From c0fba4759cd3f5116fdf6c75ffb1b2a62c76b0b6 Mon Sep 17 00:00:00 2001
From: Jun Kimura <jun.kimura@datachain.jp>
Date: Sun, 10 Nov 2024 17:43:41 +0900
Subject: [PATCH] add `get_sync_committee_at_period` function

Signed-off-by: Jun Kimura <jun.kimura@datachain.jp>
---
 crates/light-client-verifier/src/consensus.rs |  8 ++--
 crates/light-client-verifier/src/state.rs     | 39 +++++++++++--------
 2 files changed, 27 insertions(+), 20 deletions(-)

diff --git a/crates/light-client-verifier/src/consensus.rs b/crates/light-client-verifier/src/consensus.rs
index 49d4b05..55f1204 100644
--- a/crates/light-client-verifier/src/consensus.rs
+++ b/crates/light-client-verifier/src/consensus.rs
@@ -2,7 +2,7 @@ use crate::context::{ChainConsensusVerificationContext, ConsensusVerificationCon
 use crate::errors::Error;
 use crate::internal_prelude::*;
 use crate::misbehaviour::Misbehaviour;
-use crate::state::LightClientStoreReader;
+use crate::state::{get_sync_committee_at_period, LightClientStoreReader};
 use crate::updates::{ConsensusUpdate, ExecutionUpdate, LightClientBootstrap};
 use core::marker::PhantomData;
 use ethereum_consensus::beacon::{BeaconBlockHeader, Root, DOMAIN_SYNC_COMMITTEE};
@@ -163,7 +163,7 @@ impl<const SYNC_COMMITTEE_SIZE: usize, ST: LightClientStoreReader<SYNC_COMMITTEE
     ) -> Result<SyncCommittee<SYNC_COMMITTEE_SIZE>, Error> {
         let update_signature_period =
             compute_sync_committee_period_at_slot(ctx, update.signature_slot());
-        if let Some(committee) = store.get_sync_committee(ctx, update_signature_period) {
+        if let Some(committee) = get_sync_committee_at_period(ctx, store, update_signature_period) {
             Ok(committee)
         } else {
             Err(Error::UnexpectedSingaturePeriod(
@@ -331,7 +331,9 @@ pub fn validate_light_client_update<
             ctx,
             consensus_update.attested_beacon_header().slot,
         );
-        if let Some(committee) = store.get_sync_committee(ctx, update_attested_period + 1) {
+        if let Some(committee) =
+            get_sync_committee_at_period(ctx, store, update_attested_period + 1)
+        {
             if committee != *update_next_sync_committee {
                 return Err(Error::InconsistentNextSyncCommittee(
                     committee.aggregate_pubkey.clone(),
diff --git a/crates/light-client-verifier/src/state.rs b/crates/light-client-verifier/src/state.rs
index e097104..fbea558 100644
--- a/crates/light-client-verifier/src/state.rs
+++ b/crates/light-client-verifier/src/state.rs
@@ -4,6 +4,7 @@ use ethereum_consensus::{
     sync_protocol::{SyncCommittee, SyncCommitteePeriod},
 };
 
+/// A trait for reading the light client store
 pub trait LightClientStoreReader<const SYNC_COMMITTEE_SIZE: usize> {
     /// Returns the current sync committee period
     fn current_period<CC: ChainContext>(&self, ctx: &CC) -> SyncCommitteePeriod;
@@ -14,23 +15,6 @@ pub trait LightClientStoreReader<const SYNC_COMMITTEE_SIZE: usize> {
     /// Returns the next sync committee corresponding to the `current_period() + 1` if available
     fn next_sync_committee(&self) -> Option<SyncCommittee<SYNC_COMMITTEE_SIZE>>;
 
-    /// Returns the sync committee corresponding to the given signature period if available
-    fn get_sync_committee<CC: ChainContext>(
-        &self,
-        ctx: &CC,
-        signature_period: SyncCommitteePeriod,
-    ) -> Option<SyncCommittee<SYNC_COMMITTEE_SIZE>> {
-        let current_period = self.current_period(ctx);
-        let next_period = current_period + 1;
-        if signature_period == current_period {
-            self.current_sync_committee()
-        } else if signature_period == next_period {
-            self.next_sync_committee()
-        } else {
-            None
-        }
-    }
-
     /// Returns a error indicating whether the update is relevant to this store.
     ///
     /// This method should be used to determine whether the update should be applied to the store.
@@ -40,3 +24,24 @@ pub trait LightClientStoreReader<const SYNC_COMMITTEE_SIZE: usize> {
         update: &C,
     ) -> Result<(), Error>;
 }
+
+/// Returns the sync committee corresponding to the given signature period if available
+pub fn get_sync_committee_at_period<
+    CC: ChainContext,
+    const SYNC_COMMITTEE_SIZE: usize,
+    ST: LightClientStoreReader<SYNC_COMMITTEE_SIZE>,
+>(
+    ctx: &CC,
+    store: &ST,
+    signature_period: SyncCommitteePeriod,
+) -> Option<SyncCommittee<SYNC_COMMITTEE_SIZE>> {
+    let current_period = store.current_period(ctx);
+    let next_period = current_period + 1;
+    if signature_period == current_period {
+        store.current_sync_committee()
+    } else if signature_period == next_period {
+        store.next_sync_committee()
+    } else {
+        None
+    }
+}