implement block emissions

substrate/emissions/pallet/Cargo.toml

@@ -0,0 +1,65 @@
+[package]
+name = "serai-emissions-pallet"
+version = "0.1.0"
+description = "Emissions pallet for Serai"
+license = "AGPL-3.0-only"
+repository = "https://github.com/serai-dex/serai/tree/develop/substrate/emissions/pallet"
+authors = ["Akil Demir <aeg_asd@hotmail.com>"]
+edition = "2021"
+rust-version = "1.77"
+
+[package.metadata.docs.rs]
+all-features = true
+rustdoc-args = ["--cfg", "docsrs"]
+
+[package.metadata.cargo-machete]
+ignored = ["scale", "scale-info"]
+
+[lints]
+workspace = true
+
+
+[dependencies]
+scale = { package = "parity-scale-codec", version = "3", default-features = false, features = ["derive"] }
+scale-info = { version = "2", default-features = false, features = ["derive"] }
+
+frame-system = { git = "https://github.com/serai-dex/substrate", default-features = false }
+frame-support = { git = "https://github.com/serai-dex/substrate", default-features = false }
+
+sp-std = { git = "https://github.com/serai-dex/substrate", default-features = false }
+sp-session = { git = "https://github.com/serai-dex/substrate", default-features = false }
+sp-runtime = { git = "https://github.com/serai-dex/substrate", default-features = false }
+
+pallet-babe = { git = "https://github.com/serai-dex/substrate", default-features = false }
+
+coins-pallet = { package = "serai-coins-pallet", path = "../../coins/pallet", default-features = false }
+validator-sets-pallet = { package = "serai-validator-sets-pallet", path = "../../validator-sets/pallet", default-features = false }
+dex-pallet = { package = "serai-dex-pallet", path = "../../dex/pallet", default-features = false }
+
+serai-primitives = { path = "../../primitives", default-features = false }
+serai-validator-sets-primitives = { path = "../../validator-sets/primitives", default-features = false }
+emissions-primitives = { package = "serai-emissions-primitives", path = "../primitives", default-features = false }
+
+[features]
+std = [
+  "scale/std",
+  "scale-info/std",
+
+  "frame-system/std",
+  "frame-support/std",
+
+  "sp-std/std",
+  "sp-session/std",
+  "sp-runtime/std",
+
+  "pallet-babe/std",
+
+  "coins-pallet/std",
+  "validator-sets-pallet/std",
+  "dex-pallet/std",
+
+  "serai-primitives/std",
+  "emissions-primitives/std",
+]
+
+default = ["std"]

substrate/emissions/pallet/LICENSE

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+AGPL-3.0-only license
+
+Copyright (c) 2024 Luke Parker
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU Affero General Public License Version 3 as
+published by the Free Software Foundation.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+GNU Affero General Public License for more details.
+
+You should have received a copy of the GNU Affero General Public License
+along with this program. If not, see <http://www.gnu.org/licenses/>.

substrate/emissions/pallet/src/lib.rs

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+#![cfg_attr(not(feature = "std"), no_std)]
+
+#[allow(clippy::cast_possible_truncation, clippy::no_effect_underscore_binding)]
+#[frame_support::pallet]
+pub mod pallet {
+  use super::*;
+  use frame_system::pallet_prelude::*;
+  use frame_support::{pallet_prelude::*, sp_runtime::SaturatedConversion};
+
+  use sp_std::{vec, vec::Vec, collections::btree_map::BTreeMap};
+  use sp_session::ShouldEndSession;
+  use sp_runtime;
+
+  use coins_pallet::{Config as CoinsConfig, Pallet as Coins, AllowMint};
+  use dex_pallet::{Config as DexConfig, Pallet as Dex};
+
+  use validator_sets_pallet::{Pallet as ValidatorSets, Config as ValidatorSetsConfig};
+  use pallet_babe::{Pallet as Babe, Config as BabeConfig};
+
+  use serai_primitives::{NetworkId, NETWORKS, *};
+  use serai_validator_sets_primitives::MAX_KEY_SHARES_PER_SET;
+  use emissions_primitives::*;
+
+  #[pallet::config]
+  pub trait Config:
+    frame_system::Config<AccountId = PublicKey>
+    + ValidatorSetsConfig
+    + BabeConfig
+    + CoinsConfig
+    + DexConfig
+  {
+    type RuntimeEvent: From<Event<Self>> + IsType<<Self as frame_system::Config>::RuntimeEvent>;
+  }
+
+  #[pallet::genesis_config]
+  #[derive(Clone, PartialEq, Eq, Debug, Encode, Decode)]
+  pub struct GenesisConfig<T: Config> {
+    /// Networks to spawn Serai with.
+    pub networks: Vec<NetworkId>,
+    /// List of participants to place in the initial validator sets.
+    pub participants: Vec<T::AccountId>,
+  }
+
+  impl<T: Config> Default for GenesisConfig<T> {
+    fn default() -> Self {
+      GenesisConfig { networks: Default::default(), participants: Default::default() }
+    }
+  }
+
+  #[pallet::error]
+  pub enum Error<T> {
+    GenesisPeriodEnded,
+    AmountOverflowed,
+    NotEnoughLiquidity,
+    CanOnlyRemoveFullAmount,
+  }
+
+  #[pallet::event]
+  pub enum Event<T: Config> {}
+
+  #[pallet::pallet]
+  pub struct Pallet<T>(PhantomData<T>);
+
+  #[pallet::storage]
+  #[pallet::getter(fn participants)]
+  pub(crate) type Participants<T: Config> = StorageMap<
+    _,
+    Identity,
+    NetworkId,
+    BoundedVec<(PublicKey, u64), ConstU32<{ MAX_KEY_SHARES_PER_SET }>>,
+    OptionQuery,
+  >;
+
+  #[pallet::storage]
+  #[pallet::getter(fn epoch_begin_block)]
+  pub(crate) type EpochBeginBlock<T: Config> = StorageMap<_, Identity, u64, u64, ValueQuery>;
+
+  #[pallet::storage]
+  #[pallet::getter(fn economic_security_reached)]
+  pub(crate) type EconomicSecurityReached<T: Config> =
+    StorageMap<_, Identity, NetworkId, BlockNumberFor<T>, ValueQuery>;
+
+  #[pallet::storage]
+  #[pallet::getter(fn last_swap_volume)]
+  pub(crate) type LastSwapVolume<T: Config> = StorageMap<_, Identity, NetworkId, u64, OptionQuery>;
+
+  #[pallet::genesis_build]
+  impl<T: Config> BuildGenesisConfig for GenesisConfig<T> {
+    fn build(&self) {
+      for id in self.networks.clone() {
+        let mut participants = vec![];
+        for p in self.participants.clone() {
+          participants.push((p, 0u64));
+        }
+        Participants::<T>::set(id, Some(participants.try_into().unwrap()));
+      }
+
+      EpochBeginBlock::<T>::set(0, 0);
+    }
+  }
+
+  #[pallet::hooks]
+  impl<T: Config> Hooks<BlockNumberFor<T>> for Pallet<T> {
+    /// Since we are on `on_finalize`, session should have already rotated.
+    /// We can distribute the rewards for the last set.
+    fn on_finalize(n: BlockNumberFor<T>) {
+      // we accept we reached economic security once we can mint smallest amount of a network's coin
+      for coin in COINS {
+        let existing = EconomicSecurityReached::<T>::get(coin.network());
+        if existing == 0u32.into() &&
+          <T as CoinsConfig>::AllowMint::is_allowed(&Balance { coin, amount: Amount(1) })
+        {
+          EconomicSecurityReached::<T>::set(coin.network(), n);
+        }
+      }
+
+      // emissions start only after genesis period and happens once per epoch
+      // so we don't do anything before that time.
+      if !(n >= BLOCKS_PER_MONTH.into() && T::ShouldEndSession::should_end_session(n)) {
+        return;
+      }
+
+      // figure out the amount of blocks in the last epoch
+      // TODO: we use epoch index here but should we use SessionIndex since this is how we decide
+      // whether time to distribute the rewards or not? Because apparently epochs != Sessions
+      // since we can skip some epochs if the chain is offline more than epoch duration??
+      let epoch = Babe::<T>::current_epoch().epoch_index - 1;
+      let block_count = n.saturated_into::<u64>() - Self::epoch_begin_block(epoch);
+
+      // get total reward for this epoch
+      let pre_ec_security = Self::pre_ec_security();
+      let mut distances = BTreeMap::new();
+      let mut total_distance: u64 = 0;
+      let reward_this_epoch = if Self::initial_period(n) {
+        // rewards are fixed for initial period
+        block_count * INITIAL_REWARD_PER_BLOCK
+      } else if pre_ec_security {
+        // calculate distance to economic security per network
+        let mut total_required: u64 = 0;
+        let mut total_current: u64 = 0;
+        for n in NETWORKS {
+          if n == NetworkId::Serai {
+            continue;
+          }
+
+          let required = ValidatorSets::<T>::required_stake_for_network(n);
+          let mut current = ValidatorSets::<T>::total_allocated_stake(n).unwrap_or(Amount(0)).0;
+          if current > required {
+            current = required;
+          }
+
+          distances.insert(n, required - current);
+          total_required = total_required.saturating_add(required);
+          total_current = total_current.saturating_add(current);
+        }
+        total_distance = total_required.saturating_sub(total_current);
+
+        // add serai network portion(20%)
+        let new_total_distance =
+          total_distance.saturating_mul(10) / (10 - SERAI_VALIDATORS_DESIRED_PERCENTAGE);
+        distances.insert(NetworkId::Serai, new_total_distance - total_distance);
+        total_distance = new_total_distance;
+
+        // rewards for pre-economic security is
+        // (STAKE_REQUIRED - CURRENT_STAKE) / blocks_until(SECURE_BY).
+        let block_reward = total_distance / Self::blocks_until(SECURE_BY);
+        block_count * block_reward
+      } else {
+        // post ec security
+        block_count * REWARD_PER_BLOCK
+      };
+
+      // get swap volumes
+      let mut volume_per_network: BTreeMap<NetworkId, u64> = BTreeMap::new();
+      for c in COINS {
+        // this should return 0 for SRI and so it shouldn't affect the total volume.
+        let current_volume = Dex::<T>::swap_volume(c).unwrap_or(0);
+        volume_per_network.insert(
+          c.network(),
+          (*volume_per_network.get(&c.network()).unwrap_or(&0)).saturating_add(current_volume),
+        );
+      }
+
+      // map current volumes to epoch volumes
+      let mut total_volume = 0u64;
+      for (n, vol) in &mut volume_per_network {
+        let last_volume = Self::last_swap_volume(n).unwrap_or(0);
+        let vol_this_epoch = vol.saturating_sub(last_volume);
+
+        // update the current volume
+        LastSwapVolume::<T>::set(n, Some(*vol));
+
+        total_volume = total_volume.saturating_add(vol_this_epoch);
+        *vol = vol_this_epoch;
+      }
+
+      // map epoch ec-security-distance/volume to rewards
+      let rewards_per_network = distances
+        .into_iter()
+        .map(|(n, distance)| {
+          let reward = if pre_ec_security {
+            // calculate how much each network gets based on distance to ec-security
+            reward_this_epoch.saturating_mul(distance) / total_distance
+          } else {
+            // 20% of the reward goes to the Serai network and rest is distributed among others
+            // based on swap-volume.
+            if n == NetworkId::Serai {
+              reward_this_epoch / 5
+            } else {
+              let reward = reward_this_epoch - (reward_this_epoch / 5);
+              reward.saturating_mul(*volume_per_network.get(&n).unwrap_or(&0)) / total_volume
+            }
+          };
+          (n, reward)
+        })
+        .collect::<BTreeMap<NetworkId, u64>>();
+
+      // distribute the rewards within the network
+      for (n, reward) in rewards_per_network {
+        // calculate pool vs validator share
+        let capacity = ValidatorSets::<T>::total_allocated_stake(n).unwrap_or(Amount(0)).0;
+        let required = ValidatorSets::<T>::required_stake_for_network(n);
+        let unused_capacity = capacity.saturating_sub(required);
+
+        let distribution = unused_capacity.saturating_mul(ACCURACY_MULTIPLIER) / capacity;
+        let total = DESIRED_DISTRIBUTION.saturating_add(distribution);
+
+        let validators_reward = DESIRED_DISTRIBUTION.saturating_mul(reward) / total;
+        let pool_reward = total - validators_reward;
+
+        // distribute validators rewards
+        Self::distribute_to_validators(n, validators_reward);
+
+        // send the rest to the pool
+        let coin_count = u64::try_from(n.coins().len()).unwrap();
+        for c in n.coins() {
+          // TODO: we just print a warning here instead of unwrap?
+          // assumes reward is equally distributed between network coins.
+          Coins::<T>::mint(
+            Dex::<T>::get_pool_account(*c),
+            Balance { coin: Coin::Serai, amount: Amount(pool_reward / coin_count) },
+          )
+          .unwrap();
+        }
+      }
+
+      // set the begin block and participants
+      EpochBeginBlock::<T>::set(epoch, n.saturated_into::<u64>());
+      for n in NETWORKS {
+        // TODO: `participants_for_latest_decided_set` returns keys with key shares but we
+        // store keys with actual stake amounts. Pr https://github.com/serai-dex/serai/pull/518
+        // supposed to change that and so this pr relies and that pr.
+        Participants::<T>::set(n, ValidatorSets::<T>::participants_for_latest_decided_set(n));
+      }
+    }
+  }
+
+  impl<T: Config> Pallet<T> {
+    fn blocks_until(block: u64) -> u64 {
+      let current = <frame_system::Pallet<T>>::block_number().saturated_into::<u64>();
+      block.saturating_sub(current)
+    }
+
+    fn initial_period(n: BlockNumberFor<T>) -> bool {
+      n >= BLOCKS_PER_MONTH.into() && n < (3 * BLOCKS_PER_MONTH).into()
+    }
+
+    /// Returns true if any of the external networks haven't reached economic security yet.
+    fn pre_ec_security() -> bool {
+      for n in NETWORKS {
+        if n == NetworkId::Serai {
+          continue;
+        }
+
+        if Self::economic_security_reached(n) == 0u32.into() {
+          return true;
+        }
+      }
+      false
+    }
+
+    fn distribute_to_validators(n: NetworkId, reward: u64) {
+      // distribute among network's set based on
+      // -> (key shares * stake per share) + ((stake % stake per share) / 2)
+      let stake_per_share = ValidatorSets::<T>::allocation_per_key_share(n).unwrap().0;
+      let mut scores = vec![];
+      let mut total_score = 0u64;
+      for (p, amount) in Self::participants(n).unwrap() {
+        let remainder = amount % stake_per_share;
+        let score = (amount - remainder) + (remainder / 2);
+
+        total_score = total_score.saturating_add(score);
+        scores.push((p, score));
+      }
+
+      // stake the rewards
+      for (p, score) in scores {
+        let p_reward = reward.saturating_mul(score) / total_score;
+        // TODO: print a warning here?
+        let _ = ValidatorSets::<T>::deposit_stake(n, p, Amount(p_reward));
+      }
+    }
+  }
+}
+
+pub use pallet::*;