// This file is part of Substrate.

// Copyright (C) 2022 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.

#![allow(dead_code)]

use _feps::ExtendedBalance;
use frame_support::{
	parameter_types, traits,
	traits::{GenesisBuild, Hooks},
	weights::constants,
};
use frame_system::EnsureRoot;
use sp_core::{ConstU32, Get, H256};
use sp_npos_elections::{ElectionScore, VoteWeight};
use sp_runtime::{
	testing,
	traits::{IdentityLookup, Zero},
	transaction_validity, PerU16, Perbill,
};
use sp_staking::{
	offence::{DisableStrategy, OffenceDetails, OnOffenceHandler},
	EraIndex, SessionIndex,
};
use sp_std::prelude::*;
use std::collections::BTreeMap;

use frame_election_provider_support::{onchain, ElectionDataProvider, SequentialPhragmen, Weight};
use pallet_election_provider_multi_phase::{
	unsigned::MinerConfig, ElectionCompute, QueuedSolution, SolutionAccuracyOf,
};
use pallet_staking::StakerStatus;

use crate::{log, log_current_time};

pub const INIT_TIMESTAMP: u64 = 30_000;
pub const BLOCK_TIME: u64 = 1000;

type Block = frame_system::mocking::MockBlock<Runtime>;
type UncheckedExtrinsic = frame_system::mocking::MockUncheckedExtrinsic<Runtime>;
type Extrinsic = testing::TestXt<RuntimeCall, ()>;

frame_support::construct_runtime!(
	pub enum Runtime where
		Block = Block,
		NodeBlock = Block,
		UncheckedExtrinsic = UncheckedExtrinsic
	{
		System: frame_system,
		ElectionProviderMultiPhase: pallet_election_provider_multi_phase,
		Staking: pallet_staking,
		Balances: pallet_balances,
		BagsList: pallet_bags_list,
		Session: pallet_session,
		Historical: pallet_session::historical,
		Timestamp: pallet_timestamp,
	}
);

pub(crate) type AccountId = u128;
pub(crate) type AccountIndex = u32;
pub(crate) type BlockNumber = u64;
pub(crate) type Balance = u64;
pub(crate) type VoterIndex = u32;
pub(crate) type TargetIndex = u16;
pub(crate) type Moment = u64;

impl frame_system::Config for Runtime {
	type BaseCallFilter = traits::Everything;
	type BlockWeights = BlockWeights;
	type BlockLength = ();
	type DbWeight = ();
	type RuntimeOrigin = RuntimeOrigin;
	type Index = AccountIndex;
	type BlockNumber = BlockNumber;
	type RuntimeCall = RuntimeCall;
	type Hash = H256;
	type Hashing = sp_runtime::traits::BlakeTwo256;
	type AccountId = AccountId;
	type Lookup = IdentityLookup<Self::AccountId>;
	type Header = sp_runtime::testing::Header;
	type RuntimeEvent = RuntimeEvent;
	type BlockHashCount = ();
	type Version = ();
	type PalletInfo = PalletInfo;
	type AccountData = pallet_balances::AccountData<Balance>;
	type OnNewAccount = ();
	type OnKilledAccount = ();
	type SystemWeightInfo = ();
	type SS58Prefix = ();
	type OnSetCode = ();
	type MaxConsumers = traits::ConstU32<16>;
}

const NORMAL_DISPATCH_RATIO: Perbill = Perbill::from_percent(75);
parameter_types! {
	pub static ExistentialDeposit: Balance = 1;
	pub BlockWeights: frame_system::limits::BlockWeights = frame_system::limits::BlockWeights
		::with_sensible_defaults(
			Weight::from_parts(2u64 * constants::WEIGHT_REF_TIME_PER_SECOND, u64::MAX),
			NORMAL_DISPATCH_RATIO,
		);
}

impl pallet_balances::Config for Runtime {
	type MaxLocks = traits::ConstU32<1024>;
	type MaxReserves = ();
	type ReserveIdentifier = [u8; 8];
	type Balance = Balance;
	type RuntimeEvent = RuntimeEvent;
	type DustRemoval = ();
	type ExistentialDeposit = ExistentialDeposit;
	type AccountStore = System;
	type WeightInfo = ();
	type HoldIdentifier = ();
	type FreezeIdentifier = ();
	type MaxHolds = traits::ConstU32<1>;
	type MaxFreezes = traits::ConstU32<1>;
}

impl pallet_timestamp::Config for Runtime {
	type Moment = Moment;
	type OnTimestampSet = ();
	type MinimumPeriod = traits::ConstU64<5>;
	type WeightInfo = ();
}

parameter_types! {
	pub static Period: BlockNumber = 30;
	pub static Offset: BlockNumber = 0;
}

sp_runtime::impl_opaque_keys! {
	pub struct SessionKeys {
		pub other: OtherSessionHandler,
	}
}

impl pallet_session::Config for Runtime {
	type SessionManager = pallet_session::historical::NoteHistoricalRoot<Runtime, Staking>;
	type Keys = SessionKeys;
	type ShouldEndSession = pallet_session::PeriodicSessions<Period, Offset>;
	type NextSessionRotation = pallet_session::PeriodicSessions<Period, Offset>;
	type SessionHandler = (OtherSessionHandler,);
	type RuntimeEvent = RuntimeEvent;
	type ValidatorId = AccountId;
	type ValidatorIdOf = pallet_staking::StashOf<Runtime>;
	type WeightInfo = ();
}
impl pallet_session::historical::Config for Runtime {
	type FullIdentification = pallet_staking::Exposure<AccountId, Balance>;
	type FullIdentificationOf = pallet_staking::ExposureOf<Runtime>;
}

frame_election_provider_support::generate_solution_type!(
	#[compact]
	pub struct MockNposSolution::<
		VoterIndex = VoterIndex,
		TargetIndex = TargetIndex,
		Accuracy = PerU16,
		MaxVoters = ConstU32::<2_000>
	>(16)
);

parameter_types! {
	pub static SignedPhase: BlockNumber = 10;
	pub static UnsignedPhase: BlockNumber = 10;
	// we expect a minimum of 3 blocks in signed phase and unsigned phases before trying
	// enetering in emergency phase after the election failed.
	pub static MinBlocksBeforeEmergency: BlockNumber = 3;
	pub static MaxElectingVoters: VoterIndex = 1000;
	pub static MaxElectableTargets: TargetIndex = 1000;
	pub static MaxActiveValidators: u32 = 1000;
	pub static OffchainRepeat: u32 = 5;
	pub static MinerMaxLength: u32 = 256;
	pub static MinerMaxWeight: Weight = BlockWeights::get().max_block;
	pub static TransactionPriority: transaction_validity::TransactionPriority = 1;
	pub static MaxWinners: u32 = 100;
	pub static MaxVotesPerVoter: u32 = 16;
	pub static MaxNominations: u32 = 16;
}

impl pallet_election_provider_multi_phase::Config for Runtime {
	type RuntimeEvent = RuntimeEvent;
	type Currency = Balances;
	type EstimateCallFee = frame_support::traits::ConstU32<8>;
	type SignedPhase = SignedPhase;
	type UnsignedPhase = UnsignedPhase;
	type BetterSignedThreshold = ();
	type BetterUnsignedThreshold = ();
	type OffchainRepeat = OffchainRepeat;
	type MinerTxPriority = TransactionPriority;
	type MinerConfig = Self;
	type SignedMaxSubmissions = ConstU32<10>;
	type SignedRewardBase = ();
	type SignedDepositBase = ();
	type SignedDepositByte = ();
	type SignedMaxRefunds = ConstU32<3>;
	type SignedDepositWeight = ();
	type SignedMaxWeight = ();
	type SlashHandler = ();
	type RewardHandler = ();
	type DataProvider = Staking;
	type Fallback =
		frame_election_provider_support::NoElection<(AccountId, BlockNumber, Staking, MaxWinners)>;
	type GovernanceFallback = onchain::OnChainExecution<OnChainSeqPhragmen>;
	type Solver = SequentialPhragmen<AccountId, SolutionAccuracyOf<Runtime>, ()>;
	type ForceOrigin = EnsureRoot<AccountId>;
	type MaxElectableTargets = MaxElectableTargets;
	type MaxElectingVoters = MaxElectingVoters;
	type MaxWinners = MaxWinners;
	type BenchmarkingConfig = NoopElectionProviderBenchmarkConfig;
	type WeightInfo = ();
}

impl MinerConfig for Runtime {
	type AccountId = AccountId;
	type Solution = MockNposSolution;
	type MaxVotesPerVoter =
	<<Self as pallet_election_provider_multi_phase::Config>::DataProvider as ElectionDataProvider>::MaxVotesPerVoter;
	type MaxLength = MinerMaxLength;
	type MaxWeight = MinerMaxWeight;
	type MaxWinners = MaxWinners;

	fn solution_weight(_v: u32, _t: u32, _a: u32, _d: u32) -> Weight {
		Weight::zero()
	}
}

const THRESHOLDS: [VoteWeight; 9] = [10, 20, 30, 40, 50, 60, 1_000, 2_000, 10_000];

parameter_types! {
	pub static BagThresholds: &'static [sp_npos_elections::VoteWeight] = &THRESHOLDS;
	pub const SessionsPerEra: sp_staking::SessionIndex = 2;
	pub const BondingDuration: sp_staking::EraIndex = 28;
	pub const SlashDeferDuration: sp_staking::EraIndex = 7; // 1/4 the bonding duration.
	pub const MaxNominatorRewardedPerValidator: u32 = 256;
	pub const OffendingValidatorsThreshold: Perbill = Perbill::from_percent(40);
	pub HistoryDepth: u32 = 84;
}

impl pallet_bags_list::Config for Runtime {
	type RuntimeEvent = RuntimeEvent;
	type WeightInfo = ();
	type ScoreProvider = Staking;
	type BagThresholds = BagThresholds;
	type Score = VoteWeight;
}

impl pallet_staking::Config for Runtime {
	type MaxNominations = MaxNominations;
	type Currency = Balances;
	type CurrencyBalance = Balance;
	type UnixTime = Timestamp;
	type CurrencyToVote = traits::SaturatingCurrencyToVote;
	type RewardRemainder = ();
	type RuntimeEvent = RuntimeEvent;
	type Slash = (); // burn slashes
	type Reward = (); // rewards are minted from the void
	type SessionsPerEra = SessionsPerEra;
	type BondingDuration = BondingDuration;
	type SlashDeferDuration = SlashDeferDuration;
	type AdminOrigin = EnsureRoot<AccountId>; // root can cancel slashes
	type SessionInterface = Self;
	type EraPayout = ();
	type NextNewSession = Session;
	type MaxNominatorRewardedPerValidator = MaxNominatorRewardedPerValidator;
	type OffendingValidatorsThreshold = OffendingValidatorsThreshold;
	type ElectionProvider = ElectionProviderMultiPhase;
	type GenesisElectionProvider = onchain::OnChainExecution<OnChainSeqPhragmen>;
	type VoterList = BagsList;
	type TargetList = pallet_staking::UseValidatorsMap<Self>;
	type MaxUnlockingChunks = ConstU32<32>;
	type HistoryDepth = HistoryDepth;
	type OnStakerSlash = ();
	type WeightInfo = pallet_staking::weights::SubstrateWeight<Runtime>;
	type BenchmarkingConfig = pallet_staking::TestBenchmarkingConfig;
}

impl<LocalCall> frame_system::offchain::SendTransactionTypes<LocalCall> for Runtime
where
	RuntimeCall: From<LocalCall>,
{
	type OverarchingCall = RuntimeCall;
	type Extrinsic = Extrinsic;
}

pub struct OnChainSeqPhragmen;

parameter_types! {
	pub static VotersBound: u32 = 600;
	pub static TargetsBound: u32 = 400;
}

impl onchain::Config for OnChainSeqPhragmen {
	type System = Runtime;
	type Solver = SequentialPhragmen<
		AccountId,
		pallet_election_provider_multi_phase::SolutionAccuracyOf<Runtime>,
	>;
	type DataProvider = Staking;
	type WeightInfo = ();
	type MaxWinners = MaxWinners;
	type VotersBound = VotersBound;
	type TargetsBound = TargetsBound;
}

pub struct NoopElectionProviderBenchmarkConfig;

impl pallet_election_provider_multi_phase::BenchmarkingConfig
	for NoopElectionProviderBenchmarkConfig
{
	const VOTERS: [u32; 2] = [0, 0];
	const TARGETS: [u32; 2] = [0, 0];
	const ACTIVE_VOTERS: [u32; 2] = [0, 0];
	const DESIRED_TARGETS: [u32; 2] = [0, 0];
	const SNAPSHOT_MAXIMUM_VOTERS: u32 = 0;
	const MINER_MAXIMUM_VOTERS: u32 = 0;
	const MAXIMUM_TARGETS: u32 = 0;
}

pub struct OtherSessionHandler;
impl traits::OneSessionHandler<AccountId> for OtherSessionHandler {
	type Key = testing::UintAuthorityId;

	fn on_genesis_session<'a, I: 'a>(_: I)
	where
		I: Iterator<Item = (&'a AccountId, Self::Key)>,
		AccountId: 'a,
	{
	}

	fn on_new_session<'a, I: 'a>(_: bool, _: I, _: I)
	where
		I: Iterator<Item = (&'a AccountId, Self::Key)>,
		AccountId: 'a,
	{
	}

	fn on_disabled(_validator_index: u32) {}
}

impl sp_runtime::BoundToRuntimeAppPublic for OtherSessionHandler {
	type Public = testing::UintAuthorityId;
}

pub struct StakingExtBuilder {
	validator_count: u32,
	minimum_validator_count: u32,
	min_nominator_bond: Balance,
	min_validator_bond: Balance,
	status: BTreeMap<AccountId, StakerStatus<AccountId>>,
	stakes: BTreeMap<AccountId, Balance>,
	stakers: Vec<(AccountId, AccountId, Balance, StakerStatus<AccountId>)>,
}

impl Default for StakingExtBuilder {
	fn default() -> Self {
		let stakers = vec![
			// (stash, ctrl, stake, status)
			// these two will be elected in the default test where we elect 2.
			(11, 10, 1000, StakerStatus::<AccountId>::Validator),
			(21, 20, 1000, StakerStatus::<AccountId>::Validator),
			// loser validatos if validator_count() is default.
			(31, 30, 500, StakerStatus::<AccountId>::Validator),
			(41, 40, 500, StakerStatus::<AccountId>::Validator),
			(51, 50, 500, StakerStatus::<AccountId>::Validator),
			(61, 60, 500, StakerStatus::<AccountId>::Validator),
			(71, 70, 500, StakerStatus::<AccountId>::Validator),
			(81, 80, 500, StakerStatus::<AccountId>::Validator),
			(91, 90, 500, StakerStatus::<AccountId>::Validator),
			(101, 100, 500, StakerStatus::<AccountId>::Validator),
			// an idle validator
			(201, 200, 1000, StakerStatus::<AccountId>::Idle),
		];

		Self {
			validator_count: 2,
			minimum_validator_count: 0,
			min_nominator_bond: ExistentialDeposit::get(),
			min_validator_bond: ExistentialDeposit::get(),
			status: Default::default(),
			stakes: Default::default(),
			stakers,
		}
	}
}

impl StakingExtBuilder {
	pub fn validator_count(mut self, n: u32) -> Self {
		self.validator_count = n;
		self
	}
}

pub struct EpmExtBuilder {}

impl Default for EpmExtBuilder {
	fn default() -> Self {
		EpmExtBuilder {}
	}
}

impl EpmExtBuilder {
	pub fn disable_emergency_throttling(self) -> Self {
		<MinBlocksBeforeEmergency>::set(0);
		self
	}

	pub fn phases(self, signed: BlockNumber, unsigned: BlockNumber) -> Self {
		<SignedPhase>::set(signed);
		<UnsignedPhase>::set(unsigned);
		self
	}
}

pub struct BalancesExtBuilder {
	balances: Vec<(AccountId, Balance)>,
}

impl Default for BalancesExtBuilder {
	fn default() -> Self {
		let balances = vec![
			// (account_id, balance)
			(1, 10),
			(2, 20),
			(3, 300),
			(4, 400),
			// controllers
			(10, 100),
			(20, 100),
			(30, 100),
			(40, 100),
			(50, 100),
			(60, 100),
			(70, 100),
			(80, 100),
			(90, 100),
			(100, 100),
			(200, 100),
			// stashes
			(11, 1000),
			(21, 2000),
			(31, 3000),
			(41, 4000),
			(51, 5000),
			(61, 6000),
			(71, 7000),
			(81, 8000),
			(91, 9000),
			(101, 10000),
			(201, 20000),
			// This allows us to have a total_payout different from 0.
			(999, 1_000_000_000_000),
		];
		Self { balances }
	}
}

pub struct ExtBuilder {
	staking_builder: StakingExtBuilder,
	epm_builder: EpmExtBuilder,
	balances_builder: BalancesExtBuilder,
}

impl Default for ExtBuilder {
	fn default() -> Self {
		Self {
			staking_builder: StakingExtBuilder::default(),
			epm_builder: EpmExtBuilder::default(),
			balances_builder: BalancesExtBuilder::default(),
		}
	}
}

impl ExtBuilder {
	pub fn build(self) -> sp_io::TestExternalities {
		sp_tracing::try_init_simple();
		let mut storage =
			frame_system::GenesisConfig::default().build_storage::<Runtime>().unwrap();

		let _ =
			pallet_balances::GenesisConfig::<Runtime> { balances: self.balances_builder.balances }
				.assimilate_storage(&mut storage);

		let mut stakers = self.staking_builder.stakers.clone();
		self.staking_builder.status.into_iter().for_each(|(stash, status)| {
			let (_, _, _, ref mut prev_status) = stakers
				.iter_mut()
				.find(|s| s.0 == stash)
				.expect("set_status staker should exist; qed");
			*prev_status = status;
		});
		// replaced any of the stakes if needed.
		self.staking_builder.stakes.into_iter().for_each(|(stash, stake)| {
			let (_, _, ref mut prev_stake, _) = stakers
				.iter_mut()
				.find(|s| s.0 == stash)
				.expect("set_stake staker should exits; qed.");
			*prev_stake = stake;
		});

		let _ = pallet_staking::GenesisConfig::<Runtime> {
			stakers: stakers.clone(),
			validator_count: self.staking_builder.validator_count,
			minimum_validator_count: self.staking_builder.minimum_validator_count,
			slash_reward_fraction: Perbill::from_percent(10),
			min_nominator_bond: self.staking_builder.min_nominator_bond,
			min_validator_bond: self.staking_builder.min_validator_bond,
			..Default::default()
		}
		.assimilate_storage(&mut storage);

		let _ = pallet_session::GenesisConfig::<Runtime> {
			// set the keys for the first session.
			keys: stakers
				.into_iter()
				.map(|(id, ..)| (id, id, SessionKeys { other: (id as u64).into() }))
				.collect(),
		}
		.assimilate_storage(&mut storage);

		let mut ext = sp_io::TestExternalities::from(storage);

		// We consider all test to start after timestamp is initialized This must be ensured by
		// having `timestamp::on_initialize` called before `staking::on_initialize`.
		ext.execute_with(|| {
			System::set_block_number(1);
			Session::on_initialize(1);
			<Staking as Hooks<u64>>::on_initialize(1);
			Timestamp::set_timestamp(INIT_TIMESTAMP);
		});

		ext
	}
	pub fn staking(mut self, builder: StakingExtBuilder) -> Self {
		self.staking_builder = builder;
		self
	}

	pub fn epm(mut self, builder: EpmExtBuilder) -> Self {
		self.epm_builder = builder;
		self
	}

	pub fn balances(mut self, builder: BalancesExtBuilder) -> Self {
		self.balances_builder = builder;
		self
	}

	pub fn build_and_execute(self, test: impl FnOnce() -> ()) {
		self.build().execute_with(test)
	}
}

// Progress to given block, triggering session and era changes as we progress and ensuring that
// there is a solution queued when expected.
pub fn roll_to(n: BlockNumber, delay_solution: bool) {
	for b in (System::block_number()) + 1..=n {
		System::set_block_number(b);
		Session::on_initialize(b);
		Timestamp::set_timestamp(System::block_number() * BLOCK_TIME + INIT_TIMESTAMP);

		// TODO(gpestana): implement a realistic OCW worker insted of simulating it
		// https://github.com/paritytech/substrate/issues/13589
		// if there's no solution queued and the solution should not be delayed, try mining and
		// queue a solution.
		if ElectionProviderMultiPhase::current_phase().is_signed() && !delay_solution {
			let _ = try_queue_solution(ElectionCompute::Signed).map_err(|e| {
				log!(info, "failed to mine/queue solution: {:?}", e);
			});
		}
		ElectionProviderMultiPhase::on_initialize(b);

		Staking::on_initialize(b);
		if b != n {
			Staking::on_finalize(System::block_number());
		}

		log_current_time();
	}
}

/// Progresses from the current block number (whatever that may be) to the block where the session
/// `session_index` starts.
pub(crate) fn start_session(session_index: SessionIndex, delay_solution: bool) {
	let end: u64 = if Offset::get().is_zero() {
		Period::get() * (session_index as u64)
	} else {
		Offset::get() * (session_index as u64) + Period::get() * (session_index as u64)
	};

	assert!(end >= System::block_number());

	roll_to(end, delay_solution);

	// session must have progressed properly.
	assert_eq!(
		Session::current_index(),
		session_index,
		"current session index = {}, expected = {}",
		Session::current_index(),
		session_index,
	);
}

/// Go one session forward.
pub(crate) fn advance_session() {
	let current_index = Session::current_index();
	start_session(current_index + 1, false);
}

pub(crate) fn advance_session_delayed_solution() {
	let current_index = Session::current_index();
	start_session(current_index + 1, true);
}

pub(crate) fn start_next_active_era() -> Result<(), ()> {
	start_active_era(active_era() + 1, false)
}

pub(crate) fn start_next_active_era_delayed_solution() -> Result<(), ()> {
	start_active_era(active_era() + 1, true)
}

/// Progress until the given era.
pub(crate) fn start_active_era(era_index: EraIndex, delay_solution: bool) -> Result<(), ()> {
	let era_before = current_era();

	start_session((era_index * <SessionsPerEra as Get<u32>>::get()).into(), delay_solution);

	log!(
		info,
		"start_active_era - era_before: {}, current era: {} -> progress to: {} -> after era: {}",
		era_before,
		active_era(),
		era_index,
		current_era(),
	);

	// if the solution was not delayed, era should have progressed.
	if !delay_solution && (active_era() != era_index || current_era() != active_era()) {
		Err(())
	} else {
		Ok(())
	}
}

pub(crate) fn active_era() -> EraIndex {
	Staking::active_era().unwrap().index
}

pub(crate) fn current_era() -> EraIndex {
	Staking::current_era().unwrap()
}

// Fast forward until EPM signed phase.
pub fn roll_to_epm_signed() {
	while !matches!(
		ElectionProviderMultiPhase::current_phase(),
		pallet_election_provider_multi_phase::Phase::Signed
	) {
		roll_to(System::block_number() + 1, false);
	}
}

// Fast forward until EPM unsigned phase.
pub fn roll_to_epm_unsigned() {
	while !matches!(
		ElectionProviderMultiPhase::current_phase(),
		pallet_election_provider_multi_phase::Phase::Unsigned(_)
	) {
		roll_to(System::block_number() + 1, false);
	}
}

// Fast forward until EPM off.
pub fn roll_to_epm_off() {
	while !matches!(
		ElectionProviderMultiPhase::current_phase(),
		pallet_election_provider_multi_phase::Phase::Off
	) {
		roll_to(System::block_number() + 1, false);
	}
}

// Queue a solution based on the current snapshot.
pub(crate) fn try_queue_solution(when: ElectionCompute) -> Result<(), String> {
	let raw_solution = ElectionProviderMultiPhase::mine_solution()
		.map_err(|e| format!("error mining solution: {:?}", e))?;

	ElectionProviderMultiPhase::feasibility_check(raw_solution.0, when)
		.map(|ready| {
			QueuedSolution::<Runtime>::put(ready);
		})
		.map_err(|e| format!("error in solution feasibility: {:?}", e))
}

pub(crate) fn on_offence_now(
	offenders: &[OffenceDetails<
		AccountId,
		pallet_session::historical::IdentificationTuple<Runtime>,
	>],
	slash_fraction: &[Perbill],
) {
	let now = Staking::active_era().unwrap().index;
	let _ = Staking::on_offence(
		offenders,
		slash_fraction,
		Staking::eras_start_session_index(now).unwrap(),
		DisableStrategy::WhenSlashed,
	);
}

// Add offence to validator, slash it.
pub(crate) fn add_slash(who: &AccountId) {
	on_offence_now(
		&[OffenceDetails {
			offender: (*who, Staking::eras_stakers(active_era(), *who)),
			reporters: vec![],
		}],
		&[Perbill::from_percent(10)],
	);
}

// Slashes enough validators to cross the `Staking::OffendingValidatorsThreshold`.
pub(crate) fn slash_through_offending_threshold() {
	let validators = Session::validators();
	let mut remaining_slashes =
		<Runtime as pallet_staking::Config>::OffendingValidatorsThreshold::get() *
			validators.len() as u32;

	for v in validators.into_iter() {
		if remaining_slashes != 0 {
			add_slash(&v);
			remaining_slashes -= 1;
		}
	}
}

// Slashes a percentage of the active nominators that haven't been slashed yet, with
// a minimum of 1 validator slash.
pub(crate) fn slash_percentage(percentage: Perbill) -> Vec<u128> {
	let validators = Session::validators();
	let mut remaining_slashes = (percentage * validators.len() as u32).max(1);
	let mut slashed = vec![];

	for v in validators.into_iter() {
		if remaining_slashes != 0 {
			add_slash(&v);
			slashed.push(v);
			remaining_slashes -= 1;
		}
	}
	slashed
}

pub(crate) fn set_minimum_election_score(
	minimal_stake: ExtendedBalance,
	sum_stake: ExtendedBalance,
	sum_stake_squared: ExtendedBalance,
) -> Result<(), ()> {
	let election_score = ElectionScore { minimal_stake, sum_stake, sum_stake_squared };
	ElectionProviderMultiPhase::set_minimum_untrusted_score(
		RuntimeOrigin::root(),
		Some(election_score),
	)
	.map(|_| ())
	.map_err(|_| ())
}