Reworks balloon for sending balloons in freeze

Balloons can be quite a motivator for a team and it can be frustrating
to spend >4 hours solving a problem to only get an AC during the freeze.
We used to have the show_balloons_postfreeze configflag to send balloons
during the freeze but this would always send balloons during the freeze.

show_balloons_postfreeze has now been replaced with
'minimum_number_of_balloons'. This setting now expresses the minimum
number of balloons to send to a team even during the freeze. To prevent
an information leak only balloons for problems that have been solved
before the freeze can be sent out.

Leaving this value to 0 keeps the 'old' behavior of not sending any
balloons while setting it to a value >#contestproblems results in the
old behaviour of sending all balloons during the freeze.

Author: tuupke

etc/db-config.yaml

@@ -255,11 +255,11 @@
             default_value: false
             public: true
             description: Show results of TOO-LATE submissions in team interface?
-        -   name: show_balloons_postfreeze
-            type: bool
-            default_value: false
+        -   name: minimum_number_of_balloons
+            type: int
+            default_value: 0
             public: true
-            description: Give out balloon notifications after the scoreboard has been frozen?
+            description: How many balloons to hand out ignoring freeze time. Only hands out balloons for problems solved pre-freeze.
         -   name: show_relative_time
             type: bool
             default_value: false

webapp/src/Service/BalloonService.php

@@ -92,15 +92,13 @@ public function updateBalloons(
     public function collectBalloonTable(Contest $contest, bool $todo = false): array
     {
         $em = $this->em;
-        $showPostFreeze = (bool)$this->config->get('show_balloons_postfreeze');
-        if (!$showPostFreeze) {
-            $freezetime = $contest->getFreezeTime();
-        }
 
+        // Retrieve all relevant balloons in 'submit order'. This allows accurate
+        // counts when deciding whether to hand out post-freeze balloons.
         $query = $em->createQueryBuilder()
             ->select('b', 's.submittime', 'p.probid',
                 't.teamid', 's', 't', 't.location',
-                'c.categoryid AS categoryid', 'c.name AS catname',
+                'c.categoryid AS categoryid', 'c.sortorder', 'c.name AS catname',
                 'co.cid', 'co.shortname',
                 'cp.shortname AS probshortname', 'cp.color',
                 'a.affilid AS affilid', 'a.shortname AS affilshort')
@@ -114,28 +112,20 @@ public function collectBalloonTable(Contest $contest, bool $todo = false): array
             ->leftJoin('t.affiliation', 'a')
             ->andWhere('co.cid = :cid')
             ->setParameter('cid', $contest->getCid())
-            ->orderBy('b.done', 'ASC')
-            ->addOrderBy('s.submittime', 'DESC');
+            ->orderBy('b.done', 'DESC')
+            ->addOrderBy('s.submittime', 'ASC');
 
         $balloons = $query->getQuery()->getResult();
-        // Loop once over the results to get totals.
-        $TOTAL_BALLOONS = [];
-        foreach ($balloons as $balloonsData) {
-            if ($balloonsData['color'] === null) {
-                continue;
-            }
 
-            $stime = $balloonsData['submittime'];
+        $minumumNumberOfBalloons = (int)$this->config->get('minimum_number_of_balloons');
+        $freezetime = $contest->getFreezeTime();
 
-            if (isset($freezetime) && $stime >= $freezetime) {
-                continue;
-            }
+        $balloonsTable = [];
 
-            $TOTAL_BALLOONS[$balloonsData['teamid']][$balloonsData['probshortname']] = $balloonsData[0]->getSubmission()->getContestProblem();
-        }
+        // Total balloons keeps track of the total balloons for a team, will be used to fill the rhs for every row in $balloonsTable.
+        // The same summary is used for every row for a team. References to elements in this array ensure easy updates.
+        $balloonSummaryPerTeam = [];
 
-        // Loop again to construct table.
-        $balloons_table = [];
         foreach ($balloons as $balloonsData) {
             if ($balloonsData['color'] === null) {
                 continue;
@@ -144,41 +134,72 @@ public function collectBalloonTable(Contest $contest, bool $todo = false): array
             $balloon = $balloonsData[0];
             $done = $balloon->getDone();
 
-            if ($todo && $done) {
-                continue;
+            // Ensure a summary-row exists for this sortorder and take a reference to these summaries. References are needed to ensure array reuse.
+            // Summaries are used to determine whether a balloon has been handed out so they need to be separated between sortorders.
+            $balloonSummaryPerTeam[$balloonsData['sortorder']] ??= [];
+            $relevantBalloonSummaries = &$balloonSummaryPerTeam[$balloonsData['sortorder']];
+
+            // Commonly no balloons are handed out post freeze.
+            // Underperforming teams' moral can be boosted by handing out balloons post-freeze.
+            // Handing out balloons for problems that have not been solved pre-freeze poses a potential information leak, so these are always excluded.
+            // So to decide whether to skip showing a balloon:
+            //   1. Check whether the scoreboard has been frozen.
+            //   2. Check whether the team has exceeded minimum number of balloons.
+            //   3. Check whether the problem been solved pre-freeze.
+            $stime = $balloonsData['submittime'];
+            if (isset($freezetime) && $stime >= $freezetime) {
+                if (key_exists($balloonsData['teamid'], $relevantBalloonSummaries) &&
+                    count($relevantBalloonSummaries[$balloonsData['teamid']]) >= $minumumNumberOfBalloons) {
+                    continue;
+                }
+
+                // Check if problem has been solved before the freeze by someone in the same sortorder to prevent information leak.
+                // The DOMjudge team (that commonly runs jury submissions) has so must be ignored.
+                // If a balloon for this problem should've been handed out it is safe to hand out again since balloons are handled in 'submit order'.
+                if (!array_reduce($relevantBalloonSummaries, fn($c, $i) => $c ||
+                    array_key_exists($balloonsData['probshortname'], $i), false)) {
+                    continue;
+                }
             }
 
-            $balloonId = $balloon->getBalloonId();
+            // Register the balloon that is handed out in the team summary.
+            $relevantBalloonSummaries[$balloonsData['teamid']][$balloonsData['probshortname']] = $balloon->getSubmission()->getContestProblem();
 
-            $stime = $balloonsData['submittime'];
-
-            if (isset($freezetime) && $stime >= $freezetime) {
+            // This balloon might not need to be listed, entire order is needed for counts though.
+            if ($todo && $done) {
                 continue;
             }
 
-            $balloondata = [];
-            $balloondata['balloonid'] = $balloonId;
-            $balloondata['time'] = $stime;
-            $balloondata['problem'] = $balloonsData['probshortname'];
-            $balloondata['contestproblem'] = $balloon->getSubmission()->getContestProblem();
-            $balloondata['team'] = $balloon->getSubmission()->getTeam();
-            $balloondata['teamid'] = $balloonsData['teamid'];
-            $balloondata['location'] = $balloonsData['location'];
-            $balloondata['affiliation'] = $balloonsData['affilshort'];
-            $balloondata['affiliationid'] = $balloonsData['affilid'];
-            $balloondata['category'] = $balloonsData['catname'];
-            $balloondata['categoryid'] = $balloonsData['categoryid'];
-
-            ksort($TOTAL_BALLOONS[$balloonsData['teamid']]);
-            $balloondata['total'] = $TOTAL_BALLOONS[$balloonsData['teamid']];
-
-            $balloondata['done'] = $done;
-
-            $balloons_table[] = [
-                'data' => $balloondata,
+            $balloonsTable[] = [
+                'data' => [
+                    'balloonid' => $balloon->getBalloonId(),
+                    'time' => $stime,
+                    'problem' => $balloonsData['probshortname'],
+                    'contestproblem' => $balloon->getSubmission()->getContestProblem(),
+                    'team' => $balloon->getSubmission()->getTeam(),
+                    'teamid' => $balloonsData['teamid'],
+                    'location' => $balloonsData['location'],
+                    'affiliation' => $balloonsData['affilshort'],
+                    'affiliationid' => $balloonsData['affilid'],
+                    'category' => $balloonsData['catname'],
+                    'categoryid' => $balloonsData['categoryid'],
+                    'done' => $done,
+
+                    // Reuse the same total summary table by taking a reference, makes updates easier.
+                    'total' => &$relevantBalloonSummaries[$balloonsData['teamid']],
+                ]
             ];
         }
-        return $balloons_table;
+
+        // Sort the balloons, since these are handled by reference each summary item only need to be sorted once.
+        foreach ($balloonSummaryPerTeam as $relevantBalloonSummaries) {
+            foreach ($relevantBalloonSummaries as &$balloons) {
+                ksort($balloons);
+            }
+        }
+
+        // Reverse the order so the newest appear first
+        return array_reverse($balloonsTable);
     }
 
     public function setDone(int $balloonId): void