// This file is part of Substrate.

// Copyright (C) Parity Technologies (UK) Ltd.
// SPDX-License-Identifier: Apache-2.0

// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// 	http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

//! Consensus extension module tests for BABE consensus.

use super::{Call, *};
use frame_support::{
	assert_err, assert_noop, assert_ok,
	dispatch::{GetDispatchInfo, Pays},
	traits::{Currency, EstimateNextSessionRotation, KeyOwnerProofSystem, OnFinalize},
};
use mock::*;
use pallet_session::ShouldEndSession;
use sp_consensus_babe::{
	AllowedSlots, BabeEpochConfiguration, Slot, VrfSignature, RANDOMNESS_LENGTH,
};
use sp_core::crypto::Pair;

const EMPTY_RANDOMNESS: [u8; RANDOMNESS_LENGTH] = [
	74, 25, 49, 128, 53, 97, 244, 49, 222, 202, 176, 2, 231, 66, 95, 10, 133, 49, 213, 228, 86,
	161, 164, 127, 217, 153, 138, 37, 48, 192, 248, 0,
];

#[test]
fn empty_randomness_is_correct() {
	let s = compute_randomness([0; RANDOMNESS_LENGTH], 0, std::iter::empty(), None);
	assert_eq!(s, EMPTY_RANDOMNESS);
}

#[test]
fn initial_values() {
	new_test_ext(4).execute_with(|| assert_eq!(Babe::authorities().len(), 4))
}

#[test]
fn check_module() {
	new_test_ext(4).execute_with(|| {
		assert!(!Babe::should_end_session(0), "Genesis does not change sessions");
		assert!(
			!Babe::should_end_session(200000),
			"BABE does not include the block number in epoch calculations"
		);
	})
}

#[test]
fn first_block_epoch_zero_start() {
	let (pairs, mut ext) = new_test_ext_with_pairs(4);

	ext.execute_with(|| {
		let genesis_slot = Slot::from(100);
		let (vrf_signature, vrf_randomness) =
			make_vrf_signature_and_randomness(genesis_slot, &pairs[0]);

		let pre_digest = make_primary_pre_digest(0, genesis_slot, vrf_signature);

		assert_eq!(Babe::genesis_slot(), Slot::from(0));
		System::reset_events();
		System::initialize(&1, &Default::default(), &pre_digest);

		// see implementation of the function for details why: we issue an
		// epoch-change digest but don't do it via the normal session mechanism.
		assert!(!Babe::should_end_session(1));
		assert_eq!(Babe::genesis_slot(), genesis_slot);
		assert_eq!(Babe::current_slot(), genesis_slot);
		assert_eq!(Babe::epoch_index(), 0);

		Babe::on_finalize(1);
		let header = System::finalize();

		assert_eq!(Babe::author_vrf_randomness(), Some(vrf_randomness));
		assert_eq!(SegmentIndex::<Test>::get(), 0);
		assert_eq!(UnderConstruction::<Test>::get(0), vec![vrf_randomness]);
		assert_eq!(Babe::randomness(), [0; 32]);
		assert_eq!(Babe::author_vrf_randomness(), Some(vrf_randomness));
		assert_eq!(NextRandomness::<Test>::get(), [0; 32]);

		assert_eq!(header.digest.logs.len(), 2);
		assert_eq!(pre_digest.logs.len(), 1);
		assert_eq!(header.digest.logs[0], pre_digest.logs[0]);

		let consensus_log = sp_consensus_babe::ConsensusLog::NextEpochData(
			sp_consensus_babe::digests::NextEpochDescriptor {
				authorities: Babe::authorities().into_inner(),
				randomness: Babe::randomness(),
			},
		);
		let consensus_digest = DigestItem::Consensus(BABE_ENGINE_ID, consensus_log.encode());

		// first epoch descriptor has same info as last.
		assert_eq!(header.digest.logs[1], consensus_digest.clone())
	})
}

#[test]
fn current_slot_is_processed_on_initialization() {
	let (pairs, mut ext) = new_test_ext_with_pairs(1);

	ext.execute_with(|| {
		let genesis_slot = Slot::from(10);
		let (vrf_signature, vrf_randomness) =
			make_vrf_signature_and_randomness(genesis_slot, &pairs[0]);
		let pre_digest = make_primary_pre_digest(0, genesis_slot, vrf_signature);

		System::reset_events();
		System::initialize(&1, &Default::default(), &pre_digest);
		assert_eq!(Babe::current_slot(), Slot::from(0));
		assert!(Babe::initialized().is_none());

		// current slot is updated on initialization
		Babe::initialize(1);
		assert_eq!(Babe::current_slot(), genesis_slot);
		assert!(Babe::initialized().is_some());
		// but author vrf randomness isn't
		assert_eq!(Babe::author_vrf_randomness(), None);

		// instead it is updated on block finalization
		Babe::on_finalize(1);
		assert_eq!(Babe::author_vrf_randomness(), Some(vrf_randomness));
	})
}

fn test_author_vrf_output<F>(make_pre_digest: F)
where
	F: Fn(sp_consensus_babe::AuthorityIndex, Slot, VrfSignature) -> sp_runtime::Digest,
{
	let (pairs, mut ext) = new_test_ext_with_pairs(1);

	ext.execute_with(|| {
		let genesis_slot = Slot::from(10);
		let (vrf_signature, vrf_randomness) =
			make_vrf_signature_and_randomness(genesis_slot, &pairs[0]);
		let pre_digest = make_pre_digest(0, genesis_slot, vrf_signature);

		System::reset_events();
		System::initialize(&1, &Default::default(), &pre_digest);

		// author vrf randomness is not updated on initialization
		Babe::initialize(1);
		assert_eq!(Babe::author_vrf_randomness(), None);

		// instead it is updated on block finalization to account for any
		// epoch changes that might happen during the block
		Babe::on_finalize(1);
		assert_eq!(Babe::author_vrf_randomness(), Some(vrf_randomness));

		// and it is kept after finalizing the block
		System::finalize();
		assert_eq!(Babe::author_vrf_randomness(), Some(vrf_randomness));
	})
}

#[test]
fn author_vrf_output_for_primary() {
	test_author_vrf_output(make_primary_pre_digest);
}

#[test]
fn author_vrf_output_for_secondary_vrf() {
	test_author_vrf_output(make_secondary_vrf_pre_digest);
}

#[test]
fn no_author_vrf_output_for_secondary_plain() {
	new_test_ext(1).execute_with(|| {
		let genesis_slot = Slot::from(10);
		let secondary_plain_pre_digest = make_secondary_plain_pre_digest(0, genesis_slot);

		System::reset_events();
		System::initialize(&1, &Default::default(), &secondary_plain_pre_digest);
		assert_eq!(Babe::author_vrf_randomness(), None);

		Babe::initialize(1);
		assert_eq!(Babe::author_vrf_randomness(), None);

		Babe::on_finalize(1);
		System::finalize();
		assert_eq!(Babe::author_vrf_randomness(), None);
	})
}

#[test]
fn authority_index() {
	new_test_ext(4).execute_with(|| {
		assert_eq!(
			Babe::find_author((&[(BABE_ENGINE_ID, &[][..])]).into_iter().cloned()),
			None,
			"Trivially invalid authorities are ignored"
		)
	})
}

#[test]
fn can_predict_next_epoch_change() {
	new_test_ext(1).execute_with(|| {
		assert_eq!(<Test as Config>::EpochDuration::get(), 3);
		// this sets the genesis slot to 6;
		go_to_block(1, 6);
		assert_eq!(*Babe::genesis_slot(), 6);
		assert_eq!(*Babe::current_slot(), 6);
		assert_eq!(Babe::epoch_index(), 0);

		progress_to_block(5);

		assert_eq!(Babe::epoch_index(), 5 / 3);
		assert_eq!(*Babe::current_slot(), 10);

		// next epoch change will be at
		assert_eq!(*Babe::current_epoch_start(), 9); // next change will be 12, 2 slots from now
		assert_eq!(Babe::next_expected_epoch_change(System::block_number()), Some(5 + 2));
	})
}

#[test]
fn can_estimate_current_epoch_progress() {
	new_test_ext(1).execute_with(|| {
		assert_eq!(<Test as Config>::EpochDuration::get(), 3);

		// with BABE the genesis block is not part of any epoch, the first epoch starts at block #1,
		// therefore its last block should be #3
		for i in 1u64..4 {
			progress_to_block(i);

			assert_eq!(Babe::estimate_next_session_rotation(i).0.unwrap(), 4);

			// the last block of the epoch must have 100% progress.
			if Babe::estimate_next_session_rotation(i).0.unwrap() - 1 == i {
				assert_eq!(
					Babe::estimate_current_session_progress(i).0.unwrap(),
					Permill::from_percent(100)
				);
			} else {
				assert!(
					Babe::estimate_current_session_progress(i).0.unwrap() <
						Permill::from_percent(100)
				);
			}
		}

		// the first block of the new epoch counts towards the epoch progress as well
		progress_to_block(4);
		assert_eq!(
			Babe::estimate_current_session_progress(4).0.unwrap(),
			Permill::from_float(1.0 / 3.0),
		);
	})
}

#[test]
fn can_enact_next_config() {
	new_test_ext(1).execute_with(|| {
		assert_eq!(<Test as Config>::EpochDuration::get(), 3);
		// this sets the genesis slot to 6;
		go_to_block(1, 6);
		assert_eq!(*Babe::genesis_slot(), 6);
		assert_eq!(*Babe::current_slot(), 6);
		assert_eq!(Babe::epoch_index(), 0);
		go_to_block(2, 7);

		let current_config = BabeEpochConfiguration {
			c: (0, 4),
			allowed_slots: sp_consensus_babe::AllowedSlots::PrimarySlots,
		};

		let next_config = BabeEpochConfiguration {
			c: (1, 4),
			allowed_slots: sp_consensus_babe::AllowedSlots::PrimarySlots,
		};

		let next_next_config = BabeEpochConfiguration {
			c: (2, 4),
			allowed_slots: sp_consensus_babe::AllowedSlots::PrimarySlots,
		};

		EpochConfig::<Test>::put(current_config);
		NextEpochConfig::<Test>::put(next_config.clone());

		assert_eq!(NextEpochConfig::<Test>::get(), Some(next_config.clone()));

		Babe::plan_config_change(
			RuntimeOrigin::root(),
			NextConfigDescriptor::V1 {
				c: next_next_config.c,
				allowed_slots: next_next_config.allowed_slots,
			},
		)
		.unwrap();

		progress_to_block(4);
		Babe::on_finalize(9);
		let header = System::finalize();

		assert_eq!(EpochConfig::<Test>::get(), Some(next_config));
		assert_eq!(NextEpochConfig::<Test>::get(), Some(next_next_config.clone()));

		let consensus_log =
			sp_consensus_babe::ConsensusLog::NextConfigData(NextConfigDescriptor::V1 {
				c: next_next_config.c,
				allowed_slots: next_next_config.allowed_slots,
			});
		let consensus_digest = DigestItem::Consensus(BABE_ENGINE_ID, consensus_log.encode());

		assert_eq!(header.digest.logs[2], consensus_digest.clone())
	});
}

#[test]
fn only_root_can_enact_config_change() {
	use sp_runtime::DispatchError;

	new_test_ext(1).execute_with(|| {
		let next_config =
			NextConfigDescriptor::V1 { c: (1, 4), allowed_slots: AllowedSlots::PrimarySlots };

		let res = Babe::plan_config_change(RuntimeOrigin::none(), next_config.clone());

		assert_noop!(res, DispatchError::BadOrigin);

		let res = Babe::plan_config_change(RuntimeOrigin::signed(1), next_config.clone());

		assert_noop!(res, DispatchError::BadOrigin);

		let res = Babe::plan_config_change(RuntimeOrigin::root(), next_config);

		assert!(res.is_ok());
	});
}

#[test]
fn can_fetch_current_and_next_epoch_data() {
	new_test_ext(5).execute_with(|| {
		EpochConfig::<Test>::put(BabeEpochConfiguration {
			c: (1, 4),
			allowed_slots: sp_consensus_babe::AllowedSlots::PrimarySlots,
		});

		// genesis authorities should be used for the first and second epoch
		assert_eq!(Babe::current_epoch().authorities, Babe::next_epoch().authorities);
		// 1 era = 3 epochs
		// 1 epoch = 3 slots
		// Eras start from 0.
		// Therefore at era 1 we should be starting epoch 3 with slot 10.
		start_era(1);

		let current_epoch = Babe::current_epoch();
		assert_eq!(current_epoch.epoch_index, 3);
		assert_eq!(*current_epoch.start_slot, 10);
		assert_eq!(current_epoch.authorities.len(), 5);

		let next_epoch = Babe::next_epoch();
		assert_eq!(next_epoch.epoch_index, 4);
		assert_eq!(*next_epoch.start_slot, 13);
		assert_eq!(next_epoch.authorities.len(), 5);

		// the on-chain randomness should always change across epochs
		assert!(current_epoch.randomness != next_epoch.randomness);

		// but in this case the authorities stay the same
		assert!(current_epoch.authorities == next_epoch.authorities);
	});
}

#[test]
fn tracks_block_numbers_when_current_and_previous_epoch_started() {
	new_test_ext(5).execute_with(|| {
		// an epoch is 3 slots therefore at block 8 we should be in epoch #3
		// with the previous epochs having the following blocks:
		// epoch 1 - [1, 2, 3]
		// epoch 2 - [4, 5, 6]
		// epoch 3 - [7, 8, 9]
		progress_to_block(8);

		let (last_epoch, current_epoch) = EpochStart::<Test>::get();

		assert_eq!(last_epoch, 4);
		assert_eq!(current_epoch, 7);

		// once we reach block 10 we switch to epoch #4
		progress_to_block(10);

		let (last_epoch, current_epoch) = EpochStart::<Test>::get();

		assert_eq!(last_epoch, 7);
		assert_eq!(current_epoch, 10);
	});
}

#[test]
#[should_panic(
	expected = "Validator with index 0 is disabled and should not be attempting to author blocks."
)]
fn disabled_validators_cannot_author_blocks() {
	new_test_ext(4).execute_with(|| {
		start_era(1);

		// let's disable the validator at index 1
		Session::disable_index(1);

		// the mocking infrastructure always authors all blocks using authority index 0,
		// so we should still be able to author blocks
		start_era(2);

		assert_eq!(Staking::current_era().unwrap(), 2);

		// let's disable the validator at index 0
		Session::disable_index(0);

		// this should now panic as the validator authoring blocks is disabled
		start_era(3);
	});
}

#[test]
fn report_equivocation_current_session_works() {
	let (pairs, mut ext) = new_test_ext_with_pairs(3);

	ext.execute_with(|| {
		start_era(1);

		let authorities = Babe::authorities();
		let validators = Session::validators();

		// make sure that all authorities have the same balance
		for validator in &validators {
			assert_eq!(Balances::total_balance(validator), 10_000_000);
			assert_eq!(Staking::slashable_balance_of(validator), 10_000);

			assert_eq!(
				Staking::eras_stakers(1, &validator),
				pallet_staking::Exposure { total: 10_000, own: 10_000, others: vec![] },
			);
		}

		// we will use the validator at index 1 as the offending authority
		let offending_validator_index = 1;
		let offending_validator_id = Session::validators()[offending_validator_index];
		let offending_authority_pair = pairs
			.into_iter()
			.find(|p| p.public() == authorities[offending_validator_index].0)
			.unwrap();

		// generate an equivocation proof. it creates two headers at the given
		// slot with different block hashes and signed by the given key
		let equivocation_proof = generate_equivocation_proof(
			offending_validator_index as u32,
			&offending_authority_pair,
			CurrentSlot::<Test>::get(),
		);

		// create the key ownership proof
		let key = (sp_consensus_babe::KEY_TYPE, &offending_authority_pair.public());
		let key_owner_proof = Historical::prove(key).unwrap();

		// report the equivocation
		Babe::report_equivocation_unsigned(
			RuntimeOrigin::none(),
			Box::new(equivocation_proof),
			key_owner_proof,
		)
		.unwrap();

		// start a new era so that the results of the offence report
		// are applied at era end
		start_era(2);

		// check that the balance of offending validator is slashed 100%.
		assert_eq!(Balances::total_balance(&offending_validator_id), 10_000_000 - 10_000);
		assert_eq!(Staking::slashable_balance_of(&offending_validator_id), 0);
		assert_eq!(
			Staking::eras_stakers(2, &offending_validator_id),
			pallet_staking::Exposure { total: 0, own: 0, others: vec![] },
		);

		// check that the balances of all other validators are left intact.
		for validator in &validators {
			if *validator == offending_validator_id {
				continue
			}

			assert_eq!(Balances::total_balance(validator), 10_000_000);
			assert_eq!(Staking::slashable_balance_of(validator), 10_000);
			assert_eq!(
				Staking::eras_stakers(2, &validator),
				pallet_staking::Exposure { total: 10_000, own: 10_000, others: vec![] },
			);
		}
	})
}

#[test]
fn report_equivocation_old_session_works() {
	let (pairs, mut ext) = new_test_ext_with_pairs(3);

	ext.execute_with(|| {
		start_era(1);

		let authorities = Babe::authorities();

		// we will use the validator at index 0 as the offending authority
		let offending_validator_index = 1;
		let offending_validator_id = Session::validators()[offending_validator_index];
		let offending_authority_pair = pairs
			.into_iter()
			.find(|p| p.public() == authorities[offending_validator_index].0)
			.unwrap();

		// generate an equivocation proof at the current slot
		let equivocation_proof = generate_equivocation_proof(
			offending_validator_index as u32,
			&offending_authority_pair,
			CurrentSlot::<Test>::get(),
		);

		// create the key ownership proof
		let key = (sp_consensus_babe::KEY_TYPE, &offending_authority_pair.public());
		let key_owner_proof = Historical::prove(key).unwrap();

		// start a new era and report the equivocation
		// from the previous era
		start_era(2);

		// check the balance of the offending validator
		assert_eq!(Balances::total_balance(&offending_validator_id), 10_000_000);
		assert_eq!(Staking::slashable_balance_of(&offending_validator_id), 10_000);

		// report the equivocation
		Babe::report_equivocation_unsigned(
			RuntimeOrigin::none(),
			Box::new(equivocation_proof),
			key_owner_proof,
		)
		.unwrap();

		// start a new era so that the results of the offence report
		// are applied at era end
		start_era(3);

		// check that the balance of offending validator is slashed 100%.
		assert_eq!(Balances::total_balance(&offending_validator_id), 10_000_000 - 10_000);
		assert_eq!(Staking::slashable_balance_of(&offending_validator_id), 0);
		assert_eq!(
			Staking::eras_stakers(3, &offending_validator_id),
			pallet_staking::Exposure { total: 0, own: 0, others: vec![] },
		);
	})
}

#[test]
fn report_equivocation_invalid_key_owner_proof() {
	let (pairs, mut ext) = new_test_ext_with_pairs(3);

	ext.execute_with(|| {
		start_era(1);

		let authorities = Babe::authorities();

		// we will use the validator at index 0 as the offending authority
		let offending_validator_index = 0;
		let offending_authority_pair = pairs
			.into_iter()
			.find(|p| p.public() == authorities[offending_validator_index].0)
			.unwrap();

		// generate an equivocation proof at the current slot
		let equivocation_proof = generate_equivocation_proof(
			offending_validator_index as u32,
			&offending_authority_pair,
			CurrentSlot::<Test>::get(),
		);

		// create the key ownership proof
		let key = (sp_consensus_babe::KEY_TYPE, &offending_authority_pair.public());
		let mut key_owner_proof = Historical::prove(key).unwrap();

		// we change the session index in the key ownership proof
		// which should make it invalid
		key_owner_proof.session = 0;
		assert_err!(
			Babe::report_equivocation_unsigned(
				RuntimeOrigin::none(),
				Box::new(equivocation_proof.clone()),
				key_owner_proof
			),
			Error::<Test>::InvalidKeyOwnershipProof,
		);

		// it should fail as well if we create a key owner proof
		// for a different authority than the offender
		let key = (sp_consensus_babe::KEY_TYPE, &authorities[1].0);
		let key_owner_proof = Historical::prove(key).unwrap();

		// we need to progress to a new era to make sure that the key
		// ownership proof is properly checked, otherwise since the state
		// is still available the historical module will just check
		// against current session data.
		start_era(2);

		assert_err!(
			Babe::report_equivocation_unsigned(
				RuntimeOrigin::none(),
				Box::new(equivocation_proof),
				key_owner_proof,
			),
			Error::<Test>::InvalidKeyOwnershipProof,
		);
	})
}

#[test]
fn report_equivocation_invalid_equivocation_proof() {
	use sp_runtime::traits::Header;

	let (pairs, mut ext) = new_test_ext_with_pairs(3);

	ext.execute_with(|| {
		start_era(1);

		let authorities = Babe::authorities();

		// we will use the validator at index 0 as the offending authority
		let offending_validator_index = 0;
		let offending_authority_pair = pairs
			.into_iter()
			.find(|p| p.public() == authorities[offending_validator_index].0)
			.unwrap();

		// create the key ownership proof
		let key = (sp_consensus_babe::KEY_TYPE, &offending_authority_pair.public());
		let key_owner_proof = Historical::prove(key).unwrap();

		let assert_invalid_equivocation = |equivocation_proof| {
			assert_err!(
				Babe::report_equivocation_unsigned(
					RuntimeOrigin::none(),
					Box::new(equivocation_proof),
					key_owner_proof.clone(),
				),
				Error::<Test>::InvalidEquivocationProof,
			)
		};

		// both headers have the same hash, no equivocation.
		let mut equivocation_proof = generate_equivocation_proof(
			offending_validator_index as u32,
			&offending_authority_pair,
			CurrentSlot::<Test>::get(),
		);
		equivocation_proof.second_header = equivocation_proof.first_header.clone();
		assert_invalid_equivocation(equivocation_proof);

		// missing pre-runtime digest from one header
		let mut equivocation_proof = generate_equivocation_proof(
			offending_validator_index as u32,
			&offending_authority_pair,
			CurrentSlot::<Test>::get(),
		);
		equivocation_proof.first_header.digest_mut().logs.remove(0);
		assert_invalid_equivocation(equivocation_proof);

		// missing seal from one header
		let mut equivocation_proof = generate_equivocation_proof(
			offending_validator_index as u32,
			&offending_authority_pair,
			CurrentSlot::<Test>::get(),
		);
		equivocation_proof.first_header.digest_mut().logs.remove(1);
		assert_invalid_equivocation(equivocation_proof);

		// invalid slot number in proof compared to runtime digest
		let mut equivocation_proof = generate_equivocation_proof(
			offending_validator_index as u32,
			&offending_authority_pair,
			CurrentSlot::<Test>::get(),
		);
		equivocation_proof.slot = Slot::from(0);
		assert_invalid_equivocation(equivocation_proof.clone());

		// different slot numbers in headers
		let h1 = equivocation_proof.first_header;
		let mut equivocation_proof = generate_equivocation_proof(
			offending_validator_index as u32,
			&offending_authority_pair,
			CurrentSlot::<Test>::get() + 1,
		);

		// use the header from the previous equivocation generated
		// at the previous slot
		equivocation_proof.first_header = h1.clone();

		assert_invalid_equivocation(equivocation_proof.clone());

		// invalid seal signature
		let mut equivocation_proof = generate_equivocation_proof(
			offending_validator_index as u32,
			&offending_authority_pair,
			CurrentSlot::<Test>::get() + 1,
		);

		// replace the seal digest with the digest from the
		// previous header at the previous slot
		equivocation_proof.first_header.digest_mut().pop();
		equivocation_proof
			.first_header
			.digest_mut()
			.push(h1.digest().logs().last().unwrap().clone());

		assert_invalid_equivocation(equivocation_proof.clone());
	})
}

#[test]
fn report_equivocation_validate_unsigned_prevents_duplicates() {
	use sp_runtime::transaction_validity::{
		InvalidTransaction, TransactionPriority, TransactionSource, TransactionValidity,
		ValidTransaction,
	};

	let (pairs, mut ext) = new_test_ext_with_pairs(3);

	ext.execute_with(|| {
		start_era(1);

		let authorities = Babe::authorities();

		// generate and report an equivocation for the validator at index 0
		let offending_validator_index = 0;
		let offending_authority_pair = pairs
			.into_iter()
			.find(|p| p.public() == authorities[offending_validator_index].0)
			.unwrap();

		let equivocation_proof = generate_equivocation_proof(
			offending_validator_index as u32,
			&offending_authority_pair,
			CurrentSlot::<Test>::get(),
		);

		let key = (sp_consensus_babe::KEY_TYPE, &offending_authority_pair.public());
		let key_owner_proof = Historical::prove(key).unwrap();

		let inner = Call::report_equivocation_unsigned {
			equivocation_proof: Box::new(equivocation_proof.clone()),
			key_owner_proof: key_owner_proof.clone(),
		};

		// only local/inblock reports are allowed
		assert_eq!(
			<Babe as sp_runtime::traits::ValidateUnsigned>::validate_unsigned(
				TransactionSource::External,
				&inner,
			),
			InvalidTransaction::Call.into(),
		);

		// the transaction is valid when passed as local
		let tx_tag = (offending_authority_pair.public(), CurrentSlot::<Test>::get());
		assert_eq!(
			<Babe as sp_runtime::traits::ValidateUnsigned>::validate_unsigned(
				TransactionSource::Local,
				&inner,
			),
			TransactionValidity::Ok(ValidTransaction {
				priority: TransactionPriority::max_value(),
				requires: vec![],
				provides: vec![("BabeEquivocation", tx_tag).encode()],
				longevity: ReportLongevity::get(),
				propagate: false,
			})
		);

		// the pre dispatch checks should also pass
		assert_ok!(<Babe as sp_runtime::traits::ValidateUnsigned>::pre_dispatch(&inner));

		// we submit the report
		Babe::report_equivocation_unsigned(
			RuntimeOrigin::none(),
			Box::new(equivocation_proof),
			key_owner_proof,
		)
		.unwrap();

		// the report should now be considered stale and the transaction is invalid.
		// the check for staleness should be done on both `validate_unsigned` and on `pre_dispatch`
		assert_err!(
			<Babe as sp_runtime::traits::ValidateUnsigned>::validate_unsigned(
				TransactionSource::Local,
				&inner,
			),
			InvalidTransaction::Stale,
		);

		assert_err!(
			<Babe as sp_runtime::traits::ValidateUnsigned>::pre_dispatch(&inner),
			InvalidTransaction::Stale,
		);
	});
}

#[test]
fn report_equivocation_has_valid_weight() {
	// the weight depends on the size of the validator set,
	// but there's a lower bound of 100 validators.
	assert!((1..=100)
		.map(|validators| <Test as Config>::WeightInfo::report_equivocation(validators, 1000))
		.collect::<Vec<_>>()
		.windows(2)
		.all(|w| w[0] == w[1]));

	// after 100 validators the weight should keep increasing
	// with every extra validator.
	assert!((100..=1000)
		.map(|validators| <Test as Config>::WeightInfo::report_equivocation(validators, 1000))
		.collect::<Vec<_>>()
		.windows(2)
		.all(|w| w[0].ref_time() < w[1].ref_time()));
}

#[test]
fn report_equivocation_after_skipped_epochs_works() {
	let (pairs, mut ext) = new_test_ext_with_pairs(3);

	ext.execute_with(|| {
		let epoch_duration: u64 = <Test as Config>::EpochDuration::get();

		// this sets the genesis slot to 100;
		let genesis_slot = 100;
		go_to_block(1, genesis_slot);
		assert_eq!(EpochIndex::<Test>::get(), 0);

		// skip from epoch #0 to epoch #10
		go_to_block(System::block_number() + 1, genesis_slot + epoch_duration * 10);

		assert_eq!(EpochIndex::<Test>::get(), 10);
		assert_eq!(SkippedEpochs::<Test>::get(), vec![(10, 1)]);

		// generate an equivocation proof for validator at index 1
		let authorities = Babe::authorities();
		let offending_validator_index = 1;
		let offending_authority_pair = pairs
			.into_iter()
			.find(|p| p.public() == authorities[offending_validator_index].0)
			.unwrap();

		let equivocation_proof = generate_equivocation_proof(
			offending_validator_index as u32,
			&offending_authority_pair,
			CurrentSlot::<Test>::get(),
		);

		// create the key ownership proof
		let key = (sp_consensus_babe::KEY_TYPE, &offending_authority_pair.public());
		let key_owner_proof = Historical::prove(key).unwrap();

		// which is for session index 1 (while current epoch index is 10)
		assert_eq!(key_owner_proof.session, 1);

		// report the equivocation, in order for the validation to pass the mapping
		// between epoch index and session index must be checked.
		assert!(Babe::report_equivocation_unsigned(
			RuntimeOrigin::none(),
			Box::new(equivocation_proof),
			key_owner_proof
		)
		.is_ok());
	})
}

#[test]
fn valid_equivocation_reports_dont_pay_fees() {
	let (pairs, mut ext) = new_test_ext_with_pairs(3);

	ext.execute_with(|| {
		start_era(1);

		let offending_authority_pair = &pairs[0];

		// generate an equivocation proof.
		let equivocation_proof =
			generate_equivocation_proof(0, &offending_authority_pair, CurrentSlot::<Test>::get());

		// create the key ownership proof.
		let key_owner_proof =
			Historical::prove((sp_consensus_babe::KEY_TYPE, &offending_authority_pair.public()))
				.unwrap();

		// check the dispatch info for the call.
		let info = Call::<Test>::report_equivocation_unsigned {
			equivocation_proof: Box::new(equivocation_proof.clone()),
			key_owner_proof: key_owner_proof.clone(),
		}
		.get_dispatch_info();

		// it should have non-zero weight and the fee has to be paid.
		// TODO: account for proof size weight
		assert!(info.weight.ref_time() > 0);
		assert_eq!(info.pays_fee, Pays::Yes);

		// report the equivocation.
		let post_info = Babe::report_equivocation_unsigned(
			RuntimeOrigin::none(),
			Box::new(equivocation_proof.clone()),
			key_owner_proof.clone(),
		)
		.unwrap();

		// the original weight should be kept, but given that the report
		// is valid the fee is waived.
		assert!(post_info.actual_weight.is_none());
		assert_eq!(post_info.pays_fee, Pays::No);

		// report the equivocation again which is invalid now since it is
		// duplicate.
		let post_info = Babe::report_equivocation_unsigned(
			RuntimeOrigin::none(),
			Box::new(equivocation_proof),
			key_owner_proof,
		)
		.err()
		.unwrap()
		.post_info;

		// the fee is not waived and the original weight is kept.
		assert!(post_info.actual_weight.is_none());
		assert_eq!(post_info.pays_fee, Pays::Yes);
	})
}

#[test]
fn add_epoch_configurations_migration_works() {
	use frame_support::storage::migration::{get_storage_value, put_storage_value};

	impl crate::migrations::BabePalletPrefix for Test {
		fn pallet_prefix() -> &'static str {
			"Babe"
		}
	}

	new_test_ext(1).execute_with(|| {
		let next_config_descriptor =
			NextConfigDescriptor::V1 { c: (3, 4), allowed_slots: AllowedSlots::PrimarySlots };

		put_storage_value(b"Babe", b"NextEpochConfig", &[], Some(next_config_descriptor.clone()));

		assert!(get_storage_value::<Option<NextConfigDescriptor>>(
			b"Babe",
			b"NextEpochConfig",
			&[],
		)
		.is_some());

		let current_epoch = BabeEpochConfiguration {
			c: (1, 4),
			allowed_slots: sp_consensus_babe::AllowedSlots::PrimarySlots,
		};

		crate::migrations::add_epoch_configuration::<Test>(current_epoch.clone());

		assert!(get_storage_value::<Option<NextConfigDescriptor>>(
			b"Babe",
			b"NextEpochConfig",
			&[],
		)
		.is_none());

		assert_eq!(EpochConfig::<Test>::get(), Some(current_epoch));
		assert_eq!(PendingEpochConfigChange::<Test>::get(), Some(next_config_descriptor));
	});
}

#[test]
fn generate_equivocation_report_blob() {
	let (pairs, mut ext) = new_test_ext_with_pairs(3);

	let offending_authority_index = 0;
	let offending_authority_pair = &pairs[0];

	ext.execute_with(|| {
		start_era(1);

		let equivocation_proof = generate_equivocation_proof(
			offending_authority_index,
			offending_authority_pair,
			CurrentSlot::<Test>::get() + 1,
		);

		println!("equivocation_proof: {:?}", equivocation_proof);
		println!("equivocation_proof.encode(): {:?}", equivocation_proof.encode());
	});
}

#[test]
fn skipping_over_epochs_works() {
	let mut ext = new_test_ext(3);

	ext.execute_with(|| {
		let epoch_duration: u64 = <Test as Config>::EpochDuration::get();

		// this sets the genesis slot to 100;
		let genesis_slot = 100;
		go_to_block(1, genesis_slot);

		// we will author all blocks from epoch #0 and arrive at a point where
		// we are in epoch #1. we should already have the randomness ready that
		// will be used in epoch #2
		progress_to_block(epoch_duration + 1);
		assert_eq!(EpochIndex::<Test>::get(), 1);

		// genesis randomness is an array of zeros
		let randomness_for_epoch_2 = NextRandomness::<Test>::get();
		assert!(randomness_for_epoch_2 != [0; 32]);

		// we will now create a block for a slot that is part of epoch #4.
		// we should appropriately increment the epoch index as well as re-use
		// the randomness from epoch #2 on epoch #4
		go_to_block(System::block_number() + 1, genesis_slot + epoch_duration * 4);

		assert_eq!(EpochIndex::<Test>::get(), 4);
		assert_eq!(Randomness::<Test>::get(), randomness_for_epoch_2);

		// after skipping epochs the information is registered on-chain so that
		// we can map epochs to sessions
		assert_eq!(SkippedEpochs::<Test>::get(), vec![(4, 2)]);

		// before epochs are skipped the mapping should be one to one
		assert_eq!(Babe::session_index_for_epoch(0), 0);
		assert_eq!(Babe::session_index_for_epoch(1), 1);

		// otherwise the session index is offset by the number of skipped epochs
		assert_eq!(Babe::session_index_for_epoch(4), 2);
		assert_eq!(Babe::session_index_for_epoch(5), 3);
	});
}