[Enhancement] Convert fast-unstake to use StakingInterface, decouplin…

frame/fast-unstake/src/lib.rs

@@ -109,7 +109,7 @@ pub mod pallet {
 	pub struct Pallet<T>(_);
 
 	#[pallet::config]
-	pub trait Config: frame_system::Config + pallet_staking::Config {
+	pub trait Config: frame_system::Config {
 		/// The overarching event type.
 		type RuntimeEvent: From<Event<Self>>
 			+ IsType<<Self as frame_system::Config>::RuntimeEvent>
@@ -125,6 +125,9 @@ pub mod pallet {
 		/// The origin that can control this pallet.
 		type ControlOrigin: frame_support::traits::EnsureOrigin<Self::RuntimeOrigin>;
 
+		/// The access to staking functionality.
+		type Staking: StakingInterface<Balance = BalanceOf<Self>, AccountId = Self::AccountId>;
+
 		/// The weight information of this pallet.
 		type WeightInfo: WeightInfo;
 	}

frame/staking/src/pallet/mod.rs

@@ -262,7 +262,7 @@ pub mod pallet {
 		type WeightInfo: WeightInfo;
 	}
 
-	/// The ideal number of staking participants.
+	/// The ideal number of active validators.
 	#[pallet::storage]
 	#[pallet::getter(fn validator_count)]
 	pub type ValidatorCount<T> = StorageValue<_, u32, ValueQuery>;

primitives/staking/src/lib.rs

@@ -135,6 +135,23 @@ pub trait StakingInterface {
 		num_slashing_spans: u32,
 	) -> Result<bool, DispatchError>;
 
+	/// Get `StakingLedger` by controller account.
+	fn get_ledger(ctrl: &Self::AccountId) -> StakingLedger<Self>;
+
+	/// The ideal number of active validators.
+	fn validator_count() -> u32;
+
+	/// Whether or not there is an ongoing election.
+	fn ongoing() -> bool;
+
+	/// Force a current staker to become completely unstaked, immediately.
+	fn force_unstake(stash: T::AccountId) -> DispatchResult;
+
+	/// Checks whether an account `staker` has been exposed in an era.
+	/// TODO: shall we have this helper here or just expose ErasStakers
+	/// storage instead for the caller to do as they please?
+	fn is_exposed_in_era(staker: &T::AccountId, era: &EraIndex) -> bool;
+
 	/// Get the nominations of a stash, if they are a nominator, `None` otherwise.
 	#[cfg(feature = "runtime-benchmarks")]
 	fn nominations(who: Self::AccountId) -> Option<sp_std::prelude::Vec<Self::AccountId>>;