// This file is part of Tetcore.

// Copyright (C) 2020-2021 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.

//! Staking noble benchmarking.

use super::*;
use crate::Module as Staking;
use testing_utils::*;

use tp_npos_elections::CompactSolution;
use tp_runtime::traits::One;
use fabric_system::RawOrigin;
pub use fabric_benchmarking::{benchmarks, account, whitelisted_caller, whitelist_account};
const SEED: u32 = 0;
const MAX_SPANS: u32 = 100;
const MAX_VALIDATORS: u32 = 1000;
const MAX_SLASHES: u32 = 1000;

// Add slashing spans to a user account. Not relevant for actual use, only to benchmark
// read and write operations.
fn add_slashing_spans<T: Config>(who: &T::AccountId, spans: u32) {
	if spans == 0 { return }

	// For the first slashing span, we initialize
	let mut slashing_spans = crate::slashing::SlashingSpans::new(0);
	SpanSlash::<T>::insert((who, 0), crate::slashing::SpanRecord::default());

	for i in 1 .. spans {
		assert!(slashing_spans.end_span(i));
		SpanSlash::<T>::insert((who, i), crate::slashing::SpanRecord::default());
	}
	SlashingSpans::<T>::insert(who, slashing_spans);
}

// This function clears all existing validators and nominators from the set, and generates one new
// validator being nominated by n nominators, and returns the validator stash account and the
// nominators' stash and controller. It also starts an era and creates pending payouts.
pub fn create_validator_with_nominators<T: Config>(
	n: u32,
	upper_bound: u32,
	dead: bool,
	destination: RewardDestination<T::AccountId>
) -> Result<(T::AccountId, Vec<(T::AccountId, T::AccountId)>), &'static str> {
	// Clean up any existing state.
	clear_validators_and_nominators::<T>();
	let mut points_total = 0;
	let mut points_individual = Vec::new();

	let (v_stash, v_controller) = create_stash_controller::<T>(0, 100, destination.clone())?;
	let validator_prefs = ValidatorPrefs {
		commission: Perbill::from_percent(50),
		.. Default::default()
	};
	Staking::<T>::validate(RawOrigin::Signed(v_controller).into(), validator_prefs)?;
	let stash_lookup: <T::Lookup as StaticLookup>::Source = T::Lookup::unlookup(v_stash.clone());

	points_total += 10;
	points_individual.push((v_stash.clone(), 10));

	let mut nominators = Vec::new();

	// Give the validator n nominators, but keep total users in the system the same.
	for i in 0 .. upper_bound {
		let (n_stash, n_controller) = if !dead {
			create_stash_controller::<T>(u32::max_value() - i, 100, destination.clone())?
		} else {
			create_stash_and_dead_controller::<T>(u32::max_value() - i, 100, destination.clone())?
		};
		if i < n {
			Staking::<T>::nominate(RawOrigin::Signed(n_controller.clone()).into(), vec![stash_lookup.clone()])?;
			nominators.push((n_stash, n_controller));
		}
	}

	ValidatorCount::put(1);

	// Start a new Era
	let new_validators = Staking::<T>::new_era(SessionIndex::one()).unwrap();

	assert!(new_validators.len() == 1);
	assert!(new_validators[0] == v_stash, "Our validator was not selected!");

	// Give Era Points
	let reward = EraRewardPoints::<T::AccountId> {
		total: points_total,
		individual: points_individual.into_iter().collect(),
	};

	let current_era = CurrentEra::get().unwrap();
	ErasRewardPoints::<T>::insert(current_era, reward);

	// Create reward pool
	let total_payout = T::Currency::minimum_balance()
		.saturating_mul(upper_bound.into())
		.saturating_mul(1000u32.into());
	<ErasValidatorReward<T>>::insert(current_era, total_payout);

	Ok((v_stash, nominators))
}

const USER_SEED: u32 = 999666;

benchmarks! {
	bond {
		let stash = create_funded_user::<T>("stash", USER_SEED, 100);
		let controller = create_funded_user::<T>("controller", USER_SEED, 100);
		let controller_lookup: <T::Lookup as StaticLookup>::Source = T::Lookup::unlookup(controller.clone());
		let reward_destination = RewardDestination::Staked;
		let amount = T::Currency::minimum_balance() * 10u32.into();
		whitelist_account!(stash);
	}: _(RawOrigin::Signed(stash.clone()), controller_lookup, amount, reward_destination)
	verify {
		assert!(Bonded::<T>::contains_key(stash));
		assert!(Ledger::<T>::contains_key(controller));
	}

	bond_extra {
		let (stash, controller) = create_stash_controller::<T>(USER_SEED, 100, Default::default())?;
		let max_additional = T::Currency::minimum_balance() * 10u32.into();
		let ledger = Ledger::<T>::get(&controller).ok_or("ledger not created before")?;
		let original_bonded: BalanceOf<T> = ledger.active;
		whitelist_account!(stash);
	}: _(RawOrigin::Signed(stash), max_additional)
	verify {
		let ledger = Ledger::<T>::get(&controller).ok_or("ledger not created after")?;
		let new_bonded: BalanceOf<T> = ledger.active;
		assert!(original_bonded < new_bonded);
	}

	unbond {
		let (_, controller) = create_stash_controller::<T>(USER_SEED, 100, Default::default())?;
		let amount = T::Currency::minimum_balance() * 10u32.into();
		let ledger = Ledger::<T>::get(&controller).ok_or("ledger not created before")?;
		let original_bonded: BalanceOf<T> = ledger.active;
		whitelist_account!(controller);
	}: _(RawOrigin::Signed(controller.clone()), amount)
	verify {
		let ledger = Ledger::<T>::get(&controller).ok_or("ledger not created after")?;
		let new_bonded: BalanceOf<T> = ledger.active;
		assert!(original_bonded > new_bonded);
	}

	// Withdraw only updates the ledger
	withdraw_unbonded_update {
		// Slashing Spans
		let s in 0 .. MAX_SPANS;
		let (stash, controller) = create_stash_controller::<T>(0, 100, Default::default())?;
		add_slashing_spans::<T>(&stash, s);
		let amount = T::Currency::minimum_balance() * 5u32.into(); // Half of total
		Staking::<T>::unbond(RawOrigin::Signed(controller.clone()).into(), amount)?;
		CurrentEra::put(EraIndex::max_value());
		let ledger = Ledger::<T>::get(&controller).ok_or("ledger not created before")?;
		let original_total: BalanceOf<T> = ledger.total;
		whitelist_account!(controller);
	}: withdraw_unbonded(RawOrigin::Signed(controller.clone()), s)
	verify {
		let ledger = Ledger::<T>::get(&controller).ok_or("ledger not created after")?;
		let new_total: BalanceOf<T> = ledger.total;
		assert!(original_total > new_total);
	}

	// Worst case scenario, everything is removed after the bonding duration
	withdraw_unbonded_kill {
		// Slashing Spans
		let s in 0 .. MAX_SPANS;
		let (stash, controller) = create_stash_controller::<T>(0, 100, Default::default())?;
		add_slashing_spans::<T>(&stash, s);
		let amount = T::Currency::minimum_balance() * 10u32.into();
		Staking::<T>::unbond(RawOrigin::Signed(controller.clone()).into(), amount)?;
		CurrentEra::put(EraIndex::max_value());
		let ledger = Ledger::<T>::get(&controller).ok_or("ledger not created before")?;
		let original_total: BalanceOf<T> = ledger.total;
		whitelist_account!(controller);
	}: withdraw_unbonded(RawOrigin::Signed(controller.clone()), s)
	verify {
		assert!(!Ledger::<T>::contains_key(controller));
	}

	validate {
		let (stash, controller) = create_stash_controller::<T>(USER_SEED, 100, Default::default())?;
		let prefs = ValidatorPrefs::default();
		whitelist_account!(controller);
	}: _(RawOrigin::Signed(controller), prefs)
	verify {
		assert!(Validators::<T>::contains_key(stash));
	}

	kick {
		// scenario: we want to kick `k` nominators from nominating us (we are a validator).
		// we'll assume that `k` is under 128 for the purposes of determining the slope.
		// each nominator should have `MAX_NOMINATIONS` validators nominated, and our validator
		// should be somewhere in there.
		let k in 1 .. 128;

		// these are the other validators; there are `MAX_NOMINATIONS - 1` of them, so there are a
		// total of `MAX_NOMINATIONS` validators in the system.
		let rest_of_validators = create_validators::<T>(MAX_NOMINATIONS as u32 - 1, 100)?;

		// this is the validator that will be kicking.
		let (stash, controller) = create_stash_controller::<T>(MAX_NOMINATIONS as u32 - 1, 100, Default::default())?;
		let stash_lookup: <T::Lookup as StaticLookup>::Source = T::Lookup::unlookup(stash.clone());

		// they start validating.
		Staking::<T>::validate(RawOrigin::Signed(controller.clone()).into(), Default::default())?;

		// we now create the nominators. there will be `k` of them; each will nominate all
		// validators. we will then kick each of the `k` nominators from the main validator.
		let mut nominator_stashes = Vec::with_capacity(k as usize);
		for i in 0 .. k {
			// create a nominator stash.
			let (n_stash, n_controller) = create_stash_controller::<T>(MAX_NOMINATIONS as u32 + i, 100, Default::default())?;

			// bake the nominations; we first clone them from the rest of the validators.
			let mut nominations = rest_of_validators.clone();
			// then insert "our" validator somewhere in there (we vary it) to avoid accidental
			// optimisations/pessimisations.
			nominations.insert(i as usize % (nominations.len() + 1), stash_lookup.clone());
			// then we nominate.
			Staking::<T>::nominate(RawOrigin::Signed(n_controller.clone()).into(), nominations)?;

			nominator_stashes.push(n_stash);
		}

		// all nominators now should be nominating our validator...
		for n in nominator_stashes.iter() {
			assert!(Nominators::<T>::get(n).unwrap().targets.contains(&stash));
		}

		// we need the unlookuped version of the nominator stash for the kick.
		let kicks = nominator_stashes.iter()
			.map(|n| T::Lookup::unlookup(n.clone()))
			.collect::<Vec<_>>();

		whitelist_account!(controller);
	}: _(RawOrigin::Signed(controller), kicks)
	verify {
		// all nominators now should *not* be nominating our validator...
		for n in nominator_stashes.iter() {
			assert!(!Nominators::<T>::get(n).unwrap().targets.contains(&stash));
		}
	}

	// Worst case scenario, MAX_NOMINATIONS
	nominate {
		let n in 1 .. MAX_NOMINATIONS as u32;
		let (stash, controller) = create_stash_controller::<T>(n + 1, 100, Default::default())?;
		let validators = create_validators::<T>(n, 100)?;
		whitelist_account!(controller);
	}: _(RawOrigin::Signed(controller), validators)
	verify {
		assert!(Nominators::<T>::contains_key(stash));
	}

	chill {
		let (_, controller) = create_stash_controller::<T>(USER_SEED, 100, Default::default())?;
		whitelist_account!(controller);
	}: _(RawOrigin::Signed(controller))

	set_payee {
		let (stash, controller) = create_stash_controller::<T>(USER_SEED, 100, Default::default())?;
		assert_eq!(Payee::<T>::get(&stash), RewardDestination::Staked);
		whitelist_account!(controller);
	}: _(RawOrigin::Signed(controller), RewardDestination::Controller)
	verify {
		assert_eq!(Payee::<T>::get(&stash), RewardDestination::Controller);
	}

	set_controller {
		let (stash, _) = create_stash_controller::<T>(USER_SEED, 100, Default::default())?;
		let new_controller = create_funded_user::<T>("new_controller", USER_SEED, 100);
		let new_controller_lookup = T::Lookup::unlookup(new_controller.clone());
		whitelist_account!(stash);
	}: _(RawOrigin::Signed(stash), new_controller_lookup)
	verify {
		assert!(Ledger::<T>::contains_key(&new_controller));
	}

	set_validator_count {
		let validator_count = MAX_VALIDATORS;
	}: _(RawOrigin::Root, validator_count)
	verify {
		assert_eq!(ValidatorCount::get(), validator_count);
	}

	force_no_eras {}: _(RawOrigin::Root)
	verify { assert_eq!(ForceEra::get(), Forcing::ForceNone); }

	force_new_era {}: _(RawOrigin::Root)
	verify { assert_eq!(ForceEra::get(), Forcing::ForceNew); }

	force_new_era_always {}: _(RawOrigin::Root)
	verify { assert_eq!(ForceEra::get(), Forcing::ForceAlways); }

	// Worst case scenario, the list of invulnerables is very long.
	set_invulnerables {
		let v in 0 .. MAX_VALIDATORS;
		let mut invulnerables = Vec::new();
		for i in 0 .. v {
			invulnerables.push(account("invulnerable", i, SEED));
		}
	}: _(RawOrigin::Root, invulnerables)
	verify {
		assert_eq!(Invulnerables::<T>::get().len(), v as usize);
	}

	force_unstake {
		// Slashing Spans
		let s in 0 .. MAX_SPANS;
		let (stash, controller) = create_stash_controller::<T>(0, 100, Default::default())?;
		add_slashing_spans::<T>(&stash, s);
	}: _(RawOrigin::Root, stash, s)
	verify {
		assert!(!Ledger::<T>::contains_key(&controller));
	}

	cancel_deferred_slash {
		let s in 1 .. MAX_SLASHES;
		let mut unapplied_slashes = Vec::new();
		let era = EraIndex::one();
		for _ in 0 .. MAX_SLASHES {
			unapplied_slashes.push(UnappliedSlash::<T::AccountId, BalanceOf<T>>::default());
		}
		UnappliedSlashes::<T>::insert(era, &unapplied_slashes);

		let slash_indices: Vec<u32> = (0 .. s).collect();
	}: _(RawOrigin::Root, era, slash_indices)
	verify {
		assert_eq!(UnappliedSlashes::<T>::get(&era).len(), (MAX_SLASHES - s) as usize);
	}

	payout_stakers_dead_controller {
		let n in 1 .. T::MaxNominatorRewardedPerValidator::get() as u32;
		let (validator, nominators) = create_validator_with_nominators::<T>(
			n,
			T::MaxNominatorRewardedPerValidator::get() as u32,
			true,
			RewardDestination::Controller,
		)?;

		let current_era = CurrentEra::get().unwrap();
		// set the commission for this particular era as well.
		<ErasValidatorPrefs<T>>::insert(current_era, validator.clone(), <Staking<T>>::validators(&validator));

		let caller = whitelisted_caller();
		let validator_controller = <Bonded<T>>::get(&validator).unwrap();
		let balance_before = T::Currency::free_balance(&validator_controller);
		for (_, controller) in &nominators {
			let balance = T::Currency::free_balance(&controller);
			ensure!(balance.is_zero(), "Controller has balance, but should be dead.");
		}
	}: payout_stakers(RawOrigin::Signed(caller), validator.clone(), current_era)
	verify {
		let balance_after = T::Currency::free_balance(&validator_controller);
		ensure!(
			balance_before < balance_after,
			"Balance of validator controller should have increased after payout.",
		);
		for (_, controller) in &nominators {
			let balance = T::Currency::free_balance(&controller);
			ensure!(!balance.is_zero(), "Payout not given to controller.");
		}
	}

	payout_stakers_alive_staked {
		let n in 1 .. T::MaxNominatorRewardedPerValidator::get() as u32;
		let (validator, nominators) = create_validator_with_nominators::<T>(
			n,
			T::MaxNominatorRewardedPerValidator::get() as u32,
			false,
			RewardDestination::Staked,
		)?;

		let current_era = CurrentEra::get().unwrap();
		// set the commission for this particular era as well.
		<ErasValidatorPrefs<T>>::insert(current_era, validator.clone(), <Staking<T>>::validators(&validator));

		let caller = whitelisted_caller();
		let balance_before = T::Currency::free_balance(&validator);
		let mut nominator_balances_before = Vec::new();
		for (stash, _) in &nominators {
			let balance = T::Currency::free_balance(&stash);
			nominator_balances_before.push(balance);
		}
	}: payout_stakers(RawOrigin::Signed(caller), validator.clone(), current_era)
	verify {
		let balance_after = T::Currency::free_balance(&validator);
		ensure!(
			balance_before < balance_after,
			"Balance of validator stash should have increased after payout.",
		);
		for ((stash, _), balance_before) in nominators.iter().zip(nominator_balances_before.iter()) {
			let balance_after = T::Currency::free_balance(&stash);
			ensure!(
				balance_before < &balance_after,
				"Balance of nominator stash should have increased after payout.",
			);
		}
	}

	rebond {
		let l in 1 .. MAX_UNLOCKING_CHUNKS as u32;
		let (_, controller) = create_stash_controller::<T>(USER_SEED, 100, Default::default())?;
		let mut staking_ledger = Ledger::<T>::get(controller.clone()).unwrap();
		let unlock_chunk = UnlockChunk::<BalanceOf<T>> {
			value: 1u32.into(),
			era: EraIndex::zero(),
		};
		for _ in 0 .. l {
			staking_ledger.unlocking.push(unlock_chunk.clone())
		}
		Ledger::<T>::insert(controller.clone(), staking_ledger.clone());
		let original_bonded: BalanceOf<T> = staking_ledger.active;
		whitelist_account!(controller);
	}: _(RawOrigin::Signed(controller.clone()), (l + 100).into())
	verify {
		let ledger = Ledger::<T>::get(&controller).ok_or("ledger not created after")?;
		let new_bonded: BalanceOf<T> = ledger.active;
		assert!(original_bonded < new_bonded);
	}

	set_history_depth {
		let e in 1 .. 100;
		HistoryDepth::put(e);
		CurrentEra::put(e);
		for i in 0 .. e {
			<ErasStakers<T>>::insert(i, T::AccountId::default(), Exposure::<T::AccountId, BalanceOf<T>>::default());
			<ErasStakersClipped<T>>::insert(i, T::AccountId::default(), Exposure::<T::AccountId, BalanceOf<T>>::default());
			<ErasValidatorPrefs<T>>::insert(i, T::AccountId::default(), ValidatorPrefs::default());
			<ErasValidatorReward<T>>::insert(i, BalanceOf::<T>::one());
			<ErasRewardPoints<T>>::insert(i, EraRewardPoints::<T::AccountId>::default());
			<ErasTotalStake<T>>::insert(i, BalanceOf::<T>::one());
			ErasStartSessionIndex::insert(i, i);
		}
	}: _(RawOrigin::Root, EraIndex::zero(), u32::max_value())
	verify {
		assert_eq!(HistoryDepth::get(), 0);
	}

	reap_stash {
		let s in 1 .. MAX_SPANS;
		let (stash, controller) = create_stash_controller::<T>(0, 100, Default::default())?;
		add_slashing_spans::<T>(&stash, s);
		T::Currency::make_free_balance_be(&stash, T::Currency::minimum_balance());
		whitelist_account!(controller);
	}: _(RawOrigin::Signed(controller), stash.clone(), s)
	verify {
		assert!(!Bonded::<T>::contains_key(&stash));
	}

	new_era {
		let v in 1 .. 10;
		let n in 1 .. 100;

		create_validators_with_nominators_for_era::<T>(v, n, MAX_NOMINATIONS, false, None)?;
		let session_index = SessionIndex::one();
	}: {
		let validators = Staking::<T>::new_era(session_index).ok_or("`new_era` failed")?;
		assert!(validators.len() == v as usize);
	}

	#[extra]
	payout_all {
		let v in 1 .. 10;
		let n in 1 .. 100;
		create_validators_with_nominators_for_era::<T>(v, n, MAX_NOMINATIONS, false, None)?;
		// Start a new Era
		let new_validators = Staking::<T>::new_era(SessionIndex::one()).unwrap();
		assert!(new_validators.len() == v as usize);

		let current_era = CurrentEra::get().unwrap();
		let mut points_total = 0;
		let mut points_individual = Vec::new();
		let mut payout_calls_arg = Vec::new();

		for validator in new_validators.iter() {
			points_total += 10;
			points_individual.push((validator.clone(), 10));
			payout_calls_arg.push((validator.clone(), current_era));
		}

		// Give Era Points
		let reward = EraRewardPoints::<T::AccountId> {
			total: points_total,
			individual: points_individual.into_iter().collect(),
		};

		ErasRewardPoints::<T>::insert(current_era, reward);

		// Create reward pool
		let total_payout = T::Currency::minimum_balance() * 1000u32.into();
		<ErasValidatorReward<T>>::insert(current_era, total_payout);

		let caller: T::AccountId = whitelisted_caller();
	}: {
		for arg in payout_calls_arg {
			<Staking<T>>::payout_stakers(RawOrigin::Signed(caller.clone()).into(), arg.0, arg.1)?;
		}
	}

	#[extra]
	do_slash {
		let l in 1 .. MAX_UNLOCKING_CHUNKS as u32;
		let (stash, controller) = create_stash_controller::<T>(0, 100, Default::default())?;
		let mut staking_ledger = Ledger::<T>::get(controller.clone()).unwrap();
		let unlock_chunk = UnlockChunk::<BalanceOf<T>> {
			value: 1u32.into(),
			era: EraIndex::zero(),
		};
		for _ in 0 .. l {
			staking_ledger.unlocking.push(unlock_chunk.clone())
		}
		Ledger::<T>::insert(controller, staking_ledger);
		let slash_amount = T::Currency::minimum_balance() * 10u32.into();
		let balance_before = T::Currency::free_balance(&stash);
	}: {
		crate::slashing::do_slash::<T>(
			&stash,
			slash_amount,
			&mut BalanceOf::<T>::zero(),
			&mut NegativeImbalanceOf::<T>::zero()
		);
	} verify {
		let balance_after = T::Currency::free_balance(&stash);
		assert!(balance_before > balance_after);
	}

	// This benchmark create `v` validators intent, `n` nominators intent, in total creating `e`
	// edges.
	#[extra]
	submit_solution_initial {
		// number of validator intention. This will be equal to `ElectionSize::validators`.
		let v in 200 .. 400;
		// number of nominator intention. This will be equal to `ElectionSize::nominators`.
		let n in 500 .. 1000;
		// number of assignments. Basically, number of active nominators. This will be equal to
		// `compact.len()`.
		let a in 200 .. 400;
		// number of winners, also ValidatorCount. This will be equal to `winner.len()`.
		let w in 16 .. 100;

		ensure!(w as usize >= MAX_NOMINATIONS, "doesn't support lower value");

		let winners = create_validators_with_nominators_for_era::<T>(
			v,
			n,
			MAX_NOMINATIONS,
			false,
			Some(w),
		)?;

		// needed for the solution to be generates.
		assert!(<Staking<T>>::create_stakers_snapshot().0);

		// set number of winners
		ValidatorCount::put(w);

		// create a assignments in total for the w winners.
		let (winners, assignments) = create_assignments_for_offchain::<T>(a, winners)?;

		let (
			winners,
			compact,
			score,
			size
		) = offchain_election::prepare_submission::<T>(
			assignments,
			winners,
			false,
			T::BlockWeights::get().max_block,
		).unwrap();

		assert_eq!(
			winners.len(), compact.unique_targets().len(),
			"unique targets ({}) and winners ({}) count not same. This solution is not valid.",
			compact.unique_targets().len(),
			winners.len(),
		);

		// needed for the solution to be accepted
		<EraElectionStatus<T>>::put(ElectionStatus::Open(T::BlockNumber::from(1u32)));

		let era = <Staking<T>>::current_era().unwrap_or(0);
		let caller: T::AccountId = account("caller", n, SEED);
		whitelist_account!(caller);
	}: {
		let result = <Staking<T>>::submit_election_solution(
			RawOrigin::Signed(caller.clone()).into(),
			winners,
			compact,
			score.clone(),
			era,
			size,
		);
		assert!(result.is_ok());
	}
	verify {
		// new solution has been accepted.
		assert_eq!(<Staking<T>>::queued_score().unwrap(), score);
	}

	// same as submit_solution_initial but we place a very weak solution on chian first.
	submit_solution_better {
		// number of validator intention.
		let v in 200 .. 400;
		// number of nominator intention.
		let n in 500 .. 1000;
		// number of assignments. Basically, number of active nominators.
		let a in 200 .. 400;
		// number of winners, also ValidatorCount.
		let w in 16 .. 100;

		ensure!(w as usize >= MAX_NOMINATIONS, "doesn't support lower value");

		let winners = create_validators_with_nominators_for_era::<T>(
			v,
			n,
			MAX_NOMINATIONS,
			false,
			Some(w),
		)?;

		// needed for the solution to be generates.
		assert!(<Staking<T>>::create_stakers_snapshot().0);

		// set number of winners
		ValidatorCount::put(w);

		// create a assignments in total for the w winners.
		let (winners, assignments) = create_assignments_for_offchain::<T>(a, winners)?;

		let single_winner = winners[0].0.clone();

		let (
			winners,
			compact,
			score,
			size
		) = offchain_election::prepare_submission::<T>(
			assignments,
			winners,
			false,
			T::BlockWeights::get().max_block,
		).unwrap();

		assert_eq!(
			winners.len(), compact.unique_targets().len(),
			"unique targets ({}) and winners ({}) count not same. This solution is not valid.",
			compact.unique_targets().len(),
			winners.len(),
		);

		// needed for the solution to be accepted
		<EraElectionStatus<T>>::put(ElectionStatus::Open(T::BlockNumber::from(1u32)));

		let era = <Staking<T>>::current_era().unwrap_or(0);
		let caller: T::AccountId = account("caller", n, SEED);
		whitelist_account!(caller);

		// submit a very bad solution on-chain
		{
			// this is needed to fool the chain to accept this solution.
			ValidatorCount::put(1);
			let (winners, compact, score, size) = get_single_winner_solution::<T>(single_winner)?;
			assert!(
				<Staking<T>>::submit_election_solution(
					RawOrigin::Signed(caller.clone()).into(),
					winners,
					compact,
					score.clone(),
					era,
					size,
			).is_ok());

			// new solution has been accepted.
			assert_eq!(<Staking<T>>::queued_score().unwrap(), score);
			ValidatorCount::put(w);
		}
	}: {
		let result = <Staking<T>>::submit_election_solution(
			RawOrigin::Signed(caller.clone()).into(),
			winners,
			compact,
			score.clone(),
			era,
			size,
		);
		assert!(result.is_ok());
	}
	verify {
		// new solution has been accepted.
		assert_eq!(<Staking<T>>::queued_score().unwrap(), score);
	}

	// This will be early rejected based on the score.
	#[extra]
	submit_solution_weaker {
		// number of validator intention.
		let v in 200 .. 400;
		// number of nominator intention.
		let n in 500 .. 1000;

		create_validators_with_nominators_for_era::<T>(v, n, MAX_NOMINATIONS, false, None)?;

		// needed for the solution to be generates.
		assert!(<Staking<T>>::create_stakers_snapshot().0);

		// needed for the solution to be accepted
		<EraElectionStatus<T>>::put(ElectionStatus::Open(T::BlockNumber::from(1u32)));
		let era = <Staking<T>>::current_era().unwrap_or(0);
		let caller: T::AccountId = account("caller", n, SEED);
		whitelist_account!(caller);

		// submit a seq-phragmen with all the good stuff on chain.
		{
			let (winners, compact, score, size) = get_seq_phragmen_solution::<T>(true);
			assert_eq!(
				winners.len(), compact.unique_targets().len(),
				"unique targets ({}) and winners ({}) count not same. This solution is not valid.",
				compact.unique_targets().len(),
				winners.len(),
			);
			assert!(
				<Staking<T>>::submit_election_solution(
					RawOrigin::Signed(caller.clone()).into(),
					winners,
					compact,
					score.clone(),
					era,
					size,
				).is_ok()
			);

			// new solution has been accepted.
			assert_eq!(<Staking<T>>::queued_score().unwrap(), score);
		}

		// prepare a bad solution. This will be very early rejected.
		let (winners, compact, score, size) = get_weak_solution::<T>(true);
	}: {
		assert!(
			<Staking<T>>::submit_election_solution(
				RawOrigin::Signed(caller.clone()).into(),
				winners,
				compact,
				score.clone(),
				era,
				size,
			).is_err()
		);
	}
}

#[cfg(test)]
mod tests {
	use super::*;
	use crate::mock::{ExtBuilder, Test, Balances, Staking, Origin};
	use fabric_support::assert_ok;

	#[test]
	fn create_validators_with_nominators_for_era_works() {
		ExtBuilder::default().has_stakers(true).build().execute_with(|| {
			let v = 10;
			let n = 100;

			create_validators_with_nominators_for_era::<Test>(v, n, MAX_NOMINATIONS, false, None)
				.unwrap();

			let count_validators = Validators::<Test>::iter().count();
			let count_nominators = Nominators::<Test>::iter().count();

			assert_eq!(count_validators, v as usize);
			assert_eq!(count_nominators, n as usize);
		});
	}

	#[test]
	fn create_validator_with_nominators_works() {
		ExtBuilder::default().has_stakers(true).build().execute_with(|| {
			let n = 10;

			let (validator_stash, nominators) = create_validator_with_nominators::<Test>(
				n,
				<Test as Config>::MaxNominatorRewardedPerValidator::get() as u32,
				false,
				RewardDestination::Staked,
			).unwrap();

			assert_eq!(nominators.len() as u32, n);

			let current_era = CurrentEra::get().unwrap();

			let original_free_balance = Balances::free_balance(&validator_stash);
			assert_ok!(Staking::payout_stakers(Origin::signed(1337), validator_stash, current_era));
			let new_free_balance = Balances::free_balance(&validator_stash);

			assert!(original_free_balance < new_free_balance);
		});
	}

	#[test]
	fn add_slashing_spans_works() {
		ExtBuilder::default().has_stakers(true).build().execute_with(|| {
			let n = 10;

			let (validator_stash, _nominators) = create_validator_with_nominators::<Test>(
				n,
				<Test as Config>::MaxNominatorRewardedPerValidator::get() as u32,
				false,
				RewardDestination::Staked,
			).unwrap();

			// Add 20 slashing spans
			let num_of_slashing_spans = 20;
			add_slashing_spans::<Test>(&validator_stash, num_of_slashing_spans);

			let slashing_spans = SlashingSpans::<Test>::get(&validator_stash).unwrap();
			assert_eq!(slashing_spans.iter().count(), num_of_slashing_spans as usize);
			for i in 0 .. num_of_slashing_spans {
				assert!(SpanSlash::<Test>::contains_key((&validator_stash, i)));
			}

			// Test everything is cleaned up
			assert_ok!(Staking::kill_stash(&validator_stash, num_of_slashing_spans));
			assert!(SlashingSpans::<Test>::get(&validator_stash).is_none());
			for i in 0 .. num_of_slashing_spans {
				assert!(!SpanSlash::<Test>::contains_key((&validator_stash, i)));
			}
		});
	}

	#[test]
	fn test_payout_all() {
		ExtBuilder::default().has_stakers(true).build().execute_with(|| {
			let v = 10;
			let n = 100;

			let selected_benchmark = SelectedBenchmark::payout_all;
			let c = vec![(fabric_benchmarking::BenchmarkParameter::v, v), (fabric_benchmarking::BenchmarkParameter::n, n)];
			let closure_to_benchmark =
				<SelectedBenchmark as fabric_benchmarking::BenchmarkingSetup<Test>>::instance(
					&selected_benchmark,
					&c,
					true
				).unwrap();

			assert_ok!(closure_to_benchmark());
		});
	}

	#[test]
	fn test_benchmarks() {
		ExtBuilder::default().has_stakers(true).build().execute_with(|| {
			assert_ok!(test_benchmark_bond::<Test>());
			assert_ok!(test_benchmark_bond_extra::<Test>());
			assert_ok!(test_benchmark_unbond::<Test>());
			assert_ok!(test_benchmark_withdraw_unbonded_update::<Test>());
			assert_ok!(test_benchmark_withdraw_unbonded_kill::<Test>());
			assert_ok!(test_benchmark_validate::<Test>());
			assert_ok!(test_benchmark_kick::<Test>());
			assert_ok!(test_benchmark_nominate::<Test>());
			assert_ok!(test_benchmark_chill::<Test>());
			assert_ok!(test_benchmark_set_payee::<Test>());
			assert_ok!(test_benchmark_set_controller::<Test>());
			assert_ok!(test_benchmark_set_validator_count::<Test>());
			assert_ok!(test_benchmark_force_no_eras::<Test>());
			assert_ok!(test_benchmark_force_new_era::<Test>());
			assert_ok!(test_benchmark_force_new_era_always::<Test>());
			assert_ok!(test_benchmark_set_invulnerables::<Test>());
			assert_ok!(test_benchmark_force_unstake::<Test>());
			assert_ok!(test_benchmark_cancel_deferred_slash::<Test>());
			assert_ok!(test_benchmark_payout_stakers_dead_controller::<Test>());
			assert_ok!(test_benchmark_payout_stakers_alive_staked::<Test>());
			assert_ok!(test_benchmark_rebond::<Test>());
			assert_ok!(test_benchmark_set_history_depth::<Test>());
			assert_ok!(test_benchmark_reap_stash::<Test>());
			assert_ok!(test_benchmark_new_era::<Test>());
			assert_ok!(test_benchmark_do_slash::<Test>());
			assert_ok!(test_benchmark_payout_all::<Test>());
			// only run one of them to same time on the CI. ignore the other two.
			assert_ok!(test_benchmark_submit_solution_initial::<Test>());
		});
	}

	#[test]
	#[ignore]
	fn test_benchmarks_offchain() {
		ExtBuilder::default().has_stakers(false).build().execute_with(|| {
			assert_ok!(test_benchmark_submit_solution_better::<Test>());
			assert_ok!(test_benchmark_submit_solution_weaker::<Test>());
		});
	}

}
