Initial implementation of prompt-based tie breaking

html/index.js

@@ -70,6 +70,13 @@ worker.onmessage = function(evt) {
 	} else if (evt.data.type === 'finalResultSummary') {
 		divLogs2.insertAdjacentHTML('beforeend', evt.data.summary);
 		document.getElementById('printPane').style.display = 'block';
+		
+	} else if (evt.data.type === 'requireInput') {
+		let response = window.prompt(evt.data.message);
+		while (response === null) {
+			response = window.prompt(evt.data.message);
+		}
+		worker.postMessage({'type': 'userInput', 'response': response});
 	}
 }
 

html/worker.js

@@ -8,9 +8,10 @@ async function initWasm() {
 }
 initWasm();
 
+var numbers, election, opts, state, stageNum;
+
 onmessage = function(evt) {
 	if (evt.data.type === 'countElection') {
-		let numbers;
 		if (evt.data.numbers === 'fixed') {
 			numbers = 'Fixed';
 			wasm.fixed_set_dps(evt.data.decimals);
@@ -23,14 +24,14 @@ onmessage = function(evt) {
 		}
 		
 		// Init election
-		let election = wasm['election_from_blt_' + numbers](evt.data.electionData);
+		election = wasm['election_from_blt_' + numbers](evt.data.electionData);
 		
 		if (evt.data.normaliseBallots) {
 			wasm['election_normalise_ballots_' + numbers](election);
 		}
 		
 		// Init STV options
-		let opts = wasm.STVOptions.new.apply(null, evt.data.optsStr);
+		opts = wasm.STVOptions.new.apply(null, evt.data.optsStr);
 		
 		// Describe count
 		postMessage({'type': 'describeCount', 'content': wasm['describe_count_' + numbers](evt.data.filePath, election, opts)});
@@ -39,17 +40,36 @@ onmessage = function(evt) {
 		postMessage({'type': 'initResultsTable', 'content': wasm['init_results_table_' + numbers](election, opts)});
 		
 		// Step election
-		let state = wasm['CountState' + numbers].new(election);
+		state = wasm['CountState' + numbers].new(election);
 		wasm['count_init_' + numbers](state, opts);
 		
 		postMessage({'type': 'updateResultsTable', 'result': wasm['update_results_table_' + numbers](1, state, opts)});
 		postMessage({'type': 'updateStageComments', 'comment': wasm['update_stage_comments_' + numbers](state)});
 		
-		for (let stageNum = 2;; stageNum++) {
+		stageNum = 2;
+		
+		resume_count();
+		
+	} else if (evt.data.type == 'userInput') {
+		user_input_buffer = evt.data.response;
+		resume_count();
+	}
+}
+
+function resume_count() {
+	for (;; stageNum++) {
+		try {
 			let isDone = wasm['count_one_stage_' + numbers](state, opts);
 			if (isDone) {
 				break;
 			}
+		} catch (ex) {
+			if (ex === "RequireInput") {
+				return;
+			} else {
+				throw ex;
+			}
+		}
 		
 		postMessage({'type': 'updateResultsTable', 'result': wasm['update_results_table_' + numbers](stageNum, state, opts)});
 		postMessage({'type': 'updateStageComments', 'comment': wasm['update_stage_comments_' + numbers](state)});
@@ -58,4 +78,16 @@ onmessage = function(evt) {
 	postMessage({'type': 'updateResultsTable', 'result': wasm['finalise_results_table_' + numbers](state)});
 	postMessage({'type': 'finalResultSummary', 'summary': wasm['final_result_summary_' + numbers](state)});
 }
+
+var user_input_buffer = null;
+
+function read_user_input_buffer(message) {
+	if (user_input_buffer === null) {
+		postMessage({'type': 'requireInput', 'message': message});
+		return null;
+	} else {
+		let user_input = user_input_buffer;
+		user_input_buffer = null;
+		return user_input;
+	}
 }

src/lib.rs

@@ -19,6 +19,7 @@ pub mod election;
 pub mod logger;
 pub mod numbers;
 pub mod stv;
+pub mod ties;
 
 use git_version::git_version;
 use wasm_bindgen::prelude::wasm_bindgen;

src/main.rs

@@ -208,7 +208,7 @@ where
 	
 	loop {
 		let is_done = stv::count_one_stage(&mut state, &stv_opts);
-		if is_done {
+		if is_done.unwrap() {
 			break;
 		}
 		stage_num += 1;

src/stv/mod.rs

@@ -22,6 +22,7 @@ pub mod wasm;
 
 use crate::numbers::Number;
 use crate::election::{Candidate, CandidateState, CountCard, CountState, Parcel, Vote};
+use crate::ties::TieStrategy;
 
 use itertools::Itertools;
 use wasm_bindgen::prelude::wasm_bindgen;
@@ -264,13 +265,19 @@ impl ExclusionMethod {
 	}
 }
 
+#[wasm_bindgen]
+#[derive(Debug)]
+pub enum STVError {
+	RequireInput,
+}
+
 pub fn count_init<N: Number>(mut state: &mut CountState<'_, N>, opts: &STVOptions) {
 	distribute_first_preferences(&mut state);
 	calculate_quota(&mut state, opts);
 	elect_meeting_quota(&mut state, opts);
 }
 
-pub fn count_one_stage<'a, N: Number>(mut state: &mut CountState<'a, N>, opts: &STVOptions) -> bool
+pub fn count_one_stage<'a, N: Number>(mut state: &mut CountState<'a, N>, opts: &STVOptions) -> Result<bool, STVError>
 where
 	for<'r> &'r N: ops::Sub<&'r N, Output=N>,
 	for<'r> &'r N: ops::Div<&'r N, Output=N>,
@@ -281,36 +288,36 @@ where
 	
 	// Finish count
 	if finished_before_stage(&state) {
-		return true;
+		return Ok(true);
 	}
 	
 	// Continue exclusions
 	if continue_exclusion(&mut state, &opts) {
 		calculate_quota(&mut state, opts);
 		elect_meeting_quota(&mut state, opts);
-		return false;
+		return Ok(false);
 	}
 	
 	// Distribute surpluses
-	if distribute_surpluses(&mut state, &opts) {
+	if distribute_surpluses(&mut state, &opts)? {
 		calculate_quota(&mut state, opts);
 		elect_meeting_quota(&mut state, opts);
-		return false;
+		return Ok(false);
 	}
 	
 	// Attempt bulk election
 	if bulk_elect(&mut state) {
-		return false;
+		return Ok(false);
 	}
 	
 	// Exclude lowest hopeful
-	if exclude_hopefuls(&mut state, &opts) {
+	if exclude_hopefuls(&mut state, &opts)? {
 		calculate_quota(&mut state, opts);
 		elect_meeting_quota(&mut state, opts);
-		return false;
+		return Ok(false);
 	}
 	
-	todo!();
+	panic!("Count incomplete but unable to proceed");
 }
 
 struct NextPreferencesResult<'a, N> {
@@ -596,14 +603,15 @@ where
 	return true;
 }
 
-fn distribute_surpluses<N: Number>(state: &mut CountState<N>, opts: &STVOptions) -> bool
+fn distribute_surpluses<N: Number>(state: &mut CountState<N>, opts: &STVOptions) -> Result<bool, STVError>
 where
 	for<'r> &'r N: ops::Sub<&'r N, Output=N>,
 	for<'r> &'r N: ops::Div<&'r N, Output=N>,
 	for<'r> &'r N: ops::Neg<Output=N>
 {
 	let quota = state.quota.as_ref().unwrap();
-	let mut has_surplus: Vec<(&&Candidate, &CountCard<N>)> = state.candidates.iter()
+	let mut has_surplus: Vec<(&Candidate, &CountCard<N>)> = state.election.candidates.iter() // Present in order in case of tie
+		.map(|c| (c, state.candidates.get(c).unwrap()))
 		.filter(|(_, cc)| &cc.votes > quota)
 		.collect();
 	let total_surpluses = has_surplus.iter()
@@ -614,28 +622,37 @@ where
 		if opts.defer_surpluses {
 			if can_defer_surpluses(state, opts, &total_surpluses) {
 				state.logger.log_literal(format!("Distribution of surpluses totalling {:.dps$} votes will be deferred.", total_surpluses, dps=opts.pp_decimals));
-				return false;
+				return Ok(false);
 			}
 		}
 		
 		match opts.surplus_order {
 			SurplusOrder::BySize => {
 				// Compare b with a to sort high-low
-				has_surplus.sort_unstable_by(|a, b| b.1.votes.partial_cmp(&a.1.votes).unwrap());
+				has_surplus.sort_by(|a, b| b.1.votes.partial_cmp(&a.1.votes).unwrap());
 			}
 			SurplusOrder::ByOrder => {
-				has_surplus.sort_unstable_by(|a, b| a.1.order_elected.partial_cmp(&b.1.order_elected).unwrap());
+				has_surplus.sort_by(|a, b| a.1.order_elected.partial_cmp(&b.1.order_elected).unwrap());
 			}
 		}
 		
 		// Distribute top candidate's surplus
-		// TODO: Handle ties
+		let elected_candidate;
-		let elected_candidate = has_surplus.first_mut().unwrap().0;
+		
+		// Handle ties
+		if has_surplus.len() > 1 && has_surplus[0].1.votes == has_surplus[1].1.votes {
+			let max_votes = &has_surplus[0].1.votes;
+			let has_surplus = has_surplus.into_iter().filter_map(|(c, cc)| if &cc.votes == max_votes { Some(c) } else { None }).collect();
+			elected_candidate = TieStrategy::Prompt.choose_highest(has_surplus)?;
+		} else {
+			elected_candidate = has_surplus.first_mut().unwrap().0;
+		}
+		
 		distribute_surplus(state, &opts, elected_candidate);
 		
-		return true;
+		return Ok(true);
 	}
-	return false;
+	return Ok(false);
 }
 
 /// Return the denominator of the transfer value
@@ -945,7 +962,7 @@ fn hopefuls_to_bulk_exclude<'a, N: Number>(state: &CountState<'a, N>, _opts: &ST
 	return excluded_candidates;
 }
 
-fn exclude_hopefuls<'a, N: Number>(state: &mut CountState<'a, N>, opts: &STVOptions) -> bool
+fn exclude_hopefuls<'a, N: Number>(state: &mut CountState<'a, N>, opts: &STVOptions) -> Result<bool, STVError>
 where
 	for<'r> &'r N: ops::Div<&'r N, Output=N>,
 {
@@ -958,16 +975,23 @@ where
 	
 	// Exclude lowest ranked candidate
 	if excluded_candidates.len() == 0 {
-		let mut hopefuls: Vec<(&&Candidate, &CountCard<N>)> = state.candidates.iter()
+		let mut hopefuls: Vec<(&Candidate, &CountCard<N>)> = state.election.candidates.iter() // Present in order in case of tie
+			.map(|c| (c, state.candidates.get(c).unwrap()))
 			.filter(|(_, cc)| cc.state == CandidateState::Hopeful)
 			.collect();
 		
 		// Sort by votes
-		// TODO: Handle ties
+		hopefuls.sort_by(|a, b| a.1.votes.partial_cmp(&b.1.votes).unwrap());
-		hopefuls.sort_unstable_by(|a, b| a.1.votes.partial_cmp(&b.1.votes).unwrap());
 		
+		// Handle ties
+		if hopefuls.len() > 1 && hopefuls[0].1.votes == hopefuls[1].1.votes {
+			let min_votes = &hopefuls[0].1.votes;
+			let hopefuls = hopefuls.into_iter().filter_map(|(c, cc)| if &cc.votes == min_votes { Some(c) } else { None }).collect();
+			excluded_candidates = vec![TieStrategy::Prompt.choose_lowest(hopefuls)?];
+		} else {
 			excluded_candidates = vec![&hopefuls.first().unwrap().0];
 		}
+	}
 	
 	let mut names: Vec<&str> = excluded_candidates.iter().map(|c| c.name.as_str()).collect();
 	names.sort();
@@ -981,7 +1005,7 @@ where
 	
 	exclude_candidates(state, opts, excluded_candidates);
 	
-	return true;
+	return Ok(true);
 }
 
 fn continue_exclusion<'a, N: Number>(state: &mut CountState<'a, N>, opts: &STVOptions) -> bool
@@ -990,7 +1014,7 @@ where
 {
 	// Cannot filter by raw vote count, as candidates may have 0.00 votes but still have recorded ballot papers
 	let mut excluded_with_votes: Vec<(&&Candidate, &CountCard<N>)> = state.candidates.iter()
-		//.filter(|(_, cc)| cc.state == CandidateState::Excluded && !cc.votes.is_zero())
+		//.filter(|(_, cc)| cc.state == CandidateState::EXCLUDED && !cc.votes.is_zero())
 		.filter(|(_, cc)| cc.state == CandidateState::Excluded && cc.parcels.iter().any(|p| p.len() > 0))
 		.collect();
 	

src/stv/wasm.rs

@@ -22,7 +22,7 @@ use crate::stv;
 extern crate console_error_panic_hook;
 
 use js_sys::Array;
-use wasm_bindgen::prelude::wasm_bindgen;
+use wasm_bindgen::{JsValue, prelude::wasm_bindgen};
 
 // Init
 
@@ -61,8 +61,11 @@ macro_rules! impl_type {
 		
 		#[wasm_bindgen]
 		#[allow(non_snake_case)]
-		pub fn [<count_one_stage_$type>](state: &mut [<CountState$type>], opts: &stv::STVOptions) -> bool {
+		pub fn [<count_one_stage_$type>](state: &mut [<CountState$type>], opts: &stv::STVOptions) -> Result<bool, JsValue> {
-			return stv::count_one_stage(&mut state.0, &opts);
+			match stv::count_one_stage(&mut state.0, &opts) {
+				Ok(v) => Ok(v),
+				Err(stv::STVError::RequireInput) => Err("RequireInput".into()),
+			}
 		}
 		
 		// Reporting

src/ties.rs

@@ -0,0 +1,124 @@
+/*  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;
+use crate::stv::STVError;
+
+#[allow(unused_imports)]
+use wasm_bindgen::prelude::wasm_bindgen;
+
+#[allow(unused_imports)]
+use std::io::{stdin, stdout, Write};
+
+pub enum TieStrategy<'s> {
+	Forwards,
+	Backwards,
+	Random(&'s str),
+	Prompt,
+}
+
+impl<'s> TieStrategy<'s> {
+	pub fn choose_highest<'c>(&self, candidates: Vec<&'c Candidate>) -> Result<&'c Candidate, STVError> {
+		match self {
+			Self::Forwards => { todo!() }
+			Self::Backwards => { todo!() }
+			Self::Random(_seed) => { todo!() }
+			Self::Prompt => {
+				return prompt(candidates);
+			}
+		}
+	}
+	
+	pub fn choose_lowest<'c>(&self, candidates: Vec<&'c Candidate>) -> Result<&'c Candidate, STVError> {
+		match self {
+			Self::Forwards => { todo!() }
+			Self::Backwards => { todo!() }
+			Self::Random(_seed) => {
+				return self.choose_highest(candidates);
+			}
+			Self::Prompt => {
+				return self.choose_highest(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);
+		}
+	}
+}

tests/ers97.rs

@@ -83,7 +83,7 @@ fn ers97_rational() {
 		while stage_num < stage {
 			// Step through stages
 			// Assert count not yet done
-			assert_eq!(stv::count_one_stage(&mut state, &stv_opts), false);
+			assert_eq!(stv::count_one_stage(&mut state, &stv_opts).unwrap(), false);
 			stage_num += 1;
 		}
 		

tests/scotland.rs

@@ -119,11 +119,11 @@ fn scotland_linn07_fixed5() {
 			}
 		}
 		
-		assert_eq!(stv::count_one_stage(&mut state, &stv_opts), false);
+		assert_eq!(stv::count_one_stage(&mut state, &stv_opts).unwrap(), false);
 		stage_num += 1;
 	}
 	
-	assert_eq!(stv::count_one_stage(&mut state, &stv_opts), true);
+	assert_eq!(stv::count_one_stage(&mut state, &stv_opts).unwrap(), true);
 }
 
 fn get_cand_stage(candidate: &Element, idx: usize) -> &Element {

tests/utils/mod.rs

@@ -69,7 +69,7 @@ where
 		while stage_num < stage {
 			// Step through stages
 			// Assert count not yet done
-			assert_eq!(stv::count_one_stage(&mut state, &stv_opts), false);
+			assert_eq!(stv::count_one_stage(&mut state, &stv_opts).unwrap(), false);
 			stage_num += 1;
 		}
 		validate_stage(idx, &state, &records);