feat(starknet_l1_provider): add interface to query ethereum gas price

crates/papyrus_base_layer/src/base_layer_test.rs

@@ -78,3 +78,23 @@ async fn get_proved_block_at_unknown_block_number() {
             .contains("BlockOutOfRangeError")
     );
 }
+
+#[tokio::test]
+async fn get_gas_price_and_timestamps() {
+    if !in_ci() {
+        return;
+    }
+
+    let (node_handle, starknet_contract_address) = get_test_ethereum_node();
+    let node_url = node_handle.0.endpoint().parse().unwrap();
+    let contract = ethereum_base_layer_contract(node_url, starknet_contract_address);
+
+    let block_number = 30;
+    let price_sample = contract.get_price_sample(block_number).await.unwrap().unwrap();
+
+    // TODO(guyn): Figure out how these numbers are calculated, instead of just printing and testing
+    // against what we got.
+    assert_eq!(price_sample.timestamp, 1676992456);
+    assert_eq!(price_sample.base_fee_per_gas, 20168195);
+    assert_eq!(price_sample.blob_fee, 0);
+}

crates/papyrus_base_layer/src/ethereum_base_layer_contract.rs

@@ -7,7 +7,12 @@ use alloy_json_rpc::RpcError;
 use alloy_primitives::Address as EthereumContractAddress;
 use alloy_provider::network::Ethereum;
 use alloy_provider::{Provider, ProviderBuilder, RootProvider};
-use alloy_rpc_types_eth::{BlockId, BlockTransactionsKind, Filter as EthEventFilter};
+use alloy_rpc_types_eth::{
+    BlockId,
+    BlockNumberOrTag,
+    BlockTransactionsKind,
+    Filter as EthEventFilter,
+};
 use alloy_sol_types::{sol, sol_data};
 use alloy_transport::TransportErrorKind;
 use alloy_transport_http::{Client, Http};
@@ -21,7 +26,7 @@ use starknet_api::StarknetApiError;
 use url::Url;
 use validator::Validate;
 
-use crate::{BaseLayerContract, L1BlockNumber, L1BlockReference, L1Event};
+use crate::{BaseLayerContract, L1BlockNumber, L1BlockReference, L1Event, PriceSample};
 
 pub type EthereumBaseLayerResult<T> = Result<T, EthereumBaseLayerError>;
 
@@ -131,6 +136,32 @@ impl BaseLayerContract for EthereumBaseLayerContract {
             hash: block.header.hash.0,
         }))
     }
+
+    // Query the Ethereum base layer for the timestamp, gas price, and data gas price of a block.
+    async fn get_price_sample(
+        &self,
+        block_number: L1BlockNumber,
+    ) -> EthereumBaseLayerResult<Option<PriceSample>> {
+        let block = self
+            .contract
+            .provider()
+            .get_block(
+                BlockId::Number(BlockNumberOrTag::Number(block_number)),
+                BlockTransactionsKind::Hashes,
+            )
+            .await?;
+        let Some(block) = block else {
+            return Ok(None);
+        };
+        match (block.header.timestamp, block.header.base_fee_per_gas) {
+            (timestamp, Some(base_fee_per_gas)) => Ok(Some(PriceSample {
+                timestamp,
+                base_fee_per_gas,
+                blob_fee: block.header.blob_fee().unwrap_or(0),
+            })),
+            _ => Ok(None),
+        }
+    }
 }
 
 #[derive(thiserror::Error, Debug)]

crates/papyrus_base_layer/src/lib.rs

@@ -60,6 +60,18 @@ pub trait BaseLayerContract {
         block_range: RangeInclusive<L1BlockNumber>,
         event_identifiers: &[&str],
     ) -> Result<Vec<L1Event>, Self::Error>;
+
+    async fn get_price_sample(
+        &self,
+        block_number: L1BlockNumber,
+    ) -> Result<Option<PriceSample>, Self::Error>;
+}
+
+/// A struct that holds together the data on the base layer's gas prices, for a given timestamp.
+pub struct PriceSample {
+    pub timestamp: u64,
+    pub base_fee_per_gas: u128,
+    pub blob_fee: u128,
 }
 
 /// Reference to an L1 block, extend as needed.