OpenTally/src/ties.rs

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/* OpenTally: Open-source election vote counting
* Copyright © 2021 Lee Yingtong Li (RunasSudo)
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* 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 <https://www.gnu.org/licenses/>.
*/
use crate::election::{Candidate, CountState};
use crate::numbers::Number;
use crate::stv::STVError;
#[allow(unused_imports)]
use wasm_bindgen::prelude::wasm_bindgen;
#[allow(unused_imports)]
use std::io::{stdin, stdout, Write};
#[derive(PartialEq)]
pub enum TieStrategy<'s> {
Forwards,
Backwards,
Random(&'s str),
Prompt,
}
impl<'s> TieStrategy<'s> {
pub fn describe(&self) -> String {
match self {
Self::Forwards => "forwards",
Self::Backwards => "backwards",
Self::Random(_) => todo!(),
Self::Prompt => "prompt",
}.to_string()
}
pub fn choose_highest<'c, N: Number>(&self, state: &CountState<N>, candidates: &Vec<&'c Candidate>) -> Result<&'c Candidate, STVError> {
match self {
Self::Forwards => {
let mut candidates = candidates.clone();
candidates.sort_unstable_by(|a, b|
// Compare b to a to sort high-to-low
state.forwards_tiebreak.as_ref().unwrap().get(b).unwrap()
.cmp(&state.forwards_tiebreak.as_ref().unwrap().get(a).unwrap())
);
if state.forwards_tiebreak.as_ref().unwrap().get(candidates[0]).unwrap() == state.forwards_tiebreak.as_ref().unwrap().get(candidates[1]).unwrap() {
return Err(STVError::UnresolvedTie);
} else {
return Ok(candidates[0]);
}
}
Self::Backwards => {
let mut candidates = candidates.clone();
candidates.sort_unstable_by(|a, b|
state.backwards_tiebreak.as_ref().unwrap().get(b).unwrap()
.cmp(&state.backwards_tiebreak.as_ref().unwrap().get(a).unwrap())
);
if state.backwards_tiebreak.as_ref().unwrap().get(candidates[0]).unwrap() == state.backwards_tiebreak.as_ref().unwrap().get(candidates[1]).unwrap() {
return Err(STVError::UnresolvedTie);
} else {
return Ok(candidates[0]);
}
}
Self::Random(_seed) => { todo!() }
Self::Prompt => {
return prompt(candidates);
}
}
}
pub fn choose_lowest<'c, N: Number>(&self, state: &CountState<N>, candidates: &Vec<&'c Candidate>) -> Result<&'c Candidate, STVError> {
match self {
Self::Forwards => {
let mut candidates = candidates.clone();
candidates.sort_unstable_by(|a, b|
state.forwards_tiebreak.as_ref().unwrap().get(a).unwrap()
.cmp(&state.forwards_tiebreak.as_ref().unwrap().get(b).unwrap())
);
if state.forwards_tiebreak.as_ref().unwrap().get(candidates[0]).unwrap() == state.forwards_tiebreak.as_ref().unwrap().get(candidates[1]).unwrap() {
return Err(STVError::UnresolvedTie);
} else {
return Ok(candidates[0]);
}
}
Self::Backwards => {
let mut candidates = candidates.clone();
candidates.sort_unstable_by(|a, b|
state.backwards_tiebreak.as_ref().unwrap().get(a).unwrap()
.cmp(&state.backwards_tiebreak.as_ref().unwrap().get(b).unwrap())
);
if state.backwards_tiebreak.as_ref().unwrap().get(candidates[0]).unwrap() == state.backwards_tiebreak.as_ref().unwrap().get(candidates[1]).unwrap() {
return Err(STVError::UnresolvedTie);
} else {
return Ok(candidates[0]);
}
}
Self::Random(_seed) => {
return self.choose_highest(state, candidates);
}
Self::Prompt => {
return self.choose_highest(state, candidates);
}
}
}
}
#[cfg(not(target_arch = "wasm32"))]
fn prompt<'c>(candidates: &Vec<&'c Candidate>) -> Result<&'c Candidate, STVError> {
println!("Multiple tied candidates:");
for (i, candidate) in candidates.iter().enumerate() {
println!("{}. {}", i + 1, candidate.name);
}
let mut buffer = String::new();
loop {
print!("Which candidate to select? [1-{}] ", candidates.len());
stdout().flush().expect("IO Error");
stdin().read_line(&mut buffer).expect("IO Error");
match buffer.trim().parse::<usize>() {
Ok(val) => {
if val >= 1 && val <= candidates.len() {
println!();
return Ok(candidates[val - 1]);
} else {
println!("Invalid selection");
continue;
}
}
Err(_) => {
println!("Invalid selection");
continue;
}
}
}
}
#[cfg(target_arch = "wasm32")]
#[wasm_bindgen]
extern "C" {
fn read_user_input_buffer(s: &str) -> Option<String>;
}
#[cfg(target_arch = "wasm32")]
fn prompt<'c>(candidates: &Vec<&'c Candidate>) -> Result<&'c Candidate, STVError> {
let mut message = String::from("Multiple tied candidates:\n");
for (i, candidate) in candidates.iter().enumerate() {
message.push_str(&format!("{}. {}\n", i + 1, candidate.name));
}
message.push_str(&format!("Which candidate to select? [1-{}] ", candidates.len()));
match read_user_input_buffer(&message) {
Some(response) => {
match response.trim().parse::<usize>() {
Ok(val) => {
if val >= 1 && val <= candidates.len() {
return Ok(candidates[val - 1]);
} else {
let _ = read_user_input_buffer(&message);
return Err(STVError::RequireInput);
}
}
Err(_) => {
let _ = read_user_input_buffer(&message);
return Err(STVError::RequireInput);
}
}
}
None => {
return Err(STVError::RequireInput);
}
}
}