mod.rs

// This file is part of Substrate.

// Copyright (C) 2017-2021 Parity Technologies (UK) Ltd.
// SPDX-License-Identifier: Apache-2.0

// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// 	http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

//! Staking FRAME Pallet.

use frame_election_provider_support::SortedListProvider;
use frame_support::{
	pallet_prelude::*,
	traits::{
		Currency, CurrencyToVote, EnsureOrigin, EstimateNextNewSession, Get, LockIdentifier,
		LockableCurrency, OnUnbalanced, UnixTime,
	},
	weights::Weight,
};
use frame_system::{ensure_root, ensure_signed, offchain::SendTransactionTypes, pallet_prelude::*};
use sp_runtime::{
	traits::{CheckedSub, SaturatedConversion, StaticLookup, Zero},
	DispatchError, Perbill, Percent,
};
use sp_staking::SessionIndex;
use sp_std::{convert::From, prelude::*, result};

mod impls;

pub use impls::*;

use crate::{
	log, migrations, slashing, weights::WeightInfo, ActiveEraInfo, BalanceOf, EraIndex, EraPayout,
	EraRewardPoints, Exposure, Forcing, NegativeImbalanceOf, Nominations, PositiveImbalanceOf,
	Releases, RewardDestination, SessionInterface, StakingLedger, UnappliedSlash, UnlockChunk,
	ValidatorPrefs,
};

pub const MAX_UNLOCKING_CHUNKS: usize = 32;
const STAKING_ID: LockIdentifier = *b"staking ";

#[frame_support::pallet]
pub mod pallet {
	use crate::BenchmarkingConfig;

	use super::*;

	#[pallet::pallet]
	#[pallet::generate_store(pub(crate) trait Store)]
	pub struct Pallet<T>(_);

	#[pallet::config]
	pub trait Config: frame_system::Config + SendTransactionTypes<Call<Self>> {
		/// The staking balance.
		type Currency: LockableCurrency<Self::AccountId, Moment = Self::BlockNumber>;

		/// Time used for computing era duration.
		///
		/// It is guaranteed to start being called from the first `on_finalize`. Thus value at
		/// genesis is not used.
		type UnixTime: UnixTime;

		/// Convert a balance into a number used for election calculation. This must fit into a
		/// `u64` but is allowed to be sensibly lossy. The `u64` is used to communicate with the
		/// [`frame_election_provider_support`] crate which accepts u64 numbers and does operations
		/// in 128.
		/// Consequently, the backward convert is used convert the u128s from sp-elections back to a
		/// [`BalanceOf`].
		type CurrencyToVote: CurrencyToVote<BalanceOf<Self>>;

		/// Something that provides the election functionality.
		type ElectionProvider: frame_election_provider_support::ElectionProvider<
			Self::AccountId,
			Self::BlockNumber,
			// we only accept an election provider that has staking as data provider.
			DataProvider = Pallet<Self>,
		>;

		/// Something that provides the election functionality at genesis.
		type GenesisElectionProvider: frame_election_provider_support::ElectionProvider<
			Self::AccountId,
			Self::BlockNumber,
			DataProvider = Pallet<Self>,
		>;

		/// Maximum number of nominations per nominator.
		const MAX_NOMINATIONS: u32;

		/// Tokens have been minted and are unused for validator-reward.
		/// See [Era payout](./index.html#era-payout).
		type RewardRemainder: OnUnbalanced<NegativeImbalanceOf<Self>>;

		/// The overarching event type.
		type Event: From<Event<Self>> + IsType<<Self as frame_system::Config>::Event>;

		/// Handler for the unbalanced reduction when slashing a staker.
		type Slash: OnUnbalanced<NegativeImbalanceOf<Self>>;

		/// Handler for the unbalanced increment when rewarding a staker.
		type Reward: OnUnbalanced<PositiveImbalanceOf<Self>>;

		/// Number of sessions per era.
		#[pallet::constant]
		type SessionsPerEra: Get<SessionIndex>;

		/// Number of eras that staked funds must remain bonded for.
		#[pallet::constant]
		type BondingDuration: Get<EraIndex>;

		/// 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.
		#[pallet::constant]
		type SlashDeferDuration: Get<EraIndex>;

		/// The origin which can cancel a deferred slash. Root can always do this.
		type SlashCancelOrigin: EnsureOrigin<Self::Origin>;

		/// Interface for interacting with a session pallet.
		type SessionInterface: SessionInterface<Self::AccountId>;

		/// The payout for validators and the system for the current era.
		/// See [Era payout](./index.html#era-payout).
		type EraPayout: EraPayout<BalanceOf<Self>>;

		/// Something that can estimate the next session change, accurately or as a best effort
		/// guess.
		type NextNewSession: EstimateNextNewSession<Self::BlockNumber>;

		/// 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.
		#[pallet::constant]
		type MaxNominatorRewardedPerValidator: Get<u32>;

		/// The fraction of the validator set that is safe to be offending.
		/// After the threshold is reached a new era will be forced.
		type OffendingValidatorsThreshold: Get<Perbill>;

		/// Something that can provide a sorted list of voters in a somewhat sorted way. The
		/// original use case for this was designed with `pallet_bags_list::Pallet` in mind. If
		/// the bags-list is not desired, [`impls::UseNominatorsMap`] is likely the desired option.
		type SortedListProvider: SortedListProvider<Self::AccountId>;

		/// Some parameters of the benchmarking.
		type BenchmarkingConfig: BenchmarkingConfig;

		/// Weight information for extrinsics in this pallet.
		type WeightInfo: WeightInfo;
	}

	#[pallet::extra_constants]
	impl<T: Config> Pallet<T> {
		// TODO: rename to snake case after https://github.com/paritytech/substrate/issues/8826 fixed.
		#[allow(non_snake_case)]
		fn MaxNominations() -> u32 {
			T::MAX_NOMINATIONS
		}
	}

	#[pallet::type_value]
	pub(crate) fn HistoryDepthOnEmpty() -> u32 {
		84u32
	}

	/// Number of eras to keep in history.
	///
	/// Information is kept for eras in `[current_era - history_depth; current_era]`.
	///
	/// Must be more than the number of eras delayed by session otherwise. I.e. active era must
	/// always be in history. I.e. `active_era > current_era - history_depth` must be
	/// guaranteed.
	#[pallet::storage]
	#[pallet::getter(fn history_depth)]
	pub(crate) type HistoryDepth<T> = StorageValue<_, u32, ValueQuery, HistoryDepthOnEmpty>;

	/// The ideal number of staking participants.
	#[pallet::storage]
	#[pallet::getter(fn validator_count)]
	pub type ValidatorCount<T> = StorageValue<_, u32, ValueQuery>;

	/// Minimum number of staking participants before emergency conditions are imposed.
	#[pallet::storage]
	#[pallet::getter(fn minimum_validator_count)]
	pub type MinimumValidatorCount<T> = StorageValue<_, u32, ValueQuery>;

	/// Any validators that may never be slashed or forcibly kicked. It's a Vec since they're
	/// easy to initialize and the performance hit is minimal (we expect no more than four
	/// invulnerables) and restricted to testnets.