impls.rs

			);
		});

		voters.into_iter().for_each(|(v, s, t)| {
			let stake = <BalanceOf<T>>::try_from(s).unwrap_or_else(|_| {
				panic!("cannot convert a VoteWeight into BalanceOf, benchmark needs reconfiguring.")
			});
			<Bonded<T>>::insert(v.clone(), v.clone());
			<Ledger<T>>::insert(
				v.clone(),
				StakingLedger {
					stash: v.clone(),
					active: stake,
					total: stake,
					unlocking: vec![],
					claimed_rewards: vec![],
				},
			);
			Self::do_add_nominator(
				&v,
				Nominations { targets: t, submitted_in: 0, suppressed: false },
			);
		});
	}
}

/// In this implementation `new_session(session)` must be called before `end_session(session-1)`
/// i.e. the new session must be planned before the ending of the previous session.
///
/// Once the first new_session is planned, all session must start and then end in order, though
/// some session can lag in between the newest session planned and the latest session started.
impl<T: Config> pallet_session::SessionManager<T::AccountId> for Pallet<T> {
	fn new_session(new_index: SessionIndex) -> Option<Vec<T::AccountId>> {
		log!(trace, "planning new session {}", new_index);
		CurrentPlannedSession::<T>::put(new_index);
		Self::new_session(new_index, false)
	}
	fn new_session_genesis(new_index: SessionIndex) -> Option<Vec<T::AccountId>> {
		log!(trace, "planning new session {} at genesis", new_index);
		CurrentPlannedSession::<T>::put(new_index);
		Self::new_session(new_index, true)
	}
	fn start_session(start_index: SessionIndex) {
		log!(trace, "starting session {}", start_index);
		Self::start_session(start_index)
	}
	fn end_session(end_index: SessionIndex) {
		log!(trace, "ending session {}", end_index);
		Self::end_session(end_index)
	}
}

impl<T: Config> historical::SessionManager<T::AccountId, Exposure<T::AccountId, BalanceOf<T>>>
	for Pallet<T>
{
	fn new_session(
		new_index: SessionIndex,
	) -> Option<Vec<(T::AccountId, Exposure<T::AccountId, BalanceOf<T>>)>> {
		<Self as pallet_session::SessionManager<_>>::new_session(new_index).map(|validators| {
			let current_era = Self::current_era()
				// Must be some as a new era has been created.
				.unwrap_or(0);

			validators
				.into_iter()
				.map(|v| {
					let exposure = Self::eras_stakers(current_era, &v);
					(v, exposure)
				})
				.collect()
		})
	}
	fn new_session_genesis(
		new_index: SessionIndex,
	) -> Option<Vec<(T::AccountId, Exposure<T::AccountId, BalanceOf<T>>)>> {
		<Self as pallet_session::SessionManager<_>>::new_session_genesis(new_index).map(
			|validators| {
				let current_era = Self::current_era()
					// Must be some as a new era has been created.
					.unwrap_or(0);

				validators
					.into_iter()
					.map(|v| {
						let exposure = Self::eras_stakers(current_era, &v);
						(v, exposure)
					})
					.collect()
			},
		)
	}
	fn start_session(start_index: SessionIndex) {
		<Self as pallet_session::SessionManager<_>>::start_session(start_index)
	}
	fn end_session(end_index: SessionIndex) {
		<Self as pallet_session::SessionManager<_>>::end_session(end_index)
	}
}

/// Add reward points to block authors:
/// * 20 points to the block producer for producing a (non-uncle) block in the relay chain,
/// * 2 points to the block producer for each reference to a previously unreferenced uncle, and
/// * 1 point to the producer of each referenced uncle block.
impl<T> pallet_authorship::EventHandler<T::AccountId, T::BlockNumber> for Pallet<T>
where
	T: Config + pallet_authorship::Config + pallet_session::Config,
{
	fn note_author(author: T::AccountId) {
		Self::reward_by_ids(vec![(author, 20)])
	}
	fn note_uncle(author: T::AccountId, _age: T::BlockNumber) {
		Self::reward_by_ids(vec![(<pallet_authorship::Pallet<T>>::author(), 2), (author, 1)])
	}
}

/// This is intended to be used with `FilterHistoricalOffences`.
impl<T: Config>
	OnOffenceHandler<T::AccountId, pallet_session::historical::IdentificationTuple<T>, Weight>
	for Pallet<T>
where
	T: pallet_session::Config<ValidatorId = <T as frame_system::Config>::AccountId>,
	T: pallet_session::historical::Config<
		FullIdentification = Exposure<<T as frame_system::Config>::AccountId, BalanceOf<T>>,
		FullIdentificationOf = ExposureOf<T>,
	>,
	T::SessionHandler: pallet_session::SessionHandler<<T as frame_system::Config>::AccountId>,
	T::SessionManager: pallet_session::SessionManager<<T as frame_system::Config>::AccountId>,
	T::ValidatorIdOf: Convert<
		<T as frame_system::Config>::AccountId,
		Option<<T as frame_system::Config>::AccountId>,
	>,
{
	fn on_offence(
		offenders: &[OffenceDetails<
			T::AccountId,
			pallet_session::historical::IdentificationTuple<T>,
		>],
		slash_fraction: &[Perbill],
		slash_session: SessionIndex,
		disable_strategy: DisableStrategy,
	) -> Weight {
		let reward_proportion = SlashRewardFraction::<T>::get();
		let mut consumed_weight: Weight = 0;
		let mut add_db_reads_writes = |reads, writes| {
			consumed_weight += T::DbWeight::get().reads_writes(reads, writes);
		};

		let active_era = {
			let active_era = Self::active_era();
			add_db_reads_writes(1, 0);
			if active_era.is_none() {
				// This offence need not be re-submitted.
				return consumed_weight
			}
			active_era.expect("value checked not to be `None`; qed").index
		};
		let active_era_start_session_index = Self::eras_start_session_index(active_era)
			.unwrap_or_else(|| {
				frame_support::print("Error: start_session_index must be set for current_era");
				0
			});
		add_db_reads_writes(1, 0);

		let window_start = active_era.saturating_sub(T::BondingDuration::get());

		// Fast path for active-era report - most likely.
		// `slash_session` cannot be in a future active era. It must be in `active_era` or before.
		let slash_era = if slash_session >= active_era_start_session_index {
			active_era
		} else {
			let eras = BondedEras::<T>::get();
			add_db_reads_writes(1, 0);

			// Reverse because it's more likely to find reports from recent eras.
			match eras.iter().rev().filter(|&&(_, ref sesh)| sesh <= &slash_session).next() {
				Some(&(ref slash_era, _)) => *slash_era,
				// Before bonding period. defensive - should be filtered out.
				None => return consumed_weight,
			}
		};

		<Self as Store>::EarliestUnappliedSlash::mutate(|earliest| {
			if earliest.is_none() {
				*earliest = Some(active_era)
			}
		});
		add_db_reads_writes(1, 1);

		let slash_defer_duration = T::SlashDeferDuration::get();

		let invulnerables = Self::invulnerables();
		add_db_reads_writes(1, 0);

		for (details, slash_fraction) in offenders.iter().zip(slash_fraction) {
			let (stash, exposure) = &details.offender;

			// Skip if the validator is invulnerable.
			if invulnerables.contains(stash) {
				continue
			}

			let unapplied = slashing::compute_slash::<T>(slashing::SlashParams {
				stash,
				slash: *slash_fraction,
				exposure,
				slash_era,
				window_start,
				now: active_era,
				reward_proportion,
				disable_strategy,
			});

			if let Some(mut unapplied) = unapplied {
				let nominators_len = unapplied.others.len() as u64;
				let reporters_len = details.reporters.len() as u64;

				{
					let upper_bound = 1 /* Validator/NominatorSlashInEra */ + 2 /* fetch_spans */;
					let rw = upper_bound + nominators_len * upper_bound;
					add_db_reads_writes(rw, rw);
				}
				unapplied.reporters = details.reporters.clone();
				if slash_defer_duration == 0 {
					// Apply right away.
					slashing::apply_slash::<T>(unapplied);
					{
						let slash_cost = (6, 5);
						let reward_cost = (2, 2);
						add_db_reads_writes(
							(1 + nominators_len) * slash_cost.0 + reward_cost.0 * reporters_len,
							(1 + nominators_len) * slash_cost.1 + reward_cost.1 * reporters_len,
						);
					}
				} else {
					// Defer to end of some `slash_defer_duration` from now.
					<Self as Store>::UnappliedSlashes::mutate(active_era, move |for_later| {
						for_later.push(unapplied)
					});
					add_db_reads_writes(1, 1);
				}
			} else {
				add_db_reads_writes(4 /* fetch_spans */, 5 /* kick_out_if_recent */)
			}
		}

		consumed_weight
	}
}

impl<T: Config> VoteWeightProvider<T::AccountId> for Pallet<T> {
	fn vote_weight(who: &T::AccountId) -> VoteWeight {
		Self::weight_of(who)
	}

	#[cfg(feature = "runtime-benchmarks")]
	fn set_vote_weight_of(who: &T::AccountId, weight: VoteWeight) {
		// this will clearly results in an inconsistent state, but it should not matter for a
		// benchmark.
		let active: BalanceOf<T> = weight.try_into().map_err(|_| ()).unwrap();
		let mut ledger = Self::ledger(who).unwrap_or_default();
		ledger.active = active;
		<Ledger<T>>::insert(who, ledger);
		<Bonded<T>>::insert(who, who);

		// also, we play a trick to make sure that a issuance based-`CurrencyToVote` behaves well:
		// This will make sure that total issuance is zero, thus the currency to vote will be a 1-1
		// conversion.
		let imbalance = T::Currency::burn(T::Currency::total_issuance());
		// kinda ugly, but gets the job done. The fact that this works here is a HUGE exception.
		// Don't try this pattern in other places.
		sp_std::mem::forget(imbalance);
	}
}

/// A simple voter list implementation that does not require any additional pallets. Note, this
/// does not provided nominators in sorted ordered. If you desire nominators in a sorted order take
/// a look at [`pallet-bags-list].
pub struct UseNominatorsMap<T>(sp_std::marker::PhantomData<T>);
impl<T: Config> SortedListProvider<T::AccountId> for UseNominatorsMap<T> {
	type Error = ();

	/// Returns iterator over voter list, which can have `take` called on it.
	fn iter() -> Box<dyn Iterator<Item = T::AccountId>> {
		Box::new(Nominators::<T>::iter().map(|(n, _)| n))
	}
	fn count() -> u32 {
		CounterForNominators::<T>::get()
	}
	fn contains(id: &T::AccountId) -> bool {
		Nominators::<T>::contains_key(id)
	}
	fn on_insert(_: T::AccountId, _weight: VoteWeight) -> Result<(), Self::Error> {
		// nothing to do on insert.
		Ok(())
	}
	fn on_update(_: &T::AccountId, _weight: VoteWeight) {
		// nothing to do on update.
	}
	fn on_remove(_: &T::AccountId) {
		// nothing to do on remove.
	}
	fn regenerate(
		_: impl IntoIterator<Item = T::AccountId>,
		_: Box<dyn Fn(&T::AccountId) -> VoteWeight>,
	) -> u32 {
		// nothing to do upon regenerate.
		0
	}
	fn sanity_check() -> Result<(), &'static str> {
		Ok(())
	}
	fn clear(maybe_count: Option<u32>) -> u32 {
		Nominators::<T>::remove_all(maybe_count);
		if let Some(count) = maybe_count {
			CounterForNominators::<T>::mutate(|noms| *noms - count);
			count
		} else {
			CounterForNominators::<T>::take()
		}
	}
}