diff --git a/substrate/frame/asset-rewards/src/lib.rs b/substrate/frame/asset-rewards/src/lib.rs
index 35e1eaa58f3ace1f6aed9dcb02e6111e020bc5de..50ce231bc41204362b11fd262a59a042dcb862a8 100644
--- a/substrate/frame/asset-rewards/src/lib.rs
+++ b/substrate/frame/asset-rewards/src/lib.rs
@@ -23,18 +23,23 @@
//!
//! Governance can create a new incentive program for a fungible asset by creating a new pool.
//!
-//! When creating the pool, governance specifies a 'staking asset', 'reward asset', and 'reward rate
-//! per block'.
+//! When creating the pool, governance specifies a 'staking asset', 'reward asset', 'reward rate
+//! per block', and an 'expiry block'.
//!
-//! Once the pool is created, holders of the 'staking asset' can stake them in this pallet (creating
-//! a new Freeze). Once staked, the staker begins accumulating the right to claim the 'reward asset'
-//! each block, proportional to their share of the total staked tokens in the pool.
+//! Once the pool is created, holders of the 'staking asset' can stake them in this pallet, which
+//! puts a Freeze on the asset.
+//!
+//! Once staked, the staker begins accumulating the right to claim the 'reward asset' each block,
+//! proportional to their share of the total staked tokens in the pool.
//!
//! Reward assets pending distribution are held in an account derived from the pallet ID and a
//! unique pool ID.
//!
//! Care should be taken to keep pool accounts adequately funded with the reward asset.
//!
+//! The pool administator can adjust the reward rate per block, the expiry block, and the admin
+//! after the pool is created.
+//!
//! ## Permissioning
//!
//! Currently, pool creation and management is permissioned and restricted to a configured Origin.
@@ -50,14 +55,23 @@
//! pallet Call method, which while slightly more verbose, makes it much easier to understand the
//! code and reason about where side-effects occur in the pallet.
//!
-//! ## Implementation Notes
+//! ## Rewards Algorithm
//!
-//! The implementation is based on the [AccumulatedRewardsPerShare](https://dev.to/heymarkkop/understanding-sushiswaps-masterchef-staking-rewards-1m6f) algorithm.
+//! The rewards algorithm is based on the Synthetix [StakingRewards.sol](https://github.com/Synthetixio/synthetix/blob/develop/contracts/StakingRewards.sol)
+//! smart contract.
//!
-//! Rewards are calculated JIT (just-in-time), when a staker claims their rewards.
+//! Rewards are calculated JIT (just-in-time), and all operations are O(1) making the approach
+//! scalable to many pools and stakers.
//!
-//! All operations are O(1), allowing the approach to scale to an arbitrary amount of pools and
-//! stakers.
+//! The approach is widly used across the Ethereum ecosystem, there is also quite battle tested.
+//!
+//! ### Resources
+//!
+//! - [This YouTube video series](https://www.youtube.com/watch?v=6ZO5aYg1GI8), which walks through
+//! the math of the algorithm.
+//! - [This dev.to article](https://dev.to/heymarkkop/understanding-sushiswaps-masterchef-staking-rewards-1m6f),
+//! which explains the algorithm of the SushiSwap MasterChef staking. While not identical to the
+//! Synthetix approach, they are very similar.
#![deny(missing_docs)]
#![cfg_attr(not(feature = "std"), no_std)]
@@ -572,6 +586,26 @@ pub mod pallet {
)?;
Ok(())
}
+
+ /// Permissioned method to withdraw reward tokens from a pool.
+ pub fn withdraw_reward_tokens(
+ origin: OriginFor<T>,
+ pool_id: PoolId,
+ amount: T::Balance,
+ ) -> DispatchResult {
+ let caller = ensure_signed(origin)?;
+ let pool_info = Pools::<T>::get(pool_id).ok_or(Error::<T>::NonExistentPool)?;
+ ensure!(pool_info.admin == caller, BadOrigin);
+ T::Assets::transfer(
+ pool_info.reward_asset_id,
+ &caller,
+ &Self::pool_account_id(&pool_id)?,
+ amount,
+ Preservation::Preserve,
+ )?;
+
+ Ok(())
+ }
}
impl<T: Config> Pallet<T> {
diff --git a/substrate/frame/asset-rewards/src/tests.rs b/substrate/frame/asset-rewards/src/tests.rs
index 8de62643b59cbb331acc7fb404b6c76c17ef1600..7988409620220581b8f52eafecad8dfa1278d6ea 100644
--- a/substrate/frame/asset-rewards/src/tests.rs
+++ b/substrate/frame/asset-rewards/src/tests.rs
@@ -921,6 +921,127 @@ mod deposit_reward_tokens {
}
}
+mod withdraw_reward_tokens {
+ use super::*;
+
+ #[test]
+ fn success() {
+ new_test_ext().execute_with(|| {
+ let admin = 1;
+ let pool_id = 0;
+ let reward_asset_id = NativeOrWithId::<u32>::Native;
+ let initial_deposit = 10;
+ let withdraw_amount = 5;
+ create_default_pool();
+ let pool_account_id = StakingRewards::pool_account_id(&pool_id).unwrap();
+
+ let admin_balance_before =
+ <<MockRuntime as Config>::Assets>::balance(reward_asset_id.clone(), &admin);
+ let pool_balance_before = <<MockRuntime as Config>::Assets>::balance(
+ reward_asset_id.clone(),
+ &pool_account_id,
+ );
+
+ // Deposit initial reward tokens
+ assert_ok!(StakingRewards::deposit_reward_tokens(
+ RuntimeOrigin::signed(admin),
+ pool_id,
+ initial_deposit
+ ));
+
+ // Withdraw some tokens
+ assert_ok!(StakingRewards::withdraw_reward_tokens(
+ RuntimeOrigin::signed(admin),
+ pool_id,
+ withdraw_amount
+ ));
+
+ let admin_balance_after =
+ <<MockRuntime as Config>::Assets>::balance(reward_asset_id.clone(), &admin);
+ let pool_balance_after =
+ <<MockRuntime as Config>::Assets>::balance(reward_asset_id, &pool_account_id);
+
+ assert_eq!(
+ <<MockRuntime as Config>::Assets>::balance(
+ reward_asset_id.clone(),
+ &pool_account_id
+ ),
+ initial_deposit - withdraw_amount
+ );
+ assert_eq!(
+ <<MockRuntime as Config>::Assets>::balance(reward_asset_id, &admin),
+ withdraw_amount
+ );
+ });
+ }
+
+ // #[test]
+ // fn fails_for_non_existent_pool() {
+ // new_test_ext().execute_with(|| {
+ // let admin = 1;
+ // let non_existent_pool_id = 999;
+ // let withdraw_amount = 5000;
+ //
+ // assert_err!(
+ // StakingRewards::withdraw_reward_tokens(
+ // RuntimeOrigin::signed(admin),
+ // non_existent_pool_id,
+ // withdraw_amount
+ // ),
+ // Error::<MockRuntime>::NonExistentPool
+ // );
+ // });
+ // }
+ //
+ // #[test]
+ // fn fails_for_non_admin() {
+ // new_test_ext().execute_with(|| {
+ // let non_admin = 2;
+ // let pool_id = 0;
+ // let withdraw_amount = 5000;
+ // create_default_pool();
+ //
+ // assert_err!(
+ // StakingRewards::withdraw_reward_tokens(
+ // RuntimeOrigin::signed(non_admin),
+ // pool_id,
+ // withdraw_amount
+ // ),
+ // BadOrigin
+ // );
+ // });
+ // }
+ //
+ // #[test]
+ // fn fails_for_insufficient_pool_balance() {
+ // new_test_ext().execute_with(|| {
+ // let admin = 1;
+ // let pool_id = 0;
+ // let reward_asset_id = NativeOrWithId::<u32>::Native;
+ // let initial_deposit = 10000;
+ // let withdraw_amount = 15000;
+ // create_default_pool();
+ //
+ // // Deposit initial reward tokens
+ // let pool_account = StakingRewards::pool_account_id(&pool_id).unwrap();
+ // <<MockRuntime as Config>::Assets>::set_balance(
+ // reward_asset_id,
+ // &pool_account,
+ // initial_deposit,
+ // );
+ //
+ // assert_err!(
+ // StakingRewards::withdraw_reward_tokens(
+ // RuntimeOrigin::signed(admin),
+ // pool_id,
+ // withdraw_amount
+ // ),
+ // assets::Error::<MockRuntime>::BalanceLow
+ // );
+ // });
+ // }
+}
+
/// This integration test
/// 1. Considers 2 stakers each staking and unstaking at different intervals, asserts their
/// claimable rewards are adjusted as expected, and that harvesting works.