Merge pull request #7 from api3dao/proxy-utils-removal

Removes ProxyUtils library

Author: acenolaza

contracts/NormalizedApi3ReaderProxyV1.sol

@@ -2,41 +2,58 @@
 pragma solidity ^0.8.27;
 
 import "./interfaces/INormalizedApi3ReaderProxyV1.sol";
-import "./ProxyUtils.sol";
 
 /// @title An immutable proxy contract that converts a Chainlink
 /// AggregatorV2V3Interface feed output to 18 decimals to conform with
-/// IApi3ReaderProxy decimal standard
+/// IApi3ReaderProxy decimal convention
 /// @dev This contract implements the AggregatorV2V3Interface to be compatible
 /// with Chainlink aggregators. This allows the contract to be used as a drop-in
 /// replacement for Chainlink aggregators in existing dApps.
 /// Refer to https://github.com/api3dao/migrate-from-chainlink-to-api3 for more
 /// information about the Chainlink interface implementation.
 contract NormalizedApi3ReaderProxyV1 is INormalizedApi3ReaderProxyV1 {
-    using ProxyUtils for int256;
-
     /// @notice Chainlink AggregatorV2V3Interface contract address
     address public immutable override feed;
 
-    uint8 internal immutable feedDecimals;
+    /// @notice Pre-calculated factor for scaling the feed's value to 18
+    /// decimals.
+    int256 public immutable scalingFactor;
+
+    /// @notice True if upscaling (multiply by `scalingFactor`), false if
+    /// downscaling (divide by `scalingFactor`), to normalize to 18 decimals.
+    bool public immutable isUpscaling;
 
     /// @param feed_ The address of the Chainlink AggregatorV2V3Interface feed
     constructor(address feed_) {
         if (feed_ == address(0)) {
             revert ZeroProxyAddress();
         }
-
         uint8 feedDecimals_ = AggregatorV2V3Interface(feed_).decimals();
         if (feedDecimals_ == 0 || feedDecimals_ > 36) {
             revert UnsupportedFeedDecimals();
         }
+        if (feedDecimals_ == 18) {
+            revert NoNormalizationNeeded();
+        }
         feed = feed_;
-        feedDecimals = feedDecimals_;
+        uint8 delta = feedDecimals_ > 18
+            ? feedDecimals_ - 18
+            : 18 - feedDecimals_;
+        scalingFactor = int256(10 ** uint256(delta));
+        isUpscaling = feedDecimals_ < 18;
     }
 
     /// @notice Returns the price of the underlying Chainlink feed normalized to
-    /// 18 decimals
-    /// of underlying Chainlink feed
+    /// 18 decimals.
+    /// @dev Fetches an `int256` answer from the Chainlink feed and scales it
+    /// to 18 decimals using pre-calculated factors. The result is cast to
+    /// `int224` to conform to the `IApi3ReaderProxy` interface.
+    /// IMPORTANT: If the normalized `int256` value is outside the `int224`
+    /// range, this cast causes silent truncation and data loss. Deployers
+    /// must verify that the source feed's characteristics (value magnitude
+    /// and original decimals) ensure the 18-decimal normalized value fits
+    /// `int224`. Scaling arithmetic (prior to cast) reverts on `int256`
+    /// overflow.
     /// @return value The normalized signed fixed-point value with 18 decimals
     /// @return timestamp The updatedAt timestamp of the feed
     function read()
@@ -48,7 +65,9 @@ contract NormalizedApi3ReaderProxyV1 is INormalizedApi3ReaderProxyV1 {
         (, int256 answer, , uint256 updatedAt, ) = AggregatorV2V3Interface(feed)
             .latestRoundData();
 
-        value = int224(answer.scaleValue(feedDecimals, 18));
+        value = isUpscaling
+            ? int224(answer * scalingFactor)
+            : int224(answer / scalingFactor);
         timestamp = uint32(updatedAt);
     }
 

contracts/ProxyUtils.sol

@@ -2,7 +2,6 @@
 pragma solidity ^0.8.27;
 
 import "@api3/contracts/interfaces/IApi3ReaderProxy.sol";
-import "../ProxyUtils.sol";
 import "./interfaces/IScaledApi3FeedProxyV1.sol";
 
 /// @title An immutable Chainlink AggregatorV2V3Interface feed contract that
@@ -11,13 +10,20 @@ import "./interfaces/IScaledApi3FeedProxyV1.sol";
 /// @dev This contract assumes the source proxy always returns values with
 /// 18 decimals (as all IApi3ReaderProxy-compatible proxies do)
 contract ScaledApi3FeedProxyV1 is IScaledApi3FeedProxyV1 {
-    using ProxyUtils for int256;
-
     /// @notice IApi3ReaderProxy contract address
     address public immutable override proxy;
 
+    /// @dev Target decimals for the scaled value.
     uint8 private immutable targetDecimals;
 
+    /// @notice Pre-calculated factor for scaling the proxy's 18-decimal value
+    /// to `targetDecimals`.
+    int256 public immutable scalingFactor;
+
+    /// @notice True if upscaling (multiply by `scalingFactor`), false if
+    /// downscaling (divide by `scalingFactor`), to scale to `targetDecimals`.
+    bool public immutable isUpscaling;
+
     /// @param proxy_ IApi3ReaderProxy contract address
     /// @param targetDecimals_ Decimals used to scale the IApi3ReaderProxy value
     constructor(address proxy_, uint8 targetDecimals_) {
@@ -27,9 +33,16 @@ contract ScaledApi3FeedProxyV1 is IScaledApi3FeedProxyV1 {
         if (targetDecimals_ == 0 || targetDecimals_ > 36) {
             revert InvalidDecimals();
         }
-
+        if (targetDecimals_ == 18) {
+            revert NoScalingNeeded();
+        }
         proxy = proxy_;
         targetDecimals = targetDecimals_;
+        uint8 delta = targetDecimals_ > 18
+            ? targetDecimals_ - 18
+            : 18 - targetDecimals_;
+        scalingFactor = int256(10 ** uint256(delta));
+        isUpscaling = targetDecimals_ > 18;
     }
 
     /// @dev AggregatorV2V3Interface users are already responsible with
@@ -118,19 +131,26 @@ contract ScaledApi3FeedProxyV1 is IScaledApi3FeedProxyV1 {
         updatedAt = startedAt;
     }
 
-    /// @notice Reads from the IApi3ReaderProxy value and scales it to target
-    /// decimals
-    /// @dev Casting the scaled value to int224 might cause an overflow but this
-    /// is preferable to checking the value for overflows in every read due to
-    /// gas overhead
-    function _read()
-        internal
-        view
-        returns (int256 scaledValue, uint32 timestamp)
-    {
-        (int256 value, uint32 proxyTimestamp) = IApi3ReaderProxy(proxy).read();
-
-        scaledValue = int224(value.scaleValue(18, targetDecimals));
+    /// @notice Reads a value from the underlying `IApi3ReaderProxy` and
+    /// scales it to `targetDecimals`.
+    /// @dev Reads an `int224` value (assumed to be 18 decimals) from the
+    /// underlying `IApi3ReaderProxy`. This value is then scaled to
+    /// `targetDecimals` using pre-calculated factors. The scaling arithmetic
+    /// (e.g., `proxyValue * scalingFactor`) involves an `int224` (`proxyValue`)
+    /// and an `int256` (`scalingFactor`). `proxyValue` is implicitly promoted
+    /// to `int256` for this operation, resulting in an `int256` value.
+    /// This allows the scaled result to exceed the `int224` range, provided
+    /// it fits within `int256`. Arithmetic operations will revert on `int256`
+    /// overflow. The function returns the scaled value as an `int256`.
+    /// @return value The scaled signed fixed-point value with `targetDecimals`.
+    /// @return timestamp The timestamp from the underlying proxy.
+    function _read() internal view returns (int256 value, uint32 timestamp) {
+        (int224 proxyValue, uint32 proxyTimestamp) = IApi3ReaderProxy(proxy)
+            .read();
+
+        value = isUpscaling
+            ? proxyValue * scalingFactor
+            : proxyValue / scalingFactor;
         timestamp = proxyTimestamp;
     }
 }

contracts/adapters/ScaledApi3FeedProxyV1.sol

@@ -8,7 +8,13 @@ interface IScaledApi3FeedProxyV1 is AggregatorV2V3Interface {
 
     error InvalidDecimals();
 
+    error NoScalingNeeded();
+
     error FunctionIsNotSupported();
 
     function proxy() external view returns (address proxy);
+
+    function scalingFactor() external view returns (int256);
+
+    function isUpscaling() external view returns (bool);
 }

contracts/adapters/interfaces/IScaledApi3FeedProxyV1.sol

@@ -12,7 +12,13 @@ interface INormalizedApi3ReaderProxyV1 is
 
     error UnsupportedFeedDecimals();
 
+    error NoNormalizationNeeded();
+
     error FunctionIsNotSupported();
 
     function feed() external view returns (address feed);
+
+    function scalingFactor() external view returns (int256);
+
+    function isUpscaling() external view returns (bool);
 }

contracts/interfaces/INormalizedApi3ReaderProxyV1.sol

@@ -11,8 +11,8 @@ describe('NormalizedApi3ReaderProxyV1', function () {
       return { ...acc, [roleName]: accounts[index] };
     }, {});
 
-    const decimals = 20;
-    const answer = ethers.parseUnits('1824.97', decimals);
+    const decimals = 8;
+    const answer = ethers.parseUnits('0.25', decimals);
     const timestamp = await helpers.time.latest();
 
     const mockAggregatorV2V3Factory = await ethers.getContractFactory('MockAggregatorV2V3', roles.deployer);
@@ -42,9 +42,26 @@ describe('NormalizedApi3ReaderProxyV1', function () {
 
   describe('constructor', function () {
     context('feed is not zero address', function () {
-      it('constructs', async function () {
-        const { feed, normalizedApi3ReaderProxyV1 } = await helpers.loadFixture(deploy);
-        expect(await normalizedApi3ReaderProxyV1.feed()).to.equal(await feed.getAddress());
+      context('feed does not have 18 decimals', function () {
+        it('constructs', async function () {
+          const { feed, normalizedApi3ReaderProxyV1 } = await helpers.loadFixture(deploy);
+          expect(await normalizedApi3ReaderProxyV1.feed()).to.equal(await feed.getAddress());
+          expect(await normalizedApi3ReaderProxyV1.isUpscaling()).to.equal(true); // 8 < 18 is true
+          expect(await normalizedApi3ReaderProxyV1.scalingFactor()).to.equal(10_000_000_000n); // 10**(18-8)
+        });
+      });
+      context('feed has 18 decimals', function () {
+        it('reverts', async function () {
+          const { roles, mockAggregatorV2V3Factory } = await helpers.loadFixture(deploy);
+          const feed = await mockAggregatorV2V3Factory.deploy(18, ethers.parseEther('1'), await helpers.time.latest());
+          const normalizedApi3ReaderProxyV1Factory = await ethers.getContractFactory(
+            'NormalizedApi3ReaderProxyV1',
+            roles.deployer
+          );
+          await expect(normalizedApi3ReaderProxyV1Factory.deploy(feed))
+            .to.be.revertedWithCustomError(normalizedApi3ReaderProxyV1Factory, 'NoNormalizationNeeded')
+            .withArgs();
+        });
       });
     });
     context('feed is zero address', function () {

test/NormalizedApi3ReaderProxyV1.sol.ts

@@ -88,9 +88,22 @@ describe('ScaledApi3FeedProxyV1', function () {
   describe('constructor', function () {
     context('proxy is not zero address', function () {
       context('targetDecimals is not invalid', function () {
-        it('constructs', async function () {
-          const { api3ReaderProxyV1, scaledApi3FeedProxyV1 } = await helpers.loadFixture(deploy);
-          expect(await scaledApi3FeedProxyV1.proxy()).to.equal(await api3ReaderProxyV1.getAddress());
+        context('targetDecimals is not 18', function () {
+          it('constructs', async function () {
+            const { api3ReaderProxyV1, scaledApi3FeedProxyV1 } = await helpers.loadFixture(deploy);
+            expect(await scaledApi3FeedProxyV1.proxy()).to.equal(await api3ReaderProxyV1.getAddress());
+            expect(await scaledApi3FeedProxyV1.isUpscaling()).to.equal(false); // targetDecimals (8) > 18 is false
+            expect(await scaledApi3FeedProxyV1.scalingFactor()).to.equal(10_000_000_000n); // 10**(18-8)
+          });
+        });
+        context('targetDecimals is 18', function () {
+          it('reverts', async function () {
+            const { api3ReaderProxyV1, roles } = await helpers.loadFixture(deploy);
+            const scaledApi3FeedProxyV1 = await ethers.getContractFactory('ScaledApi3FeedProxyV1', roles.deployer);
+            await expect(scaledApi3FeedProxyV1.deploy(await api3ReaderProxyV1.getAddress(), 18))
+              .to.be.revertedWithCustomError(scaledApi3FeedProxyV1, 'NoScalingNeeded')
+              .withArgs();
+          });
         });
       });
       context('targetDecimals is invalid', function () {