root
107 lines
3.6 KiB
PHP
107 lines
3.6 KiB
PHP
<?php
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namespace App\Services\Promotions\Placement;
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class BalancedSectionPlacementService
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{
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public const ALGORITHM = 'score_band_balanced_v1';
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public function assign(array $students, int $capacity): array
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{
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$total = count($students);
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if ($total === 0) {
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return [
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'section_count' => 0,
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'target_sizes' => [],
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'sections' => [],
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'assignments' => [],
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];
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}
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$sectionCount = $total <= $capacity ? 1 : (int) ceil($total / $capacity);
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$targetSizes = $this->targetSizes($total, $sectionCount);
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$sections = [];
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for ($i = 1; $i <= $sectionCount; $i++) {
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$sections[$i] = [
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'section_index' => $i,
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'target_size' => $targetSizes[$i],
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'total' => 0,
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'bands' => ['A' => 0, 'B' => 0, 'C' => 0, 'D' => 0],
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'students' => [],
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];
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}
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$grouped = ['A' => [], 'B' => [], 'C' => [], 'D' => []];
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foreach ($students as $student) {
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$band = $student['score_band'] ?? 'D';
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$grouped[$band][] = $student;
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}
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foreach (array_keys($grouped) as $band) {
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usort($grouped[$band], function (array $a, array $b): int {
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$scoreA = $a['final_score'] ?? $a['placement_score'] ?? -1;
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$scoreB = $b['final_score'] ?? $b['placement_score'] ?? -1;
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if ($scoreA !== $scoreB) {
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return $scoreB <=> $scoreA;
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}
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$name = strcmp((string) ($a['student_name'] ?? ''), (string) ($b['student_name'] ?? ''));
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return $name !== 0 ? $name : ((int) $a['student_id'] <=> (int) $b['student_id']);
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});
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}
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$assignments = [];
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$order = 1;
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foreach (['A', 'B', 'C', 'D'] as $band) {
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foreach ($grouped[$band] as $student) {
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$sectionIndex = $this->selectSection($sections, $band);
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$sections[$sectionIndex]['total']++;
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$sections[$sectionIndex]['bands'][$band]++;
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$sections[$sectionIndex]['students'][] = (int) $student['student_id'];
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$student['planned_section_index'] = $sectionIndex;
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$student['assignment_order'] = $order++;
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$assignments[] = $student;
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}
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}
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return [
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'section_count' => $sectionCount,
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'target_sizes' => $targetSizes,
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'sections' => array_values($sections),
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'assignments' => $assignments,
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];
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}
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private function targetSizes(int $total, int $sectionCount): array
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{
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$base = intdiv($total, $sectionCount);
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$remainder = $total % $sectionCount;
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$sizes = [];
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for ($i = 1; $i <= $sectionCount; $i++) {
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$sizes[$i] = $base + ($i <= $remainder ? 1 : 0);
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}
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return $sizes;
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}
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private function selectSection(array $sections, string $band): int
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{
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$eligible = array_filter($sections, fn ($s) => $s['total'] < $s['target_size']);
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if (empty($eligible)) {
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$eligible = $sections;
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}
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uasort($eligible, function (array $a, array $b) use ($band): int {
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$cmp = $a['total'] <=> $b['total'];
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if ($cmp !== 0) {
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return $cmp;
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}
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$cmp = ($a['bands'][$band] ?? 0) <=> ($b['bands'][$band] ?? 0);
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if ($cmp !== 0) {
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return $cmp;
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}
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return $a['section_index'] <=> $b['section_index'];
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});
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return (int) array_key_first($eligible);
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}
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}
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