refactor(storage): add Store::current_slot

crates/blockchain/src/lib.rs

@@ -1413,7 +1413,7 @@ impl Handler<NewAttestation> for BlockChainServer {
         // Early aggregation only advances the current slot's group counts, so a
         // late- or future-slot attestation can never cross the threshold; skip
         // the check unless this attestation is for the store's current slot.
-        let current_slot = self.store.time().expect("store time exists") / INTERVALS_PER_SLOT;
+        let current_slot = self.store.current_slot();
         if msg.attestation.data.slot == current_slot {
             self.maybe_start_early_aggregation(ctx).await;
         }

crates/blockchain/src/store.rs

@@ -348,7 +348,7 @@ pub fn on_tick(store: &mut Store, timestamp_ms: u64, has_proposal: bool) {
             .set_time(store.time().unwrap() + 1)
             .expect("set_time should succeed");
 
-        let slot = store.time().unwrap() / INTERVALS_PER_SLOT;
+        let slot = store.current_slot();
         let interval = SlotInterval::from_intervals_since_genesis(store.time().unwrap());
 
         trace!(%slot, ?interval, "processing tick");
@@ -637,7 +637,7 @@ fn on_block_core(
     // Horizon is the current slot plus one whole slot of margin, so an intended
     // early block still imports (mirrors the attestation future-slot guard, but
     // with a whole-slot rather than one-interval margin).
-    let current_slot = store.time().expect("DB read should succeed") / INTERVALS_PER_SLOT;
+    let current_slot = store.current_slot();
     if slot > current_slot + 1 {
         return Err(StoreError::BlockTooFarInFuture {
             block_slot: slot,

crates/storage/src/store.rs

@@ -14,6 +14,7 @@ use ethlambda_types::{
         Block, BlockBody, BlockHeader, MultiMessageAggregate, SignedBlock, SingleMessageAggregate,
     },
     checkpoint::Checkpoint,
+    constants::INTERVALS_PER_SLOT,
     genesis::GenesisConfig,
     primitives::{H256, HashTreeRoot as _},
     state::{ChainConfig, State, anchor_pair_is_consistent},
@@ -817,9 +818,8 @@ impl Store {
 
     /// Returns the current store time in interval counts since genesis.
     ///
-    /// Each increment represents one 800ms interval. Derive slot/interval as:
-    ///   slot     = time() / INTERVALS_PER_SLOT
-    ///   interval = time() % INTERVALS_PER_SLOT
+    /// Each increment represents one 800ms interval. Use [`Self::current_slot`]
+    /// for the slot; the interval within it is `time() % INTERVALS_PER_SLOT`.
     pub fn time(&self) -> Result<u64, Error> {
         self.get_metadata(KEY_TIME)
     }
@@ -829,6 +829,11 @@ impl Store {
         self.set_metadata(KEY_TIME, &time)
     }
 
+    /// The current slot, derived from the store clock.
+    pub fn current_slot(&self) -> u64 {
+        self.time().expect("store time exists") / INTERVALS_PER_SLOT
+    }
+
     // ============ Config ============
 
     /// Returns the chain configuration.