Refactoring Checkpoint: (WIP)
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// This file is part of Bizinikiwi.
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// Copyright (C) Parity Technologies (UK) Ltd.
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// SPDX-License-Identifier: Apache-2.0
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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//! Support code to ease the process of generating bag thresholds.
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//!
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//! NOTE: this assume the runtime implements [`pezpallet_staking::Config`], as it requires an
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//! implementation of the traits [`pezframe_support::traits::Currency`] and `CurrencyToVote`.
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//!
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//! The process of adding bags to a runtime requires only four steps.
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//!
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//! 1. Update the runtime definition.
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//!
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//! ```ignore
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//! parameter_types!{
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//! pub const BagThresholds: &'static [u64] = &[];
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//! }
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//!
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//! impl pezpallet_bags_list::Config for Runtime {
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//! // <snip>
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//! type BagThresholds = BagThresholds;
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//! }
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//! ```
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//!
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//! 2. Write a little program to generate the definitions. This program exists only to hook together
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//! the runtime definitions with the various calculations here. Take a look at
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//! _utils/pezframe/pez_generate_bags/node-runtime_ for an example.
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//!
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//! 3. Run that program:
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//!
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//! ```sh,notrust
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//! $ cargo run -p node-runtime-pez-generate-bags -- --total-issuance 1234 --minimum-balance 1
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//! output.rs ```
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//!
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//! 4. Update the runtime definition.
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//!
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//! ```diff,notrust
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//! + mod output;
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//! - pub const BagThresholds: &'static [u64] = &[];
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//! + pub const BagThresholds: &'static [u64] = &output::THRESHOLDS;
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//! ```
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use pezframe_election_provider_support::VoteWeight;
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use pezframe_support::traits::Get;
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use std::{
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io::Write,
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path::{Path, PathBuf},
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};
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/// Compute the existential weight for the specified configuration.
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///
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/// Note that this value depends on the current issuance, a quantity known to change over time.
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/// This makes the project of computing a static value suitable for inclusion in a static,
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/// generated file _excitingly unstable_.
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fn existential_weight<T: pezpallet_staking::Config>(
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total_issuance: u128,
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minimum_balance: u128,
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) -> VoteWeight {
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use pezsp_staking::currency_to_vote::CurrencyToVote;
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T::CurrencyToVote::to_vote(
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minimum_balance
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.try_into()
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.map_err(|_| "failed to convert minimum_balance to type Balance")
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.unwrap(),
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total_issuance
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.try_into()
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.map_err(|_| "failed to convert total_issuance to type Balance")
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.unwrap(),
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)
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}
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/// Return the path to a header file used in this repository if is exists.
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///
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/// Just searches the git working directory root for files matching certain patterns; it's
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/// pretty naive.
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fn path_to_header_file() -> Option<PathBuf> {
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let mut workdir: &Path = &std::env::current_dir().ok()?;
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while !workdir.join(".git").exists() {
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workdir = workdir.parent()?;
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}
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for file_name in &["HEADER-APACHE2", "HEADER-GPL3", "HEADER", "file_header.txt"] {
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let path = workdir.join(file_name);
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if path.exists() {
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return Some(path);
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}
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}
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None
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}
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/// Create an underscore formatter: a formatter which inserts `_` every 3 digits of a number.
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fn underscore_formatter() -> num_format::CustomFormat {
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num_format::CustomFormat::builder()
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.grouping(num_format::Grouping::Standard)
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.separator("_")
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.build()
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.expect("format described here meets all constraints")
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}
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/// Compute the constant ratio for the thresholds.
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///
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/// This ratio ensures that each bag, with the possible exceptions of certain small ones and the
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/// final one, is a constant multiple of the previous, while fully occupying the `VoteWeight`
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/// space.
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pub fn constant_ratio(existential_weight: VoteWeight, n_bags: usize) -> f64 {
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((VoteWeight::MAX as f64 / existential_weight as f64).ln() / ((n_bags - 1) as f64)).exp()
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}
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/// Compute the list of bag thresholds.
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///
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/// Returns a list of exactly `n_bags` elements, except in the case of overflow.
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/// The first element is always `existential_weight`.
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/// The last element is always `VoteWeight::MAX`.
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///
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/// All other elements are computed from the previous according to the formula
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/// `threshold[k + 1] = (threshold[k] * ratio).max(threshold[k] + 1);`
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pub fn thresholds(
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existential_weight: VoteWeight,
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constant_ratio: f64,
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n_bags: usize,
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) -> Vec<VoteWeight> {
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const WEIGHT_LIMIT: f64 = VoteWeight::MAX as f64;
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let mut thresholds = Vec::with_capacity(n_bags);
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if n_bags > 1 {
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thresholds.push(existential_weight);
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}
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while n_bags > 0 && thresholds.len() < n_bags - 1 {
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let last = thresholds.last().copied().unwrap_or(existential_weight);
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let successor = (last as f64 * constant_ratio).round().max(last as f64 + 1.0);
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if successor < WEIGHT_LIMIT {
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thresholds.push(successor as VoteWeight);
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} else {
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eprintln!("unexpectedly exceeded weight limit; breaking threshold generation loop");
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break;
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}
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}
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thresholds.push(VoteWeight::MAX);
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debug_assert_eq!(thresholds.len(), n_bags);
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debug_assert!(n_bags == 0 || thresholds[0] == existential_weight);
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debug_assert!(n_bags == 0 || thresholds[thresholds.len() - 1] == VoteWeight::MAX);
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thresholds
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}
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/// Write a thresholds module to the path specified.
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///
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/// Parameters:
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/// - `n_bags` the number of bags to generate.
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/// - `output` the path to write to; should terminate with a Rust module name, i.e.
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/// `foo/bar/thresholds.rs`.
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/// - `total_issuance` the total amount of the currency in the network.
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/// - `minimum_balance` the minimum balance of the currency required for an account to exist (i.e.
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/// existential deposit).
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///
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/// This generated module contains, in order:
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///
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/// - The contents of the header file in this repository's root, if found.
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/// - Module documentation noting that this is autogenerated and when.
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/// - Some associated constants.
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/// - The constant array of thresholds.
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pub fn generate_thresholds<T: pezpallet_staking::Config>(
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n_bags: usize,
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output: &Path,
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total_issuance: u128,
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minimum_balance: u128,
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) -> Result<(), std::io::Error> {
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// ensure the file is accessible
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if let Some(parent) = output.parent() {
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if !parent.exists() {
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std::fs::create_dir_all(parent)?;
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}
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}
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// copy the header file
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if let Some(header_path) = path_to_header_file() {
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std::fs::copy(header_path, output)?;
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}
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// open an append buffer
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let file = std::fs::OpenOptions::new().create(true).append(true).open(output)?;
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let mut buf = std::io::BufWriter::new(file);
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// create underscore formatter and format buffer
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let mut num_buf = num_format::Buffer::new();
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let format = underscore_formatter();
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// module docs
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let now = chrono::Utc::now();
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writeln!(buf)?;
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writeln!(buf, "//! Autogenerated bag thresholds.")?;
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writeln!(buf, "//!")?;
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writeln!(buf, "//! Generated on {}", now.to_rfc3339())?;
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writeln!(buf, "//! Arguments")?;
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writeln!(buf, "//! Total issuance: {}", &total_issuance)?;
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writeln!(buf, "//! Minimum balance: {}", &minimum_balance)?;
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writeln!(
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buf,
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"//! for the {} runtime.",
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<T as pezframe_system::Config>::Version::get().spec_name,
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)?;
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let existential_weight = existential_weight::<T>(total_issuance, minimum_balance);
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num_buf.write_formatted(&existential_weight, &format);
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writeln!(buf)?;
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writeln!(buf, "/// Existential weight for this runtime.")?;
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writeln!(buf, "#[cfg(any(test, feature = \"std\"))]")?;
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writeln!(buf, "#[allow(unused)]")?;
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writeln!(buf, "pub const EXISTENTIAL_WEIGHT: u64 = {};", num_buf.as_str())?;
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// constant ratio
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let constant_ratio = constant_ratio(existential_weight, n_bags);
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writeln!(buf)?;
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writeln!(buf, "/// Constant ratio between bags for this runtime.")?;
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writeln!(buf, "#[cfg(any(test, feature = \"std\"))]")?;
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writeln!(buf, "#[allow(unused)]")?;
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writeln!(buf, "pub const CONSTANT_RATIO: f64 = {:.16};", constant_ratio)?;
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// thresholds
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let thresholds = thresholds(existential_weight, constant_ratio, n_bags);
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writeln!(buf)?;
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writeln!(buf, "/// Upper thresholds delimiting the bag list.")?;
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writeln!(buf, "pub const THRESHOLDS: [u64; {}] = [", thresholds.len())?;
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for threshold in &thresholds {
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num_buf.write_formatted(threshold, &format);
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// u64::MAX, with spacers every 3 digits, is 26 characters wide
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writeln!(buf, " {:>26},", num_buf.as_str())?;
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}
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writeln!(buf, "];")?;
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// thresholds balance
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writeln!(buf)?;
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writeln!(buf, "/// Upper thresholds delimiting the bag list.")?;
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writeln!(buf, "pub const THRESHOLDS_BALANCES: [u128; {}] = [", thresholds.len())?;
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for threshold in thresholds {
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num_buf.write_formatted(&threshold, &format);
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// u64::MAX, with spacers every 3 digits, is 26 characters wide
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writeln!(buf, " {:>26},", num_buf.as_str())?;
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}
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writeln!(buf, "];")?;
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Ok(())
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}
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