326 lines
10 KiB
Rust
326 lines
10 KiB
Rust
/* OpenTally: Open-source election vote counting
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* Copyright © 2021–2022 Lee Yingtong Li (RunasSudo)
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU Affero General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Affero General Public License for more details.
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*
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* You should have received a copy of the GNU Affero General Public License
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* along with this program. If not, see <https://www.gnu.org/licenses/>.
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*/
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use crate::election::{Candidate, CountState};
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use crate::logger::smart_join;
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use crate::numbers::Number;
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use crate::stv::{STVError, STVOptions};
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#[allow(unused_imports)]
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use wasm_bindgen::prelude::wasm_bindgen;
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#[allow(unused_imports)]
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use std::io::{stdin, stdout, Write};
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/// Strategy for breaking ties
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#[derive(Clone, PartialEq)]
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pub enum TieStrategy {
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/// Break ties according to the candidate who first had more/fewer votes
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Forwards,
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/// Break ties according to the candidate who most recently had more/fewer votes
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Backwards,
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/// Break ties randomly (see [crate::sharandom])
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Random(String),
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/// Prompt the user to break ties
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Prompt,
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}
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/// Get a [Vec] of [TieStrategy] based on string representations
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pub fn from_strs<S: AsRef<str>>(strs: Vec<S>, mut random_seed: Option<String>) -> Vec<TieStrategy> {
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strs.into_iter().map(|t| match t.as_ref() {
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"forwards" => TieStrategy::Forwards,
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"backwards" => TieStrategy::Backwards,
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"random" => TieStrategy::Random(random_seed.take().expect("Must provide a --random-seed if using --ties random")),
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"prompt" => TieStrategy::Prompt,
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_ => panic!("Invalid --ties"),
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}).collect()
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}
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impl TieStrategy {
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/// Convert to CLI argument representation
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pub fn describe(&self) -> String {
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match self {
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Self::Forwards => "forwards",
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Self::Backwards => "backwards",
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Self::Random(_) => "random",
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Self::Prompt => "prompt",
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}.to_string()
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}
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/// Break a tie between the given candidates, selecting the highest candidate
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///
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/// The given candidates are assumed to be tied in this round
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pub fn choose_highest<'c, N: Number>(&self, state: &mut CountState<N>, opts: &STVOptions, candidates: &[&'c Candidate], prompt_text: &str) -> Result<&'c Candidate, STVError> {
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match self {
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Self::Forwards => {
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match &state.forwards_tiebreak {
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Some(tb) => {
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let mut candidates: Vec<&Candidate> = candidates.iter().copied().collect();
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// Compare b to a to sort high-to-low
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candidates.sort_unstable_by(|a, b| tb[b].cmp(&tb[a]));
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if tb[candidates[0]] == tb[candidates[1]] {
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return Err(STVError::UnresolvedTie);
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} else {
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state.logger.log_literal(format!("Tie between {} broken forwards.", smart_join(&candidates.iter().map(|c| c.name.as_str()).collect())));
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return Ok(candidates[0]);
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}
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}
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None => {
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// First stage
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return Err(STVError::UnresolvedTie);
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}
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}
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}
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Self::Backwards => {
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match &state.backwards_tiebreak {
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Some(tb) => {
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let mut candidates: Vec<&Candidate> = candidates.iter().copied().collect();
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candidates.sort_unstable_by(|a, b| tb[b].cmp(&tb[a]));
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if tb[candidates[0]] == tb[candidates[1]] {
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return Err(STVError::UnresolvedTie);
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} else {
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state.logger.log_literal(format!("Tie between {} broken backwards.", smart_join(&candidates.iter().map(|c| c.name.as_str()).collect())));
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return Ok(candidates[0]);
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}
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}
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None => {
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// First stage
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return Err(STVError::UnresolvedTie);
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}
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}
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}
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Self::Random(_) => {
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state.logger.log_literal(format!("Tie between {} broken at random.", smart_join(&candidates.iter().map(|c| c.name.as_str()).collect())));
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return Ok(candidates[state.random.as_mut().unwrap().next(candidates.len())]);
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}
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Self::Prompt => {
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match prompt(state, opts, candidates, prompt_text) {
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Ok(c) => {
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state.logger.log_literal(format!("Tie between {} broken by manual intervention.", smart_join(&candidates.iter().map(|c| c.name.as_str()).collect())));
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return Ok(c);
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}
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Err(e) => { return Err(e); }
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}
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}
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}
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}
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/// Break a tie between the given candidates, selecting the lowest candidate
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///
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/// The given candidates are assumed to be tied in this round
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pub fn choose_lowest<'c, N: Number>(&self, state: &mut CountState<N>, opts: &STVOptions, candidates: &[&'c Candidate], prompt_text: &str) -> Result<&'c Candidate, STVError> {
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match self {
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Self::Forwards => {
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let mut candidates: Vec<&Candidate> = candidates.iter().copied().collect();
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candidates.sort_unstable_by(|a, b|
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state.forwards_tiebreak.as_ref().unwrap()[a]
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.cmp(&state.forwards_tiebreak.as_ref().unwrap()[b])
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);
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if state.forwards_tiebreak.as_ref().unwrap()[candidates[0]] == state.forwards_tiebreak.as_ref().unwrap()[candidates[1]] {
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return Err(STVError::UnresolvedTie);
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} else {
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state.logger.log_literal(format!("Tie between {} broken forwards.", smart_join(&candidates.iter().map(|c| c.name.as_str()).collect())));
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return Ok(candidates[0]);
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}
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}
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Self::Backwards => {
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let mut candidates: Vec<&Candidate> = candidates.iter().copied().collect();
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candidates.sort_unstable_by(|a, b|
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state.backwards_tiebreak.as_ref().unwrap()[a]
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.cmp(&state.backwards_tiebreak.as_ref().unwrap()[b])
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);
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if state.backwards_tiebreak.as_ref().unwrap()[candidates[0]] == state.backwards_tiebreak.as_ref().unwrap()[candidates[1]] {
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return Err(STVError::UnresolvedTie);
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} else {
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state.logger.log_literal(format!("Tie between {} broken backwards.", smart_join(&candidates.iter().map(|c| c.name.as_str()).collect())));
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return Ok(candidates[0]);
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}
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}
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Self::Random(_seed) => {
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return self.choose_highest(state, opts, candidates, prompt_text);
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}
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Self::Prompt => {
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return self.choose_highest(state, opts, candidates, prompt_text);
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}
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}
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}
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}
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/// Return all maximal items according to the given key
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pub fn multiple_max_by<E: Copy, K, C: Ord>(items: &[E], key: K) -> Vec<E>
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where
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K: Fn(&E) -> C
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{
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let mut max_key = None;
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let mut max_items = Vec::new();
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for item in items.iter() {
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let item_key = key(item);
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match &max_key {
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Some(v) => {
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if &item_key > v {
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max_key = Some(item_key);
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max_items.clear();
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max_items.push(*item);
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} else if &item_key == v {
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max_items.push(*item);
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}
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}
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None => {
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max_key = Some(item_key);
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max_items.clear();
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max_items.push(*item);
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}
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}
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}
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return max_items;
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}
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/// Return all minimal items according to the given key
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pub fn multiple_min_by<E: Copy, K, C: Ord>(items: &[E], key: K) -> Vec<E>
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where
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K: Fn(&E) -> C
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{
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let mut min_key = None;
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let mut min_items = Vec::new();
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for item in items.iter() {
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let item_key = key(item);
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match &min_key {
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Some(v) => {
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if &item_key < v {
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min_key = Some(item_key);
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min_items.clear();
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min_items.push(*item);
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} else if &item_key == v {
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min_items.push(*item);
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}
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}
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None => {
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min_key = Some(item_key);
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min_items.clear();
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min_items.push(*item);
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}
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}
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}
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return min_items;
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}
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/// Prompt the candidate for input, depending on CLI or WebAssembly target
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#[cfg(not(target_arch = "wasm32"))]
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pub fn prompt<'c, N: Number>(state: &CountState<N>, opts: &STVOptions, candidates: &[&'c Candidate], prompt_text: &str) -> Result<&'c Candidate, STVError> {
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// Show intrastage progress if required
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if !state.logger.entries.is_empty() {
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// Print stage details
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println!("Tie during: {}", state.title);
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println!("{}", state.logger.render().join(" "));
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// Print candidates
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print!("{}", state.describe_candidates(opts));
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// Print summary rows
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print!("{}", state.describe_summary(opts));
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println!();
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}
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println!("Multiple tied candidates:");
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for (i, candidate) in candidates.iter().enumerate() {
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println!("{}. {}", i + 1, candidate.name);
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}
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let mut buffer = String::new();
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loop {
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print!("{} [1-{}] ", prompt_text, candidates.len());
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stdout().flush().expect("IO Error");
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stdin().read_line(&mut buffer).expect("IO Error");
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match buffer.trim().parse::<usize>() {
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Ok(val) => {
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if val >= 1 && val <= candidates.len() {
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println!();
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return Ok(candidates[val - 1]);
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} else {
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println!("Invalid selection");
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continue;
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}
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}
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Err(_) => {
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println!("Invalid selection");
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continue;
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}
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}
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}
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}
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#[cfg(target_arch = "wasm32")]
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#[wasm_bindgen]
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extern "C" {
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fn get_user_input(s: &str) -> Option<String>;
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}
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/// Prompt the candidate for input, depending on CLI or WebAssembly target
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#[cfg(target_arch = "wasm32")]
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pub fn prompt<'c, N: Number>(state: &CountState<N>, opts: &STVOptions, candidates: &[&'c Candidate], prompt_text: &str) -> Result<&'c Candidate, STVError> {
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let mut message = String::new();
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// Show intrastage progress if required
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if !state.logger.entries.is_empty() {
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// Print stage details
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message.push_str(&format!("Tie during: {}\n", state.title));
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message.push_str(&state.logger.render().join(" "));
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message.push('\n');
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// Print candidates
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message.push_str(&state.describe_candidates(opts));
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message.push('\n');
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// Print summary rows
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message.push_str(&state.describe_summary(opts));
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message.push('\n');
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}
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message.push_str(&"Multiple tied candidates:\n");
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for (i, candidate) in candidates.iter().enumerate() {
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message.push_str(&format!("{}. {}\n", i + 1, candidate.name));
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}
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message.push_str(&format!("{} [1-{}] ", prompt_text, candidates.len()));
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loop {
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let response = get_user_input(&message);
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match response {
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Some(response) => {
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match response.trim().parse::<usize>() {
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Ok(val) => {
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if val >= 1 && val <= candidates.len() {
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return Ok(candidates[val - 1]);
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} else {
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// Invalid selection
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continue;
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}
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}
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Err(_) => {
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// Invalid selection
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continue;
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}
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}
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}
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None => {
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// No available user input in buffer - stack will be unwound
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unreachable!();
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}
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}
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}
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}
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