From f3314d2d24c3f8e52be9ce593ee3538f36e49d6e Mon Sep 17 00:00:00 2001
From: Bastin <43618253+Inspector-Butters@users.noreply.github.com>
Date: Thu, 17 Jul 2025 16:58:18 +0200
Subject: [PATCH] Abstract validation logic for saving LC updates into the
 store function (#15504)

* Unify LC API (updates)

* Remove unused fields in LC beacon API server

* refactor lc logic into core

* fix tests
---
 .../blockchain/process_block_helpers.go       | 28 +----------------
 beacon-chain/core/light-client/BUILD.bazel    |  1 +
 beacon-chain/core/light-client/store.go       | 30 +++++++++++++++++--
 beacon-chain/sync/rpc_light_client_test.go    |  2 +-
 changelog/bastin_abstract-save-update.md      |  3 ++
 5 files changed, 34 insertions(+), 30 deletions(-)
 create mode 100644 changelog/bastin_abstract-save-update.md

diff --git a/beacon-chain/blockchain/process_block_helpers.go b/beacon-chain/blockchain/process_block_helpers.go
index a74518a15f..70a1823aa2 100644
--- a/beacon-chain/blockchain/process_block_helpers.go
+++ b/beacon-chain/blockchain/process_block_helpers.go
@@ -189,33 +189,7 @@ func (s *Service) processLightClientUpdate(cfg *postBlockProcessConfig) error {
 
 	period := slots.SyncCommitteePeriod(slots.ToEpoch(attestedState.Slot()))
 
-	oldUpdate, err := s.lcStore.LightClientUpdate(cfg.ctx, period)
-	if err != nil {
-		return errors.Wrapf(err, "could not get current light client update")
-	}
-
-	if oldUpdate == nil {
-		if err := s.lcStore.SaveLightClientUpdate(cfg.ctx, period, update); err != nil {
-			return errors.Wrapf(err, "could not save light client update")
-		}
-		log.WithField("period", period).Debug("Saved new light client update")
-		return nil
-	}
-
-	isNewUpdateBetter, err := lightclient.IsBetterUpdate(update, oldUpdate)
-	if err != nil {
-		return errors.Wrapf(err, "could not compare light client updates")
-	}
-
-	if isNewUpdateBetter {
-		if err := s.lcStore.SaveLightClientUpdate(cfg.ctx, period, update); err != nil {
-			return errors.Wrapf(err, "could not save light client update")
-		}
-		log.WithField("period", period).Debug("Saved new light client update")
-		return nil
-	}
-	log.WithField("period", period).Debug("New light client update is not better than the current one, skipping save")
-	return nil
+	return s.lcStore.SaveLightClientUpdate(cfg.ctx, period, update)
 }
 
 // processLightClientBootstrap saves a light client bootstrap for this block
diff --git a/beacon-chain/core/light-client/BUILD.bazel b/beacon-chain/core/light-client/BUILD.bazel
index c3ce3f88eb..6d3d664d87 100644
--- a/beacon-chain/core/light-client/BUILD.bazel
+++ b/beacon-chain/core/light-client/BUILD.bazel
@@ -26,6 +26,7 @@ go_library(
         "//runtime/version:go_default_library",
         "//time/slots:go_default_library",
         "@com_github_pkg_errors//:go_default_library",
+        "@com_github_sirupsen_logrus//:go_default_library",
         "@org_golang_google_protobuf//proto:go_default_library",
     ],
 )
diff --git a/beacon-chain/core/light-client/store.go b/beacon-chain/core/light-client/store.go
index 337ddbebbb..aa56c605a2 100644
--- a/beacon-chain/core/light-client/store.go
+++ b/beacon-chain/core/light-client/store.go
@@ -7,6 +7,7 @@ import (
 	"github.com/OffchainLabs/prysm/v6/beacon-chain/db/iface"
 	"github.com/OffchainLabs/prysm/v6/consensus-types/interfaces"
 	"github.com/pkg/errors"
+	log "github.com/sirupsen/logrus"
 )
 
 var ErrLightClientBootstrapNotFound = errors.New("light client bootstrap not found")
@@ -92,8 +93,33 @@ func (s *Store) SaveLightClientUpdate(ctx context.Context, period uint64, update
 	s.mu.Lock()
 	defer s.mu.Unlock()
 
-	// Save the light client update to the database
-	return s.beaconDB.SaveLightClientUpdate(ctx, period, update)
+	oldUpdate, err := s.beaconDB.LightClientUpdate(ctx, period)
+	if err != nil {
+		return errors.Wrapf(err, "could not get current light client update")
+	}
+
+	if oldUpdate == nil {
+		if err := s.beaconDB.SaveLightClientUpdate(ctx, period, update); err != nil {
+			return errors.Wrapf(err, "could not save light client update")
+		}
+		log.WithField("period", period).Debug("Saved new light client update")
+		return nil
+	}
+
+	isNewUpdateBetter, err := IsBetterUpdate(update, oldUpdate)
+	if err != nil {
+		return errors.Wrapf(err, "could not compare light client updates")
+	}
+
+	if isNewUpdateBetter {
+		if err := s.beaconDB.SaveLightClientUpdate(ctx, period, update); err != nil {
+			return errors.Wrapf(err, "could not save light client update")
+		}
+		log.WithField("period", period).Debug("Saved new light client update")
+		return nil
+	}
+	log.WithField("period", period).Debug("New light client update is not better than the current one, skipping save")
+	return nil
 }
 
 func (s *Store) SetLastFinalityUpdate(update interfaces.LightClientFinalityUpdate) {
diff --git a/beacon-chain/sync/rpc_light_client_test.go b/beacon-chain/sync/rpc_light_client_test.go
index f1820773e5..acd42f1c9f 100644
--- a/beacon-chain/sync/rpc_light_client_test.go
+++ b/beacon-chain/sync/rpc_light_client_test.go
@@ -441,7 +441,7 @@ func TestRPC_LightClientUpdatesByRange(t *testing.T) {
 				l := util.NewTestLightClient(t, i, util.WithIncreasedAttestedSlot(uint64(j)))
 				update, err := lightClient.NewLightClientUpdateFromBeaconState(ctx, l.State.Slot(), l.State, l.Block, l.AttestedState, l.AttestedBlock, l.FinalizedBlock)
 				require.NoError(t, err)
-				require.NoError(t, r.lcStore.SaveLightClientUpdate(ctx, uint64(j), update))
+				require.NoError(t, r.cfg.beaconDB.SaveLightClientUpdate(ctx, uint64(j), update))
 			}
 
 			var wg sync.WaitGroup
diff --git a/changelog/bastin_abstract-save-update.md b/changelog/bastin_abstract-save-update.md
new file mode 100644
index 0000000000..ae9233b6af
--- /dev/null
+++ b/changelog/bastin_abstract-save-update.md
@@ -0,0 +1,3 @@
+### Ignored
+
+- Moved the validation logic for saving LC updates to the store function.
\ No newline at end of file