<?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    public const WITHDRAWN_MESSAGE = 'Re-enrollment is not available because the final deliberation decision is withdrawn.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 KG_MISSING_DECISION_ELIGIBLE_MESSAGE = 'KG students may complete registration now. Their new-year grade placement will be based on the school age-placement rule.';
    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 = 'This student will be 18 years old or older on September 1 of the selected school year. A parent or guardian cannot complete registration because the student can no longer enroll in the school.';
    public const ADULT_STUDENT_PARENT_PORTAL_MESSAGE = self::ADULT_STUDENT_MESSAGE;
    public const WITHDRAWN_PORTAL_MESSAGE = 'This student is currently marked as Withdrawn and cannot be enrolled at this time. Please contact school administration.';
    public const SIBLING_PORTAL_MESSAGE = 'Enrollment cannot continue because the family record requires administrative review. Please contact school administration.';
    public const BALANCE_PORTAL_MESSAGE = 'Enrollment cannot continue because there is an outstanding balance. Please contact school administration.';
    public const EXPELLED_PORTAL_MESSAGE = 'This student cannot be enrolled through the parent portal. Please contact school administration.';
    public const FINANCE_APPROVAL_PORTAL_MESSAGE = 'Registration requires administrative financial approval. Please contact school administration.';
    public const ALREADY_ENROLLED_MESSAGE = 'This student is already enrolled for the selected school year.';
    public const ALREADY_SUBMITTED_MESSAGE = 'This student already has an enrollment for the selected school year.';

    public const ADULT_STUDENT_MIN_AGE = 18;

    /** @var array<string, int> Lower numbers win when selecting the primary parent-facing blocker. */
    public const BLOCKER_PRIORITY = [
        'ALREADY_ENROLLED' => 0,
        'ADULT_STUDENT_PARENT_BLOCKED' => 1,
        'ADULT_STUDENT_ACTION_REQUIRED' => 1,
        'EXPELLED' => 2,
        'WITHDRAWN' => 3,
        'OUTSTANDING_BALANCE_BLOCKED' => 4,
        'SIBLING_LAST_NAME_MISMATCH' => 5,
        'FINANCE_APPROVAL_REQUIRED' => 6,
        'DEFERRED_DECISION' => 7,
        'NO_FINAL_DECISION' => 8,
        'UNRECOGNIZED_DECISION' => 9,
    ];

    public static function messageForRuleCode(string $ruleCode): string
    {
        return match ($ruleCode) {
            'ADULT_STUDENT_PARENT_BLOCKED', 'ADULT_STUDENT_ACTION_REQUIRED' => self::ADULT_STUDENT_PARENT_PORTAL_MESSAGE,
            'EXPELLED' => self::EXPELLED_PORTAL_MESSAGE,
            'WITHDRAWN' => self::WITHDRAWN_PORTAL_MESSAGE,
            'OUTSTANDING_BALANCE_BLOCKED' => self::BALANCE_PORTAL_MESSAGE,
            'SIBLING_LAST_NAME_MISMATCH' => self::SIBLING_PORTAL_MESSAGE,
            'FINANCE_APPROVAL_REQUIRED' => self::FINANCE_APPROVAL_PORTAL_MESSAGE,
            'DEFERRED_DECISION' => self::DEFERRED_MESSAGE,
            'NO_FINAL_DECISION', 'UNRECOGNIZED_DECISION' => self::MISSING_DECISION_MESSAGE,
            'ALREADY_ENROLLED' => self::ALREADY_ENROLLED_MESSAGE,
            default => 'Enrollment cannot continue at this time. Please contact school administration.',
        };
    }

    public static function alreadyEnrolledMessage(?string $enrollmentStatus = null): string
    {
        return match (strtolower(trim((string) $enrollmentStatus))) {
            'payment pending' => 'This student already has an enrollment for the selected school year. Payment is still pending.',
            'admission under review', 'review & decision' => 'This student already has an enrollment submitted for the selected school year and it is under review.',
            'waitlist' => 'This student is already on the waitlist for the selected school year.',
            'withdraw under review' => 'This student is already enrolled and has a withdrawal request under review.',
            'refund pending' => 'This student already has an enrollment for the selected school year. A refund is pending.',
            'enrolled' => self::ALREADY_ENROLLED_MESSAGE,
            default => self::ALREADY_SUBMITTED_MESSAGE,
        };
    }

    public static function alreadyEnrolledTitle(?string $enrollmentStatus = null): string
    {
        return match (strtolower(trim((string) $enrollmentStatus))) {
            'payment pending', 'admission under review', 'review & decision' => 'Enrollment Already Submitted',
            'waitlist' => 'Already on Waitlist',
            'withdraw under review' => 'Withdrawal Under Review',
            'refund pending' => 'Refund Pending',
            default => 'Already Enrolled',
        };
    }

    /**
     * @param array<string, mixed> $student
     */
    public static function isMarkedWithdrawn(array $student): bool
    {
        if ((int) ($student['is_withdrawn'] ?? 0) === 1) {
            return true;
        }

        $status = strtolower(trim((string) ($student['enrollment_status'] ?? '')));

        return $status === 'withdrawn' || $status === 'withdrawn student';
    }

    /**
     * @param list<string> $blockers
     */
    public static function selectPrimaryBlocker(array $blockers): ?string
    {
        $blockers = array_values(array_unique(array_filter(array_map('strval', $blockers))));
        if ($blockers === []) {
            return null;
        }

        usort($blockers, static function (string $a, string $b): int {
            $priorityA = self::BLOCKER_PRIORITY[$a] ?? 999;
            $priorityB = self::BLOCKER_PRIORITY[$b] ?? 999;

            return $priorityA <=> $priorityB ?: strcmp($a, $b);
        });

        return $blockers[0];
    }

    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');
        }

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

        if ($decision === DeliberationDecision::WITHDRAWN || self::isMarkedWithdrawn($student)) {
            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');
        }

        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,
        ];
    }
}