<?php

declare(strict_types=1);

namespace App\Scolarite\Application\Query\GetChildrenGrades;

use function array_sum;
use function count;
use function round;

/**
 * Calcule les moyennes par matière et la moyenne générale
 * à partir des notes visibles (respectant le délai parent).
 *
 * Ne lit PAS les agrégats pré-calculés (student_averages) car ceux-ci
 * incluent des notes encore dans la période de délai.
 */
final readonly class GetChildrenGradesSummaryHandler
{
    public function __construct(
        private GetChildrenGradesHandler $gradesHandler,
    ) {
    }

    /** @return array<ChildGradesSummaryDto> */
    public function __invoke(GetChildrenGradesSummaryQuery $query): array
    {
        // Réutilise le handler notes qui applique le délai de visibilité
        $childrenGrades = ($this->gradesHandler)(new GetChildrenGradesQuery(
            parentId: $query->parentId,
            tenantId: $query->tenantId,
        ));

        $result = [];

        foreach ($childrenGrades as $child) {
            // Grouper par matière et calculer les moyennes pondérées
            $subjectData = [];

            foreach ($child->grades as $grade) {
                if ($grade->value === null) {
                    continue;
                }

                $key = $grade->subjectId;

                if (!isset($subjectData[$key])) {
                    $subjectData[$key] = [
                        'subjectId' => $grade->subjectId,
                        'subjectName' => $grade->subjectName,
                        'weightedSum' => 0.0,
                        'coefficientSum' => 0.0,
                        'gradeCount' => 0,
                    ];
                }

                $subjectData[$key]['weightedSum'] += $grade->value * $grade->coefficient;
                $subjectData[$key]['coefficientSum'] += $grade->coefficient;
                ++$subjectData[$key]['gradeCount'];
            }

            $subjectAverages = [];

            foreach ($subjectData as $data) {
                if ($data['coefficientSum'] > 0) {
                    $subjectAverages[] = [
                        'subjectId' => $data['subjectId'],
                        'subjectName' => $data['subjectName'],
                        'average' => round($data['weightedSum'] / $data['coefficientSum'], 2),
                        'gradeCount' => $data['gradeCount'],
                    ];
                }
            }

            $generalAverage = null;

            if ($subjectAverages !== []) {
                $averages = array_map(static fn (array $a): float => $a['average'], $subjectAverages);
                $generalAverage = round(array_sum($averages) / count($averages), 2);
            }

            $result[] = new ChildGradesSummaryDto(
                childId: $child->childId,
                firstName: $child->firstName,
                lastName: $child->lastName,
                periodId: null,
                subjectAverages: $subjectAverages,
                generalAverage: $generalAverage,
            );
        }

        return $result;
    }
}