feat(etherscan, middleware): implement gas-related endpoints and use them in gas oracle

Cargo.lock

@@ -1073,6 +1073,7 @@ dependencies = [
  "ethers-core",
  "reqwest",
  "serde",
+ "serde-aux",
  "serde_json",
  "thiserror",
  "tokio",
@@ -1085,6 +1086,7 @@ dependencies = [
  "async-trait",
  "ethers-contract",
  "ethers-core",
+ "ethers-etherscan",
  "ethers-providers",
  "ethers-signers",
  "ethers-solc",

ethers-core/src/types/chain.rs

@@ -14,6 +14,7 @@ pub enum Chain {
     PolygonMumbai,
     Avalanche,
     AvalancheFuji,
+    Sepolia,
 }
 
 impl fmt::Display for Chain {
@@ -35,6 +36,7 @@ impl From<Chain> for u32 {
             Chain::PolygonMumbai => 80001,
             Chain::Avalanche => 43114,
             Chain::AvalancheFuji => 43113,
+            Chain::Sepolia => 11155111,
         }
     }
 }

ethers-etherscan/Cargo.toml

@@ -18,6 +18,7 @@ ethers-core = { version = "^0.6.0", path = "../ethers-core", default-features =
 reqwest = { version = "0.11.6", features = ["json"] }
 serde = { version = "1.0.124", default-features = false, features = ["derive"] }
 serde_json = { version = "1.0.64", default-features = false }
+serde-aux = { version = "3.0.1", default-features = false }
 thiserror = "1.0.29"
 
 [dev-dependencies]

ethers-etherscan/src/errors.rs

@@ -9,6 +9,8 @@ pub enum EtherscanError {
     ExecutionFailed(String),
     #[error("tx receipt failed")]
     TransactionReceiptFailed,
+    #[error("gas estimation failed")]
+    GasEstimationFailed,
     #[error("bad status code {0}")]
     BadStatusCode(String),
     #[error(transparent)]

ethers-etherscan/src/gas.rs

@@ -0,0 +1,107 @@
+use std::{collections::HashMap, str::FromStr};
+
+use ethers_core::types::U256;
+use serde::{de, Deserialize};
+use serde_aux::prelude::*;
+
+use crate::{Client, EtherscanError, Response, Result};
+
+#[derive(Deserialize)]
+#[serde(rename_all = "PascalCase")]
+pub struct GasOracle {
+    #[serde(deserialize_with = "deserialize_number_from_string")]
+    pub safe_gas_price: u64,
+    #[serde(deserialize_with = "deserialize_number_from_string")]
+    pub propose_gas_price: u64,
+    #[serde(deserialize_with = "deserialize_number_from_string")]
+    pub fast_gas_price: u64,
+    #[serde(deserialize_with = "deserialize_number_from_string")]
+    pub last_block: u64,
+    #[serde(deserialize_with = "deserialize_number_from_string")]
+    #[serde(rename = "suggestBaseFee")]
+    pub suggested_base_fee: f64,
+    #[serde(deserialize_with = "deserialize_f64_vec")]
+    #[serde(rename = "gasUsedRatio")]
+    pub gas_used_ratio: Vec<f64>,
+}
+
+fn deserialize_f64_vec<'de, D>(deserializer: D) -> core::result::Result<Vec<f64>, D::Error>
+where
+    D: de::Deserializer<'de>,
+{
+    let str_sequence = String::deserialize(deserializer)?;
+    str_sequence
+        .split(',')
+        .map(|item| f64::from_str(item).map_err(|err| de::Error::custom(err.to_string())))
+        .collect()
+}
+
+impl Client {
+    /// Returns the estimated time, in seconds, for a transaction to be confirmed on the blockchain
+    /// for the specified gas price
+    pub async fn gas_estimate(&self, gas_price: U256) -> Result<u32> {
+        let query = self.create_query(
+            "gastracker",
+            "gasestimate",
+            HashMap::from([("gasprice", gas_price.to_string())]),
+        );
+        let response: Response<String> = self.get_json(&query).await?;
+
+        if response.status == "1" {
+            Ok(u32::from_str(&response.result).map_err(|_| EtherscanError::GasEstimationFailed)?)
+        } else {
+            Err(EtherscanError::GasEstimationFailed)
+        }
+    }
+
+    /// Returns the gas oracle
+    pub async fn gas_oracle(&self) -> Result<GasOracle> {
+        let query = self.create_query("gastracker", "gasoracle", serde_json::Value::Null);
+        let response: Response<GasOracle> = self.get_json(&query).await?;
+
+        Ok(response.result)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use ethers_core::types::Chain;
+
+    use super::*;
+
+    #[tokio::test]
+    async fn gas_estimate_success() {
+        let client = Client::new_from_env(Chain::Mainnet).unwrap();
+
+        let result = client.gas_estimate(2000000000u32.into()).await;
+
+        assert!(result.is_ok());
+    }
+
+    #[tokio::test]
+    async fn gas_estimate_error() {
+        let client = Client::new_from_env(Chain::Mainnet).unwrap();
+
+        let err = client.gas_estimate(7123189371829732819379218u128.into()).await.unwrap_err();
+
+        assert!(matches!(err, EtherscanError::GasEstimationFailed));
+    }
+
+    #[tokio::test]
+    async fn gas_oracle_success() {
+        let client = Client::new_from_env(Chain::Mainnet).unwrap();
+
+        let result = client.gas_oracle().await;
+
+        assert!(result.is_ok());
+
+        let oracle = result.unwrap();
+
+        assert!(oracle.safe_gas_price > 0);
+        assert!(oracle.propose_gas_price > 0);
+        assert!(oracle.fast_gas_price > 0);
+        assert!(oracle.last_block > 0);
+        assert!(oracle.suggested_base_fee > 0.0);
+        assert!(oracle.gas_used_ratio.len() > 0);
+    }
+}

ethers-etherscan/src/lib.rs

@@ -2,7 +2,8 @@
 
 pub mod contract;
 pub mod errors;
-mod transaction;
+pub mod gas;
+pub mod transaction;
 
 use errors::EtherscanError;
 use ethers_core::{abi::Address, types::Chain};
@@ -76,6 +77,7 @@ impl Client {
                 std::env::var("ETHERSCAN_API_KEY")?
             }
             Chain::XDai => String::default(),
+            chain => return Err(EtherscanError::ChainNotSupported(chain)),
         };
         Self::new(chain, api_key)
     }

ethers-etherscan/src/transaction.rs

@@ -19,9 +19,6 @@ struct TransactionReceiptStatus {
 impl Client {
     /// Returns the status of a contract execution
     pub async fn check_contract_execution_status(&self, tx_hash: impl AsRef<str>) -> Result<()> {
-        let mut map = HashMap::new();
-        map.insert("txhash", tx_hash.as_ref());
-
         let query = self.create_query(
             "transaction",
             "getstatus",

ethers-middleware/Cargo.toml

@@ -16,6 +16,7 @@ rustdoc-args = ["--cfg", "docsrs"]
 [dependencies]
 ethers-contract = { version = "^0.6.0", path = "../ethers-contract", default-features = false, features = ["abigen"] }
 ethers-core = { version = "^0.6.0", path = "../ethers-core", default-features = false }
+ethers-etherscan = { version = "^0.2.0", path = "../ethers-etherscan", default-features = false }
 ethers-providers = { version = "^0.6.0", path = "../ethers-providers", default-features = false }
 ethers-signers = { version = "^0.6.0", path = "../ethers-signers", default-features = false }
 

ethers-middleware/src/gas_oracle/etherscan.rs

@@ -1,73 +1,22 @@
-use ethers_core::types::U256;
-
 use async_trait::async_trait;
-use reqwest::Client;
-use serde::Deserialize;
-use serde_aux::prelude::*;
-use url::Url;
+
+use ethers_core::types::U256;
+use ethers_etherscan::Client;
 
 use crate::gas_oracle::{GasCategory, GasOracle, GasOracleError, GWEI_TO_WEI};
 
-const ETHERSCAN_URL_PREFIX: &str =
-    "https://api.etherscan.io/api?module=gastracker&action=gasoracle";
-
 /// A client over HTTP for the [Etherscan](https://api.etherscan.io/api?module=gastracker&action=gasoracle) gas tracker API
 /// that implements the `GasOracle` trait
 #[derive(Clone, Debug)]
 pub struct Etherscan {
     client: Client,
-    url: Url,
     gas_category: GasCategory,
 }
 
-#[derive(Deserialize)]
-struct EtherscanResponseWrapper {
-    result: EtherscanResponse,
-}
-
-#[derive(Clone, Debug, Deserialize, PartialEq, PartialOrd)]
-#[serde(rename_all = "PascalCase")]
-pub struct EtherscanResponse {
-    #[serde(deserialize_with = "deserialize_number_from_string")]
-    pub safe_gas_price: u64,
-    #[serde(deserialize_with = "deserialize_number_from_string")]
-    pub propose_gas_price: u64,
-    #[serde(deserialize_with = "deserialize_number_from_string")]
-    pub fast_gas_price: u64,
-    #[serde(deserialize_with = "deserialize_number_from_string")]
-    pub last_block: u64,
-    #[serde(deserialize_with = "deserialize_number_from_string")]
-    #[serde(rename = "suggestBaseFee")]
-    pub suggested_base_fee: f64,
-    #[serde(deserialize_with = "deserialize_f64_vec")]
-    #[serde(rename = "gasUsedRatio")]
-    pub gas_used_ratio: Vec<f64>,
-}
-
-use serde::de;
-use std::str::FromStr;
-fn deserialize_f64_vec<'de, D>(deserializer: D) -> Result<Vec<f64>, D::Error>
-where
-    D: de::Deserializer<'de>,
-{
-    let str_sequence = String::deserialize(deserializer)?;
-    str_sequence
-        .split(',')
-        .map(|item| f64::from_str(item).map_err(|err| de::Error::custom(err.to_string())))
-        .collect()
-}
-
 impl Etherscan {
     /// Creates a new [Etherscan](https://etherscan.io/gastracker) gas price oracle.
-    pub fn new(api_key: Option<&str>) -> Self {
-        let url = match api_key {
-            Some(key) => format!("{}&apikey={}", ETHERSCAN_URL_PREFIX, key),
-            None => ETHERSCAN_URL_PREFIX.to_string(),
-        };
-
-        let url = Url::parse(&url).expect("invalid url");
-
-        Etherscan { client: Client::new(), url, gas_category: GasCategory::Standard }
+    pub fn new(client: Client) -> Self {
+        Etherscan { client, gas_category: GasCategory::Standard }
     }
 
     /// Sets the gas price category to be used when fetching the gas price.
@@ -75,17 +24,6 @@ impl Etherscan {
         self.gas_category = gas_category;
         self
     }
-
-    pub async fn query(&self) -> Result<EtherscanResponse, GasOracleError> {
-        let res = self
-            .client
-            .get(self.url.as_ref())
-            .send()
-            .await?
-            .json::<EtherscanResponseWrapper>()
-            .await?;
-        Ok(res.result)
-    }
 }
 
 #[cfg_attr(target_arch = "wasm32", async_trait(?Send))]
@@ -96,12 +34,12 @@ impl GasOracle for Etherscan {
             return Err(GasOracleError::GasCategoryNotSupported)
         }
 
-        let res = self.query().await?;
+        let result = self.client.gas_oracle().await?;
 
         match self.gas_category {
-            GasCategory::SafeLow => Ok(U256::from(res.safe_gas_price * GWEI_TO_WEI)),
-            GasCategory::Standard => Ok(U256::from(res.propose_gas_price * GWEI_TO_WEI)),
-            GasCategory::Fast => Ok(U256::from(res.fast_gas_price * GWEI_TO_WEI)),
+            GasCategory::SafeLow => Ok(U256::from(result.safe_gas_price * GWEI_TO_WEI)),
+            GasCategory::Standard => Ok(U256::from(result.propose_gas_price * GWEI_TO_WEI)),
+            GasCategory::Fast => Ok(U256::from(result.fast_gas_price * GWEI_TO_WEI)),
             _ => Err(GasOracleError::GasCategoryNotSupported),
         }
     }

ethers-middleware/src/gas_oracle/mod.rs

@@ -35,6 +35,11 @@ pub enum GasOracleError {
     #[error(transparent)]
     HttpClientError(#[from] ReqwestError),
 
+    /// An internal error in the Etherscan client request made from the underlying
+    /// gas oracle
+    #[error(transparent)]
+    EtherscanError(#[from] ethers_etherscan::errors::EtherscanError),
+
     /// An internal error thrown when the required gas category is not
     /// supported by the gas oracle API
     #[error("gas category not supported")]

ethers-middleware/tests/gas_oracle.rs

@@ -61,17 +61,16 @@ async fn eth_gas_station() {
 
 #[tokio::test]
 async fn etherscan() {
-    let api_key = std::env::var("ETHERSCAN_API_KEY").unwrap();
-    let api_key = Some(api_key.as_str());
+    let etherscan_client = ethers_etherscan::Client::new_from_env(Chain::Mainnet).unwrap();
 
     // initialize and fetch gas estimates from Etherscan
     // since etherscan does not support `fastest` category, we expect an error
-    let etherscan_oracle = Etherscan::new(api_key).category(GasCategory::Fastest);
+    let etherscan_oracle = Etherscan::new(etherscan_client.clone()).category(GasCategory::Fastest);
     let data = etherscan_oracle.fetch().await;
     assert!(data.is_err());
 
     // but fetching the `standard` gas price should work fine
-    let etherscan_oracle_2 = Etherscan::new(api_key).category(GasCategory::SafeLow);
+    let etherscan_oracle_2 = Etherscan::new(etherscan_client).category(GasCategory::SafeLow);
 
     let data = etherscan_oracle_2.fetch().await;
     assert!(data.is_ok());