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Inflation pallet documentation
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pallets/inflation/src/lib.rsdiffbeforeafterboth1// Copyright 2019-2022 Unique Network (Gibraltar) Ltd.2// This file is part of Unique Network.34// Unique Network is free software: you can redistribute it and/or modify5// it under the terms of the GNU General Public License as published by6// the Free Software Foundation, either version 3 of the License, or7// (at your option) any later version.89// Unique Network is distributed in the hope that it will be useful,10// but WITHOUT ANY WARRANTY; without even the implied warranty of11// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the12// GNU General Public License for more details.1314// You should have received a copy of the GNU General Public License15// along with Unique Network. If not, see <http://www.gnu.org/licenses/>.1617//! # Inflation18//!19//! The inflation pallet is designed to increase the number of tokens at certain intervals.20//! With each iteration, increases the `total_issuance` value for the native token.21//! Executing an `on_initialize` hook at the beginning of each block, causing inflation to begin.22//!23//! ## Interface24//!25//! ### Dispatchable Functions26//!27//! * `start_inflation` - This method sets the inflation start date. Can be only called once.28//! Inflation start block can be backdated and will catch up. The method will create Treasury29//! account if it does not exist and perform the first inflation deposit.3031// #![recursion_limit = "1024"]32#![cfg_attr(not(feature = "std"), no_std)]3334#[cfg(feature = "runtime-benchmarks")]35mod benchmarking;3637#[cfg(test)]38mod tests;3940use frame_support::{41 dispatch::{DispatchResult},42 traits::{Currency, Get},43};44pub use pallet::*;45use sp_runtime::{46 Perbill,47 traits::{BlockNumberProvider},48};4950use sp_std::convert::TryInto;5152type BalanceOf<T> =53 <<T as Config>::Currency as Currency<<T as frame_system::Config>::AccountId>>::Balance;5455pub const YEAR: u32 = 5_259_600; // 6-second block56 // pub const YEAR: u32 = 2_629_800; // 12-second block57pub const TOTAL_YEARS_UNTIL_FLAT: u32 = 9;58pub const START_INFLATION_PERCENT: u32 = 10;59pub const END_INFLATION_PERCENT: u32 = 4;6061#[frame_support::pallet]62pub mod pallet {63 use super::*;64 use frame_support::pallet_prelude::*;65 use frame_system::pallet_prelude::*;6667 #[pallet::config]68 pub trait Config: frame_system::Config {69 type Currency: Currency<Self::AccountId>;70 type TreasuryAccountId: Get<Self::AccountId>;7172 // The block number provider73 type BlockNumberProvider: BlockNumberProvider<BlockNumber = Self::BlockNumber>;7475 /// Number of blocks that pass between treasury balance updates due to inflation76 #[pallet::constant]77 type InflationBlockInterval: Get<Self::BlockNumber>;78 }7980 #[pallet::pallet]81 #[pallet::generate_store(pub(super) trait Store)]82 pub struct Pallet<T>(_);8384 /// starting year total issuance85 #[pallet::storage]86 pub type StartingYearTotalIssuance<T: Config> =87 StorageValue<Value = BalanceOf<T>, QueryKind = ValueQuery>;8889 /// Current inflation for `InflationBlockInterval` number of blocks90 #[pallet::storage]91 pub type BlockInflation<T: Config> = StorageValue<Value = BalanceOf<T>, QueryKind = ValueQuery>;9293 /// Next target (relay) block when inflation will be applied94 #[pallet::storage]95 pub type NextInflationBlock<T: Config> =96 StorageValue<Value = T::BlockNumber, QueryKind = ValueQuery>;9798 /// Next target (relay) block when inflation is recalculated99 #[pallet::storage]100 pub type NextRecalculationBlock<T: Config> =101 StorageValue<Value = T::BlockNumber, QueryKind = ValueQuery>;102103 /// Relay block when inflation has started104 #[pallet::storage]105 pub type StartBlock<T: Config> = StorageValue<Value = T::BlockNumber, QueryKind = ValueQuery>;106107 #[pallet::hooks]108 impl<T: Config> Hooks<BlockNumberFor<T>> for Pallet<T> {109 fn on_initialize(_: T::BlockNumber) -> Weight110 where111 <T as frame_system::Config>::BlockNumber: From<u32>,112 {113 let mut consumed_weight = 0;114 let mut add_weight = |reads, writes, weight| {115 consumed_weight += T::DbWeight::get().reads_writes(reads, writes);116 consumed_weight += weight;117 };118119 let block_interval: u32 = T::InflationBlockInterval::get().try_into().unwrap_or(0);120 let current_relay_block = T::BlockNumberProvider::current_block_number();121 let next_inflation: T::BlockNumber = <NextInflationBlock<T>>::get();122 add_weight(1, 0, 5_000_000);123124 // Apply inflation every InflationBlockInterval blocks125 // If next_inflation == 0, this means inflation wasn't yet initialized126 if (next_inflation != 0u32.into()) && (current_relay_block >= next_inflation) {127 // Recalculate inflation on the first block of the year (or if it is not initialized yet)128 // Do the "current_relay_block >= next_recalculation" check in the "current_relay_block >= next_inflation"129 // block because it saves InflationBlockInterval DB reads for NextRecalculationBlock.130 let next_recalculation: T::BlockNumber = <NextRecalculationBlock<T>>::get();131 add_weight(1, 0, 0);132 if current_relay_block >= next_recalculation {133 Self::recalculate_inflation(next_recalculation);134 add_weight(0, 4, 5_000_000);135 }136137 T::Currency::deposit_into_existing(138 &T::TreasuryAccountId::get(),139 <BlockInflation<T>>::get(),140 )141 .ok();142143 // Update inflation block144 <NextInflationBlock<T>>::set(next_inflation + block_interval.into());145146 add_weight(3, 3, 10_000_000);147 }148149 consumed_weight150 }151 }152153 #[pallet::call]154 impl<T: Config> Pallet<T> {155 /// This method sets the inflation start date. Can be only called once.156 /// Inflation start block can be backdated and will catch up. The method will create Treasury157 /// account if it does not exist and perform the first inflation deposit.158 ///159 /// # Permissions160 ///161 /// * Root162 ///163 /// # Arguments164 ///165 /// * inflation_start_relay_block: The relay chain block at which inflation should start166 #[pallet::weight(0)]167 pub fn start_inflation(168 origin: OriginFor<T>,169 inflation_start_relay_block: T::BlockNumber,170 ) -> DispatchResult171 where172 <T as frame_system::Config>::BlockNumber: From<u32>,173 {174 ensure_root(origin)?;175176 // Start inflation if it has not been yet initialized177 if <StartBlock<T>>::get() == 0u32.into() {178 // Set inflation global start block179 <StartBlock<T>>::set(inflation_start_relay_block);180181 // Recalculate inflation. This can be backdated and will catch up.182 Self::recalculate_inflation(inflation_start_relay_block);183 let block_interval: u32 = T::InflationBlockInterval::get().try_into().unwrap_or(0);184 <NextInflationBlock<T>>::set(inflation_start_relay_block + block_interval.into());185186 // First time deposit - create Treasury account so that we can call deposit_into_existing everywhere else187 T::Currency::deposit_creating(188 &T::TreasuryAccountId::get(),189 <BlockInflation<T>>::get(),190 );191 }192193 Ok(())194 }195 }196}197198impl<T: Config> Pallet<T> {199 pub fn recalculate_inflation(recalculation_block: T::BlockNumber) {200 let current_year: u32 = ((recalculation_block - <StartBlock<T>>::get())201 / T::BlockNumber::from(YEAR))202 .try_into()203 .unwrap_or(0);204 let block_interval: u32 = T::InflationBlockInterval::get().try_into().unwrap_or(0);205206 let one_percent = Perbill::from_percent(1);207208 if current_year <= TOTAL_YEARS_UNTIL_FLAT {209 let amount: BalanceOf<T> = Perbill::from_rational(210 block_interval211 * (START_INFLATION_PERCENT * TOTAL_YEARS_UNTIL_FLAT212 - current_year * (START_INFLATION_PERCENT - END_INFLATION_PERCENT)),213 YEAR * TOTAL_YEARS_UNTIL_FLAT,214 ) * (one_percent * T::Currency::total_issuance());215 <BlockInflation<T>>::put(amount);216 } else {217 let amount: BalanceOf<T> =218 Perbill::from_rational(block_interval * END_INFLATION_PERCENT, YEAR)219 * (one_percent * T::Currency::total_issuance());220 <BlockInflation<T>>::put(amount);221 }222 <StartingYearTotalIssuance<T>>::set(T::Currency::total_issuance());223224 // Update recalculation and inflation blocks225 <NextRecalculationBlock<T>>::set(recalculation_block + YEAR.into());226 }227}