impls.rs

// This file is part of Substrate.

// Copyright (C) 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.

//! Implementations for the Staking FRAME Pallet.

use frame_election_provider_support::{
	bounds::{CountBound, SizeBound},
	data_provider, BoundedSupportsOf, DataProviderBounds, ElectionDataProvider, ElectionProvider,
	ScoreProvider, SortedListProvider, VoteWeight, VoterOf,
};
use frame_support::{
	defensive,
	dispatch::WithPostDispatchInfo,
	pallet_prelude::*,
	traits::{
		Currency, Defensive, DefensiveSaturating, EstimateNextNewSession, Get, Imbalance,
		InspectLockableCurrency, Len, LockableCurrency, OnUnbalanced, TryCollect, UnixTime,
	},
	weights::Weight,
};
use frame_system::{pallet_prelude::BlockNumberFor, RawOrigin};
use pallet_session::historical;
use sp_runtime::{
	traits::{
		Bounded, CheckedAdd, CheckedSub, Convert, One, SaturatedConversion, Saturating,
		StaticLookup, Zero,
	},
	ArithmeticError, Perbill, Percent,
};
use sp_staking::{
	currency_to_vote::CurrencyToVote,
	offence::{OffenceDetails, OnOffenceHandler},
	EraIndex, OnStakingUpdate, Page, SessionIndex, Stake,
	StakingAccount::{self, Controller, Stash},
	StakingInterface,
};
use sp_std::prelude::*;

use crate::{
	election_size_tracker::StaticTracker, log, slashing, weights::WeightInfo, ActiveEraInfo,
	BalanceOf, EraInfo, EraPayout, Exposure, ExposureOf, Forcing, IndividualExposure,
	LedgerIntegrityState, MaxNominationsOf, MaxWinnersOf, Nominations, NominationsQuota,
	PositiveImbalanceOf, RewardDestination, SessionInterface, StakingLedger, ValidatorPrefs,
};

use super::pallet::*;

#[cfg(feature = "try-runtime")]
use frame_support::ensure;
#[cfg(any(test, feature = "try-runtime"))]
use sp_runtime::TryRuntimeError;

/// The maximum number of iterations that we do whilst iterating over `T::VoterList` in
/// `get_npos_voters`.
///
/// In most cases, if we want n items, we iterate exactly n times. In rare cases, if a voter is
/// invalid (for any reason) the iteration continues. With this constant, we iterate at most 2 * n
/// times and then give up.
const NPOS_MAX_ITERATIONS_COEFFICIENT: u32 = 2;

impl<T: Config> Pallet<T> {
	/// Fetches the ledger associated with a controller or stash account, if any.
	pub fn ledger(account: StakingAccount<T::AccountId>) -> Result<StakingLedger<T>, Error<T>> {
		StakingLedger::<T>::get(account)
	}

	pub fn payee(account: StakingAccount<T::AccountId>) -> Option<RewardDestination<T::AccountId>> {
		StakingLedger::<T>::reward_destination(account)
	}

	/// Fetches the controller bonded to a stash account, if any.
	pub fn bonded(stash: &T::AccountId) -> Option<T::AccountId> {
		StakingLedger::<T>::paired_account(Stash(stash.clone()))
	}

	/// Inspects and returns the corruption state of a ledger and bond, if any.
	///
	/// Note: all operations in this method access directly the `Bonded` and `Ledger` storage maps
	/// instead of using the [`StakingLedger`] API since the bond and/or ledger may be corrupted.
	pub(crate) fn inspect_bond_state(
		stash: &T::AccountId,
	) -> Result<LedgerIntegrityState, Error<T>> {
		let lock = T::Currency::balance_locked(crate::STAKING_ID, &stash);

		let controller = <Bonded<T>>::get(stash).ok_or_else(|| {
			if lock == Zero::zero() {
				Error::<T>::NotStash
			} else {
				Error::<T>::BadState
			}
		})?;

		match Ledger::<T>::get(controller) {
			Some(ledger) =>
				if ledger.stash != *stash {
					Ok(LedgerIntegrityState::Corrupted)
				} else {
					if lock != ledger.total {
						Ok(LedgerIntegrityState::LockCorrupted)
					} else {
						Ok(LedgerIntegrityState::Ok)
					}
				},
			None => Ok(LedgerIntegrityState::CorruptedKilled),
		}
	}

	/// 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::ledger(Stash(stash.clone())).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 weight_of_fn() -> Box<dyn Fn(&T::AccountId) -> VoteWeight> {
		// NOTE: changing this to unboxed `impl Fn(..)` return type and the pallet 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)
		})
	}

	/// Same as `weight_of_fn`, but made for one time use.
	pub fn weight_of(who: &T::AccountId) -> VoteWeight {
		let issuance = T::Currency::total_issuance();
		Self::slashable_balance_of_vote_weight(who, issuance)
	}

	pub(super) fn do_bond_extra(stash: &T::AccountId, additional: BalanceOf<T>) -> DispatchResult {
		let mut ledger = Self::ledger(StakingAccount::Stash(stash.clone()))?;

		// for virtual stakers, we don't need to check the balance. Since they are only accessed
		// via low level apis, we can assume that the caller has done the due diligence.
		let extra = if Self::is_virtual_staker(stash) {
			additional
		} else {
			// additional amount or actual balance of stash whichever is lower.
			additional.min(
				T::Currency::free_balance(stash)
					.checked_sub(&ledger.total)
					.ok_or(ArithmeticError::Overflow)?,
			)
		};

		ledger.total = ledger.total.checked_add(&extra).ok_or(ArithmeticError::Overflow)?;
		ledger.active = ledger.active.checked_add(&extra).ok_or(ArithmeticError::Overflow)?;
		// last check: the new active amount of ledger must be more than ED.
		ensure!(ledger.active >= T::Currency::minimum_balance(), Error::<T>::InsufficientBond);

		// NOTE: ledger must be updated prior to calling `Self::weight_of`.
		ledger.update()?;
		// update this staker in the sorted list, if they exist in it.
		if T::VoterList::contains(stash) {
			let _ = T::VoterList::on_update(&stash, Self::weight_of(stash)).defensive();
		}

		Self::deposit_event(Event::<T>::Bonded { stash: stash.clone(), amount: extra });

		Ok(())
	}

	pub(super) fn do_withdraw_unbonded(
		controller: &T::AccountId,
		num_slashing_spans: u32,
	) -> Result<Weight, DispatchError> {
		let mut ledger = Self::ledger(Controller(controller.clone()))?;
		let (stash, old_total) = (ledger.stash.clone(), ledger.total);
		if let Some(current_era) = Self::current_era() {
			ledger = ledger.consolidate_unlocked(current_era)
		}
		let new_total = ledger.total;

		let used_weight =
			if ledger.unlocking.is_empty() && ledger.active < T::Currency::minimum_balance() {