<?php

namespace App\Libraries\Tuition;

use App\Interfaces\TuitionCalculatorInterface;

final class OldTuitionCalculatorService implements TuitionCalculatorInterface
{
    public function calculateFamilyTuition(array $students, array $config): array
    {
        $gradeFee = (int) ($config['grade_fee'] ?? 9);
        $firstStudentFee = $this->toCents($config['first_student_fee'] ?? 370);
        $secondStudentFee = $this->toCents($config['second_student_fee'] ?? 200);
        $youthFee = $this->toCents($config['youth_fee'] ?? 200);

        usort($students, function (array $left, array $right) use ($gradeFee): int {
            $leftLevel = GradeLevelParser::parse($left['grade_level'] ?? null, $gradeFee);
            $rightLevel = GradeLevelParser::parse($right['grade_level'] ?? null, $gradeFee);

            return [$leftLevel, (int) ($left['student_id'] ?? 0)] <=> [$rightLevel, (int) ($right['student_id'] ?? 0)];
        });

        $regularCount = 0;
        $details = [];

        foreach ($students as $student) {
            $level = GradeLevelParser::parse($student['grade_level'] ?? null, $gradeFee);

            if ($level > $gradeFee) {
                $amountCents = $youthFee;
                $rule = 'old_youth_fee';
            } else {
                $regularCount++;
                $amountCents = $regularCount === 1 ? $firstStudentFee : $secondStudentFee;
                $rule = $regularCount === 1 ? 'old_first_student_fee' : 'old_second_student_fee';
            }

            $details[] = [
                'student_id' => (int) ($student['student_id'] ?? 0),
                'student_name' => (string) ($student['student_name'] ?? ''),
                'grade_level' => $student['grade_level'] ?? null,
                'rule' => $rule,
                'amount' => $this->fromCents($amountCents),
            ];
        }

        $total = array_sum(array_map(fn (array $detail): int => $this->toCents($detail['amount']), $details));

        return [
            'calculator' => 'old',
            'total' => $this->fromCents($total),
            'details' => $details,
        ];
    }

    private function toCents($amount): int
    {
        return (int) round(((float) $amount) * 100);
    }

    private function fromCents(int $cents): string
    {
        return number_format($cents / 100, 2, '.', '');
    }
}