lib.rs

		/// Slashing spans for stash accounts.
		SlashingSpans get(fn slashing_spans): map hasher(twox_64_concat) T::AccountId => Option<slashing::SlashingSpans>;

		/// Records information about the maximum slash of a stash within a slashing span,
		/// as well as how much reward has been paid out.
		SpanSlash:
			map hasher(twox_64_concat) (T::AccountId, slashing::SpanIndex)
			=> slashing::SpanRecord<BalanceOf<T>>;

		/// The earliest era for which we have a pending, unapplied slash.
		EarliestUnappliedSlash: Option<EraIndex>;

		/// The last planned session scheduled by the session pallet.
		///
		/// This is basically in sync with the call to [`SessionManager::new_session`].
		pub CurrentPlannedSession get(fn current_planned_session): SessionIndex;

		/// True if network has been upgraded to this version.
		/// Storage version of the pallet.
		///
		/// This is set to v6.0.0 for new networks.
		StorageVersion build(|_: &GenesisConfig<T>| Releases::V6_0_0): Releases;
	}
	add_extra_genesis {
		config(stakers):
			Vec<(T::AccountId, T::AccountId, BalanceOf<T>, StakerStatus<T::AccountId>)>;
		build(|config: &GenesisConfig<T>| {
			for &(ref stash, ref controller, balance, ref status) in &config.stakers {
				assert!(
					T::Currency::free_balance(&stash) >= balance,
					"Stash does not have enough balance to bond."
				);
				let _ = <Module<T>>::bond(
					T::Origin::from(Some(stash.clone()).into()),
					T::Lookup::unlookup(controller.clone()),
					balance,
					RewardDestination::Staked,
				);
				let _ = match status {
					StakerStatus::Validator => {
						<Module<T>>::validate(
							T::Origin::from(Some(controller.clone()).into()),
							Default::default(),
						)
					},
					StakerStatus::Nominator(votes) => {
						<Module<T>>::nominate(
							T::Origin::from(Some(controller.clone()).into()),
							votes.iter().map(|l| T::Lookup::unlookup(l.clone())).collect(),
						)
					}, _ => Ok(())
				};
			}
		});
	}
}

pub mod migrations {
	use super::*;

	pub mod v6 {
		use super::*;
		use frame_support::{traits::Get, weights::Weight, pallet_prelude::*};

		macro_rules! generate_storage_types {
			($name:ident => Value<$value:ty>) => {
				paste::paste! {
					struct [<$name Instance>];
					impl frame_support::traits::StorageInstance for [<$name Instance>] {
						fn pallet_prefix() -> &'static str {
							"Staking"
						}
						const STORAGE_PREFIX: &'static str = stringify!($name);
					}
					type $name = StorageValue<[<$name Instance>], $value, ValueQuery>;
				}
			}
		}

		// NOTE: value type doesn't matter, we just set it to () here.
		generate_storage_types!(SnapshotValidators => Value<()>);
		generate_storage_types!(SnapshotNominators => Value<()>);
		generate_storage_types!(QueuedElected => Value<()>);
		generate_storage_types!(QueuedScore => Value<()>);
		generate_storage_types!(EraElectionStatus => Value<()>);
		generate_storage_types!(IsCurrentSessionFinal => Value<()>);

		/// check to execute prior to migration.
		pub fn pre_migrate<T: Config>() -> Result<(), &'static str> {
			// these may or may not exist.
			log!(info, "SnapshotValidators.exits()? {:?}", SnapshotValidators::exists());
			log!(info, "SnapshotNominators.exits()? {:?}", SnapshotNominators::exists());
			log!(info, "QueuedElected.exits()? {:?}", QueuedElected::exists());
			log!(info, "QueuedScore.exits()? {:?}", QueuedScore::exists());
			// these must exist.
			assert!(IsCurrentSessionFinal::exists(), "IsCurrentSessionFinal storage item not found!");
			assert!(EraElectionStatus::exists(), "EraElectionStatus storage item not found!");
			Ok(())
		}

		/// Migrate storage to v6.
		pub fn migrate<T: Config>() -> Weight {
			log!(info, "Migrating staking to Releases::V6_0_0");

			SnapshotValidators::kill();
			SnapshotNominators::kill();
			QueuedElected::kill();
			QueuedScore::kill();
			EraElectionStatus::kill();
			IsCurrentSessionFinal::kill();

			StorageVersion::put(Releases::V6_0_0);
			log!(info, "Done.");
			T::DbWeight::get().writes(6 + 1)
		}
	}
}

decl_event!(
	pub enum Event<T> where Balance = BalanceOf<T>, <T as frame_system::Config>::AccountId {
		/// The era payout has been set; the first balance is the validator-payout; the second is
		/// the remainder from the maximum amount of reward.
		/// \[era_index, validator_payout, remainder\]
		EraPayout(EraIndex, Balance, Balance),
		/// The staker has been rewarded by this amount. \[stash, amount\]
		Reward(AccountId, Balance),
		/// One validator (and its nominators) has been slashed by the given amount.
		/// \[validator, amount\]
		Slash(AccountId, Balance),
		/// An old slashing report from a prior era was discarded because it could
		/// not be processed. \[session_index\]
		OldSlashingReportDiscarded(SessionIndex),
		/// A new set of stakers was elected.
		StakingElection,
		/// An account has bonded this amount. \[stash, amount\]
		///
		/// NOTE: This event is only emitted when funds are bonded via a dispatchable. Notably,
		/// it will not be emitted for staking rewards when they are added to stake.
		Bonded(AccountId, Balance),
		/// An account has unbonded this amount. \[stash, amount\]
		Unbonded(AccountId, Balance),
		/// An account has called `withdraw_unbonded` and removed unbonding chunks worth `Balance`
		/// from the unlocking queue. \[stash, amount\]
		Withdrawn(AccountId, Balance),
		/// A nominator has been kicked from a validator. \[nominator, stash\]
		Kicked(AccountId, AccountId),
	}
);

decl_error! {
	/// Error for the staking module.
	pub enum Error for Module<T: Config> {
		/// Not a controller account.
		NotController,
		/// Not a stash account.
		NotStash,
		/// Stash is already bonded.
		AlreadyBonded,
		/// Controller is already paired.
		AlreadyPaired,
		/// Targets cannot be empty.
		EmptyTargets,
		/// Duplicate index.
		DuplicateIndex,
		/// Slash record index out of bounds.
		InvalidSlashIndex,
		/// Can not bond with value less than minimum balance.
		InsufficientValue,
		/// Can not schedule more unlock chunks.
		NoMoreChunks,
		/// Can not rebond without unlocking chunks.
		NoUnlockChunk,
		/// Attempting to target a stash that still has funds.
		FundedTarget,
		/// Invalid era to reward.
		InvalidEraToReward,
		/// Invalid number of nominations.
		InvalidNumberOfNominations,
		/// Items are not sorted and unique.
		NotSortedAndUnique,
		/// Rewards for this era have already been claimed for this validator.
		AlreadyClaimed,
		/// Incorrect previous history depth input provided.
		IncorrectHistoryDepth,
		/// Incorrect number of slashing spans provided.
		IncorrectSlashingSpans,
		/// Internal state has become somehow corrupted and the operation cannot continue.
		BadState,
		/// Too many nomination targets supplied.
		TooManyTargets,
		/// A nomination target was supplied that was blocked or otherwise not a validator.
		BadTarget,
	}
}

decl_module! {
	pub struct Module<T: Config> for enum Call where origin: T::Origin {
		/// Number of sessions per era.
		const SessionsPerEra: SessionIndex = T::SessionsPerEra::get();

		/// Number of eras that staked funds must remain bonded for.
		const BondingDuration: EraIndex = T::BondingDuration::get();

		/// Number of eras that slashes are deferred by, after computation.
		///
		/// This should be less than the bonding duration.
		/// Set to 0 if slashes should be applied immediately, without opportunity for
		/// intervention.
		const SlashDeferDuration: EraIndex = T::SlashDeferDuration::get();

		/// The maximum number of nominators rewarded for each validator.
		///
		/// For each validator only the `$MaxNominatorRewardedPerValidator` biggest stakers can claim
		/// their reward. This used to limit the i/o cost for the nominator payout.
		const MaxNominatorRewardedPerValidator: u32 = T::MaxNominatorRewardedPerValidator::get();

		type Error = Error<T>;

		fn deposit_event() = default;

		fn on_runtime_upgrade() -> Weight {
			if StorageVersion::get() == Releases::V5_0_0 {
				migrations::v6::migrate::<T>()
			} else {
				T::DbWeight::get().reads(1)
			}
		}

		fn on_finalize() {
			// Set the start of the first era.
			if let Some(mut active_era) = Self::active_era() {
				if active_era.start.is_none() {
					let now_as_millis_u64 = T::UnixTime::now().as_millis().saturated_into::<u64>();
					active_era.start = Some(now_as_millis_u64);
					// This write only ever happens once, we don't include it in the weight in general
					ActiveEra::put(active_era);
				}
			}
			// `on_finalize` weight is tracked in `on_initialize`
		}

		fn integrity_test() {
			sp_io::TestExternalities::new_empty().execute_with(||
				assert!(
					T::SlashDeferDuration::get() < T::BondingDuration::get() || T::BondingDuration::get() == 0,
					"As per documentation, slash defer duration ({}) should be less than bonding duration ({}).",
					T::SlashDeferDuration::get(),
					T::BondingDuration::get(),
				)
			);

			use sp_runtime::UpperOf;
			// 1. Maximum sum of Vec<OffchainAccuracy> must fit into `UpperOf<OffchainAccuracy>`.
			assert!(
				<usize as TryInto<UpperOf<OffchainAccuracy>>>::try_into(MAX_NOMINATIONS)
				.unwrap()
				.checked_mul(<OffchainAccuracy>::one().deconstruct().try_into().unwrap())
				.is_some()
			);
		}

		/// Take the origin account as a stash and lock up `value` of its balance. `controller` will
		/// be the account that controls it.
		///
		/// `value` must be more than the `minimum_balance` specified by `T::Currency`.
		///
		/// The dispatch origin for this call must be _Signed_ by the stash account.
		///
		/// Emits `Bonded`.
		///
		/// # <weight>
		/// - Independent of the arguments. Moderate complexity.
		/// - O(1).
		/// - Three extra DB entries.
		///
		/// NOTE: Two of the storage writes (`Self::bonded`, `Self::payee`) are _never_ cleaned
		/// unless the `origin` falls below _existential deposit_ and gets removed as dust.
		/// ------------------
		/// Weight: O(1)
		/// DB Weight:
		/// - Read: Bonded, Ledger, [Origin Account], Current Era, History Depth, Locks
		/// - Write: Bonded, Payee, [Origin Account], Locks, Ledger
		/// # </weight>
		#[weight = T::WeightInfo::bond()]
		pub fn bond(origin,
			controller: <T::Lookup as StaticLookup>::Source,
			#[compact] value: BalanceOf<T>,
			payee: RewardDestination<T::AccountId>,
		) {
			let stash = ensure_signed(origin)?;

			if <Bonded<T>>::contains_key(&stash) {
				Err(Error::<T>::AlreadyBonded)?
			}

			let controller = T::Lookup::lookup(controller)?;

			if <Ledger<T>>::contains_key(&controller) {
				Err(Error::<T>::AlreadyPaired)?
			}

			// reject a bond which is considered to be _dust_.
			if value < T::Currency::minimum_balance() {
				Err(Error::<T>::InsufficientValue)?
			}

			system::Pallet::<T>::inc_consumers(&stash).map_err(|_| Error::<T>::BadState)?;

			// You're auto-bonded forever, here. We might improve this by only bonding when
			// you actually validate/nominate and remove once you unbond __everything__.
			<Bonded<T>>::insert(&stash, &controller);
			<Payee<T>>::insert(&stash, payee);

			let current_era = CurrentEra::get().unwrap_or(0);
			let history_depth = Self::history_depth();
			let last_reward_era = current_era.saturating_sub(history_depth);

			let stash_balance = T::Currency::free_balance(&stash);
			let value = value.min(stash_balance);
			Self::deposit_event(RawEvent::Bonded(stash.clone(), value));
			let item = StakingLedger {
				stash,
				total: value,
				active: value,
				unlocking: vec![],
				claimed_rewards: (last_reward_era..current_era).collect(),
			};
			Self::update_ledger(&controller, &item);
		}

		/// Add some extra amount that have appeared in the stash `free_balance` into the balance up
		/// for staking.
		///
		/// Use this if there are additional funds in your stash account that you wish to bond.
		/// Unlike [`bond`] or [`unbond`] this function does not impose any limitation on the amount
		/// that can be added.
		///
		/// The dispatch origin for this call must be _Signed_ by the stash, not the controller and
		/// it can be only called when [`EraElectionStatus`] is `Closed`.
		///
		/// Emits `Bonded`.
		///
		/// # <weight>
		/// - Independent of the arguments. Insignificant complexity.
		/// - O(1).
		/// - One DB entry.
		/// ------------
		/// DB Weight:
		/// - Read: Era Election Status, Bonded, Ledger, [Origin Account], Locks
		/// - Write: [Origin Account], Locks, Ledger
		/// # </weight>
		#[weight = T::WeightInfo::bond_extra()]
		fn bond_extra(origin, #[compact] max_additional: BalanceOf<T>) {
			let stash = ensure_signed(origin)?;

			let controller = Self::bonded(&stash).ok_or(Error::<T>::NotStash)?;
			let mut ledger = Self::ledger(&controller).ok_or(Error::<T>::NotController)?;

			let stash_balance = T::Currency::free_balance(&stash);
			if let Some(extra) = stash_balance.checked_sub(&ledger.total) {
				let extra = extra.min(max_additional);
				ledger.total += extra;
				ledger.active += extra;
				// last check: the new active amount of ledger must be more than ED.
				ensure!(ledger.active >= T::Currency::minimum_balance(), Error::<T>::InsufficientValue);

				Self::deposit_event(RawEvent::Bonded(stash, extra));
				Self::update_ledger(&controller, &ledger);
			}
		}

		/// Schedule a portion of the stash to be unlocked ready for transfer out after the bond
		/// period ends. If this leaves an amount actively bonded less than
		/// T::Currency::minimum_balance(), then it is increased to the full amount.
		///
		/// Once the unlock period is done, you can call `withdraw_unbonded` to actually move
		/// the funds out of management ready for transfer.
		///
		/// No more than a limited number of unlocking chunks (see `MAX_UNLOCKING_CHUNKS`)
		/// can co-exists at the same time. In that case, [`Call::withdraw_unbonded`] need
		/// to be called first to remove some of the chunks (if possible).
		///
		/// The dispatch origin for this call must be _Signed_ by the controller, not the stash.
		/// And, it can be only called when [`EraElectionStatus`] is `Closed`.
		///
		/// Emits `Unbonded`.
		///
		/// See also [`Call::withdraw_unbonded`].
		///
		/// # <weight>
		/// - Independent of the arguments. Limited but potentially exploitable complexity.
		/// - Contains a limited number of reads.
		/// - Each call (requires the remainder of the bonded balance to be above `minimum_balance`)
		///   will cause a new entry to be inserted into a vector (`Ledger.unlocking`) kept in storage.
		///   The only way to clean the aforementioned storage item is also user-controlled via
		///   `withdraw_unbonded`.
		/// - One DB entry.
		/// ----------
		/// Weight: O(1)
		/// DB Weight:
		/// - Read: EraElectionStatus, Ledger, CurrentEra, Locks, BalanceOf Stash,
		/// - Write: Locks, Ledger, BalanceOf Stash,
		/// </weight>
		#[weight = T::WeightInfo::unbond()]
		fn unbond(origin, #[compact] value: BalanceOf<T>) {
			let controller = ensure_signed(origin)?;
			let mut ledger = Self::ledger(&controller).ok_or(Error::<T>::NotController)?;
			ensure!(
				ledger.unlocking.len() < MAX_UNLOCKING_CHUNKS,
				Error::<T>::NoMoreChunks,
			);

			let mut value = value.min(ledger.active);

			if !value.is_zero() {
				ledger.active -= value;

				// Avoid there being a dust balance left in the staking system.
				if ledger.active < T::Currency::minimum_balance() {
					value += ledger.active;
					ledger.active = Zero::zero();
				}

				// Note: in case there is no current era it is fine to bond one era more.
				let era = Self::current_era().unwrap_or(0) + T::BondingDuration::get();
				ledger.unlocking.push(UnlockChunk { value, era });
				Self::update_ledger(&controller, &ledger);
				Self::deposit_event(RawEvent::Unbonded(ledger.stash, value));
			}
		}

		/// Remove any unlocked chunks from the `unlocking` queue from our management.
		///
		/// This essentially frees up that balance to be used by the stash account to do
		/// whatever it wants.
		///
		/// The dispatch origin for this call must be _Signed_ by the controller, not the stash.
		/// And, it can be only called when [`EraElectionStatus`] is `Closed`.
		///
		/// Emits `Withdrawn`.
		///
		/// See also [`Call::unbond`].
		///
		/// # <weight>
		/// - Could be dependent on the `origin` argument and how much `unlocking` chunks exist.
		///  It implies `consolidate_unlocked` which loops over `Ledger.unlocking`, which is
		///  indirectly user-controlled. See [`unbond`] for more detail.
		/// - Contains a limited number of reads, yet the size of which could be large based on `ledger`.
		/// - Writes are limited to the `origin` account key.
		/// ---------------
		/// Complexity O(S) where S is the number of slashing spans to remove
		/// Update:
		/// - Reads: EraElectionStatus, Ledger, Current Era, Locks, [Origin Account]
		/// - Writes: [Origin Account], Locks, Ledger
		/// Kill:
		/// - Reads: EraElectionStatus, Ledger, Current Era, Bonded, Slashing Spans, [Origin
		///   Account], Locks, BalanceOf stash
		/// - Writes: Bonded, Slashing Spans (if S > 0), Ledger, Payee, Validators, Nominators,
		///   [Origin Account], Locks, BalanceOf stash.
		/// - Writes Each: SpanSlash * S
		/// NOTE: Weight annotation is the kill scenario, we refund otherwise.
		/// # </weight>
		#[weight = T::WeightInfo::withdraw_unbonded_kill(*num_slashing_spans)]
		fn withdraw_unbonded(origin, num_slashing_spans: u32) -> DispatchResultWithPostInfo {
			let controller = ensure_signed(origin)?;
			let mut ledger = Self::ledger(&controller).ok_or(Error::<T>::NotController)?;
			let (stash, old_total) = (ledger.stash.clone(), ledger.total);
			if let Some(current_era) = Self::current_era() {
				ledger = ledger.consolidate_unlocked(current_era)
			}

			let post_info_weight = if ledger.unlocking.is_empty() && ledger.active < T::Currency::minimum_balance() {
				// This account must have called `unbond()` with some value that caused the active
				// portion to fall below existential deposit + will have no more unlocking chunks
				// left. We can now safely remove all staking-related information.
				Self::kill_stash(&stash, num_slashing_spans)?;
				// remove the lock.
				T::Currency::remove_lock(STAKING_ID, &stash);
				// This is worst case scenario, so we use the full weight and return None
				None
			} else {
				// This was the consequence of a partial unbond. just update the ledger and move on.
				Self::update_ledger(&controller, &ledger);

				// This is only an update, so we use less overall weight.
				Some(T::WeightInfo::withdraw_unbonded_update(num_slashing_spans))
			};

			// `old_total` should never be less than the new total because
			// `consolidate_unlocked` strictly subtracts balance.
			if ledger.total < old_total {
				// Already checked that this won't overflow by entry condition.
				let value = old_total - ledger.total;
				Self::deposit_event(RawEvent::Withdrawn(stash, value));
			}

			Ok(post_info_weight.into())
		}

		/// Declare the desire to validate for the origin controller.
		///
		/// Effects will be felt at the beginning of the next era.
		///
		/// The dispatch origin for this call must be _Signed_ by the controller, not the stash.
		/// And, it can be only called when [`EraElectionStatus`] is `Closed`.
		///
		/// # <weight>
		/// - Independent of the arguments. Insignificant complexity.
		/// - Contains a limited number of reads.
		/// - Writes are limited to the `origin` account key.
		/// -----------
		/// Weight: O(1)
		/// DB Weight:
		/// - Read: Era Election Status, Ledger
		/// - Write: Nominators, Validators
		/// # </weight>
		#[weight = T::WeightInfo::validate()]
		pub fn validate(origin, prefs: ValidatorPrefs) {
			let controller = ensure_signed(origin)?;
			let ledger = Self::ledger(&controller).ok_or(Error::<T>::NotController)?;
			let stash = &ledger.stash;
			<Nominators<T>>::remove(stash);
			<Validators<T>>::insert(stash, prefs);
		}

		/// Declare the desire to nominate `targets` for the origin controller.
		///
		/// Effects will be felt at the beginning of the next era. This can only be called when
		/// [`EraElectionStatus`] is `Closed`.
		///
		/// The dispatch origin for this call must be _Signed_ by the controller, not the stash.
		/// And, it can be only called when [`EraElectionStatus`] is `Closed`.
		///
		/// # <weight>
		/// - The transaction's complexity is proportional to the size of `targets` (N)
		/// which is capped at CompactAssignments::LIMIT (MAX_NOMINATIONS).
		/// - Both the reads and writes follow a similar pattern.
		/// ---------
		/// Weight: O(N)
		/// where N is the number of targets
		/// DB Weight:
		/// - Reads: Era Election Status, Ledger, Current Era
		/// - Writes: Validators, Nominators
		/// # </weight>
		#[weight = T::WeightInfo::nominate(targets.len() as u32)]
		pub fn nominate(origin, targets: Vec<<T::Lookup as StaticLookup>::Source>) {
			let controller = ensure_signed(origin)?;
			let ledger = Self::ledger(&controller).ok_or(Error::<T>::NotController)?;
			let stash = &ledger.stash;
			ensure!(!targets.is_empty(), Error::<T>::EmptyTargets);
			ensure!(targets.len() <= MAX_NOMINATIONS, Error::<T>::TooManyTargets);

			let old = Nominators::<T>::get(stash).map_or_else(Vec::new, |x| x.targets);

			let targets = targets.into_iter()
				.map(|t| T::Lookup::lookup(t).map_err(DispatchError::from))
				.map(|n| n.and_then(|n| if old.contains(&n) || !Validators::<T>::get(&n).blocked {
					Ok(n)
				} else {
					Err(Error::<T>::BadTarget.into())
				}))
				.collect::<result::Result<Vec<T::AccountId>, _>>()?;

			let nominations = Nominations {
				targets,
				// initial nominations are considered submitted at era 0. See `Nominations` doc
				submitted_in: Self::current_era().unwrap_or(0),
				suppressed: false,
			};

			<Validators<T>>::remove(stash);
			<Nominators<T>>::insert(stash, &nominations);
		}

		/// Declare no desire to either validate or nominate.
		///
		/// Effects will be felt at the beginning of the next era.
		///
		/// The dispatch origin for this call must be _Signed_ by the controller, not the stash.
		/// And, it can be only called when [`EraElectionStatus`] is `Closed`.
		///
		/// # <weight>
		/// - Independent of the arguments. Insignificant complexity.
		/// - Contains one read.
		/// - Writes are limited to the `origin` account key.
		/// --------
		/// Weight: O(1)
		/// DB Weight:
		/// - Read: EraElectionStatus, Ledger
		/// - Write: Validators, Nominators
		/// # </weight>
		#[weight = T::WeightInfo::chill()]
		fn chill(origin) {
			let controller = ensure_signed(origin)?;
			let ledger = Self::ledger(&controller).ok_or(Error::<T>::NotController)?;
			Self::chill_stash(&ledger.stash);
		}

		/// (Re-)set the payment target for a controller.
		///
		/// Effects will be felt at the beginning of the next era.
		///
		/// The dispatch origin for this call must be _Signed_ by the controller, not the stash.
		///
		/// # <weight>
		/// - Independent of the arguments. Insignificant complexity.
		/// - Contains a limited number of reads.
		/// - Writes are limited to the `origin` account key.
		/// ---------
		/// - Weight: O(1)
		/// - DB Weight:
		///     - Read: Ledger
		///     - Write: Payee
		/// # </weight>
		#[weight = T::WeightInfo::set_payee()]
		fn set_payee(origin, payee: RewardDestination<T::AccountId>) {
			let controller = ensure_signed(origin)?;
			let ledger = Self::ledger(&controller).ok_or(Error::<T>::NotController)?;
			let stash = &ledger.stash;
			<Payee<T>>::insert(stash, payee);
		}

		/// (Re-)set the controller of a stash.
		///
		/// Effects will be felt at the beginning of the next era.
		///
		/// The dispatch origin for this call must be _Signed_ by the stash, not the controller.
		///
		/// # <weight>
		/// - Independent of the arguments. Insignificant complexity.
		/// - Contains a limited number of reads.
		/// - Writes are limited to the `origin` account key.
		/// ----------
		/// Weight: O(1)
		/// DB Weight:
		/// - Read: Bonded, Ledger New Controller, Ledger Old Controller
		/// - Write: Bonded, Ledger New Controller, Ledger Old Controller
		/// # </weight>
		#[weight = T::WeightInfo::set_controller()]
		fn set_controller(origin, controller: <T::Lookup as StaticLookup>::Source) {
			let stash = ensure_signed(origin)?;
			let old_controller = Self::bonded(&stash).ok_or(Error::<T>::NotStash)?;
			let controller = T::Lookup::lookup(controller)?;
			if <Ledger<T>>::contains_key(&controller) {
				Err(Error::<T>::AlreadyPaired)?
			}
			if controller != old_controller {
				<Bonded<T>>::insert(&stash, &controller);
				if let Some(l) = <Ledger<T>>::take(&old_controller) {
					<Ledger<T>>::insert(&controller, l);
				}
			}
		}

		/// Sets the ideal number of validators.
		///
		/// The dispatch origin must be Root.
		///
		/// # <weight>
		/// Weight: O(1)
		/// Write: Validator Count
		/// # </weight>
		#[weight = T::WeightInfo::set_validator_count()]
		fn set_validator_count(origin, #[compact] new: u32) {
			ensure_root(origin)?;
			ValidatorCount::put(new);
		}

		/// Increments the ideal number of validators.
		///
		/// The dispatch origin must be Root.
		///
		/// # <weight>
		/// Same as [`set_validator_count`].
		/// # </weight>
		#[weight = T::WeightInfo::set_validator_count()]
		fn increase_validator_count(origin, #[compact] additional: u32) {
			ensure_root(origin)?;
			ValidatorCount::mutate(|n| *n += additional);
		}

		/// Scale up the ideal number of validators by a factor.
		///
		/// The dispatch origin must be Root.
		///
		/// # <weight>
		/// Same as [`set_validator_count`].
		/// # </weight>
		#[weight = T::WeightInfo::set_validator_count()]
		fn scale_validator_count(origin, factor: Percent) {
			ensure_root(origin)?;
			ValidatorCount::mutate(|n| *n += factor * *n);
		}

		/// Force there to be no new eras indefinitely.
		///
		/// The dispatch origin must be Root.
		///
		/// # <weight>
		/// - No arguments.
		/// - Weight: O(1)
		/// - Write: ForceEra
		/// # </weight>
		#[weight = T::WeightInfo::force_no_eras()]
		fn force_no_eras(origin) {
			ensure_root(origin)?;
			ForceEra::put(Forcing::ForceNone);
		}

		/// Force there to be a new era at the end of the next session. After this, it will be
		/// reset to normal (non-forced) behaviour.
		///
		/// The dispatch origin must be Root.
		///
		/// # <weight>
		/// - No arguments.
		/// - Weight: O(1)
		/// - Write ForceEra
		/// # </weight>
		#[weight = T::WeightInfo::force_new_era()]
		fn force_new_era(origin) {
			ensure_root(origin)?;
			ForceEra::put(Forcing::ForceNew);
		}

		/// Set the validators who cannot be slashed (if any).
		///
		/// The dispatch origin must be Root.
		///
		/// # <weight>
		/// - O(V)
		/// - Write: Invulnerables
		/// # </weight>
		#[weight = T::WeightInfo::set_invulnerables(invulnerables.len() as u32)]
		fn set_invulnerables(origin, invulnerables: Vec<T::AccountId>) {
			ensure_root(origin)?;
			<Invulnerables<T>>::put(invulnerables);
		}

		/// Force a current staker to become completely unstaked, immediately.
		///
		/// The dispatch origin must be Root.
		///
		/// # <weight>
		/// O(S) where S is the number of slashing spans to be removed
		/// Reads: Bonded, Slashing Spans, Account, Locks
		/// Writes: Bonded, Slashing Spans (if S > 0), Ledger, Payee, Validators, Nominators, Account, Locks
		/// Writes Each: SpanSlash * S
		/// # </weight>
		#[weight = T::WeightInfo::force_unstake(*num_slashing_spans)]
		fn force_unstake(origin, stash: T::AccountId, num_slashing_spans: u32) {
			ensure_root(origin)?;

			// remove all staking-related information.
			Self::kill_stash(&stash, num_slashing_spans)?;

			// remove the lock.
			T::Currency::remove_lock(STAKING_ID, &stash);
		}

		/// Force there to be a new era at the end of sessions indefinitely.
		///
		/// The dispatch origin must be Root.
		///
		/// # <weight>
		/// - Weight: O(1)
		/// - Write: ForceEra
		/// # </weight>
		#[weight = T::WeightInfo::force_new_era_always()]
		fn force_new_era_always(origin) {
			ensure_root(origin)?;
			ForceEra::put(Forcing::ForceAlways);
		}

		/// Cancel enactment of a deferred slash.
		///
		/// Can be called by the `T::SlashCancelOrigin`.
		///
		/// Parameters: era and indices of the slashes for that era to kill.
		///
		/// # <weight>
		/// Complexity: O(U + S)
		/// with U unapplied slashes weighted with U=1000
		/// and S is the number of slash indices to be canceled.
		/// - Read: Unapplied Slashes
		/// - Write: Unapplied Slashes
		/// # </weight>
		#[weight = T::WeightInfo::cancel_deferred_slash(slash_indices.len() as u32)]
		fn cancel_deferred_slash(origin, era: EraIndex, slash_indices: Vec<u32>) {
			T::SlashCancelOrigin::ensure_origin(origin)?;

			ensure!(!slash_indices.is_empty(), Error::<T>::EmptyTargets);
			ensure!(is_sorted_and_unique(&slash_indices), Error::<T>::NotSortedAndUnique);

			let mut unapplied = <Self as Store>::UnappliedSlashes::get(&era);
			let last_item = slash_indices[slash_indices.len() - 1];
			ensure!((last_item as usize) < unapplied.len(), Error::<T>::InvalidSlashIndex);

			for (removed, index) in slash_indices.into_iter().enumerate() {
				let index = (index as usize) - removed;
				unapplied.remove(index);
			}

			<Self as Store>::UnappliedSlashes::insert(&era, &unapplied);
		}

		/// Pay out all the stakers behind a single validator for a single era.
		///
		/// - `validator_stash` is the stash account of the validator. Their nominators, up to
		///   `T::MaxNominatorRewardedPerValidator`, will also receive their rewards.
		/// - `era` may be any era between `[current_era - history_depth; current_era]`.
		///
		/// The origin of this call must be _Signed_. Any account can call this function, even if
		/// it is not one of the stakers.
		///
		/// This can only be called when [`EraElectionStatus`] is `Closed`.
		///
		/// # <weight>
		/// - Time complexity: at most O(MaxNominatorRewardedPerValidator).
		/// - Contains a limited number of reads and writes.
		/// -----------
		/// N is the Number of payouts for the validator (including the validator)
		/// Weight:
		/// - Reward Destination Staked: O(N)
		/// - Reward Destination Controller (Creating): O(N)
		/// DB Weight:
		/// - Read: EraElectionStatus, CurrentEra, HistoryDepth, ErasValidatorReward,
		///         ErasStakersClipped, ErasRewardPoints, ErasValidatorPrefs (8 items)
		/// - Read Each: Bonded, Ledger, Payee, Locks, System Account (5 items)
		/// - Write Each: System Account, Locks, Ledger (3 items)
		///
		///   NOTE: weights are assuming that payouts are made to alive stash account (Staked).
		///   Paying even a dead controller is cheaper weight-wise. We don't do any refunds here.
		/// # </weight>
		#[weight = T::WeightInfo::payout_stakers_alive_staked(T::MaxNominatorRewardedPerValidator::get())]
		fn payout_stakers(origin, validator_stash: T::AccountId, era: EraIndex) -> DispatchResult {
			ensure_signed(origin)?;
			Self::do_payout_stakers(validator_stash, era)
		}

		/// Rebond a portion of the stash scheduled to be unlocked.
		///
		/// The dispatch origin must be signed by the controller, and it can be only called when
		/// [`EraElectionStatus`] is `Closed`.
		///
		/// # <weight>
		/// - Time complexity: O(L), where L is unlocking chunks
		/// - Bounded by `MAX_UNLOCKING_CHUNKS`.
		/// - Storage changes: Can't increase storage, only decrease it.
		/// ---------------
		/// - DB Weight:
		///     - Reads: EraElectionStatus, Ledger, Locks, [Origin Account]
		///     - Writes: [Origin Account], Locks, Ledger
		/// # </weight>
		#[weight = T::WeightInfo::rebond(MAX_UNLOCKING_CHUNKS as u32)]
		fn rebond(origin, #[compact] value: BalanceOf<T>) -> DispatchResultWithPostInfo {
			let controller = ensure_signed(origin)?;
			let ledger = Self::ledger(&controller).ok_or(Error::<T>::NotController)?;
			ensure!(!ledger.unlocking.is_empty(), Error::<T>::NoUnlockChunk);

			let ledger = ledger.rebond(value);
			// last check: the new active amount of ledger must be more than ED.
			ensure!(ledger.active >= T::Currency::minimum_balance(), Error::<T>::InsufficientValue);

			Self::update_ledger(&controller, &ledger);
			Ok(Some(
				35 * WEIGHT_PER_MICROS
				+ 50 * WEIGHT_PER_NANOS * (ledger.unlocking.len() as Weight)
				+ T::DbWeight::get().reads_writes(3, 2)
			).into())
		}

		/// Set `HistoryDepth` value. This function will delete any history information
		/// when `HistoryDepth` is reduced.
		///
		/// Parameters:
		/// - `new_history_depth`: The new history depth you would like to set.
		/// - `era_items_deleted`: The number of items that will be deleted by this dispatch.
		///    This should report all the storage items that will be deleted by clearing old
		///    era history. Needed to report an accurate weight for the dispatch. Trusted by
		///    `Root` to report an accurate number.
		///
		/// Origin must be root.
		///
		/// # <weight>
		/// - E: Number of history depths removed, i.e. 10 -> 7 = 3
		/// - Weight: O(E)
		/// - DB Weight:
		///     - Reads: Current Era, History Depth
		///     - Writes: History Depth
		///     - Clear Prefix Each: Era Stakers, EraStakersClipped, ErasValidatorPrefs
		///     - Writes Each: ErasValidatorReward, ErasRewardPoints, ErasTotalStake, ErasStartSessionIndex
		/// # </weight>
		#[weight = T::WeightInfo::set_history_depth(*_era_items_deleted)]
		fn set_history_depth(origin,
			#[compact] new_history_depth: EraIndex,
			#[compact] _era_items_deleted: u32,
		) {
			ensure_root(origin)?;
			if let Some(current_era) = Self::current_era() {
				HistoryDepth::mutate(|history_depth| {
					let last_kept = current_era.checked_sub(*history_depth).unwrap_or(0);
					let new_last_kept = current_era.checked_sub(new_history_depth).unwrap_or(0);
					for era_index in last_kept..new_last_kept {
						Self::clear_era_information(era_index);
					}
					*history_depth = new_history_depth
				})
			}
		}

		/// Remove all data structure concerning a staker/stash once its balance is at the minimum.
		/// This is essentially equivalent to `withdraw_unbonded` except it can be called by anyone
		/// and the target `stash` must have no funds left beyond the ED.
		///
		/// This can be called from any origin.
		///
		/// - `stash`: The stash account to reap. Its balance must be zero.
		///
		/// # <weight>
		/// Complexity: O(S) where S is the number of slashing spans on the account.
		/// DB Weight:
		/// - Reads: Stash Account, Bonded, Slashing Spans, Locks
		/// - Writes: Bonded, Slashing Spans (if S > 0), Ledger, Payee, Validators, Nominators, Stash Account, Locks
		/// - Writes Each: SpanSlash * S
		/// # </weight>
		#[weight = T::WeightInfo::reap_stash(*num_slashing_spans)]
		fn reap_stash(_origin, stash: T::AccountId, num_slashing_spans: u32) {
			let at_minimum = T::Currency::total_balance(&stash) == T::Currency::minimum_balance();
			ensure!(at_minimum, Error::<T>::FundedTarget);
			Self::kill_stash(&stash, num_slashing_spans)?;
			T::Currency::remove_lock(STAKING_ID, &stash);
		}

		/// Remove the given nominations from the calling validator.
		///
		/// Effects will be felt at the beginning of the next era.
		///
		/// The dispatch origin for this call must be _Signed_ by the controller, not the stash.
		/// And, it can be only called when [`EraElectionStatus`] is `Closed`. The controller
		/// account should represent a validator.
		///
		/// - `who`: A list of nominator stash accounts who are nominating this validator which
		///   should no longer be nominating this validator.
		///
		/// Note: Making this call only makes sense if you first set the validator preferences to
		/// block any further nominations.
		#[weight = T::WeightInfo::kick(who.len() as u32)]
		pub fn kick(origin, who: Vec<<T::Lookup as StaticLookup>::Source>) -> DispatchResult {
			let controller = ensure_signed(origin)?;
			let ledger = Self::ledger(&controller).ok_or(Error::<T>::NotController)?;
			let stash = &ledger.stash;

			for nom_stash in who.into_iter()
				.map(T::Lookup::lookup)
				.collect::<Result<Vec<T::AccountId>, _>>()?
				.into_iter()
			{
				Nominators::<T>::mutate(&nom_stash, |maybe_nom| if let Some(ref mut nom) = maybe_nom {
					if let Some(pos) = nom.targets.iter().position(|v| v == stash) {
						nom.targets.swap_remove(pos);
						Self::deposit_event(RawEvent::Kicked(nom_stash.clone(), stash.clone()));
					}
				});
			}

			Ok(())
		}
	}
}

impl<T: Config> Module<T> {
	/// The total balance that can be slashed from a stash account as of right now.
	pub fn slashable_balance_of(stash: &T::AccountId) -> BalanceOf<T> {
		// Weight note: consider making the stake accessible through stash.
		Self::bonded(stash).and_then(Self::ledger).map(|l| l.active).unwrap_or_default()
	}

	/// Internal impl of [`Self::slashable_balance_of`] that returns [`VoteWeight`].
	pub fn slashable_balance_of_vote_weight(
		stash: &T::AccountId,
		issuance: BalanceOf<T>,
	) -> VoteWeight {
		T::CurrencyToVote::to_vote(Self::slashable_balance_of(stash), issuance)
	}

	/// Returns a closure around `slashable_balance_of_vote_weight` that can be passed around.
	///
	/// This prevents call sites from repeatedly requesting `total_issuance` from backend. But it is
	/// important to be only used while the total issuance is not changing.
	pub fn slashable_balance_of_fn() -> Box<dyn Fn(&T::AccountId) -> VoteWeight> {
		// NOTE: changing this to unboxed `impl Fn(..)` return type and the module will still
		// compile, while some types in mock fail to resolve.
		let issuance = T::Currency::total_issuance();
		Box::new(move |who: &T::AccountId| -> VoteWeight {
			Self::slashable_balance_of_vote_weight(who, issuance)
		})
	}

	fn do_payout_stakers(validator_stash: T::AccountId, era: EraIndex) -> DispatchResult {