<?php

namespace App\Services;

use App\Libraries\IssueInvoiceCommand;
use App\Libraries\InvoiceIssuanceService;
use App\Libraries\InvoiceLedgerService;
use App\Libraries\Tuition\GradeLevelParser;
use App\Models\ClassSectionModel;
use App\Models\ConfigurationModel;
use App\Models\DiscountUsageModel;
use App\Models\DiscountVoucherModel;
use App\Models\EnrollmentModel;
use App\Models\EventChargesModel;
use App\Models\FinancialAidRequestModel;
use App\Models\InvoiceModel;
use App\Models\StudentClassModel;
use App\Models\UserModel;
use DateTime;
use DateTimeZone;
use RuntimeException;

final class FinancialAidService
{
    public function __construct(
        private readonly FinancialAidRequestModel $requestModel,
        private readonly InvoiceModel $invoiceModel,
        private readonly DiscountVoucherModel $voucherModel,
        private readonly DiscountUsageModel $usageModel,
        private readonly InvoiceLedgerService $invoiceLedgerService,
        private readonly ?InvoiceIssuanceService $invoiceIssuanceService = null,
        private readonly ?EnrollmentModel $enrollmentModel = null,
        private readonly ?StudentClassModel $studentClassModel = null,
        private readonly ?ClassSectionModel $classSectionModel = null,
        private readonly ?EventChargesModel $eventChargesModel = null,
        private readonly ?ConfigurationModel $configurationModel = null,
        private readonly ?UserModel $userModel = null,
    ) {
    }

    public function applyApprovedAmount(array $request, float $amount, int $reviewedBy, string $adminNote = ''): array
    {
        if ($amount <= 0) {
            throw new RuntimeException('Enter a financial aid amount greater than zero.');
        }

        $parentId = (int) ($request['parent_id'] ?? 0);
        $schoolYear = (string) ($request['school_year'] ?? '');
        $invoice = $this->latestInvoice($parentId, $schoolYear);
        if ($invoice === null) {
            $invoice = $this->createInvoiceForParentYear($parentId, $schoolYear);
        }

        $db = $this->requestModel->db;
        $db->transStart();

        $code = 'FA-' . (int) ($request['id'] ?? 0) . '-' . date('YmdHis');
        $voucherId = $this->voucherModel->insert([
            'code' => $code,
            'discount_type' => 'fixed',
            'discount_value' => $amount,
            'max_uses' => 1,
            'times_used' => 0,
            'valid_from' => date('Y-m-d'),
            'valid_until' => date('Y-m-d', strtotime('+1 year')),
            'school_year' => $schoolYear,
            'is_active' => 1,
            'description' => 'Financial aid request #' . (int) ($request['id'] ?? 0),
        ], true);

        if ($voucherId === false) {
            $db->transRollback();
            throw new RuntimeException('Unable to create the financial aid voucher.');
        }

        $now = function_exists('utc_now') ? utc_now() : date('Y-m-d H:i:s');
        $amountCents = (int) round($amount * 100);
        $usagePayload = [
            'voucher_id' => (int) $voucherId,
            'invoice_id' => (int) $invoice['id'],
            'parent_id' => $parentId,
            'discount_amount' => $amount,
            'description' => 'Financial aid',
            'school_year' => $schoolYear,
            'updated_by' => $reviewedBy,
            'used_at' => $now,
            'created_at' => $now,
            'updated_at' => $now,
        ];
        if ($db->fieldExists('requested_discount_cents', 'discount_usages')) {
            $usagePayload['requested_discount_cents'] = $amountCents;
            $usagePayload['eligible_base_cents'] = $amountCents;
            $usagePayload['eligible_base_before_cents'] = $amountCents;
            $usagePayload['applied_discount_cents'] = $amountCents;
            $usagePayload['application_order'] = 1;
        }

        $usageId = $this->usageModel->insert($usagePayload, true);
        if ($usageId === false) {
            $db->transRollback();
            throw new RuntimeException('Unable to record the financial aid discount.');
        }

        $this->voucherModel->update((int) $voucherId, ['times_used' => 1, 'is_active' => 0]);
        $this->invoiceLedgerService->recalculateInvoice((int) $invoice['id']);

        $this->requestModel->update((int) $request['id'], [
            'status' => 'approved',
            'admin_amount' => $amount,
            'admin_note' => $adminNote,
            'reviewed_by' => $reviewedBy,
            'reviewed_at' => $now,
            'invoice_id' => (int) $invoice['id'],
            'discount_usage_id' => (int) $usageId,
            'voucher_id' => (int) $voucherId,
        ]);

        $db->transComplete();
        if ($db->transStatus() === false) {
            throw new RuntimeException('Unable to apply the financial aid discount.');
        }

        return $this->requestModel->find((int) $request['id']) ?? $request;
    }

    private function latestInvoice(int $parentId, string $schoolYear): ?array
    {
        if ($parentId <= 0 || $schoolYear === '') {
            return null;
        }

        return $this->invoiceModel
            ->where('parent_id', $parentId)
            ->where('school_year', $schoolYear)
            ->orderBy('id', 'DESC')
            ->first();
    }

    private function createInvoiceForParentYear(int $parentId, string $schoolYear): array
    {
        if ($parentId <= 0 || $schoolYear === '') {
            throw new RuntimeException('Cannot create an invoice because the parent or school year is missing.');
        }

        $enrollmentModel = $this->enrollmentModel ?? new EnrollmentModel();
        $studentClassModel = $this->studentClassModel ?? new StudentClassModel();
        $classSectionModel = $this->classSectionModel ?? new ClassSectionModel();
        $eventChargesModel = $this->eventChargesModel ?? new EventChargesModel();
        $configurationModel = $this->configurationModel ?? new ConfigurationModel();
        $invoiceIssuanceService = $this->invoiceIssuanceService ?? new InvoiceIssuanceService(
            $this->requestModel->db,
            $this->invoiceModel,
            null,
            $this->invoiceLedgerService
        );

        $semester = (string) (getSemester() ?: '');
        $enrollments = $enrollmentModel
            ->where('parent_id', $parentId)
            ->where('school_year', $schoolYear)
            ->findAll();

        if ($enrollments === []) {
            throw new RuntimeException('No enrollment records were found, so an invoice could not be created for this parent.');
        }

        $registeredKids = [];
        $withdrawnKids = [];
        foreach ($enrollments as $enrollment) {
            $studentData = [
                'student_id' => (int) ($enrollment['student_id'] ?? 0),
                'parent_id' => (int) ($enrollment['parent_id'] ?? 0),
                'class_section_id' => (int) ($enrollment['class_section_id'] ?? 0),
                'enrollment_status' => (string) ($enrollment['enrollment_status'] ?? ''),
                'school_year' => (string) ($enrollment['school_year'] ?? ''),
                'semester' => (string) ($enrollment['semester'] ?? ''),
                'admission_status' => (string) ($enrollment['admission_status'] ?? ''),
                'is_withdrawn' => (int) ($enrollment['is_withdrawn'] ?? 0),
            ];

            if (in_array($studentData['enrollment_status'], ['enrolled', 'payment pending'], true)) {
                $registeredKids[] = $studentData;
            } elseif (in_array($studentData['enrollment_status'], ['withdrawn', 'refund pending', 'withdraw under review'], true)) {
                $withdrawnKids[] = $studentData;
            }
        }

        $registeredKids = $this->onlyStudentsWithClassAssignment($registeredKids, $studentClassModel, $schoolYear);
        $withdrawnKids = $this->onlyStudentsWithClassAssignment($withdrawnKids, $studentClassModel, $schoolYear);
        $tuitionAmount = $this->calculateTuitionAmount($registeredKids, $withdrawnKids, $classSectionModel, $configurationModel);
        $eventAmount = array_sum(array_map(
            static fn(array $row): float => (float) ($row['charged'] ?? 0),
            $eventChargesModel->getChargesWithEventInfo($parentId, $schoolYear)
        ));
        $totalAmount = $tuitionAmount + $eventAmount;

        if ($totalAmount <= 0) {
            throw new RuntimeException('Invoice could not be created because this parent has no billable tuition or event charges.');
        }

        $issueUtc = (new DateTime('now', new DateTimeZone('UTC')))->format('Y-m-d H:i:s');
        $dueUtc = $this->invoiceDueUtc($configurationModel);

        $result = $invoiceIssuanceService->issueInvoice(new IssueInvoiceCommand([
            'parent_id' => $parentId,
            'invoice_number' => $invoiceIssuanceService->generateInvoiceNumber($schoolYear, $parentId),
            'total_amount' => $totalAmount,
            'paid_amount' => 0,
            'balance' => $totalAmount,
            'school_year' => $schoolYear,
            'semester' => $semester,
            'issue_date' => $issueUtc,
            'due_date' => $dueUtc,
            'created_at' => function_exists('utc_now') ? utc_now() : $issueUtc,
            'updated_at' => function_exists('utc_now') ? utc_now() : $issueUtc,
        ], $tuitionAmount, $eventAmount, [
            'parent_id' => $parentId,
            'school_year' => $schoolYear,
            'semester' => $semester,
            'registered_student_count' => count($registeredKids),
            'withdrawn_student_count' => count($withdrawnKids),
        ]));

        $invoice = $this->invoiceModel->find($result->invoiceId);
        if (!is_array($invoice)) {
            throw new RuntimeException('Invoice was created but could not be reloaded.');
        }

        return $invoice;
    }

    private function onlyStudentsWithClassAssignment(array $students, StudentClassModel $studentClassModel, string $schoolYear): array
    {
        return array_values(array_filter($students, static function (array $student) use ($studentClassModel, $schoolYear): bool {
            $studentId = (int) ($student['student_id'] ?? 0);
            return $studentId > 0 && $studentClassModel->hasNonEventAssignment($studentId, $schoolYear);
        }));
    }

    private function calculateTuitionAmount(
        array $registeredKids,
        array $withdrawnKids,
        ClassSectionModel $classSectionModel,
        ConfigurationModel $configurationModel
    ): float {
        $tuitionStudents = $this->isBeforeRefundDeadline($configurationModel)
            ? $registeredKids
            : array_merge($registeredKids, $withdrawnKids);

        foreach ($tuitionStudents as &$student) {
            $gradeName = $classSectionModel->getClassSectionNameBySectionId((int) ($student['class_section_id'] ?? 0));
            $student['grade'] = strtoupper(trim((string) $gradeName));
        }
        unset($student);

        usort($tuitionStudents, static fn(array $left, array $right): int => GradeLevelParser::parse($left['grade'] ?? null) <=> GradeLevelParser::parse($right['grade'] ?? null));

        $firstStudentFee = (float) ($configurationModel->getConfig('first_student_fee') ?? 380);
        $secondStudentFee = (float) ($configurationModel->getConfig('second_student_fee') ?? 280);
        $total = 0.0;
        foreach (array_values($tuitionStudents) as $index => $student) {
            $total += $index === 0 ? $firstStudentFee : $secondStudentFee;
        }

        return $total;
    }

    private function isBeforeRefundDeadline(ConfigurationModel $configurationModel): bool
    {
        try {
            $refundDeadline = (string) ($configurationModel->getConfig('refund_deadline') ?? '');
            if ($refundDeadline === '') {
                return true;
            }
            $tzName = (string) (config('School')->attendance['timezone'] ?? user_timezone());
            $tz = new DateTimeZone($tzName);
            return new \DateTimeImmutable('today', $tz) <= new \DateTimeImmutable($refundDeadline, $tz);
        } catch (\Throwable) {
            return true;
        }
    }

    private function invoiceDueUtc(ConfigurationModel $configurationModel): ?string
    {
        $dueDate = (string) ($configurationModel->getConfig('first_day_of_school') ?: $configurationModel->getConfig('due_date') ?: '');
        if ($dueDate === '') {
            return null;
        }

        $tzName = (string) (config('School')->attendance['timezone'] ?? user_timezone());
        $dueLocal = new DateTime($dueDate . ' 19:59:59', new DateTimeZone($tzName));
        $dueLocal->setTimezone(new DateTimeZone('UTC'));
        return $dueLocal->format('Y-m-d H:i:s');
    }
}