feat: expose latest answer on static a token (#3)

Makefile

@@ -35,4 +35,5 @@ coverage :; forge coverage --report lcov && \
 download :; cast etherscan-source --chain ${chain} -d src/etherscan/${chain}_${address} ${address}
 git-diff :
  @mkdir -p diffs
+ @npx prettier ${before} ${after} --write
  @printf '%s\n%s\n%s\n' "\`\`\`diff" "$$(git diff --no-index --diff-algorithm=patience --ignore-space-at-eol ${before} ${after})" "\`\`\`" > diffs/${out}.md

src/periphery/contracts/static-a-token/README.md

@@ -36,3 +36,20 @@ For this project, the security procedures applied/being finished are:
 
 - The test suite of the codebase itself.
 - Certora audit/property checking for all the dynamics of the `stataToken`, including respecting all the specs of [EIP-4626](https://eips.ethereum.org/EIPS/eip-4626).
+
+## Upgrade Notes Umbrella
+
+- Interface inheritance has been changed so that `IStaticATokenLM` implements `IERC4626`, making it easier for integrators to work with the interface.
+- The static A tokens are given a `rescuable`, which can be used by the ACL admin to rescue tokens locked to the contract.
+- Permit params have been excluded from the METADEPOSIT_TYPEHASH as they are not necessary. Even if someone were to frontrun the permit via mempool observation the permit is wrapped in a `try..catch` to prevent griefing attacks.
+- The static a token not implements pausability, which allows the ACL admin to pause all transfers.
+
+The storage layout diff was generated via:
+
+```
+git checkout main
+forge inspect src/periphery/contracts/static-a-token/StaticATokenLM.sol:StaticATokenLM storage-layout --pretty > reports/StaticATokenStorageBefore.md
+git checkout project-a
+forge inspect src/periphery/contracts/static-a-token/StaticATokenLM.sol:StaticATokenLM storage-layout --pretty > reports/StaticATokenStorageAfter.md
+make git-diff before=reports/StaticATokenStorageBefore.md after=reports/StaticATokenStorageAfter.md out=StaticATokenStorageDiff
+```

src/periphery/contracts/static-a-token/StaticATokenLM.sol

@@ -2,6 +2,8 @@
 pragma solidity ^0.8.10;
 
 import {IPool} from '../../../core/contracts/interfaces/IPool.sol';
+import {IPoolAddressesProvider} from '../../../core/contracts/interfaces/IPoolAddressesProvider.sol';
+import {IAaveOracle} from '../../../core/contracts/interfaces/IAaveOracle.sol';
 import {DataTypes, ReserveConfiguration} from '../../../core/contracts/protocol/libraries/configuration/ReserveConfiguration.sol';
 import {WadRayMath} from '../../../core/contracts/protocol/libraries/math/WadRayMath.sol';
 import {MathUtils} from '../../../core/contracts/protocol/libraries/math/MathUtils.sol';
@@ -55,6 +57,7 @@ contract StaticATokenLM is
  uint256 public constant STATIC__ATOKEN_LM_REVISION = 3;
 
  IPool public immutable POOL;
+ IPoolAddressesProvider immutable POOL_ADDRESSES_PROVIDER;
  IRewardsController public immutable INCENTIVES_CONTROLLER;
 
  IERC20 internal _aToken;
@@ -67,6 +70,7 @@ contract StaticATokenLM is
  _disableInitializers();
  POOL = pool;
  INCENTIVES_CONTROLLER = rewardsController;
+ POOL_ADDRESSES_PROVIDER = pool.ADDRESSES_PROVIDER();
  }
 
  modifier onlyPauseGuardian() {
@@ -75,7 +79,7 @@ contract StaticATokenLM is
  }
 
  function canPause(address actor) public view returns (bool) {
- return IACLManager(POOL.ADDRESSES_PROVIDER().getACLManager()).isEmergencyAdmin(actor);
+ return IACLManager(POOL_ADDRESSES_PROVIDER.getACLManager()).isEmergencyAdmin(actor);
  }
 
  ///@inheritdoc IInitializableStaticATokenLM
@@ -103,7 +107,7 @@ contract StaticATokenLM is
 
  /// @inheritdoc IRescuable
  function whoCanRescue() public view override returns (address) {
- return POOL.ADDRESSES_PROVIDER().getACLAdmin();
+ return POOL_ADDRESSES_PROVIDER.getACLAdmin();
  }
 
  ///@inheritdoc IStaticATokenLM
@@ -468,6 +472,15 @@ contract StaticATokenLM is
  return _withdraw(owner, receiver, shares, 0, withdrawFromAave);
  }
 
+ ///@inheritdoc IStaticATokenLM
+ function latestAnswer() external view returns (int256) {
+ return
+ int256(
+ (IAaveOracle(POOL_ADDRESSES_PROVIDER.getPriceOracle()).getAssetPrice(_aTokenUnderlying) *
+ POOL.getReserveNormalizedIncome(_aTokenUnderlying)) / 1e27
+ );
+ }
+
  function _deposit(
  address depositor,
  address receiver,

src/periphery/contracts/static-a-token/interfaces/IStaticATokenLM.sol

@@ -219,4 +219,15 @@ interface IStaticATokenLM is IInitializableStaticATokenLM, IERC4626 {
  * @param paused boolean determining if the token should be paused or unpaused
  */
  function setPaused(bool paused) external;
+
+ /**
+ * @notice Returns the current asset price of the stataToken.
+ * The price is calculated as `underlying_price * exchangeRate`.
+ * It is important to note that:
+ * - `underlying_price` is the price obtained by the aave-oracle and is subject to it's internal pricing mechanisms.
+ * - as the price is scaled over the exchangeRate, but maintains the same precision as the underlying the price might be underestimated by 1 unit.
+ * - when pricing multiple `shares` as `shares * price` keep in mind that the error compounds.
+ * @return price the current asset price.
+ */
+ function latestAnswer() external view returns (int256);
 }

tests/periphery/static-a-token/StaticATokenLM.t.sol

@@ -10,6 +10,7 @@ import {RayMathExplicitRounding} from '../../../src/periphery/contracts/librarie
 import {IStaticATokenLM} from '../../../src/periphery/contracts/static-a-token/interfaces/IStaticATokenLM.sol';
 import {SigUtils} from '../../utils/SigUtils.sol';
 import {BaseTest, TestnetERC20} from './TestBase.sol';
+import {IPool} from '../../../src/core/contracts/interfaces/IPool.sol';
 
 contract StaticATokenLMTest is BaseTest {
  using RayMathExplicitRounding for uint256;
@@ -48,6 +49,34 @@ contract StaticATokenLMTest is BaseTest {
  );
  }
 
+ function test_latestAnswer_priceShouldBeEqualOnDefaultIndex() public {
+ vm.mockCall(
+ address(POOL),
+ abi.encodeWithSelector(IPool.getReserveNormalizedIncome.selector),
+ abi.encode(1e27)
+ );
+ uint256 stataPrice = uint256(staticATokenLM.latestAnswer());
+ uint256 underlyingPrice = contracts.aaveOracle.getAssetPrice(UNDERLYING);
+ assertEq(stataPrice, underlyingPrice);
+ }
+
+ function test_latestAnswer_priceShouldReflectIndexAccrual(uint256 liquidityIndex) public {
+ liquidityIndex = bound(liquidityIndex, 1e27, 1e29);
+ vm.mockCall(
+ address(POOL),
+ abi.encodeWithSelector(IPool.getReserveNormalizedIncome.selector),
+ abi.encode(liquidityIndex)
+ );
+ uint256 stataPrice = uint256(staticATokenLM.latestAnswer());
+ uint256 underlyingPrice = contracts.aaveOracle.getAssetPrice(UNDERLYING);
+ uint256 expectedStataPrice = (underlyingPrice * liquidityIndex) / 1e27;
+ assertEq(stataPrice, expectedStataPrice);
+
+ // reverse the math to ensure precision loss is within bounds
+ uint256 reversedUnderlying = (stataPrice * 1e27) / liquidityIndex;
+ assertApproxEqAbs(underlyingPrice, reversedUnderlying, 1);
+ }
+
  function test_convertersAndPreviews() public view {
  uint128 amount = 5 ether;
  uint256 shares = staticATokenLM.convertToShares(amount);