fix: conversion from price to ratio reciprocal error

core/lib/external_price_api/src/coingecko_api.rs

@@ -49,6 +49,7 @@ impl CoinGeckoPriceAPIClient {
         }
     }
 
+    /// returns ETH/BaseToken price of a token by address
     async fn get_token_price_by_address(&self, address: Address) -> anyhow::Result<f64> {
         let address_str = address_to_string(&address);
         let price_url = self
@@ -87,11 +88,13 @@ impl CoinGeckoPriceAPIClient {
 impl PriceAPIClient for CoinGeckoPriceAPIClient {
     async fn fetch_ratio(&self, token_address: Address) -> anyhow::Result<BaseTokenAPIRatio> {
         let base_token_in_eth = self.get_token_price_by_address(token_address).await?;
-        let (numerator, denominator) = get_fraction(base_token_in_eth);
+        let (num_in_eth, denom_in_eth) = get_fraction(base_token_in_eth);
+        // take reciprocal of price as returned price is ETH/BaseToken and BaseToken/ETH is needed
+        let (num_in_base, denom_in_base) = (denom_in_eth, num_in_eth);
 
         return Ok(BaseTokenAPIRatio {
-            numerator,
-            denominator,
+            numerator: num_in_base,
+            denominator: denom_in_base,
             ratio_timestamp: Utc::now(),
         });
     }

core/lib/external_price_api/src/forced_price_client.rs

@@ -7,7 +7,7 @@ use zksync_types::{base_token_ratio::BaseTokenAPIRatio, Address};
 
 use crate::PriceAPIClient;
 
-// Struct for a a forced price "client" (conversion ratio is always a configured "forced" ratio).
+// Struct for a forced price "client" (conversion ratio is always a configured "forced" ratio).
 #[derive(Debug, Clone)]
 pub struct ForcedPriceClient {
     ratio: BaseTokenAPIRatio,

core/lib/external_price_api/src/lib.rs

@@ -13,6 +13,7 @@ use zksync_types::{base_token_ratio::BaseTokenAPIRatio, Address};
 #[async_trait]
 pub trait PriceAPIClient: Sync + Send + fmt::Debug + 'static {
     /// Returns the BaseToken<->ETH ratio for the input token address.
+    /// The returned unit is BaseToken/ETH. Example if 1 BaseToken = 0.002 ETH, then ratio is 500/1
     async fn fetch_ratio(&self, token_address: Address) -> anyhow::Result<BaseTokenAPIRatio>;
 }
 

core/lib/external_price_api/src/tests.rs

@@ -19,17 +19,19 @@ pub(crate) async fn happy_day_test(setup: SetupFn) {
     let server = MockServer::start();
     let address_str = "0x1f9840a85d5af5bf1d1762f925bdaddc4201f984"; //Uniswap (UNI)
     let address = Address::from_str(address_str).unwrap();
-    let base_token_price = 198.9;
+    let base_token_price = 0.00269; //ETH costs one token
 
     let SetupResult { client } = setup(&server, address, base_token_price);
     let api_price = client.fetch_ratio(address).await.unwrap();
 
-    let (numerator, denominator) = get_fraction(base_token_price);
+    let (num_in_eth, denom_in_eth) = get_fraction(base_token_price);
+    let (ratio_num, ratio_denom) = (denom_in_eth, num_in_eth);
+    assert!(((ratio_num.get() as f64) / (ratio_denom.get() as f64) - 371.74).abs() < 0.1);
 
     assert_eq!(
         BaseTokenAPIRatio {
-            numerator,
-            denominator,
+            numerator: ratio_num,
+            denominator: ratio_denom,
             ratio_timestamp: api_price.ratio_timestamp,
         },
         api_price