From 6639e908e5a74d691a93edf1a16217911f4e4eb4 Mon Sep 17 00:00:00 2001
From: "Steinar H. Gunderson" <sgunderson@bigfoot.com>
Date: Wed, 21 Feb 2018 18:46:14 +0100
Subject: [PATCH] Activate tiebreak rules #3 and #5 only if everybody in the
 tiebreak group have played.

---
 carousel.js | 64 +++++++++++++++++++++++++++++------------------------
 1 file changed, 35 insertions(+), 29 deletions(-)

diff --git a/carousel.js b/carousel.js
index fcf5cc5..ac48db4 100644
--- a/carousel.js
+++ b/carousel.js
@@ -154,6 +154,7 @@ function rank(games, teams, start_rank, tiebreakers) {
 	}
 
 	// Rule #1: Head-to-head wins.
+	let num_relevant_games = 0;
 	let beat_parts = partition_by_beat(teams, function(beat, teams_to_idx) {
 		for (let i = 0; i < games.length; ++i) {
 			let idx1 = teams_to_idx[games[i].name1];
@@ -161,9 +162,10 @@ function rank(games, teams, start_rank, tiebreakers) {
 			if (idx1 !== undefined && idx2 !== undefined) {
 				if (games[i].score1 > games[i].score2) {
 					beat[idx1][idx2] = 1;
-				}
-				if (games[i].score1 < games[i].score2) {
+					++num_relevant_games;
+				} else if (games[i].score1 < games[i].score2) {
 					beat[idx2][idx1] = 1;
+					++num_relevant_games;
 				}
 			}
 		}
@@ -182,30 +184,32 @@ function rank(games, teams, start_rank, tiebreakers) {
 		return subrank_partitions(games, nplayed_parts, start_rank, tiebreakers);
 	}
 
-	// Rule #3: Head-to-head goal difference. 
+	// Rule #3: Head-to-head goal difference (if all have played).
 	let teams_to_idx = make_teams_to_idx(teams);
-	for (let i = 0; i < teams.length; i++) {
-		teams[i].h2h_gd = 0;
-		teams[i].h2h_goals = 0;
-	}
-	for (let i = 0; i < games.length; ++i) {
-		let idx1 = teams_to_idx[games[i].name1];
-		let idx2 = teams_to_idx[games[i].name2];
-		if (idx1 !== undefined && idx2 !== undefined &&
-		    !isNaN(games[i].score1) && !isNaN(games[i].score2)) {
-			teams[idx1].h2h_gd += games[i].score1;
-			teams[idx1].h2h_gd -= games[i].score2;
-			teams[idx2].h2h_gd += games[i].score2;
-			teams[idx2].h2h_gd -= games[i].score1;
-
-			teams[idx1].h2h_goals += games[i].score1;
-			teams[idx2].h2h_goals += games[i].score2;
+	if (num_relevant_games >= teams.length * (teams.length - 1) / 2) {
+		for (let i = 0; i < teams.length; i++) {
+			teams[i].h2h_gd = 0;
+			teams[i].h2h_goals = 0;
+		}
+		for (let i = 0; i < games.length; ++i) {
+			let idx1 = teams_to_idx[games[i].name1];
+			let idx2 = teams_to_idx[games[i].name2];
+			if (idx1 !== undefined && idx2 !== undefined &&
+			    !isNaN(games[i].score1) && !isNaN(games[i].score2)) {
+				teams[idx1].h2h_gd += games[i].score1;
+				teams[idx1].h2h_gd -= games[i].score2;
+				teams[idx2].h2h_gd += games[i].score2;
+				teams[idx2].h2h_gd -= games[i].score1;
+
+				teams[idx1].h2h_goals += games[i].score1;
+				teams[idx2].h2h_goals += games[i].score2;
+			}
+		}
+		let h2h_gd_parts = partition(teams, function(a, b) { return b.h2h_gd - a.h2h_gd });
+		if (h2h_gd_parts.length > 1) {
+			tiebreakers.push(explain_tiebreaker(h2h_gd_parts, 'head-to-head goal difference'));
+			return subrank_partitions(games, h2h_gd_parts, start_rank, tiebreakers);
 		}
-	}
-	let h2h_gd_parts = partition(teams, function(a, b) { return b.h2h_gd - a.h2h_gd });
-	if (h2h_gd_parts.length > 1) {
-		tiebreakers.push(explain_tiebreaker(h2h_gd_parts, 'head-to-head goal difference'));
-		return subrank_partitions(games, h2h_gd_parts, start_rank, tiebreakers);
 	}
 
 	// Rule #4: Goal difference against common opponents.
@@ -250,11 +254,13 @@ function rank(games, teams, start_rank, tiebreakers) {
 		return subrank_partitions(games, gd_parts, start_rank, tiebreakers);
 	}
 
-	// Rule #5: Head-to-head scored goals.
-	let h2h_goals_parts = partition(teams, function(a, b) { return b.h2h_goals - a.h2h_goals });
-	if (h2h_goals_parts.length > 1) {
-		tiebreakers.push(explain_tiebreaker(h2h_goals_parts, 'head-to-head scored goals'));
-		return subrank_partitions(games, h2h_goals_parts, start_rank, tiebreakers);
+	// Rule #5: Head-to-head scored goals (if all have played).
+	if (num_relevant_games >= teams.length * (teams.length - 1) / 2) {
+		let h2h_goals_parts = partition(teams, function(a, b) { return b.h2h_goals - a.h2h_goals });
+		if (h2h_goals_parts.length > 1) {
+			tiebreakers.push(explain_tiebreaker(h2h_goals_parts, 'head-to-head scored goals'));
+			return subrank_partitions(games, h2h_goals_parts, start_rank, tiebreakers);
+		}
 	}
 
 	// Rule #6: Goals scored against common opponents.
-- 
2.39.2