<?php

namespace App\Services;

use App\Models\ConfigurationModel;
use App\Support\Enrollment\DeliberationDecision;
use CodeIgniter\Database\BaseConnection;
use DateTimeInterface;

final class EnrollmentRegistrationEmailService
{
    public const TEMPLATE_VERSION = 'phase5_consolidated_v3';

    public function __construct(
        private readonly BaseConnection $db,
        private readonly EnrollmentTransitionService $transitionService,
        private readonly EmailService $emailService,
        private readonly ?ConfigurationModel $configurationModel = null,
    ) {
    }

    public function sendForDate(DateTimeInterface $date, bool $force = false, ?string $testEmail = null, bool $dryRun = false): array
    {
        $summary = [
            'school_years' => 0,
            'recipients' => 0,
            'sent' => 0,
            'failed' => 0,
            'skipped' => 0,
            'dry_run' => $dryRun,
            'messages' => [],
        ];

        foreach ($this->registrationYearsForDate($date, $force) as $schoolYear) {
            $summary['school_years']++;
            if (! $dryRun && empty($schoolYear['registration_launch_approved_at'])) {
                $summary['messages'][] = 'Registration launch is not approved for ' . (string) ($schoolYear['name'] ?? '') . '.';
                $summary['skipped']++;
                continue;
            }

            $result = $this->sendForSchoolYear($schoolYear, $testEmail, $dryRun, $force);
            foreach (['recipients', 'sent', 'failed', 'skipped'] as $key) {
                $summary[$key] += $result[$key] ?? 0;
            }
            array_push($summary['messages'], ...($result['messages'] ?? []));
        }

        return $summary;
    }

    public function sendForSchoolYear(array $schoolYear, ?string $testEmail = null, bool $dryRun = false, bool $force = false): array
    {
        $summary = ['recipients' => 0, 'sent' => 0, 'failed' => 0, 'skipped' => 0, 'messages' => []];
        if (! $dryRun && empty($schoolYear['registration_launch_approved_at'])) {
            $summary['messages'][] = 'Registration launch is not approved for ' . (string) ($schoolYear['name'] ?? '') . '.';
            $summary['skipped']++;
            return $summary;
        }

        $families = $this->recipientFamilies($schoolYear, $testEmail);
        if ($families === []) {
            $summary['messages'][] = 'No recipient families found for ' . (string) ($schoolYear['name'] ?? '') . '.';
            return $summary;
        }

        foreach ($families as $family) {
            if ($testEmail === null && ! $force && $this->alreadySent((string) $schoolYear['name'], (int) $family['parent_user_id'])) {
                $summary['skipped']++;
                continue;
            }

            $message = $this->buildMessage($schoolYear, $family);
            if ($testEmail !== null) {
                $message['subject'] = '[TEST] ' . $message['subject'];
                $message['recipients'] = [$testEmail];
            }

            $summary['recipients']++;
            $recordId = $dryRun || ! $this->db->tableExists('enrollment_email_records') ? null : $this->recordGenerated($schoolYear, $family, $message);
            $sent = $dryRun || $this->emailService->send($message['recipients'][0], $message['subject'], $message['body'], 'general');
            $sent ? $summary['sent']++ : $summary['failed']++;

            if (! $dryRun && $recordId !== null) {
                $this->recordDelivery($recordId, $sent, $sent ? null : 'Email send failed');
            }
        }

        return $summary;
    }

    public function previewForParent(string $schoolYearName, int $parentId): ?array
    {
        $schoolYear = $this->schoolYearByName($schoolYearName);
        if ($schoolYear === null) {
            return null;
        }

        foreach ($this->recipientFamilies($schoolYear, null) as $family) {
            if ((int) $family['parent_user_id'] === $parentId) {
                return $this->buildMessage($schoolYear, $family);
            }
        }

        return null;
    }

    public function previewExamplesForSchoolYear(string $schoolYearName): array
    {
        $schoolYear = $this->schoolYearByName($schoolYearName);
        if ($schoolYear === null) {
            return [];
        }

        $examples = [];
        foreach ($this->recipientFamilies($schoolYear, null) as $family) {
            $message = $this->buildMessage($schoolYear, $family);
            $latest = $this->latestEmailRecord($schoolYearName, (int) $family['parent_user_id']);

            $examples[] = [
                'parent_user_id' => (int) $family['parent_user_id'],
                'parent_name' => (string) $family['name'],
                'recipients' => $message['recipients'],
                'student_names' => array_map(
                    static fn (array $student): string => trim((string) ($student['firstname'] ?? '') . ' ' . (string) ($student['lastname'] ?? '')) ?: 'Student #' . (int) ($student['id'] ?? 0),
                    $family['students']
                ),
                'subject' => (string) $message['subject'],
                'delivery_status' => (string) ($latest['delivery_status'] ?? 'not sent'),
                'sent_at' => $latest['sent_at'] ?? null,
                'failure_reason' => $latest['failure_reason'] ?? null,
            ];
        }

        return $examples;
    }

    public function sendForSchoolYearName(string $schoolYearName, bool $force = false): array
    {
        $schoolYear = $this->schoolYearByName($schoolYearName);
        if ($schoolYear === null) {
            return ['recipients' => 0, 'sent' => 0, 'failed' => 0, 'skipped' => 1, 'messages' => ['School year was not found.']];
        }

        return $this->sendForSchoolYear($schoolYear, null, false, $force);
    }

    private function buildMessage(array $schoolYear, array $family): array
    {
        $schoolYearName = (string) ($schoolYear['name'] ?? '');
        $previousYear = $this->previousSchoolYearName($schoolYearName);
        $deadline = $this->dateText($schoolYear['registration_deadline_at'] ?? $schoolYear['registration_ends_on'] ?? null);
        $opens = $this->dateText($schoolYear['registration_opens_at'] ?? $schoolYear['registration_starts_on'] ?? null);
        $studentRows = [];
        $studentIds = [];
        $hasReEnrollmentEligibleStudent = false;

        foreach ($family['students'] as $student) {
            $studentId = (int) ($student['id'] ?? 0);
            if ($studentId <= 0 || $previousYear === null) {
                continue;
            }

            $evaluation = $this->transitionService->evaluate($studentId, $previousYear, $schoolYearName, 'parent');
            $studentRows[] = $this->studentRow($student, $evaluation, $opens, $deadline, $schoolYear);
            $studentIds[] = $studentId;
            $hasReEnrollmentEligibleStudent = $hasReEnrollmentEligibleStudent || $this->canCompleteParentReEnrollment($evaluation);
        }

        $financial = $this->financialSection((int) $family['parent_user_id'], $schoolYear, $previousYear);
        $subject = 'Registration for ' . $schoolYearName . ' Is Now Open';
        $bodyHtml = '<p>Dear ' . esc($family['name']) . ',</p>'
            . '<p>Registration for the ' . esc($schoolYearName) . ' school year is now open. Please review the student(s) summary below and complete the portal steps before ' . esc($deadline) . '.</p>'
            . $this->studentsTable($studentRows)
            . $financial
            . $this->registrationStepsSection($opens, $deadline, $hasReEnrollmentEligibleStudent)
            . '<p>For assistance, please contact the school administration.</p>'
            . '<p>Sincerely,<br>Al Rahma Sunday School<br>School Administration</p>';

        $body = view('emails/_wrap_layout', [
            'title' => $subject,
            'body_html' => $bodyHtml,
        ], ['saveData' => true]);

        return [
            'subject' => $subject,
            'body' => $body,
            'recipients' => $family['recipients'],
            'student_ids' => array_values(array_unique($studentIds)),
        ];
    }

    private function canCompleteParentReEnrollment(array $evaluation): bool
    {
        return (bool) ($evaluation['parent_enrollment_allowed'] ?? false);
    }

    private function registrationStepsSection(string $opens, string $deadline, bool $include): string
    {
        if (! $include) {
            return '';
        }

        return '<h3>Re-enrollment Steps</h3>'
            . '<p>Re-enrollment opens on ' . esc($opens) . ' and closes on ' . esc($deadline) . '. Complete re-enrollment for each eligible student before the deadline to secure their enrollment for the upcoming school year.</p>'
            . '<ol><li>Sign in to the parent portal.</li><li>Review/update student and contact information.</li><li>Acknowledge school policies.</li><li>Review tuition, fees and any carry-over balance.</li><li>Submit Enrollment.</li></ol>'
            . '<p>Registration portal: <a href="' . esc(site_url('parent/enroll_classes')) . '">' . esc(site_url('parent/enroll_classes')) . '</a></p>';
    }

    private function studentsTable(array $studentRows): string
    {
        if ($studentRows === []) {
            return '<p>No eligible linked students were found for this email.</p>';
        }

        return '<div style="margin:12px 0 18px;">'
            . implode('', $studentRows)
            . '</div>';
    }

    private function studentRow(array $student, array $evaluation, string $opens, string $deadline, array $schoolYear = []): string
    {
        $name = trim((string) ($student['firstname'] ?? '') . ' ' . (string) ($student['lastname'] ?? '')) ?: 'Student';
        $decision = DeliberationDecision::display((string) ($evaluation['deliberation_decision'] ?? ''));
        $status = $this->registrationStatus($evaluation);
        $placement = $this->placementText($evaluation);
        $requiredAction = $this->requiredAction($evaluation, $deadline, $name);
        $message = $this->decisionMessage($name, $evaluation, $opens, $deadline, $schoolYear);
        $nextStepHtml = $this->decisionMessageHtml($message, (string) ($evaluation['deliberation_decision'] ?? ''));
        if ($requiredAction !== '') {
            $nextStepHtml .= '<br><strong>' . esc($requiredAction) . '</strong>';
        }

        return '<table role="presentation" cellpadding="0" cellspacing="0" style="width:100%; border:1px solid #d9e2ec; border-collapse:collapse; margin:0 0 12px; font-size:14px; line-height:1.45;">'
            . '<tbody>'
            . '<tr>'
            . '<td style="background:#f4f8fb; border-bottom:1px solid #d9e2ec; padding:10px 12px; vertical-align:top; word-break:break-word;">'
            . '<strong style="font-size:16px; color:#1f2937;">' . esc($name) . '</strong>'
            . '</td>'
            . '</tr>'
            . $this->studentDetailRow('Decision', esc($decision ?: 'Pending'))
            . $this->studentDetailRow('Registration Status', '<strong>' . esc($status) . '</strong><br>' . esc($placement))
            . $this->studentDetailRow('Next Step', $nextStepHtml)
            . '</tbody></table>';
    }

    private function studentDetailRow(string $label, string $valueHtml): string
    {
        return '<tr>'
            . '<td style="border-bottom:1px solid #edf2f7; padding:10px 12px; vertical-align:top; word-break:break-word;">'
            . '<div style="font-size:12px; line-height:1.3; color:#64748b; text-transform:uppercase; font-weight:bold; margin:0 0 4px;">' . esc($label) . '</div>'
            . '<div style="color:#1f2937;">' . $valueHtml . '</div>'
            . '</td>'
            . '</tr>';
    }

    private function decisionMessageHtml(string $message, string $decision): string
    {
        if ($decision !== DeliberationDecision::MAKE_UP_EXAM) {
            return nl2br(esc($message), false);
        }

        $lines = explode("\n", $message);
        $lastIndex = count($lines) - 1;
        foreach ($lines as $index => $line) {
            $escaped = esc($line);
            $lines[$index] = $index === $lastIndex ? '<strong>' . $escaped . '</strong>' : $escaped;
        }

        return implode('<br>', $lines);
    }

    private function decisionMessage(string $name, array $evaluation, string $opens, string $deadline, array $schoolYear = []): string
    {
        if ((string) ($evaluation['deliberation_decision'] ?? '') === DeliberationDecision::PASSED) {
            $grade = $this->currentGradeText($evaluation);

            return $name . ' has successfully passed ' . $grade . '.';
        }

        if (($evaluation['blockers'] ?? []) !== []) {
            return implode(' ', array_map('strval', $evaluation['blockers']));
        }

        return match ((string) ($evaluation['deliberation_decision'] ?? '')) {
            DeliberationDecision::REPEAT_CLASS => 'The deliberation decision for ' . $name . ' is to repeat the current grade. After re-enrollment is completed, the student will remain in the same grade.',
            DeliberationDecision::MAKE_UP_EXAM => 'The final academic decision for ' . $name . ' is currently pending the result of a make-up exam. This exam is scheduled for ' . $this->makeupExamDateText($schoolYear) . ' from 9:30 AM to 11:00 AM at ISGL.'
                . "\n" . 'The exam result will determine whether the student advances to the next grade or repeats the current class. Failure to attend the make-up exam will automatically result in the student repeating the class, as no further retake opportunities will be available.'
                . "\n" . 'You must re-enroll ' . $name . ' before the make-up exam can be taken.',
            default => 'Please review the registration portal for the current enrollment status.',
        };
    }

    private function makeupExamDateText(array $schoolYear = []): string
    {
        $raw = trim((string) ($schoolYear['fall_makeup_exam_on'] ?? ''));
        if ($raw === '') {
            $configModel = $this->configurationModel ?? new ConfigurationModel();
            foreach (['make-up-exam', 'make_up_exam', 'makeup_exam_day'] as $key) {
                $raw = trim((string) ($configModel->getConfig($key) ?? ''));
                if ($raw !== '') {
                    break;
                }
            }
        }

        if ($raw === '') {
            return 'a date to be announced';
        }

        $timestamp = strtotime($raw);
        if ($timestamp !== false) {
            return date('m-d-Y', $timestamp);
        }

        return $raw;
    }

    private function financialSection(int $parentId, array $schoolYear, ?string $previousYear): string
    {
        $carry = $previousYear !== null ? $this->invoiceBalance($parentId, $previousYear) : 0.0;
        $registrationFee = (float) ($schoolYear['registration_fee'] ?? 0);
        $tuition = (float) ($schoolYear['tuition_due_at_registration'] ?? 0);
        $mandatory = (float) ($schoolYear['mandatory_fees'] ?? 0);
        $total = max(0, $carry) + $registrationFee + $tuition + $mandatory;
        if ($total <= 0.0) {
            return '';
        }

        $message = trim((string) ($schoolYear['financial_policy_message'] ?? ''));
        if ($message === '') {
            $message = 'The balance needs to be settled with the school before the re-enrollment process can be started.';
        }

        return '<h3>Family Account Information</h3>'
            . '<p><strong>Carry-over balance:</strong> $' . number_format($carry, 2) . '<br>'
            . '<strong>Total currently due:</strong> $' . number_format($total, 2) . '</p>'
            . '<p>' . esc($message) . '</p>';
    }

    private function recipientFamilies(array $schoolYear, ?string $testEmail): array
    {
        $builder = $this->db->table('users u')
            ->select('u.id AS parent_user_id, u.firstname, u.lastname, u.email')
            ->where('u.email IS NOT NULL')
            ->where('u.email !=', '');

        if ($this->db->fieldExists('user_type', 'users')) {
            $builder->where('u.user_type', 'primary');
        }

        if ($testEmail !== null) {
            $builder->limit(1);
        }

        $families = [];
        foreach ($builder->get()->getResultArray() as $row) {
            $parentId = (int) ($row['parent_user_id'] ?? 0);
            $students = $this->studentsForParent($parentId);
            if ($students === []) {
                continue;
            }

            $email = $testEmail ?? strtolower(trim((string) ($row['email'] ?? '')));
            if (! filter_var($email, FILTER_VALIDATE_EMAIL)) {
                continue;
            }

            $name = trim((string) ($row['firstname'] ?? '') . ' ' . (string) ($row['lastname'] ?? '')) ?: 'Parent or Guardian';
            $families[$parentId] = [
                'parent_user_id' => $parentId,
                'family_account_id' => $parentId,
                'name' => $name,
                'recipients' => [$email],
                'students' => $students,
            ];
        }

        return array_values($families);
    }

    private function studentsForParent(int $parentId): array
    {
        return $this->db->table('students')
            ->select('id, firstname, lastname, dob')
            ->where('parent_id', $parentId)
            ->orderBy('lastname', 'ASC')
            ->orderBy('firstname', 'ASC')
            ->get()
            ->getResultArray();
    }

    private function recordGenerated(array $schoolYear, array $family, array $message): int
    {
        $now = date('Y-m-d H:i:s');
        $this->db->table('enrollment_email_records')->insert([
            'school_year' => (string) ($schoolYear['name'] ?? ''),
            'school_year_id' => (int) ($schoolYear['id'] ?? 0) ?: null,
            'family_account_id' => (int) ($family['family_account_id'] ?? 0) ?: null,
            'parent_user_id' => (int) ($family['parent_user_id'] ?? 0) ?: null,
            'recipient_addresses_json' => json_encode($message['recipients']),
            'template_version' => self::TEMPLATE_VERSION,
            'generated_subject' => $message['subject'],
            'generated_body' => $message['body'],
            'student_ids_included_json' => json_encode($message['student_ids']),
            'generated_at' => $now,
            'delivery_status' => 'generated',
            'created_at' => $now,
            'updated_at' => $now,
        ]);

        return (int) $this->db->insertID();
    }

    private function recordDelivery(int $recordId, bool $sent, ?string $failure): void
    {
        $this->db->table('enrollment_email_records')
            ->where('id', $recordId)
            ->update([
                'delivery_status' => $sent ? 'sent' : 'failed',
                'sent_at' => $sent ? date('Y-m-d H:i:s') : null,
                'failure_reason' => $failure,
                'retry_count' => $sent ? 0 : 1,
                'updated_at' => date('Y-m-d H:i:s'),
            ]);
    }

    private function alreadySent(string $schoolYear, int $parentId): bool
    {
        if (! $this->db->tableExists('enrollment_email_records')) {
            return false;
        }

        return $this->db->table('enrollment_email_records')
            ->where('school_year', $schoolYear)
            ->where('parent_user_id', $parentId)
            ->where('delivery_status', 'sent')
            ->countAllResults() > 0;
    }

    private function latestEmailRecord(string $schoolYear, int $parentId): ?array
    {
        if (! $this->db->tableExists('enrollment_email_records')) {
            return null;
        }

        return $this->db->table('enrollment_email_records')
            ->select('delivery_status, sent_at, failure_reason')
            ->where('school_year', $schoolYear)
            ->where('parent_user_id', $parentId)
            ->orderBy('created_at', 'DESC')
            ->orderBy('id', 'DESC')
            ->limit(1)
            ->get()
            ->getRowArray() ?: null;
    }

    private function registrationYearsForDate(DateTimeInterface $date, bool $force): array
    {
        $builder = $this->db->table('school_years')->where('registration_starts_on IS NOT NULL');
        if (! $force) {
            $builder->where('registration_starts_on', $date->format('Y-m-d'));
        }

        return $builder->orderBy('registration_starts_on', 'ASC')->get()->getResultArray();
    }

    private function schoolYearByName(string $schoolYear): ?array
    {
        return $this->db->table('school_years')->where('name', $schoolYear)->limit(1)->get()->getRowArray() ?: null;
    }

    private function invoiceBalance(int $parentId, string $schoolYear): float
    {
        if (! $this->db->tableExists('invoices')) {
            return 0.0;
        }

        $row = $this->db->table('invoices')
            ->select('COALESCE(SUM(balance), 0) AS balance', false)
            ->where('parent_id', $parentId)
            ->where('school_year', $schoolYear)
            ->get()
            ->getRowArray();

        return round((float) ($row['balance'] ?? 0), 2);
    }

    private function registrationStatus(array $evaluation): string
    {
        if ((string) ($evaluation['deliberation_decision'] ?? '') === DeliberationDecision::PASSED) {
            return 'Eligible';
        }

        if (($evaluation['blockers'] ?? []) !== []) {
            return ($evaluation['adult_student'] ?? false) ? 'Student Action Required' : 'Not Eligible';
        }
        return ($evaluation['deliberation_decision'] ?? '') === DeliberationDecision::MAKE_UP_EXAM ? 'Eligible with pending placement' : 'Eligible';
    }

    private function placementText(array $evaluation): string
    {
        return match ((string) ($evaluation['placement_status'] ?? '')) {
            'automatic_distribution_pending' => $this->assignedGradeText($evaluation),
            'same_class_assigned' => 'Same grade and class',
            'temporary_same_grade' => 'Same grade initially',
            'manual_class_required' => 'Same grade',
            'exit_required' => 'Completion or exit process required',
            default => 'Pending',
        };
    }

    private function requiredAction(array $evaluation, string $deadline, string $name = 'The student'): string
    {
        if ((string) ($evaluation['deliberation_decision'] ?? '') === DeliberationDecision::PASSED) {
            return 'Complete re-enrollment before ' . $deadline . '.';
        }

        if (($evaluation['blockers'] ?? []) !== []) {
            return ($evaluation['adult_student'] ?? false) ? 'Student must complete the authorized adult-student process or contact administration.' : 'Contact the school administration.';
        }
        return ($evaluation['deliberation_decision'] ?? '') === DeliberationDecision::MAKE_UP_EXAM
            ? ''
            : 'Complete re-enrollment before ' . $deadline . '.';
    }

    private function previousSchoolYearName(string $schoolYear): ?string
    {
        return preg_match('/^(\d{4})-(\d{4})$/', $schoolYear, $m) ? ((int) $m[1] - 1) . '-' . ((int) $m[2] - 1) : null;
    }

    private function dateText(mixed $value): string
    {
        $value = trim((string) $value);
        if ($value === '') {
            return 'the posted date';
        }
        try {
            return (new \DateTimeImmutable($value))->format('F j, Y');
        } catch (\Throwable) {
            return $value;
        }
    }

    private function currentGradeText(array $evaluation): string
    {
        return $this->gradeText(
            $evaluation['source_grade_name'] ?? $evaluation['source_class_section_name'] ?? null,
            'the current grade'
        );
    }

    private function assignedGradeText(array $evaluation): string
    {
        return $this->gradeText(
            $evaluation['assigned_grade_name'] ?? null,
            'Grade to be assigned'
        );
    }

    private function gradeText(mixed $value, string $fallback): string
    {
        $grade = trim((string) $value);

        if ($grade === '') {
            return $fallback;
        }

        return preg_match('/^grade\b/i', $grade) === 1 ? $grade : 'Grade ' . $grade;
    }
}