add inclusion committee assignment helper

ethereum/spec/src/main/java/tech/pegasys/teku/spec/Spec.java

@@ -891,6 +891,13 @@ public Optional<CommitteeAssignment> getCommitteeAssignment(
     return atEpoch(epoch).getValidatorsUtil().getCommitteeAssignment(state, epoch, validatorIndex);
   }
 
+  public Optional<UInt64> getInclusionCommitteeAssignment(
+      final BeaconState state, final UInt64 epoch, final int validatorIndex) {
+    return atEpoch(epoch)
+        .getValidatorsUtil()
+        .getInclusionCommitteeAssignment(state, epoch, validatorIndex);
+  }
+
   public Int2ObjectMap<CommitteeAssignment> getValidatorIndexToCommitteeAssignmentMap(
       final BeaconState state, final UInt64 epoch) {
     return atEpoch(epoch)

ethereum/spec/src/main/java/tech/pegasys/teku/spec/logic/common/util/ValidatorsUtil.java

@@ -33,6 +33,7 @@
 import tech.pegasys.teku.spec.datastructures.state.versions.electra.PendingPartialWithdrawal;
 import tech.pegasys.teku.spec.logic.common.helpers.BeaconStateAccessors;
 import tech.pegasys.teku.spec.logic.common.helpers.MiscHelpers;
+import tech.pegasys.teku.spec.logic.versions.eip7805.helpers.BeaconStateAccessorsEip7805;
 
 public class ValidatorsUtil {
   private final SpecConfig specConfig;
@@ -136,6 +137,35 @@ private Optional<CommitteeAssignment> getCommitteeAssignment(
     return Optional.empty();
   }
 
+  /**
+   * Returns the slot during the requested epoch in which the validator with index
+   * ``validator_index`` is a member of the ILC. Returns None if no assignment is found.
+   *
+   * @param state the BeaconState.
+   * @param epoch either on or between previous or current epoch.
+   * @param validatorIndex the validator that is calling this function.
+   * @return Optional containing the slot if any, empty otherwise
+   */
+  public Optional<UInt64> getInclusionCommitteeAssignment(
+      final BeaconState state, final UInt64 epoch, final int validatorIndex) {
+    final UInt64 nextEpoch = beaconStateAccessors.getCurrentEpoch(state).plus(UInt64.ONE);
+    checkArgument(
+        epoch.compareTo(nextEpoch) <= 0,
+        "get_inclusion_committee_assignment: Epoch number too high");
+    final UInt64 startSlot = miscHelpers.computeStartSlotAtEpoch(epoch);
+    for (UInt64 slot = startSlot;
+        slot.isLessThan(startSlot.plus(specConfig.getSlotsPerEpoch()));
+        slot = slot.plus(UInt64.ONE)) {
+      final IntList inclusionListCommittee =
+          BeaconStateAccessorsEip7805.required(beaconStateAccessors)
+              .getInclusionListCommittee(state, slot);
+      if (inclusionListCommittee.contains(validatorIndex)) {
+        return Optional.of(slot);
+      }
+    }
+    return Optional.empty();
+  }
+
   public EpochAttestationSchedule getAttestationCommitteesAtEpoch(
       final BeaconState state, final UInt64 epoch, final UInt64 committeeCountPerSlot) {
     final UInt64 nextEpoch = beaconStateAccessors.getCurrentEpoch(state).plus(UInt64.ONE);

ethereum/spec/src/main/java/tech/pegasys/teku/spec/logic/versions/eip7805/helpers/BeaconStateAccessorsEip7805.java

@@ -13,6 +13,8 @@
 
 package tech.pegasys.teku.spec.logic.versions.eip7805.helpers;
 
+import static com.google.common.base.Preconditions.checkArgument;
+
 import it.unimi.dsi.fastutil.ints.IntArrayList;
 import it.unimi.dsi.fastutil.ints.IntList;
 import org.apache.tuweni.bytes.Bytes32;
@@ -22,6 +24,7 @@
 import tech.pegasys.teku.spec.config.SpecConfigElectra;
 import tech.pegasys.teku.spec.constants.Domain;
 import tech.pegasys.teku.spec.datastructures.state.beaconstate.BeaconState;
+import tech.pegasys.teku.spec.logic.common.helpers.BeaconStateAccessors;
 import tech.pegasys.teku.spec.logic.versions.electra.helpers.BeaconStateAccessorsElectra;
 import tech.pegasys.teku.spec.logic.versions.electra.helpers.MiscHelpersElectra;
 import tech.pegasys.teku.spec.logic.versions.electra.helpers.PredicatesElectra;
@@ -38,6 +41,16 @@ public BeaconStateAccessorsEip7805(
     this.specConfigEip7805 = config.toVersionEip7805().orElseThrow();
   }
 
+  public static BeaconStateAccessorsEip7805 required(
+      final BeaconStateAccessors beaconStateAccessors) {
+    checkArgument(
+        beaconStateAccessors instanceof BeaconStateAccessorsEip7805,
+        "Expected %s but it was %s",
+        BeaconStateAccessorsEip7805.class,
+        beaconStateAccessors.getClass());
+    return (BeaconStateAccessorsEip7805) beaconStateAccessors;
+  }
+
   public IntList getInclusionListCommittee(final BeaconState state, final UInt64 slot) {
     final UInt64 epoch = miscHelpers.computeEpochAtSlot(slot);
     final Bytes32 seed = getSeed(state, epoch, Domain.DOMAIN_IL_COMMITTEE);