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// 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.
//! # Delegated Staking Pallet
//!
//! This pallet implements [`sp_staking::DelegationInterface`] that provides delegation
//! functionality to `delegators` and `agents`. It is designed to be used in conjunction with
//! [`StakingInterface`] and relies on [`Config::CoreStaking`] to provide primitive staking
//! functions.
//!
//! Currently, it does not expose any dispatchable calls but is written with a vision to expose them
//! in the future such that it can be utilised by any external account, off-chain entity or xcm
//! `MultiLocation` such as a parachain or a smart contract.
//!
//! ## Key Terminologies
//! - **Agent**: An account who accepts delegations from other accounts and act as an agent on their
//! behalf for staking these delegated funds. Also, sometimes referred as `Delegatee`.
//! - **Delegator**: An account who delegates their funds to an `agent` and authorises them to use
//! it for staking.
//! - **AgentLedger**: A data structure that holds important information about the `agent` such as
//! total delegations they have received, any slashes posted to them, etc.
//! - **Delegation**: A data structure that stores the amount of funds delegated to an `agent` by a
//! `delegator`.
//!
//! ## Goals
//!
//! Direct nomination on the Staking pallet does not scale well. Nominations pools were created to
//! address this by pooling delegator funds into one account and then staking it. This though had
//! a very critical limitation that the funds were moved from delegator account to pool account
//! and hence the delegator lost control over their funds for using it for other purposes such as
//! governance. This pallet aims to solve this by extending the staking pallet to support a new
//! primitive function: delegation of funds to an `agent` with the intent of staking. The agent can
//! then stake the delegated funds to [`Config::CoreStaking`] on behalf of the delegators.
//!
//! ### Withdrawal Management
//! Agent unbonding does not regulate ordering of consequent withdrawal for delegators. This is upto
//! the consumer of this pallet to implement in what order unbondable funds from
//! [`Config::CoreStaking`] can be withdrawn by the delegators.
//!
//! ### Reward and Slashing
//! This pallet does not enforce any specific strategy for how rewards or slashes are applied. It
//! is upto the `agent` account to decide how to apply the rewards and slashes.
//!
//! This importantly allows clients of this pallet to build their own strategies for reward/slashes.
//! For example, an `agent` account can choose to first slash the reward pot before slashing the
//! delegators. Or part of the reward can go to an insurance fund that can be used to cover any
//! potential future slashes. The goal is to eventually allow foreign MultiLocations
//! (smart contracts or pallets on another chain) to build their own pooled staking solutions
//! similar to `NominationPools`.
//! ## Core functions
//!
//! - Allow an account to receive delegations. See [`Pallet::register_agent`].
//! - Delegate funds to an `agent` account. See [`Pallet::delegate_to_agent`].
//! - Release delegated funds from an `agent` account to the `delegator`. See
//! [`Pallet::release_delegation`].
//! - Migrate a `Nominator` account to an `agent` account. See [`Pallet::migrate_to_agent`].
//! Explained in more detail in the `Migration` section.
//! - Migrate unclaimed delegated funds from `agent` to delegator. When a nominator migrates to an
//! agent, the funds are held in a proxy account. This function allows the delegator to claim
//! their share of the funds from the proxy account. See [`Pallet::migrate_delegation`].
//!
//! ## Lazy Slashing
//! One of the reasons why direct nominators on staking pallet cannot scale well is because all
//! nominators are slashed at the same time. This is expensive and needs to be bounded operation.
//!
//! This pallet implements a lazy slashing mechanism. Any slashes to the `agent` are posted in its
//! `AgentLedger` as a pending slash. Since the actual amount is held in the multiple
//! `delegator` accounts, this pallet has no way to know how to apply slash. It is the `agent`'s
//! responsibility to apply slashes for each delegator, one at a time. Staking pallet ensures the
//! pending slash never exceeds staked amount and would freeze further withdraws until all pending
//! slashes are cleared.
//!
//! The user of this pallet can apply slash using
//! [DelegationInterface::delegator_slash](sp_staking::DelegationInterface::delegator_slash).
//!
//! ## Migration from Nominator to Agent
//! More details [here](https://hackmd.io/@ak0n/454-np-governance).
//!
//! ## Nomination Pool vs Delegation Staking
//! This pallet is not a replacement for Nomination Pool but adds a new primitive in addition to
//! staking pallet that can be used by Nomination Pool to support delegation based staking. It can
//! be thought of as an extension to the Staking Pallet in relation to Nomination Pools.
//! Technically, these changes could be made in one of those pallets as well but that would have
//! meant significant refactoring and high chances of introducing a regression. With this approach,
//! we can keep the existing pallets with minimal changes and introduce a new pallet that can be
//! optionally used by Nomination Pool. The vision is to build this in a configurable way such that
//! runtime can choose whether to use this pallet or not.
//!
//! With that said, following is the main difference between
//! #### Nomination Pool without delegation support
//! 1) transfer fund from delegator to pool account, and
//! 2) stake from pool account as a direct nominator.
//!
//! #### Nomination Pool with delegation support
//! 1) delegate fund from delegator to pool account, and
//! 2) stake from pool account as an `Agent` account on the staking pallet.
//!
//! The difference being, in the second approach, the delegated funds will be locked in-place in
//! user's account enabling them to participate in use cases that allows use of `held` funds such
//! as participation in governance voting.
//!
//! Nomination pool still does all the heavy lifting around pool administration, reward
//! distribution, lazy slashing and as such, is not meant to be replaced with this pallet.
//!
//! ## Limitations
//! - Rewards can not be auto-compounded.
//! - Slashes are lazy and hence there could be a period of time when an account can use funds for
//! operations such as voting in governance even though they should be slashed.
#![cfg_attr(not(feature = "std"), no_std)]
#![deny(rustdoc::broken_intra_doc_links)]
mod impls;
pub mod migration;
#[cfg(test)]
mod mock;
#[cfg(test)]
mod tests;
mod types;
extern crate alloc;
pub use pallet::*;
use types::*;
use core::convert::TryInto;
use frame_support::{
pallet_prelude::*,
traits::{
fungible::{
hold::{
Balanced as FunHoldBalanced, Inspect as FunHoldInspect, Mutate as FunHoldMutate,
},
Balanced, Inspect as FunInspect, Mutate as FunMutate,
},
tokens::{fungible::Credit, Fortitude, Precision, Preservation, Restriction},
Defensive, DefensiveOption, Imbalance, OnUnbalanced,
},
};
use sp_io::hashing::blake2_256;
use sp_runtime::{
traits::{CheckedAdd, CheckedSub, TrailingZeroInput, Zero},
ArithmeticError, DispatchResult, Perbill, RuntimeDebug, Saturating,
};
use sp_staking::{Agent, Delegator, EraIndex, StakingInterface, StakingUnchecked};
/// The log target of this pallet.
pub const LOG_TARGET: &str = "runtime::delegated-staking";
// syntactic sugar for logging.
#[macro_export]
macro_rules! log {
($level:tt, $patter:expr $(, $values:expr)* $(,)?) => {
log::$level!(
target: $crate::LOG_TARGET,
concat!("[{:?}] ๐โโ๏ธ ", $patter), <frame_system::Pallet<T>>::block_number() $(, $values)*
)
};
}
pub type BalanceOf<T> =
<<T as Config>::Currency as FunInspect<<T as frame_system::Config>::AccountId>>::Balance;
use frame_system::{ensure_signed, pallet_prelude::*, RawOrigin};
#[frame_support::pallet]
pub mod pallet {
use super::*;
/// The in-code storage version.
const STORAGE_VERSION: StorageVersion = StorageVersion::new(0);
#[pallet::pallet]
#[pallet::storage_version(STORAGE_VERSION)]
pub struct Pallet<T>(PhantomData<T>);
#[pallet::config]
pub trait Config: frame_system::Config {
/// The overarching event type.
type RuntimeEvent: From<Event<Self>> + IsType<<Self as frame_system::Config>::RuntimeEvent>;
/// Injected identifier for the pallet.
#[pallet::constant]
type PalletId: Get<frame_support::PalletId>;
/// Currency type.
type Currency: FunHoldMutate<Self::AccountId, Reason = Self::RuntimeHoldReason>
+ FunMutate<Self::AccountId>
+ FunHoldBalanced<Self::AccountId>;
/// Handler for the unbalanced reduction when slashing a delegator.
type OnSlash: OnUnbalanced<Credit<Self::AccountId, Self::Currency>>;
/// Fraction of the slash that is rewarded to the caller of pending slash to the agent.
#[pallet::constant]
type SlashRewardFraction: Get<Perbill>;
/// Overarching hold reason.
type RuntimeHoldReason: From<HoldReason>;
/// Core staking implementation.
type CoreStaking: StakingUnchecked<Balance = BalanceOf<Self>, AccountId = Self::AccountId>;
}
#[pallet::error]
pub enum Error<T> {
/// The account cannot perform this operation.
NotAllowed,
/// An existing staker cannot perform this action.
AlreadyStaking,
/// Reward Destination cannot be same as `Agent` account.
InvalidRewardDestination,
/// Delegation conditions are not met.
///
/// Possible issues are
/// 1) Cannot delegate to self,
/// 2) Cannot delegate to multiple delegates.
InvalidDelegation,
/// The account does not have enough funds to perform the operation.
NotEnoughFunds,
/// Not an existing `Agent` account.
NotAgent,
/// Not a Delegator account.
NotDelegator,
/// Some corruption in internal state.
BadState,
/// Unapplied pending slash restricts operation on `Agent`.
UnappliedSlash,
/// `Agent` has no pending slash to be applied.
NothingToSlash,
/// Failed to withdraw amount from Core Staking.
WithdrawFailed,
/// Operation not supported by this pallet.
NotSupported,
}
/// A reason for placing a hold on funds.
#[pallet::composite_enum]
pub enum HoldReason {
/// Funds held for stake delegation to another account.
#[codec(index = 0)]
StakingDelegation,
}
#[pallet::event]
#[pallet::generate_deposit(pub (super) fn deposit_event)]
pub enum Event<T: Config> {
/// Funds delegated by a delegator.
Delegated { agent: T::AccountId, delegator: T::AccountId, amount: BalanceOf<T> },
/// Funds released to a delegator.
Released { agent: T::AccountId, delegator: T::AccountId, amount: BalanceOf<T> },
/// Funds slashed from a delegator.
Slashed { agent: T::AccountId, delegator: T::AccountId, amount: BalanceOf<T> },
/// Unclaimed delegation funds migrated to delegator.
MigratedDelegation { agent: T::AccountId, delegator: T::AccountId, amount: BalanceOf<T> },
}
/// Map of Delegators to their `Delegation`.
///
/// Implementation note: We are not using a double map with `delegator` and `agent` account
/// as keys since we want to restrict delegators to delegate only to one account at a time.
#[pallet::storage]
pub(crate) type Delegators<T: Config> =
CountedStorageMap<_, Twox64Concat, T::AccountId, Delegation<T>, OptionQuery>;
/// Map of `Agent` to their `Ledger`.
#[pallet::storage]
pub(crate) type Agents<T: Config> =
CountedStorageMap<_, Twox64Concat, T::AccountId, AgentLedger<T>, OptionQuery>;
// This pallet is not currently written with the intention of exposing any calls. But the
// functions defined in the following impl block should act as a good reference for how the
// exposed calls would look like when exposed.
impl<T: Config> Pallet<T> {
/// Register an account to become a stake `Agent`. Sometimes also called a `Delegatee`.
///
/// Delegators can authorize `Agent`s to stake on their behalf by delegating their funds to
/// them. The `Agent` can then use the delegated funds to stake to [`Config::CoreStaking`].
///
/// An account that is directly staked to [`Config::CoreStaking`] cannot become an `Agent`.
/// However, they can migrate to become an agent using [`Self::migrate_to_agent`].
///
/// Implementation note: This function allows any account to become an agent. It is
/// important though that accounts that call [`StakingUnchecked::virtual_bond`] are keyless
/// accounts. This is not a problem for now since this is only used by other pallets in the
/// runtime which use keyless account as agents. If we later want to expose this as a
/// dispatchable call, we should derive a sub-account from the caller and use that as the
/// agent account.
pub fn register_agent(
origin: OriginFor<T>,
reward_account: T::AccountId,
) -> DispatchResult {
let who = ensure_signed(origin)?;
// Existing `agent` cannot register again and a delegator cannot become an `agent`.
ensure!(!Self::is_agent(&who) && !Self::is_delegator(&who), Error::<T>::NotAllowed);
// They cannot be already a direct staker in the staking pallet.
ensure!(!Self::is_direct_staker(&who), Error::<T>::AlreadyStaking);
// Reward account cannot be same as `agent` account.
ensure!(reward_account != who, Error::<T>::InvalidRewardDestination);
Self::do_register_agent(&who, &reward_account);
Ok(())
}
/// Remove an account from being an `Agent`.
///
/// This can only be called if the agent has no delegated funds, no pending slashes and no
/// unclaimed withdrawals.
pub fn remove_agent(origin: OriginFor<T>) -> DispatchResult {
let who = ensure_signed(origin)?;
let ledger = AgentLedger::<T>::get(&who).ok_or(Error::<T>::NotAgent)?;
ensure!(
ledger.total_delegated == Zero::zero() &&
ledger.pending_slash == Zero::zero() &&
ledger.unclaimed_withdrawals == Zero::zero(),
Error::<T>::NotAllowed
);
AgentLedger::<T>::remove(&who);
Ok(())
}
/// Migrate from a `Nominator` account to `Agent` account.
///
/// The origin needs to
/// - be a `Nominator` with [`Config::CoreStaking`],
/// - not already an `Agent`,
///
/// This function will create a proxy account to the agent called `proxy_delegator` and
/// transfer the directly staked amount by the agent to it. The `proxy_delegator` delegates
/// the funds to the origin making origin an `Agent` account. The real `delegator`
/// accounts of the origin can later migrate their funds using [Self::migrate_delegation] to
/// claim back their share of delegated funds from `proxy_delegator` to self.
///
/// Any free fund in the agent's account will be marked as unclaimed withdrawal.
pub fn migrate_to_agent(
origin: OriginFor<T>,
reward_account: T::AccountId,
) -> DispatchResult {
let who = ensure_signed(origin)?;
// ensure who is a staker in `CoreStaking` but not already an agent or a delegator.
ensure!(
Self::is_direct_staker(&who) && !Self::is_agent(&who) && !Self::is_delegator(&who),
Error::<T>::NotAllowed
);
// Reward account cannot be same as `agent` account.
ensure!(reward_account != who, Error::<T>::InvalidRewardDestination);
Self::do_migrate_to_agent(&who, &reward_account)
}
/// Release previously delegated funds by delegator to origin.
///
/// Only agents can call this.
///
/// Tries to withdraw unbonded funds from `CoreStaking` if needed and release amount to
/// `delegator`.
pub fn release_delegation(
origin: OriginFor<T>,
delegator: T::AccountId,
amount: BalanceOf<T>,
num_slashing_spans: u32,
) -> DispatchResult {
let who = ensure_signed(origin)?;
Self::do_release(
Agent::from(who),
Delegator::from(delegator),
amount,
num_slashing_spans,
)
}
/// Migrate delegated funds that are held in `proxy_delegator` to the claiming `delegator`'s
/// account. If successful, the specified funds will be moved and delegated from `delegator`
/// account to the agent.
///
/// This can be called by `agent` accounts that were previously a direct `Nominator` with
/// [`Config::CoreStaking`] and has some remaining unclaimed delegations.
///
/// Internally, it moves some delegations from `proxy_delegator` account to `delegator`
/// account and reapplying the holds.
pub fn migrate_delegation(
origin: OriginFor<T>,
delegator: T::AccountId,
amount: BalanceOf<T>,
) -> DispatchResult {
let agent = ensure_signed(origin)?;
// Ensure delegator is sane.
ensure!(!Self::is_agent(&delegator), Error::<T>::NotAllowed);
ensure!(!Self::is_delegator(&delegator), Error::<T>::NotAllowed);
ensure!(!Self::is_direct_staker(&delegator), Error::<T>::AlreadyStaking);
// ensure agent is sane.
ensure!(Self::is_agent(&agent), Error::<T>::NotAgent);
// and has enough delegated balance to migrate.
let proxy_delegator = Self::generate_proxy_delegator(Agent::from(agent));
let balance_remaining = Self::held_balance_of(proxy_delegator.clone());
ensure!(balance_remaining >= amount, Error::<T>::NotEnoughFunds);
Self::do_migrate_delegation(proxy_delegator, Delegator::from(delegator), amount)
}
/// Delegate given `amount` of tokens to an `Agent` account.
///
/// If `origin` is the first time delegator, we add them to state. If they are already
/// delegating, we increase the delegation.
///
/// Conditions:
/// - Delegators cannot delegate to more than one agent.
/// - The `agent` account should already be registered as such. See
/// [`Self::register_agent`].
pub fn delegate_to_agent(
origin: OriginFor<T>,
agent: T::AccountId,
amount: BalanceOf<T>,
) -> DispatchResult {
let delegator = ensure_signed(origin)?;
// ensure delegator is sane.
ensure!(
Delegation::<T>::can_delegate(&delegator, &agent),
Error::<T>::InvalidDelegation
);
// Implementation note: Staking uses deprecated locks (similar to freeze) which are not
// mutually exclusive of holds. This means, if we allow delegating for existing stakers,
// already staked funds might be reused for delegation. We avoid that by just blocking
// this.
ensure!(!Self::is_direct_staker(&delegator), Error::<T>::AlreadyStaking);
// ensure agent is sane.
ensure!(Self::is_agent(&agent), Error::<T>::NotAgent);
// add to delegation.
Self::do_delegate(Delegator::from(delegator), Agent::from(agent.clone()), amount)?;
// bond the newly delegated amount to `CoreStaking`.
Self::do_bond(Agent::from(agent), amount)
}
}
#[pallet::hooks]
impl<T: Config> Hooks<BlockNumberFor<T>> for Pallet<T> {
#[cfg(feature = "try-runtime")]
fn try_state(_n: BlockNumberFor<T>) -> Result<(), sp_runtime::TryRuntimeError> {
Self::do_try_state()
}
}
}
impl<T: Config> Pallet<T> {
/// Derive an account from the migrating agent account where the unclaimed delegation funds
/// are held.
pub fn generate_proxy_delegator(agent: Agent<T::AccountId>) -> Delegator<T::AccountId> {
Delegator::from(Self::sub_account(AccountType::ProxyDelegator, agent.get()))
}
/// Derive a (keyless) pot account from the given agent account and account type.
fn sub_account(account_type: AccountType, acc: T::AccountId) -> T::AccountId {
let entropy = (T::PalletId::get(), acc, account_type).using_encoded(blake2_256);
Decode::decode(&mut TrailingZeroInput::new(entropy.as_ref()))
.expect("infinite length input; no invalid inputs for type; qed")
}
/// Held balance of a delegator.
pub(crate) fn held_balance_of(who: Delegator<T::AccountId>) -> BalanceOf<T> {
T::Currency::balance_on_hold(&HoldReason::StakingDelegation.into(), &who.get())
}
/// Returns true if who is registered as an `Agent`.
fn is_agent(who: &T::AccountId) -> bool {
<Agents<T>>::contains_key(who)
}
/// Returns true if who is delegating to an `Agent` account.
fn is_delegator(who: &T::AccountId) -> bool {
<Delegators<T>>::contains_key(who)
}
/// Returns true if who is already staking on [`Config::CoreStaking`].
fn is_direct_staker(who: &T::AccountId) -> bool {
T::CoreStaking::status(who).is_ok()
}
/// Registers a new agent in the system.
fn do_register_agent(who: &T::AccountId, reward_account: &T::AccountId) {
// TODO: Consider taking a deposit for being an agent.
AgentLedger::<T>::new(reward_account).update(who);
}
/// Migrate existing staker account `who` to an `Agent` account.
fn do_migrate_to_agent(who: &T::AccountId, reward_account: &T::AccountId) -> DispatchResult {
Self::do_register_agent(who, reward_account);
// We create a proxy delegator that will keep all the delegation funds until funds are
// transferred to actual delegator.
let proxy_delegator = Self::generate_proxy_delegator(Agent::from(who.clone()));
// Get current stake
let stake = T::CoreStaking::stake(who)?;
// release funds from core staking.
T::CoreStaking::migrate_to_virtual_staker(who);
// transfer just released staked amount plus any free amount.
let amount_to_transfer =
T::Currency::reducible_balance(who, Preservation::Expendable, Fortitude::Polite);
// This should never fail but if it does, it indicates bad state and we abort.
T::Currency::transfer(
who,
&proxy_delegator.clone().get(),
amount_to_transfer,
Preservation::Expendable,
)?;
T::CoreStaking::set_payee(who, reward_account)?;
// delegate all transferred funds back to agent.
Self::do_delegate(proxy_delegator, Agent::from(who.clone()), amount_to_transfer)?;
// if the transferred/delegated amount was greater than the stake, mark the extra as
// unclaimed withdrawal.
let unclaimed_withdraws = amount_to_transfer
.checked_sub(&stake.total)
.defensive_ok_or(ArithmeticError::Underflow)?;
if !unclaimed_withdraws.is_zero() {
let mut ledger = AgentLedger::<T>::get(who).ok_or(Error::<T>::NotAgent)?;
ledger.unclaimed_withdrawals = ledger
.unclaimed_withdrawals
.checked_add(&unclaimed_withdraws)
.defensive_ok_or(ArithmeticError::Overflow)?;
ledger.update(who);
}
Ok(())
}
/// Bond `amount` to `agent_acc` in [`Config::CoreStaking`].
fn do_bond(agent_acc: Agent<T::AccountId>, amount: BalanceOf<T>) -> DispatchResult {
let agent_ledger = AgentLedgerOuter::<T>::get(&agent_acc.get())?;
let available_to_bond = agent_ledger.available_to_bond();
defensive_assert!(amount == available_to_bond, "not expected value to bond");
if agent_ledger.is_bonded() {
T::CoreStaking::bond_extra(&agent_ledger.key, amount)
} else {
T::CoreStaking::virtual_bond(&agent_ledger.key, amount, agent_ledger.reward_account())
}
}
/// Delegate `amount` from `delegator` to `agent`.
fn do_delegate(
delegator: Delegator<T::AccountId>,
agent: Agent<T::AccountId>,
amount: BalanceOf<T>,
) -> DispatchResult {
// get inner type
let agent = agent.get();
let delegator = delegator.get();
let mut ledger = AgentLedger::<T>::get(&agent).ok_or(Error::<T>::NotAgent)?;
if let Some(mut existing_delegation) = Delegation::<T>::get(&delegator) {
ensure!(existing_delegation.agent == agent, Error::<T>::InvalidDelegation);
// update amount and return the updated delegation.
existing_delegation.amount = existing_delegation
.amount
.checked_add(&amount)
.ok_or(ArithmeticError::Overflow)?;
existing_delegation
} else {
Delegation::<T>::new(&agent, amount)
}
.update(&delegator);
// try to hold the funds.
T::Currency::hold(&HoldReason::StakingDelegation.into(), &delegator, amount)?;
ledger.total_delegated =
ledger.total_delegated.checked_add(&amount).ok_or(ArithmeticError::Overflow)?;
ledger.update(&agent);
Self::deposit_event(Event::<T>::Delegated { agent, delegator, amount });
Ok(())
}
/// Release `amount` of delegated funds from `agent` to `delegator`.
fn do_release(
who: Agent<T::AccountId>,
delegator: Delegator<T::AccountId>,
amount: BalanceOf<T>,
num_slashing_spans: u32,
) -> DispatchResult {
// get inner type
let agent = who.get();
let delegator = delegator.get();
let mut agent_ledger = AgentLedgerOuter::<T>::get(&agent)?;
let mut delegation = Delegation::<T>::get(&delegator).ok_or(Error::<T>::NotDelegator)?;
// make sure delegation to be released is sound.
ensure!(delegation.agent == agent, Error::<T>::NotAgent);
ensure!(delegation.amount >= amount, Error::<T>::NotEnoughFunds);
// if we do not already have enough funds to be claimed, try to withdraw some more.
if agent_ledger.ledger.unclaimed_withdrawals < amount {
// withdraw account.
let _ = T::CoreStaking::withdraw_unbonded(agent.clone(), num_slashing_spans)
.map_err(|_| Error::<T>::WithdrawFailed)?;
// reload agent from storage since withdrawal might have changed the state.
agent_ledger = agent_ledger.reload()?;
}
// if we still do not have enough funds to release, abort.
ensure!(agent_ledger.ledger.unclaimed_withdrawals >= amount, Error::<T>::NotEnoughFunds);
agent_ledger.remove_unclaimed_withdraw(amount)?.update();
delegation.amount = delegation
.amount
.checked_sub(&amount)
.defensive_ok_or(ArithmeticError::Overflow)?;
let released = T::Currency::release(
&HoldReason::StakingDelegation.into(),
&delegator,
amount,
Precision::BestEffort,
)?;
defensive_assert!(released == amount, "hold should have been released fully");
// update delegation.
delegation.update(&delegator);
Self::deposit_event(Event::<T>::Released { agent, delegator, amount });
Ok(())
}
/// Migrates delegation of `amount` from `source` account to `destination` account.
fn do_migrate_delegation(
source_delegator: Delegator<T::AccountId>,
destination_delegator: Delegator<T::AccountId>,
amount: BalanceOf<T>,
) -> DispatchResult {
// get inner type
let source_delegator = source_delegator.get();
let destination_delegator = destination_delegator.get();
let mut source_delegation =
Delegators::<T>::get(&source_delegator).defensive_ok_or(Error::<T>::BadState)?;
// ensure source has enough funds to migrate.
ensure!(source_delegation.amount >= amount, Error::<T>::NotEnoughFunds);
debug_assert!(
!Self::is_delegator(&destination_delegator) && !Self::is_agent(&destination_delegator)
);
let agent = source_delegation.agent.clone();
// create a new delegation for destination delegator.
Delegation::<T>::new(&agent, amount).update(&destination_delegator);
source_delegation.amount = source_delegation
.amount
.checked_sub(&amount)
.defensive_ok_or(Error::<T>::BadState)?;
// transfer the held amount in `source_delegator` to `destination_delegator`.
let _ = T::Currency::transfer_on_hold(
&HoldReason::StakingDelegation.into(),
&source_delegator,
&destination_delegator,
amount,
Precision::Exact,
Restriction::OnHold,
Fortitude::Polite,
)?;
// update source delegation.
source_delegation.update(&source_delegator);
Self::deposit_event(Event::<T>::MigratedDelegation {
agent,
delegator: destination_delegator,
amount,
});
Ok(())
}
/// Take slash `amount` from agent's `pending_slash`counter and apply it to `delegator` account.
pub fn do_slash(
agent: Agent<T::AccountId>,
delegator: Delegator<T::AccountId>,
amount: BalanceOf<T>,
maybe_reporter: Option<T::AccountId>,
) -> DispatchResult {
// get inner type
let agent = agent.get();
let delegator = delegator.get();
let agent_ledger = AgentLedgerOuter::<T>::get(&agent)?;
// ensure there is something to slash
ensure!(agent_ledger.ledger.pending_slash > Zero::zero(), Error::<T>::NothingToSlash);
let mut delegation = <Delegators<T>>::get(&delegator).ok_or(Error::<T>::NotDelegator)?;
ensure!(delegation.agent == agent.clone(), Error::<T>::NotAgent);
ensure!(delegation.amount >= amount, Error::<T>::NotEnoughFunds);
// slash delegator
let (mut credit, missing) =
T::Currency::slash(&HoldReason::StakingDelegation.into(), &delegator, amount);
defensive_assert!(missing.is_zero(), "slash should have been fully applied");
let actual_slash = credit.peek();
// remove the applied slashed amount from agent.
agent_ledger.remove_slash(actual_slash).save();
delegation.amount =
delegation.amount.checked_sub(&actual_slash).ok_or(ArithmeticError::Overflow)?;
delegation.update(&delegator);
if let Some(reporter) = maybe_reporter {
let reward_payout: BalanceOf<T> = T::SlashRewardFraction::get() * actual_slash;
let (reporter_reward, rest) = credit.split(reward_payout);
// credit is the amount that we provide to `T::OnSlash`.
credit = rest;
// reward reporter or drop it.
let _ = T::Currency::resolve(&reporter, reporter_reward);
}
T::OnSlash::on_unbalanced(credit);
Self::deposit_event(Event::<T>::Slashed { agent, delegator, amount });
Ok(())
}
/// Total balance that is available for stake. Includes already staked amount.
#[cfg(test)]
pub(crate) fn stakeable_balance(who: Agent<T::AccountId>) -> BalanceOf<T> {
AgentLedgerOuter::<T>::get(&who.get())
.map(|agent| agent.ledger.stakeable_balance())
.unwrap_or_default()
}
}
#[cfg(any(test, feature = "try-runtime"))]
use alloc::collections::btree_map::BTreeMap;
#[cfg(any(test, feature = "try-runtime"))]
impl<T: Config> Pallet<T> {
pub(crate) fn do_try_state() -> Result<(), sp_runtime::TryRuntimeError> {
// build map to avoid reading storage multiple times.
let delegation_map = Delegators::<T>::iter().collect::<BTreeMap<_, _>>();
let ledger_map = Agents::<T>::iter().collect::<BTreeMap<_, _>>();
Self::check_delegates(ledger_map.clone())?;
Self::check_delegators(delegation_map, ledger_map)?;
Ok(())
}
fn check_delegates(
ledgers: BTreeMap<T::AccountId, AgentLedger<T>>,
) -> Result<(), sp_runtime::TryRuntimeError> {
for (agent, ledger) in ledgers {
let staked_value = ledger.stakeable_balance();
if !staked_value.is_zero() {
ensure!(
matches!(
T::CoreStaking::status(&agent).expect("agent should be bonded"),
sp_staking::StakerStatus::Nominator(_) | sp_staking::StakerStatus::Idle
),
"agent should be bonded and not validator"
);
}
ensure!(
ledger.stakeable_balance() >=
T::CoreStaking::total_stake(&agent).unwrap_or_default(),
"Cannot stake more than balance"
);
}
Ok(())
}
fn check_delegators(
delegations: BTreeMap<T::AccountId, Delegation<T>>,
ledger: BTreeMap<T::AccountId, AgentLedger<T>>,
) -> Result<(), sp_runtime::TryRuntimeError> {
let mut delegation_aggregation = BTreeMap::<T::AccountId, BalanceOf<T>>::new();
for (delegator, delegation) in delegations.iter() {
ensure!(!Self::is_agent(delegator), "delegator cannot be an agent");
delegation_aggregation
.entry(delegation.agent.clone())
.and_modify(|e| *e += delegation.amount)
.or_insert(delegation.amount);
}
for (agent, total_delegated) in delegation_aggregation {
ensure!(!Self::is_delegator(&agent), "agent cannot be delegator");
let ledger = ledger.get(&agent).expect("ledger should exist");
ensure!(
ledger.total_delegated == total_delegated,
"ledger total delegated should match delegations"
);
}
Ok(())
}
}