remove OnStakerSlash replace with OnStakingEvents (#14527)

* remove 'OnStakerSlash', replace with 'OnStakingEvents'

* fix other features in pallets

* small fixes

* fix docs

* fix docs

* fix docs

* Update primitives/staking/src/lib.rs

Co-authored-by: Gonçalo Pestana <g6pestana@gmail.com>

---------

Co-authored-by: Gonçalo Pestana <g6pestana@gmail.com>

substrate/primitives/staking/src/lib.rs

@@ -20,13 +20,17 @@
 //! A crate which contains primitives that are useful for implementation that uses staking
 //! approaches in general. Definitions related to sessions, slashing, etc go here.
 
+use crate::currency_to_vote::CurrencyToVote;
+use codec::{FullCodec, MaxEncodedLen};
 use scale_info::TypeInfo;
 use sp_core::RuntimeDebug;
-use sp_runtime::{DispatchError, DispatchResult};
-use sp_std::{collections::btree_map::BTreeMap, vec::Vec};
+use sp_runtime::{DispatchError, DispatchResult, Saturating};
+use sp_std::{collections::btree_map::BTreeMap, ops::Sub, vec::Vec};
 
 pub mod offence;
 
+pub mod currency_to_vote;
+
 /// Simple index type with which we can count sessions.
 pub type SessionIndex = u32;
 
@@ -45,32 +49,9 @@ pub enum StakerStatus<AccountId> {
 	Nominator(Vec<AccountId>),
 }
 
-/// Trait describing something that implements a hook for any operations to perform when a staker is
-/// slashed.
-pub trait OnStakerSlash<AccountId, Balance> {
-	/// A hook for any operations to perform when a staker is slashed.
-	///
-	/// # Arguments
-	///
-	/// * `stash` - The stash of the staker whom the slash was applied to.
-	/// * `slashed_active` - The new bonded balance of the staker after the slash was applied.
-	/// * `slashed_unlocking` - A map of slashed eras, and the balance of that unlocking chunk after
-	///   the slash is applied. Any era not present in the map is not affected at all.
-	fn on_slash(
-		stash: &AccountId,
-		slashed_active: Balance,
-		slashed_unlocking: &BTreeMap<EraIndex, Balance>,
-	);
-}
-
-impl<AccountId, Balance> OnStakerSlash<AccountId, Balance> for () {
-	fn on_slash(_: &AccountId, _: Balance, _: &BTreeMap<EraIndex, Balance>) {
-		// Nothing to do here
-	}
-}
-
 /// A struct that reflects stake that an account has in the staking system. Provides a set of
 /// methods to operate on it's properties. Aimed at making `StakingInterface` more concise.
+#[derive(RuntimeDebug, Clone, Copy, Eq, PartialEq, Default)]
 pub struct Stake<Balance> {
 	/// The total stake that `stash` has in the staking system. This includes the
 	/// `active` stake, and any funds currently in the process of unbonding via
@@ -87,16 +68,88 @@ pub struct Stake<Balance> {
 	pub active: Balance,
 }
 
+/// A generic staking event listener.
+///
+/// Note that the interface is designed in a way that the events are fired post-action, so any
+/// pre-action data that is needed needs to be passed to interface methods. The rest of the data can
+/// be retrieved by using `StakingInterface`.
+#[impl_trait_for_tuples::impl_for_tuples(10)]
+pub trait OnStakingUpdate<AccountId, Balance> {
+	/// Fired when the stake amount of someone updates.
+	///
+	/// This is effectively any changes to the bond amount, such as bonding more funds, and
+	/// unbonding.
+	fn on_stake_update(_who: &AccountId, _prev_stake: Option<Stake<Balance>>) {}
+
+	/// Fired when someone sets their intention to nominate.
+	///
+	/// This should never be fired for existing nominators.
+	fn on_nominator_add(_who: &AccountId) {}
+
+	/// Fired when an existing nominator updates their nominations.
+	///
+	/// Note that this is not fired when a nominator changes their stake. For that,
+	/// `on_stake_update` should be used, followed by querying whether `who` was a validator or a
+	/// nominator.
+	fn on_nominator_update(_who: &AccountId, _prev_nominations: Vec<AccountId>) {}
+
+	/// Fired when someone removes their intention to nominate, either due to chill or validating.
+	///
+	/// The set of nominations at the time of removal is provided as it can no longer be fetched in
+	/// any way.
+	fn on_nominator_remove(_who: &AccountId, _nominations: Vec<AccountId>) {}
+
+	/// Fired when someone sets their intention to validate.
+	///
+	/// Note validator preference changes are not communicated, but could be added if needed.
+	fn on_validator_add(_who: &AccountId) {}
+
+	/// Fired when an existing validator updates their preferences.
+	///
+	/// Note validator preference changes are not communicated, but could be added if needed.
+	fn on_validator_update(_who: &AccountId) {}
+
+	/// Fired when someone removes their intention to validate, either due to chill or nominating.
+	fn on_validator_remove(_who: &AccountId) {}
+
+	/// Fired when someone is fully unstaked.
+	fn on_unstake(_who: &AccountId) {}
+
+	/// Fired when a staker is slashed.
+	///
+	/// * `stash` - The stash of the staker whom the slash was applied to.
+	/// * `slashed_active` - The new bonded balance of the staker after the slash was applied.
+	/// * `slashed_unlocking` - A map of slashed eras, and the balance of that unlocking chunk after
+	///   the slash is applied. Any era not present in the map is not affected at all.
+	fn on_slash(
+		_stash: &AccountId,
+		_slashed_active: Balance,
+		_slashed_unlocking: &BTreeMap<EraIndex, Balance>,
+	) {
+	}
+}
+
 /// A generic representation of a staking implementation.
 ///
 /// This interface uses the terminology of NPoS, but it is aims to be generic enough to cover other
 /// implementations as well.
 pub trait StakingInterface {
 	/// Balance type used by the staking system.
-	type Balance: PartialEq;
+	type Balance: Sub<Output = Self::Balance>
+		+ Ord
+		+ PartialEq
+		+ Default
+		+ Copy
+		+ MaxEncodedLen
+		+ FullCodec
+		+ TypeInfo
+		+ Saturating;
 
-	/// AccountId type used by the staking system
-	type AccountId;
+	/// AccountId type used by the staking system.
+	type AccountId: Clone + sp_std::fmt::Debug;
+
+	/// Means of converting Currency to VoteWeight.
+	type CurrencyToVote: CurrencyToVote<Self::Balance>;
 
 	/// The minimum amount required to bond in order to set nomination intentions. This does not
 	/// necessarily mean the nomination will be counted in an election, but instead just enough to
@@ -195,8 +248,12 @@ pub trait StakingInterface {
 	/// Return the status of the given staker, `None` if not staked at all.
 	fn status(who: &Self::AccountId) -> Result<StakerStatus<Self::AccountId>, DispatchError>;
 
+	/// Checks whether or not this is a validator account.
+	fn is_validator(who: &Self::AccountId) -> bool {
+		Self::status(who).map(|s| matches!(s, StakerStatus::Validator)).unwrap_or(false)
+	}
+
 	/// Get the nominations of a stash, if they are a nominator, `None` otherwise.
-	#[cfg(feature = "runtime-benchmarks")]
 	fn nominations(who: &Self::AccountId) -> Option<Vec<Self::AccountId>> {
 		match Self::status(who) {
 			Ok(StakerStatus::Nominator(t)) => Some(t),