lib.rs

		/// (Note: the field `total` and `own` of the exposure remains unchanged).
		/// This is used to limit the i/o cost for the nominator payout.
		///
		/// This is keyed fist by the era index to allow bulk deletion and then the stash account.
		///
		/// Is it removed after `HISTORY_DEPTH` eras.
		/// If stakers hasn't been set or has been removed then empty exposure is returned.
		pub ErasStakersClipped get(fn eras_stakers_clipped):
			double_map hasher(twox_64_concat) EraIndex, hasher(twox_64_concat) T::AccountId
			=> Exposure<T::AccountId, BalanceOf<T>>;

		/// Similar to `ErasStakers`, this holds the preferences of validators.
		///
		/// This is keyed first by the era index to allow bulk deletion and then the stash account.
		///
		/// Is it removed after `HISTORY_DEPTH` eras.
		// If prefs hasn't been set or has been removed then 0 commission is returned.
		pub ErasValidatorPrefs get(fn eras_validator_prefs):
			double_map hasher(twox_64_concat) EraIndex, hasher(twox_64_concat) T::AccountId
			=> ValidatorPrefs;

		/// The total validator era payout for the last `HISTORY_DEPTH` eras.
		///
		/// Eras that haven't finished yet or has been removed doesn't have reward.
		pub ErasValidatorReward get(fn eras_validator_reward):
			map hasher(twox_64_concat) EraIndex => Option<BalanceOf<T>>;

		/// Rewards for the last `HISTORY_DEPTH` eras.
		/// If reward hasn't been set or has been removed then 0 reward is returned.
		pub ErasRewardPoints get(fn eras_reward_points):
			map hasher(twox_64_concat) EraIndex => EraRewardPoints<T::AccountId>;

		/// The total amount staked for the last `HISTORY_DEPTH` eras.
		/// If total hasn't been set or has been removed then 0 stake is returned.
		pub ErasTotalStake get(fn eras_total_stake):
			map hasher(twox_64_concat) EraIndex => BalanceOf<T>;

		/// Mode of era forcing.
		pub ForceEra get(fn force_era) config(): Forcing;

		/// The percentage of the slash that is distributed to reporters.
		///
		/// The rest of the slashed value is handled by the `Slash`.
		pub SlashRewardFraction get(fn slash_reward_fraction) config(): Perbill;

		/// The amount of currency given to reporters of a slash event which was
		/// canceled by extraordinary circumstances (e.g. governance).
		pub CanceledSlashPayout get(fn canceled_payout) config(): BalanceOf<T>;

		/// All unapplied slashes that are queued for later.
		pub UnappliedSlashes:
			map hasher(twox_64_concat) EraIndex => Vec<UnappliedSlash<T::AccountId, BalanceOf<T>>>;

		/// A mapping from still-bonded eras to the first session index of that era.
		///
		/// Must contains information for eras for the range:
		/// `[active_era - bounding_duration; active_era]`
		BondedEras: Vec<(EraIndex, SessionIndex)>;

		/// All slashing events on validators, mapped by era to the highest slash proportion
		/// and slash value of the era.
		ValidatorSlashInEra:
			double_map hasher(twox_64_concat) EraIndex, hasher(twox_64_concat) T::AccountId
			=> Option<(Perbill, BalanceOf<T>)>;

		/// All slashing events on nominators, mapped by era to the highest slash value of the era.
		NominatorSlashInEra:
			double_map hasher(twox_64_concat) EraIndex, hasher(twox_64_concat) T::AccountId
			=> Option<BalanceOf<T>>;

		/// 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;

		/// Snapshot of validators at the beginning of the current election window. This should only
		/// have a value when [`EraElectionStatus`] == `ElectionStatus::Open(_)`.
		///
		/// TWO_PHASE_NOTE: should be removed once we switch to multi-phase.
		pub SnapshotValidators get(fn snapshot_validators): Option<Vec<T::AccountId>>;

		/// Snapshot of nominators at the beginning of the current election window. This should only
		/// have a value when [`EraElectionStatus`] == `ElectionStatus::Open(_)`.
		///
		/// TWO_PHASE_NOTE: should be removed once we switch to multi-phase.
		pub SnapshotNominators get(fn snapshot_nominators): Option<Vec<T::AccountId>>;

		/// The next validator set. At the end of an era, if this is available (potentially from the
		/// result of an offchain worker), it is immediately used. Otherwise, the on-chain election
		/// is executed.
		///
		/// TWO_PHASE_NOTE: should be removed once we switch to multi-phase.
		pub QueuedElected get(fn queued_elected): Option<ElectionResult<T::AccountId, BalanceOf<T>>>;

		/// The score of the current [`QueuedElected`].
		///
		/// TWO_PHASE_NOTE: should be removed once we switch to multi-phase.
		pub QueuedScore get(fn queued_score): Option<ElectionScore>;

		/// Flag to control the execution of the offchain election. When `Open(_)`, we accept
		/// solutions to be submitted.
		///
		/// TWO_PHASE_NOTE: should be removed once we switch to multi-phase.
		pub EraElectionStatus get(fn era_election_status): ElectionStatus<T::BlockNumber>;

		/// True if the current **planned** session is final. Note that this does not take era
		/// forcing into account.
		///
		/// TWO_PHASE_NOTE: should be removed once we switch to multi-phase.
		pub IsCurrentSessionFinal get(fn is_current_session_final): bool = false;

		/// True if network has been upgraded to this version.
		/// Storage version of the pallet.
		///
		/// This is set to v5.0.0 for new networks.
		StorageVersion build(|_: &GenesisConfig<T>| Releases::V5_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::*;

	#[derive(Decode)]
	struct OldValidatorPrefs {
		#[codec(compact)]
		pub commission: Perbill
	}
	impl OldValidatorPrefs {
		fn upgraded(self) -> ValidatorPrefs {
			ValidatorPrefs {
				commission: self.commission,
				.. Default::default()
			}
		}
	}
	pub fn migrate_to_blockable<T: Config>() -> frame_support::weights::Weight {
		Validators::<T>::translate::<OldValidatorPrefs, _>(|_, p| Some(p.upgraded()));
		ErasValidatorPrefs::<T>::translate::<OldValidatorPrefs, _>(|_, _, p| Some(p.upgraded()));
		T::BlockWeights::get().max_block
	}
}

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 with the given \[compute\].
		StakingElection(ElectionCompute),
		/// A new solution for the upcoming election has been stored. \[compute\]
		SolutionStored(ElectionCompute),
		/// 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,
		/// The submitted result is received out of the open window.
		OffchainElectionEarlySubmission,
		/// The submitted result is not as good as the one stored on chain.
		OffchainElectionWeakSubmission,
		/// The snapshot data of the current window is missing.
		SnapshotUnavailable,
		/// Incorrect number of winners were presented.
		OffchainElectionBogusWinnerCount,
		/// One of the submitted winners is not an active candidate on chain (index is out of range
		/// in snapshot).
		OffchainElectionBogusWinner,
		/// Error while building the assignment type from the compact. This can happen if an index
		/// is invalid, or if the weights _overflow_.
		OffchainElectionBogusCompact,
		/// One of the submitted nominators is not an active nominator on chain.
		OffchainElectionBogusNominator,
		/// One of the submitted nominators has an edge to which they have not voted on chain.
		OffchainElectionBogusNomination,
		/// One of the submitted nominators has an edge which is submitted before the last non-zero
		/// slash of the target.
		OffchainElectionSlashedNomination,
		/// A self vote must only be originated from a validator to ONLY themselves.
		OffchainElectionBogusSelfVote,
		/// The submitted result has unknown edges that are not among the presented winners.
		OffchainElectionBogusEdge,
		/// The claimed score does not match with the one computed from the data.
		OffchainElectionBogusScore,
		/// The election size is invalid.
		OffchainElectionBogusElectionSize,
		/// The call is not allowed at the given time due to restrictions of election period.
		CallNotAllowed,
		/// 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 number of blocks before the end of the era from which election submissions are allowed.
		///
		/// Setting this to zero will disable the offchain compute and only on-chain seq-phragmen will
		/// be used.
		///
		/// This is bounded by being within the last session. Hence, setting it to a value more than the
		/// length of a session will be pointless.
		const ElectionLookahead: T::BlockNumber = T::ElectionLookahead::get();

		/// Maximum number of balancing iterations to run in the offchain submission.
		///
		/// If set to 0, balance_solution will not be executed at all.
		const MaxIterations: u32 = T::MaxIterations::get();

		/// The threshold of improvement that should be provided for a new solution to be accepted.
		const MinSolutionScoreBump: Perbill = T::MinSolutionScoreBump::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() -> frame_support::weights::Weight {
			if StorageVersion::get() == Releases::V4_0_0 {
				StorageVersion::put(Releases::V5_0_0);
				migrations::migrate_to_blockable::<T>()
			} else {
				0
			}
		}

		/// sets `ElectionStatus` to `Open(now)` where `now` is the block number at which the
		/// election window has opened, if we are at the last session and less blocks than
		/// `T::ElectionLookahead` is remaining until the next new session schedule. The offchain
		/// worker, if applicable, will execute at the end of the current block, and solutions may
		/// be submitted.
		fn on_initialize(now: T::BlockNumber) -> Weight {
			let mut consumed_weight = 0;
			let mut add_weight = |reads, writes, weight| {
				consumed_weight += T::DbWeight::get().reads_writes(reads, writes);
				consumed_weight += weight;
			};

			if
				// if we don't have any ongoing offchain compute.
				Self::era_election_status().is_closed() &&
				// either current session final based on the plan, or we're forcing.
				(Self::is_current_session_final() || Self::will_era_be_forced())
			{
				if let Some(next_session_change) = T::NextNewSession::estimate_next_new_session(now) {
					if let Some(remaining) = next_session_change.checked_sub(&now) {
						if remaining <= T::ElectionLookahead::get() && !remaining.is_zero() {
							// create snapshot.
							let (did_snapshot, snapshot_weight) = Self::create_stakers_snapshot();
							add_weight(0, 0, snapshot_weight);
							if did_snapshot {
								// Set the flag to make sure we don't waste any compute here in the same era
								// after we have triggered the offline compute.
								<EraElectionStatus<T>>::put(
									ElectionStatus::<T::BlockNumber>::Open(now)
								);
								add_weight(0, 1, 0);
								log!(info, "Election window is Open({:?}). Snapshot created", now);
							} else {
								log!(warn, "Failed to create snapshot at {:?}.", now);
							}
						}
					}
				} else {
					log!(warn, "Estimating next session change failed.");
				}
				add_weight(0, 0, T::NextNewSession::weight(now))
			}
			// For `era_election_status`, `is_current_session_final`, `will_era_be_forced`
			add_weight(3, 0, 0);
			// Additional read from `on_finalize`
			add_weight(1, 0, 0);
			consumed_weight
		}

		/// Check if the current block number is the one at which the election window has been set
		/// to open. If so, it runs the offchain worker code.
		fn offchain_worker(now: T::BlockNumber) {
			use offchain_election::{set_check_offchain_execution_status, compute_offchain_election};
			if Self::era_election_status().is_open_at(now) {
				let offchain_status = set_check_offchain_execution_status::<T>(now);
				if let Err(why) = offchain_status {
					log!(warn, "skipping offchain worker in open election window due to [{}]", why);
				} else {
					if let Err(e) = compute_offchain_election::<T>() {
						log!(error, "Error in election offchain worker: {:?}", e);
					} else {
						log!(debug, "Executed offchain worker thread without errors.");
					}
				}
			}
		}

		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;
			// see the documentation of `Assignment::try_normalize`. Now we can ensure that this
			// will always return `Ok`.
			// 1. Maximum sum of Vec<ChainAccuracy> must fit into `UpperOf<ChainAccuracy>`.
			assert!(
				<usize as TryInto<UpperOf<ChainAccuracy>>>::try_into(MAX_NOMINATIONS)
				.unwrap()
				.checked_mul(<ChainAccuracy>::one().deconstruct().try_into().unwrap())
				.is_some()
			);

			// 2. 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::Module::<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>) {
			ensure!(Self::era_election_status().is_closed(), Error::<T>::CallNotAllowed);
			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>) {
			ensure!(Self::era_election_status().is_closed(), Error::<T>::CallNotAllowed);
			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 {
			ensure!(Self::era_election_status().is_closed(), Error::<T>::CallNotAllowed);
			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) {
			ensure!(Self::era_election_status().is_closed(), Error::<T>::CallNotAllowed);
			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>) {
			ensure!(Self::era_election_status().is_closed(), Error::<T>::CallNotAllowed);
			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) {
			ensure!(Self::era_election_status().is_closed(), Error::<T>::CallNotAllowed);
			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);