Implement --surplus-order

src/main.rs

@@ -72,6 +72,9 @@ struct STV {
 	#[clap(help_heading=Some("STV VARIANTS"), long, possible_values=&["wig", "uig", "eg", "meek"], default_value="wig", value_name="method")]
 	surplus: String,
 	
+	#[clap(help_heading=Some("STV VARIANTS"), long, possible_values=&["by_size", "by_order"], default_value="by_size", value_name="order")]
+	surplus_order: String,
+	
 	/// Examine only transferable papers during surplus distributions
 	#[clap(help_heading=Some("STV VARIANTS"), long)]
 	transferable_only: bool,
@@ -131,6 +134,11 @@ where
 			"meek" => stv::SurplusMethod::Meek,
 			_ => panic!("Invalid --surplus"),
 		},
+		surplus_order: match cmd_opts.surplus_order.as_str() {
+			"by_size" => stv::SurplusOrder::BySize,
+			"by_order" => stv::SurplusOrder::ByOrder,
+			_ => panic!("Invalid --surplus-order"),
+		},
 		transferable_only: cmd_opts.transferable_only,
 		exclusion: match cmd_opts.exclusion.as_str() {
 			"single_stage" => stv::ExclusionMethod::SingleStage,

src/stv/mod.rs

@@ -32,6 +32,7 @@ use std::ops;
 pub struct STVOptions {
 	pub round_votes: Option<usize>,
 	pub surplus: SurplusMethod,
+	pub surplus_order: SurplusOrder,
 	pub transferable_only: bool,
 	pub exclusion: ExclusionMethod,
 	pub pp_decimals: usize,
@@ -46,6 +47,13 @@ pub enum SurplusMethod {
 	Meek,
 }
 
+#[wasm_bindgen]
+#[derive(Clone, Copy)]
+pub enum SurplusOrder {
+	BySize,
+	ByOrder,
+}
+
 #[wasm_bindgen]
 #[derive(Clone, Copy)]
 pub enum ExclusionMethod {
@@ -253,8 +261,14 @@ where
 		.collect();
 	
 	if has_surplus.len() > 0 {
-		// TODO: Different sorting orders
+		match opts.surplus_order {
+			SurplusOrder::BySize => {
+				has_surplus.sort_unstable_by(|a, b| a.1.votes.partial_cmp(&b.1.votes).unwrap());
+			}
+			SurplusOrder::ByOrder => {
 				has_surplus.sort_unstable_by(|a, b| a.1.order_elected.partial_cmp(&b.1.order_elected).unwrap());
+			}
+		}
 		
 		// Distribute top candidate's surplus
 		// TODO: Handle ties

tests/aec.rs

@@ -56,6 +56,7 @@ fn aec_tas19_rational() {
 	let stv_opts = stv::STVOptions {
 		round_votes: Some(0),
 		surplus: stv::SurplusMethod::UIG,
+		surplus_order: stv::SurplusOrder::ByOrder,
 		transferable_only: false,
 		exclusion: stv::ExclusionMethod::ByValue,
 		pp_decimals: 2,