<?php

namespace App\Support\Enrollment;

final class EnrollmentEligibility
{
    public const EXPELLED_MESSAGE = 'Re-enrollment is not available because the final deliberation decision is expelled. Please contact the school administration for further information.';
    public const WITHDRAWN_MESSAGE = 'Re-enrollment is not available because the final deliberation decision is withdrawn. Please contact the school administration if this status needs to be reviewed.';
    public const DEFERRED_MESSAGE = 'Re-enrollment cannot currently be completed because the final deliberation decision is deferred. Please contact the school administration for the next required step.';
    public const MISSING_DECISION_MESSAGE = 'Re-enrollment cannot currently be completed because no final deliberation decision is recorded for the student. Registration will become available after the school records a final decision.';
    public const ADULT_STUDENT_MESSAGE = 'The student will be 18 years old or older on September 1. A parent or guardian cannot complete registration on the student’s behalf. The student must complete the authorized adult-student registration process or contact the school administration.';

    public static function ageOnSeptemberFirst(?string $dob, string $targetSchoolYear): ?int
    {
        $dob = trim((string) $dob);
        if ($dob === '' || ! preg_match('/^(\d{4})/', trim($targetSchoolYear), $matches)) {
            return null;
        }

        try {
            $birthDate = \DateTimeImmutable::createFromFormat('!Y-m-d', $dob);
            $errors = \DateTimeImmutable::getLastErrors();
            if (
                $birthDate === false
                || (is_array($errors) && (($errors['warning_count'] ?? 0) > 0 || ($errors['error_count'] ?? 0) > 0))
            ) {
                return null;
            }

            $referenceDate = new \DateTimeImmutable($matches[1] . '-09-01');
        } catch (\Throwable) {
            return null;
        }

        return $birthDate > $referenceDate ? null : $birthDate->diff($referenceDate)->y;
    }

    public static function parentDecisionMessage(
        array $student,
        ?array $decisionRow,
        string $targetSchoolYear,
        ?string $fallMakeupExamOn = null
    ): array {
        $name = trim((string) ($student['firstname'] ?? '') . ' ' . (string) ($student['lastname'] ?? ''));
        $name = $name !== '' ? $name : 'The student';
        $decision = DeliberationDecision::normalize($decisionRow['decision'] ?? null);
        $source = strtolower(trim((string) ($decisionRow['source'] ?? '')));

        if ($decision === DeliberationDecision::EXPELLED) {
            return self::message($name . ': ' . self::EXPELLED_MESSAGE, true, 'danger');
        }

        if ($decision === DeliberationDecision::WITHDRAWN || ($student['enrollment_status'] ?? null) === 'withdrawn') {
            return self::message($name . ': ' . self::WITHDRAWN_MESSAGE, true, 'warning');
        }

        if ($decision === DeliberationDecision::DEFERRED_DECISION) {
            return self::message($name . ': ' . self::DEFERRED_MESSAGE, true, 'warning');
        }

        if ($decision === null && $source === 'pending') {
            return self::message($name . ': ' . self::MISSING_DECISION_MESSAGE, true, 'warning');
        }

        $age = self::ageOnSeptemberFirst($student['dob'] ?? null, $targetSchoolYear);
        if ($age !== null && $age >= 18) {
            return self::message(str_replace('The student', $name, self::ADULT_STUDENT_MESSAGE), true, 'danger');
        }

        if ($decision === DeliberationDecision::MAKE_UP_EXAM) {
            $dateText = $fallMakeupExamOn !== null ? ' on ' . local_date($fallMakeupExamOn, 'm-d-Y') : '';
            return self::message(
                $name . ' has a make-up exam decision. Enrollment is allowed, but the student will initially remain in the same grade as the closed school year until the fall make-up exam' . $dateText . ' is passed and administration confirms promotion.',
                false,
                'warning'
            );
        }

        if ($decision === DeliberationDecision::REPEAT_CLASS) {
            $previousClass = trim((string) ($decisionRow['class_section_name'] ?? ''));
            $previousClass = $previousClass !== '' ? $previousClass : 'the same class';

            return self::message($name . ' has a repeat class decision and is accepted only in ' . $previousClass . '.', false, 'info');
        }

        if ($decision === DeliberationDecision::PASSED || ($decision === null && $source !== 'pending' && trim((string) ($decisionRow['decision'] ?? '')) === '')) {
            return self::message('', false, 'info');
        }

        return self::message(
            $name . ' does not have a final academic decision that permits online re-enrollment. Please contact the administration.',
            true,
            'warning'
        );
    }

    private static function message(string $message, bool $blocking, string $level): array
    {
        return [
            'message' => $message,
            'blocking' => $blocking,
            'level' => $level,
        ];
    }
}