It should pause the stream.
- test_Pause();
+ _test_Pause();
  }
 
  function test_GivenNoUncoveredDebt() external whenNoDelegateCall givenNotNull givenNotPaused whenCallerSender {
@@ -62,19 +62,20 @@ contract Pause_Integration_Concrete_Test is Integration_Test {
  assertEq(flow.uncoveredDebtOf(defaultStreamId), 0, "uncovered debt");
 
  // It should pause the stream.
- test_Pause();
+ _test_Pause();
  }
 
- function test_Pause() internal {
- uint256 initialTotalDebt = flow.totalDebtOf(defaultStreamId);
+ function _test_Pause() private {
+ uint256 expectedSnapshotDebt =
+ calculateScaledOngoingDebt(RATE_PER_SECOND_U128, flow.getSnapshotTime(defaultStreamId));
 
  // It should emit 1 {PauseFlowStream}, 1 {MetadataUpdate} events.
  vm.expectEmit({ emitter: address(flow) });
  emit ISablierFlow.PauseFlowStream({
  streamId: defaultStreamId,
  sender: users.sender,
  recipient: users.recipient,
- totalDebt: initialTotalDebt
+ totalDebt: flow.totalDebtOf(defaultStreamId)
  });
 
  vm.expectEmit({ emitter: address(flow) });
@@ -91,6 +92,6 @@ contract Pause_Integration_Concrete_Test is Integration_Test {
 
  // It should update the snapshot debt.
  uint256 actualSnapshotDebt = flow.getSnapshotDebt(defaultStreamId);
- assertEq(actualSnapshotDebt, initialTotalDebt, "snapshot debt");
+ assertEq(actualSnapshotDebt, expectedSnapshotDebt, "snapshot debt");
  }
 }