#![cfg(not(debug_assertions))]

#[macro_use]
extern crate lazy_static;

use beacon_chain::test_utils::{
    AttestationStrategy, BeaconChainHarness, BlockStrategy, DiskHarnessType,
};
use beacon_chain::AttestationProcessingOutcome;
use rand::Rng;
use sloggers::{null::NullLoggerBuilder, Build};
use std::sync::Arc;
use store::{
    iter::{BlockRootsIterator, StateRootsIterator},
    DiskStore, Store, StoreConfig,
};
use tempfile::{tempdir, TempDir};
use tree_hash::TreeHash;
use types::test_utils::{SeedableRng, XorShiftRng};
use types::*;

// Should ideally be divisible by 3.
pub const LOW_VALIDATOR_COUNT: usize = 24;
pub const HIGH_VALIDATOR_COUNT: usize = 64;

lazy_static! {
    /// A cached set of keys.
    static ref KEYPAIRS: Vec<Keypair> = types::test_utils::generate_deterministic_keypairs(HIGH_VALIDATOR_COUNT);
}

type E = MinimalEthSpec;
type TestHarness = BeaconChainHarness<DiskHarnessType<E>>;

fn get_store(db_path: &TempDir) -> Arc<DiskStore<E>> {
    let spec = MinimalEthSpec::default_spec();
    let hot_path = db_path.path().join("hot_db");
    let cold_path = db_path.path().join("cold_db");
    let config = StoreConfig::default();
    let log = NullLoggerBuilder.build().expect("logger should build");
    Arc::new(
        DiskStore::open(&hot_path, &cold_path, config, spec, log)
            .expect("disk store should initialize"),
    )
}

fn get_harness(store: Arc<DiskStore<E>>, validator_count: usize) -> TestHarness {
    let harness = BeaconChainHarness::new_with_disk_store(
        MinimalEthSpec,
        store,
        KEYPAIRS[0..validator_count].to_vec(),
    );
    harness.advance_slot();
    harness
}

#[test]
fn full_participation_no_skips() {
    let num_blocks_produced = E::slots_per_epoch() * 5;
    let db_path = tempdir().unwrap();
    let store = get_store(&db_path);
    let harness = get_harness(store.clone(), LOW_VALIDATOR_COUNT);

    harness.extend_chain(
        num_blocks_produced as usize,
        BlockStrategy::OnCanonicalHead,
        AttestationStrategy::AllValidators,
    );

    check_finalization(&harness, num_blocks_produced);
    check_split_slot(&harness, store);
    check_chain_dump(&harness, num_blocks_produced + 1);
    check_iterators(&harness);
}

#[test]
fn randomised_skips() {
    let num_slots = E::slots_per_epoch() * 5;
    let mut num_blocks_produced = 0;
    let db_path = tempdir().unwrap();
    let store = get_store(&db_path);
    let harness = get_harness(store.clone(), LOW_VALIDATOR_COUNT);
    let rng = &mut XorShiftRng::from_seed([42; 16]);

    let mut head_slot = 0;

    for slot in 1..=num_slots {
        if rng.gen_bool(0.8) {
            harness.extend_chain(
                1,
                BlockStrategy::ForkCanonicalChainAt {
                    previous_slot: Slot::new(head_slot),
                    first_slot: Slot::new(slot),
                },
                AttestationStrategy::AllValidators,
            );
            harness.advance_slot();
            num_blocks_produced += 1;
            head_slot = slot;
        } else {
            harness.advance_slot();
        }
    }

    let state = &harness.chain.head().expect("should get head").beacon_state;

    assert_eq!(state.slot, num_slots, "head should be at the current slot");

    check_split_slot(&harness, store);
    check_chain_dump(&harness, num_blocks_produced + 1);
    check_iterators(&harness);
}

#[test]
fn long_skip() {
    let db_path = tempdir().unwrap();
    let store = get_store(&db_path);
    let harness = get_harness(store.clone(), LOW_VALIDATOR_COUNT);

    // Number of blocks to create in the first run, intentionally not falling on an epoch
    // boundary in order to check that the DB hot -> cold migration is capable of reaching
    // back across the skip distance, and correctly migrating those extra non-finalized states.
    let initial_blocks = E::slots_per_epoch() * 5 + E::slots_per_epoch() / 2;
    let skip_slots = E::slots_per_historical_root() as u64 * 8;
    // Create the minimum ~2.5 epochs of extra blocks required to re-finalize the chain.
    // Having this set lower ensures that we start justifying and finalizing quickly after a skip.
    let final_blocks = 2 * E::slots_per_epoch() + E::slots_per_epoch() / 2;

    harness.extend_chain(
        initial_blocks as usize,
        BlockStrategy::OnCanonicalHead,
        AttestationStrategy::AllValidators,
    );

    check_finalization(&harness, initial_blocks);

    // 2. Skip slots
    for _ in 0..skip_slots {
        harness.advance_slot();
    }

    // 3. Produce more blocks, establish a new finalized epoch
    harness.extend_chain(
        final_blocks as usize,
        BlockStrategy::ForkCanonicalChainAt {
            previous_slot: Slot::new(initial_blocks),
            first_slot: Slot::new(initial_blocks + skip_slots as u64 + 1),
        },
        AttestationStrategy::AllValidators,
    );

    check_finalization(&harness, initial_blocks + skip_slots + final_blocks);
    check_split_slot(&harness, store);
    check_chain_dump(&harness, initial_blocks + final_blocks + 1);
    check_iterators(&harness);
}

/// Go forward to the point where the genesis randao value is no longer part of the vector.
///
/// This implicitly checks that:
/// 1. The chunked vector scheme doesn't attempt to store an incorrect genesis value
/// 2. We correctly load the genesis value for all required slots
/// NOTE: this test takes about a minute to run
#[test]
fn randao_genesis_storage() {
    let validator_count = 8;
    let db_path = tempdir().unwrap();
    let store = get_store(&db_path);
    let harness = get_harness(store.clone(), validator_count);

    let num_slots = E::slots_per_epoch() * (E::epochs_per_historical_vector() - 1) as u64;

    // Check we have a non-trivial genesis value
    let genesis_value = *harness
        .chain
        .head()
        .expect("should get head")
        .beacon_state
        .get_randao_mix(Epoch::new(0))
        .expect("randao mix ok");
    assert!(!genesis_value.is_zero());

    harness.extend_chain(
        num_slots as usize - 1,
        BlockStrategy::OnCanonicalHead,
        AttestationStrategy::AllValidators,
    );

    // Check that genesis value is still present
    assert!(harness
        .chain
        .head()
        .expect("should get head")
        .beacon_state
        .randao_mixes
        .iter()
        .find(|x| **x == genesis_value)
        .is_some());

    // Then upon adding one more block, it isn't
    harness.advance_slot();
    harness.extend_chain(
        1,
        BlockStrategy::OnCanonicalHead,
        AttestationStrategy::AllValidators,
    );
    assert!(harness
        .chain
        .head()
        .expect("should get head")
        .beacon_state
        .randao_mixes
        .iter()
        .find(|x| **x == genesis_value)
        .is_none());

    check_finalization(&harness, num_slots);
    check_split_slot(&harness, store);
    check_chain_dump(&harness, num_slots + 1);
    check_iterators(&harness);
}

// Check that closing and reopening a freezer DB restores the split slot to its correct value.
#[test]
fn split_slot_restore() {
    let db_path = tempdir().unwrap();

    let split_slot = {
        let store = get_store(&db_path);
        let harness = get_harness(store.clone(), LOW_VALIDATOR_COUNT);

        let num_blocks = 4 * E::slots_per_epoch();

        harness.extend_chain(
            num_blocks as usize,
            BlockStrategy::OnCanonicalHead,
            AttestationStrategy::AllValidators,
        );

        store.get_split_slot()
    };
    assert_ne!(split_slot, Slot::new(0));

    // Re-open the store
    let store = get_store(&db_path);

    assert_eq!(store.get_split_slot(), split_slot);
}

// Check attestation processing and `load_epoch_boundary_state` in the presence of a split DB.
// This is a bit of a monster test in that it tests lots of different things, but until they're
// tested elsewhere, this is as good a place as any.
#[test]
fn epoch_boundary_state_attestation_processing() {
    let num_blocks_produced = E::slots_per_epoch() * 5;
    let db_path = tempdir().unwrap();
    let store = get_store(&db_path);
    let harness = get_harness(store.clone(), LOW_VALIDATOR_COUNT);

    let late_validators = vec![0, 1];
    let timely_validators = (2..LOW_VALIDATOR_COUNT).collect::<Vec<_>>();

    let mut late_attestations = vec![];

    for _ in 0..num_blocks_produced {
        harness.extend_chain(
            1,
            BlockStrategy::OnCanonicalHead,
            AttestationStrategy::SomeValidators(timely_validators.clone()),
        );

        let head = harness.chain.head().expect("head ok");
        late_attestations.extend(harness.get_free_attestations(
            &AttestationStrategy::SomeValidators(late_validators.clone()),
            &head.beacon_state,
            head.beacon_block_root,
            head.beacon_block.slot(),
        ));

        harness.advance_slot();
    }

    check_finalization(&harness, num_blocks_produced);
    check_split_slot(&harness, store.clone());
    check_chain_dump(&harness, num_blocks_produced + 1);
    check_iterators(&harness);

    let mut checked_pre_fin = false;

    for attestation in late_attestations {
        // load_epoch_boundary_state is idempotent!
        let block_root = attestation.data.beacon_block_root;
        let block = store.get_block(&block_root).unwrap().expect("block exists");
        let epoch_boundary_state = store
            .load_epoch_boundary_state(&block.state_root())
            .expect("no error")
            .expect("epoch boundary state exists");
        let ebs_of_ebs = store
            .load_epoch_boundary_state(&epoch_boundary_state.canonical_root())
            .expect("no error")
            .expect("ebs of ebs exists");
        assert_eq!(epoch_boundary_state, ebs_of_ebs);

        // If the attestation is pre-finalization it should be rejected.
        let finalized_epoch = harness
            .chain
            .head_info()
            .expect("head ok")
            .finalized_checkpoint
            .epoch;
        let res = harness
            .chain
            .process_attestation_internal(attestation.clone());

        let current_epoch = harness.chain.epoch().expect("should get epoch");
        let attestation_epoch = attestation.data.target.epoch;

        if attestation.data.slot <= finalized_epoch.start_slot(E::slots_per_epoch())
            || attestation_epoch + 1 < current_epoch
        {
            checked_pre_fin = true;
            assert_eq!(
                res,
                Ok(AttestationProcessingOutcome::PastEpoch {
                    attestation_epoch,
                    current_epoch,
                })
            );
        } else {
            assert_eq!(res, Ok(AttestationProcessingOutcome::Processed));
        }
    }
    assert!(checked_pre_fin);
}

#[test]
fn delete_blocks_and_states() {
    let db_path = tempdir().unwrap();
    let store = get_store(&db_path);
    let harness = get_harness(store.clone(), LOW_VALIDATOR_COUNT);

    let unforked_blocks = 4 * E::slots_per_epoch();

    // Finalize an initial portion of the chain.
    harness.extend_chain(
        unforked_blocks as usize,
        BlockStrategy::OnCanonicalHead,
        AttestationStrategy::AllValidators,
    );

    // Create a fork post-finalization.
    let two_thirds = (LOW_VALIDATOR_COUNT / 3) * 2;
    let honest_validators: Vec<usize> = (0..two_thirds).collect();
    let faulty_validators: Vec<usize> = (two_thirds..LOW_VALIDATOR_COUNT).collect();

    let fork_blocks = 2 * E::slots_per_epoch();

    let (honest_head, faulty_head) = harness.generate_two_forks_by_skipping_a_block(
        &honest_validators,
        &faulty_validators,
        fork_blocks as usize,
        fork_blocks as usize,
    );

    assert!(honest_head != faulty_head, "forks should be distinct");
    let head_info = harness.chain.head_info().expect("should get head");
    assert_eq!(head_info.slot, unforked_blocks + fork_blocks);

    assert_eq!(
        head_info.block_root, honest_head,
        "the honest chain should be the canonical chain",
    );

    let faulty_head_block = store
        .get_block(&faulty_head)
        .expect("no errors")
        .expect("faulty head block exists");

    let faulty_head_state = store
        .get_state(
            &faulty_head_block.state_root(),
            Some(faulty_head_block.slot()),
        )
        .expect("no db error")
        .expect("faulty head state exists");

    let states_to_delete = StateRootsIterator::new(store.clone(), &faulty_head_state)
        .take_while(|(_, slot)| *slot > unforked_blocks)
        .collect::<Vec<_>>();

    // Delete faulty fork
    // Attempting to load those states should find them unavailable
    for (state_root, slot) in &states_to_delete {
        assert_eq!(store.delete_state(state_root, *slot), Ok(()));
        assert_eq!(store.get_state(state_root, Some(*slot)), Ok(None));
    }

    // Double-deleting should also be OK (deleting non-existent things is fine)
    for (state_root, slot) in &states_to_delete {
        assert_eq!(store.delete_state(state_root, *slot), Ok(()));
    }

    // Deleting the blocks from the fork should remove them completely
    let blocks_to_delete = BlockRootsIterator::new(store.clone(), &faulty_head_state)
        // Extra +1 here accounts for the skipped slot that started this fork
        .take_while(|(_, slot)| *slot > unforked_blocks + 1)
        .collect::<Vec<_>>();

    for (block_root, _) in blocks_to_delete {
        assert_eq!(store.delete_block(&block_root), Ok(()));
        assert_eq!(store.get_block(&block_root), Ok(None));
    }

    // Deleting frozen states should do nothing
    let split_slot = store.get_split_slot();
    let finalized_states = harness
        .chain
        .rev_iter_state_roots()
        .expect("rev iter ok")
        .filter(|(_, slot)| *slot < split_slot);

    for (state_root, slot) in finalized_states {
        assert_eq!(store.delete_state(&state_root, slot), Ok(()));
    }

    // After all that, the chain dump should still be OK
    check_chain_dump(&harness, unforked_blocks + fork_blocks + 1);
}

// Check that we never produce invalid blocks when there is deep forking that changes the shuffling.
// See https://github.com/sigp/lighthouse/issues/845
fn multi_epoch_fork_valid_blocks_test(
    initial_blocks: usize,
    num_fork1_blocks: usize,
    num_fork2_blocks: usize,
    num_fork1_validators: usize,
) -> (TempDir, TestHarness, Hash256, Hash256) {
    let db_path = tempdir().unwrap();
    let store = get_store(&db_path);
    let harness = get_harness(store.clone(), LOW_VALIDATOR_COUNT);

    // Create the initial portion of the chain
    if initial_blocks > 0 {
        harness.extend_chain(
            initial_blocks,
            BlockStrategy::OnCanonicalHead,
            AttestationStrategy::AllValidators,
        );
    }

    assert!(num_fork1_validators <= LOW_VALIDATOR_COUNT);
    let fork1_validators: Vec<usize> = (0..num_fork1_validators).collect();
    let fork2_validators: Vec<usize> = (num_fork1_validators..LOW_VALIDATOR_COUNT).collect();

    let (head1, head2) = harness.generate_two_forks_by_skipping_a_block(
        &fork1_validators,
        &fork2_validators,
        num_fork1_blocks,
        num_fork2_blocks,
    );

    (db_path, harness, head1, head2)
}

// This is the minimal test of block production with different shufflings.
#[test]
fn block_production_different_shuffling_early() {
    let slots_per_epoch = E::slots_per_epoch() as usize;
    multi_epoch_fork_valid_blocks_test(
        slots_per_epoch - 2,
        slots_per_epoch + 3,
        slots_per_epoch + 3,
        LOW_VALIDATOR_COUNT / 2,
    );
}

#[test]
fn block_production_different_shuffling_long() {
    let slots_per_epoch = E::slots_per_epoch() as usize;
    multi_epoch_fork_valid_blocks_test(
        2 * slots_per_epoch - 2,
        3 * slots_per_epoch,
        3 * slots_per_epoch,
        LOW_VALIDATOR_COUNT / 2,
    );
}

// Check that the op pool safely includes multiple attestations per block when necessary.
// This checks the correctness of the shuffling compatibility memoization.
#[test]
fn multiple_attestations_per_block() {
    let db_path = tempdir().unwrap();
    let store = get_store(&db_path);
    let harness = get_harness(store, HIGH_VALIDATOR_COUNT);
    let chain = &harness.chain;

    harness.extend_chain(
        MainnetEthSpec::slots_per_epoch() as usize * 3,
        BlockStrategy::OnCanonicalHead,
        AttestationStrategy::AllValidators,
    );

    let head = chain.head().unwrap();
    let committees_per_slot = head
        .beacon_state
        .get_committee_count_at_slot(head.beacon_state.slot)
        .unwrap();
    assert!(committees_per_slot > 1);

    for snapshot in chain.chain_dump().unwrap() {
        assert_eq!(
            snapshot.beacon_block.message.body.attestations.len() as u64,
            if snapshot.beacon_block.slot() <= 1 {
                0
            } else {
                committees_per_slot
            }
        );
    }
}

#[test]
fn shuffling_compatible_linear_chain() {
    let db_path = tempdir().unwrap();
    let store = get_store(&db_path);
    let harness = get_harness(store.clone(), LOW_VALIDATOR_COUNT);

    // Skip the block at the end of the first epoch.
    let head_block_root = harness.extend_chain(
        4 * E::slots_per_epoch() as usize,
        BlockStrategy::OnCanonicalHead,
        AttestationStrategy::AllValidators,
    );

    check_shuffling_compatible(
        &harness,
        &get_state_for_block(&harness, head_block_root),
        head_block_root,
        true,
        true,
        None,
        None,
    );
}

#[test]
fn shuffling_compatible_missing_pivot_block() {
    let db_path = tempdir().unwrap();
    let store = get_store(&db_path);
    let harness = get_harness(store.clone(), LOW_VALIDATOR_COUNT);

    // Skip the block at the end of the first epoch.
    harness.extend_chain(
        E::slots_per_epoch() as usize - 2,
        BlockStrategy::OnCanonicalHead,
        AttestationStrategy::AllValidators,
    );
    harness.advance_slot();
    harness.advance_slot();
    let head_block_root = harness.extend_chain(
        2 * E::slots_per_epoch() as usize,
        BlockStrategy::OnCanonicalHead,
        AttestationStrategy::AllValidators,
    );

    check_shuffling_compatible(
        &harness,
        &get_state_for_block(&harness, head_block_root),
        head_block_root,
        true,
        true,
        Some(E::slots_per_epoch() - 2),
        Some(E::slots_per_epoch() - 2),
    );
}

#[test]
fn shuffling_compatible_simple_fork() {
    let slots_per_epoch = E::slots_per_epoch() as usize;
    let (db_path, harness, head1, head2) = multi_epoch_fork_valid_blocks_test(
        2 * slots_per_epoch,
        3 * slots_per_epoch,
        3 * slots_per_epoch,
        LOW_VALIDATOR_COUNT / 2,
    );

    let head1_state = get_state_for_block(&harness, head1);
    let head2_state = get_state_for_block(&harness, head2);

    check_shuffling_compatible(&harness, &head1_state, head1, true, true, None, None);
    check_shuffling_compatible(&harness, &head1_state, head2, false, false, None, None);
    check_shuffling_compatible(&harness, &head2_state, head1, false, false, None, None);
    check_shuffling_compatible(&harness, &head2_state, head2, true, true, None, None);

    drop(db_path);
}

#[test]
fn shuffling_compatible_short_fork() {
    let slots_per_epoch = E::slots_per_epoch() as usize;
    let (db_path, harness, head1, head2) = multi_epoch_fork_valid_blocks_test(
        2 * slots_per_epoch - 2,
        slots_per_epoch + 2,
        slots_per_epoch + 2,
        LOW_VALIDATOR_COUNT / 2,
    );

    let head1_state = get_state_for_block(&harness, head1);
    let head2_state = get_state_for_block(&harness, head2);

    check_shuffling_compatible(&harness, &head1_state, head1, true, true, None, None);
    check_shuffling_compatible(&harness, &head1_state, head2, false, true, None, None);
    // NOTE: don't check this case, as block 14 from the first chain appears valid on the second
    // chain due to it matching the second chain's block 15.
    // check_shuffling_compatible(&harness, &head2_state, head1, false, true, None, None);
    check_shuffling_compatible(
        &harness,
        &head2_state,
        head2,
        true,
        true,
        // Required because of the skipped slot.
        Some(2 * E::slots_per_epoch() - 2),
        None,
    );

    drop(db_path);
}

fn get_state_for_block(harness: &TestHarness, block_root: Hash256) -> BeaconState<E> {
    let head_block = harness.chain.get_block(&block_root).unwrap().unwrap();
    harness
        .chain
        .get_state(&head_block.state_root(), Some(head_block.slot()))
        .unwrap()
        .unwrap()
}

/// Check the invariants that apply to `shuffling_is_compatible`.
fn check_shuffling_compatible(
    harness: &TestHarness,
    head_state: &BeaconState<E>,
    head_block_root: Hash256,
    current_epoch_valid: bool,
    previous_epoch_valid: bool,
    current_epoch_cutoff_slot: Option<u64>,
    previous_epoch_cutoff_slot: Option<u64>,
) {
    let shuffling_lookahead = harness.chain.spec.min_seed_lookahead.as_u64() + 1;
    let current_pivot_slot =
        (head_state.current_epoch() - shuffling_lookahead).end_slot(E::slots_per_epoch());
    let previous_pivot_slot =
        (head_state.previous_epoch() - shuffling_lookahead).end_slot(E::slots_per_epoch());

    for (block_root, slot) in harness
        .chain
        .rev_iter_block_roots_from(head_block_root)
        .unwrap()
    {
        // Shuffling is compatible targeting the current epoch,
        // iff slot is greater than or equal to the current epoch pivot block
        assert_eq!(
            harness.chain.shuffling_is_compatible(
                &block_root,
                head_state.current_epoch(),
                &head_state
            ),
            current_epoch_valid
                && slot >= current_epoch_cutoff_slot.unwrap_or(current_pivot_slot.as_u64())
        );
        // Similarly for the previous epoch
        assert_eq!(
            harness.chain.shuffling_is_compatible(
                &block_root,
                head_state.previous_epoch(),
                &head_state
            ),
            previous_epoch_valid
                && slot >= previous_epoch_cutoff_slot.unwrap_or(previous_pivot_slot.as_u64())
        );
        // Targeting the next epoch should always return false
        assert_eq!(
            harness.chain.shuffling_is_compatible(
                &block_root,
                head_state.current_epoch() + 1,
                &head_state
            ),
            false
        );
        // Targeting two epochs before the current epoch should also always return false
        if head_state.current_epoch() >= 2 {
            assert_eq!(
                harness.chain.shuffling_is_compatible(
                    &block_root,
                    head_state.current_epoch() - 2,
                    &head_state
                ),
                false
            );
        }
    }
}

/// Check that the head state's slot matches `expected_slot`.
fn check_slot(harness: &TestHarness, expected_slot: u64) {
    let state = &harness.chain.head().expect("should get head").beacon_state;

    assert_eq!(
        state.slot, expected_slot,
        "head should be at the current slot"
    );
}

/// Check that the chain has finalized under best-case assumptions, and check the head slot.
fn check_finalization(harness: &TestHarness, expected_slot: u64) {
    let state = &harness.chain.head().expect("should get head").beacon_state;

    check_slot(harness, expected_slot);

    assert_eq!(
        state.current_justified_checkpoint.epoch,
        state.current_epoch() - 1,
        "the head should be justified one behind the current epoch"
    );
    assert_eq!(
        state.finalized_checkpoint.epoch,
        state.current_epoch() - 2,
        "the head should be finalized two behind the current epoch"
    );
}

/// Check that the DiskStore's split_slot is equal to the start slot of the last finalized epoch.
fn check_split_slot(harness: &TestHarness, store: Arc<DiskStore<E>>) {
    let split_slot = store.get_split_slot();
    assert_eq!(
        harness
            .chain
            .head()
            .expect("should get head")
            .beacon_state
            .finalized_checkpoint
            .epoch
            .start_slot(E::slots_per_epoch()),
        split_slot
    );
    assert_ne!(split_slot, 0);
}

/// Check that all the states in a chain dump have the correct tree hash.
fn check_chain_dump(harness: &TestHarness, expected_len: u64) {
    let chain_dump = harness.chain.chain_dump().unwrap();

    assert_eq!(chain_dump.len() as u64, expected_len);

    for checkpoint in &chain_dump {
        // Check that the tree hash of the stored state is as expected
        assert_eq!(
            checkpoint.beacon_state_root,
            checkpoint.beacon_state.tree_hash_root(),
            "tree hash of stored state is incorrect"
        );

        // Check that looking up the state root with no slot hint succeeds.
        // This tests the state root -> slot mapping.
        assert_eq!(
            harness
                .chain
                .store
                .get_state(&checkpoint.beacon_state_root, None)
                .expect("no error")
                .expect("state exists")
                .slot,
            checkpoint.beacon_state.slot
        );
    }

    // Check the forwards block roots iterator against the chain dump
    let chain_dump_block_roots = chain_dump
        .iter()
        .map(|checkpoint| (checkpoint.beacon_block_root, checkpoint.beacon_block.slot()))
        .collect::<Vec<_>>();

    let head = harness.chain.head().expect("should get head");
    let mut forward_block_roots = Store::forwards_block_roots_iterator(
        harness.chain.store.clone(),
        Slot::new(0),
        head.beacon_state,
        head.beacon_block_root,
        &harness.spec,
    )
    .collect::<Vec<_>>();

    // Drop the block roots for skipped slots.
    forward_block_roots.dedup_by_key(|(block_root, _)| *block_root);

    for i in 0..std::cmp::max(chain_dump_block_roots.len(), forward_block_roots.len()) {
        assert_eq!(
            chain_dump_block_roots[i],
            forward_block_roots[i],
            "split slot is {}",
            harness.chain.store.get_split_slot()
        );
    }
}

/// Check that state and block root iterators can reach genesis
fn check_iterators(harness: &TestHarness) {
    assert_eq!(
        harness
            .chain
            .rev_iter_state_roots()
            .expect("should get iter")
            .last()
            .map(|(_, slot)| slot),
        Some(Slot::new(0))
    );
    assert_eq!(
        harness
            .chain
            .rev_iter_block_roots()
            .expect("should get iter")
            .last()
            .map(|(_, slot)| slot),
        Some(Slot::new(0))
    );
}