fix: comments

Signed-off-by: Pablo Maldonado <pablo@umaproject.org>

src/oracles/CoinbaseOracle.sol

@@ -8,7 +8,9 @@ import {IAggregatorV3SourceCoinbase} from "../interfaces/coinbase/IAggregatorV3S
  * @notice A smart contract that serves as an oracle for price data reported by a designated reporter.
  */
 contract CoinbaseOracle is IAggregatorV3SourceCoinbase {
-    uint8 public immutable decimals = 6;
+    address public reporter = 0xfCEAdAFab14d46e20144F48824d0C09B1a03F2BC;
+    uint8 public immutable DECIMALS = 6;
+    bytes32 public immutable KIND_HASH = keccak256(abi.encodePacked("prices"));
 
     struct RoundData {
         int256 answer;
@@ -25,11 +27,11 @@ contract CoinbaseOracle is IAggregatorV3SourceCoinbase {
     event PricePushed(string indexed ticker, uint80 indexed roundId, int256 price, uint256 timestamp);
 
     /**
-     * @notice Returns the address of the reporter.
-     * @return The address of the reporter.
+     * @notice Returns the number of decimals used by the oracle.
+     * @return The number of decimals used by the oracle.
      */
-    function reporter() public view virtual returns (address) {
-        return 0xfCEAdAFab14d46e20144F48824d0C09B1a03F2BC;
+    function decimals() external pure returns (uint8) {
+        return DECIMALS;
     }
 
     /**
@@ -85,13 +87,13 @@ contract CoinbaseOracle is IAggregatorV3SourceCoinbase {
             uint256 price // 6 decimals
         ) = abi.decode(priceData, (string, uint256, string, uint256));
 
-        require(keccak256(abi.encodePacked(kind)) == keccak256(abi.encodePacked("prices")), "Invalid kind.");
+        require(keccak256(abi.encodePacked(kind)) == KIND_HASH, "Invalid kind.");
 
         PriceData storage priceDataStruct = prices[ticker];
         uint256 latestTimestamp = priceDataStruct.rounds[priceDataStruct.lastRoundId].timestamp;
 
         require(timestamp > latestTimestamp, "Invalid timestamp.");
-        require(recoverSigner(priceData, signature) == reporter(), "Invalid signature.");
+        require(recoverSigner(priceData, signature) == reporter, "Invalid signature.");
         require(price <= uint256(type(int256).max), "Price exceeds max value.");
 
         priceDataStruct.lastRoundId++;

test/mocks/MockCoinbaseOracle.sol

@@ -4,13 +4,7 @@ pragma solidity 0.8.17;
 import {CoinbaseOracle} from "../../src/oracles/CoinbaseOracle.sol";
 
 contract MockCoinbaseOracle is CoinbaseOracle {
-    address public customReporter;
-
     constructor(address _customReporter) {
-        customReporter = _customReporter;
-    }
-
-    function reporter() public view override returns (address) {
-        return customReporter;
+        reporter = _customReporter;
     }
 }