Adding API endpoint to get fee balance per account

sequencer/api/merklized_state.toml

@@ -0,0 +1,4 @@
+[route.getfeebalance]
+PATH = ["fee-balance/:address"]
+":address" = "Literal"
+DOC = "Get current balance in fee state. Expected parameter is an Ethereum address in hex format."

sequencer/src/api.rs

@@ -1326,6 +1326,17 @@ mod test {
             assert_eq!(*path.index(), account);
             assert!(*path.elem().unwrap() > 0.into(), "{:?}", path.elem());
         }
+
+        // testing fee_balance api
+        let account = TestConfig::<5>::builder_key().fee_account();
+        let amount = client
+            .get::<Option<FeeAmount>>(&format!("fee-state/fee-balance/{}", account))
+            .send()
+            .await
+            .unwrap()
+            .unwrap();
+        let expected = ethers::types::U256::max_value();
+        assert_eq!(expected, amount.0);
     }
 
     #[async_std::test]

sequencer/src/api/endpoints.rs

@@ -7,8 +7,11 @@ use std::{
 
 use anyhow::Result;
 use committable::Committable;
-use espresso_types::{FeeAccount, NamespaceId, NsProof, PubKey, Transaction};
+use espresso_types::{
+    FeeAccount, FeeMerkleTree, NamespaceId, NsProof, PubKey, Transaction, FEE_MERKLE_TREE_ARITY,
+};
 use futures::{try_join, FutureExt};
+use hotshot_query_service::merklized_state::Snapshot;
 use hotshot_query_service::{
     availability::{self, AvailabilityDataSource, CustomSnafu, FetchBlockSnafu},
     explorer::{self, ExplorerDataSource},
@@ -45,6 +48,41 @@ pub struct NamespaceProofQueryData {
     pub transactions: Vec<Transaction>,
 }
 
+pub(super) fn get_balance<State, Ver>() -> Result<Api<State, merklized_state::Error, Ver>>
+where
+    State: 'static + Send + Sync + ReadState,
+    Ver: 'static + StaticVersionType,
+    <State as ReadState>::State: Send
+        + Sync
+        + MerklizedStateDataSource<SeqTypes, FeeMerkleTree, FEE_MERKLE_TREE_ARITY>
+        + MerklizedStateHeightPersistence,
+{
+    let mut options = merklized_state::Options::default();
+    let extension = toml::from_str(include_str!("../../api/merklized_state.toml"))?;
+    options.extensions.push(extension);
+
+    let mut api =
+        merklized_state::define_api::<State, SeqTypes, FeeMerkleTree, Ver, 256>(&options)?;
+
+    api.get("getfeebalance", move |req, state| {
+        async move {
+            let address = req.string_param("address")?;
+            let height = state.get_last_state_height().await?;
+            let snapshot = Snapshot::Index(height as u64);
+            let key = address
+                .parse()
+                .map_err(|_| merklized_state::Error::Custom {
+                    message: "failed to parse address".to_string(),
+                    status: StatusCode::BAD_REQUEST,
+                })?;
+            let path = state.get_path(snapshot, key).await?;
+            Ok(path.elem().copied())
+        }
+        .boxed()
+    })?;
+    Ok(api)
+}
+
 pub(super) type AvailState<N, P, D, ApiVer> = ApiState<StorageState<N, P, D, ApiVer>>;
 
 type AvailabilityApi<N, P, D, V, ApiVer> = Api<AvailState<N, P, D, V>, availability::Error, ApiVer>;

sequencer/src/api/options.rs

@@ -5,7 +5,7 @@ use async_std::sync::Arc;
 use clap::Parser;
 use espresso_types::{
     v0::traits::{EventConsumer, NullEventConsumer, SequencerPersistence},
-    BlockMerkleTree, FeeMerkleTree, PubKey,
+    BlockMerkleTree, PubKey,
 };
 use futures::{
     channel::oneshot,
@@ -357,7 +357,7 @@ impl Options {
             // Initialize merklized state module for fee merkle tree
             app.register_module(
                 "fee-state",
-                endpoints::merklized_state::<N, P, _, FeeMerkleTree, _, 256>()?,
+                endpoints::get_balance::<_, SequencerApiVersion>()?,
             )?;
 
             let state = state.clone();

types/src/v0/mod.rs

@@ -181,7 +181,7 @@ pub type NetworkConfig = hotshot_types::network::NetworkConfig<PubKey>;
 
 pub use self::impls::{NodeState, SolverAuctionResultsProvider, ValidatedState};
 pub use crate::v0_1::{
-    BLOCK_MERKLE_TREE_HEIGHT, FEE_MERKLE_TREE_HEIGHT, NS_ID_BYTE_LEN, NS_OFFSET_BYTE_LEN,
-    NUM_NSS_BYTE_LEN, NUM_TXS_BYTE_LEN, TX_OFFSET_BYTE_LEN,
+    BLOCK_MERKLE_TREE_HEIGHT, FEE_MERKLE_TREE_ARITY, FEE_MERKLE_TREE_HEIGHT, NS_ID_BYTE_LEN,
+    NS_OFFSET_BYTE_LEN, NUM_NSS_BYTE_LEN, NUM_TXS_BYTE_LEN, TX_OFFSET_BYTE_LEN,
 };
 use crate::v0_3::SolverAuctionResults;

types/src/v0/v0_1/state.rs

@@ -15,11 +15,12 @@ use std::collections::HashSet;
 pub type BlockMerkleTree = LightWeightSHA3MerkleTree<Commitment<Header>>;
 pub type BlockMerkleCommitment = <BlockMerkleTree as MerkleTreeScheme>::Commitment;
 
-pub type FeeMerkleTree = UniversalMerkleTree<FeeAmount, Sha3Digest, FeeAccount, 256, Sha3Node>;
+pub type FeeMerkleTree = UniversalMerkleTree<FeeAmount, Sha3Digest, FeeAccount, FEE_MERKLE_TREE_ARITY, Sha3Node>;
 pub type FeeMerkleCommitment = <FeeMerkleTree as MerkleTreeScheme>::Commitment;
 
 pub const BLOCK_MERKLE_TREE_HEIGHT: usize = 32;
 pub const FEE_MERKLE_TREE_HEIGHT: usize = 20;
+pub const FEE_MERKLE_TREE_ARITY: usize = 256;
 
 #[derive(Clone, Debug, Default, Deserialize, Serialize, PartialEq, Eq)]
 pub struct Delta {