<?php

declare(strict_types=1);

namespace App\Mail;

use App\App\Bootstrap;
use App\Form\FormSchema;

final class Mailer
{
    private const NACHWEISE_FIELD_KEY = 'qualifikationsnachweise';
    private const NACHWEISE_MAX_ATTACHMENT_BYTES = 25 * 1024 * 1024;

    /** @var array<string, mixed> */
    private array $mailConfig;
    /** @var array<string, mixed> */
    private array $appConfig;
    private FormSchema $schema;
    private SubmissionFormatter $formatter;
    private PdfGenerator $pdfGenerator;

    public function __construct()
    {
        $this->mailConfig = Bootstrap::config('mail');
        $this->appConfig = Bootstrap::config('app');
        $this->schema = new FormSchema();
        $this->formatter = new SubmissionFormatter($this->schema);
        $this->pdfGenerator = new PdfGenerator($this->formatter, $this->schema);
    }

    public function sendOtpMail(string $email, string $code, int $ttlSeconds): bool
    {
        $email = strtolower(trim($email));
        if ($email === '') {
            return false;
        }

        $subject = (string) ($this->mailConfig['subjects']['otp'] ?? 'Ihr Sicherheitscode');
        $textBody = $this->renderOtpText($code, $ttlSeconds);
        $htmlBody = $this->renderOtpHtml($code, $ttlSeconds);

        try {
            $mail = $this->createMailBuilder();
            $mail->setTo($email)
                ->setSubject($subject)
                ->setTextBody($textBody)
                ->setHtmlBody($htmlBody);

            if (!$mail->send()) {
                Bootstrap::log('mail', 'Versand OTP fehlgeschlagen: ' . $email . ' - ' . $mail->getErrorInfo());
                return false;
            }
        } catch (\Throwable $e) {
            Bootstrap::log('mail', 'Versand OTP fehlgeschlagen: ' . $email . ' - ' . $e->getMessage());
            return false;
        }

        return true;
    }

    /** @param array<string, mixed> $submission */
    public function sendSubmissionMails(array $submission): void
    {
        $formDataPdf = $this->pdfGenerator->generateFormDataPdf($submission);
        $minorSignaturePdf = $this->pdfGenerator->generateMinorSignaturePdf($submission);
        $isMinorSubmission = $this->isMinorSubmission($submission);

        try {
            $this->sendAdminMails($submission, $formDataPdf, $isMinorSubmission);
            $this->sendApplicantMail($submission, $minorSignaturePdf);
        } finally {
            if ($formDataPdf !== null) {
                @unlink($formDataPdf);
            }
            if ($minorSignaturePdf !== null) {
                @unlink($minorSignaturePdf);
            }
        }
    }

    private function sendAdminMails(
        array $submission,
        ?string $formDataPdf,
        bool $isMinorSubmission,
    ): void {
        $recipients = (array) ($this->mailConfig['recipients'] ?? []);
        $subject = (string) ($this->mailConfig['subjects']['admin'] ?? 'Neuer Mitgliedsantrag');
        $attachmentInfo = $this->collectAdminUploadAttachments($submission);
        $uploadWarning = null;

        if ($attachmentInfo['nachweise_skipped']) {
            $uploadWarning = $this->buildNachweiseOversizeWarning((int) $attachmentInfo['nachweise_total_bytes']);
            Bootstrap::log('mail', 'Qualifikationsnachweise nicht angehängt (zu groß): ' . $uploadWarning);
        }

        $htmlBody = $this->renderAdminHtml($submission, $isMinorSubmission, $uploadWarning);
        $textBody = $this->renderAdminText($submission, $isMinorSubmission, $uploadWarning);

        $formData = (array) ($submission['form_data'] ?? []);
        $ccEmails = [];
        $notifications = (array) ($this->schema->raw()['additional_notifications'] ?? []);
        $validator = new \App\Form\Validator($this->schema);
        
        foreach ($notifications as $notification) {
            if (!isset($notification['condition']) || !is_array($notification['condition'])) {
                continue;
            }
            if ($validator->evaluateCondition($notification['condition'], $formData)) {
                $ccs = (array) ($notification['cc'] ?? []);
                foreach ($ccs as $cc) {
                    if (is_string($cc) && filter_var($cc, FILTER_VALIDATE_EMAIL)) {
                        $ccEmails[] = trim($cc);
                    }
                }
            }
        }

        foreach ($recipients as $recipient) {
            if (!is_string($recipient) || $recipient === '') {
                continue;
            }

            try {
                $mail = $this->createMailBuilder();
                $mail->setTo($recipient)
                    ->setSubject($subject)
                    ->setHtmlBody($htmlBody)
                    ->setTextBody($textBody);

                foreach ($ccEmails as $ccEmail) {
                    $mail->addCc($ccEmail);
                }

                if ($formDataPdf !== null) {
                    $mail->addAttachment($formDataPdf, 'Antragsdaten.pdf', 'application/pdf');
                }
                foreach ($attachmentInfo['attachments'] as $att) {
                    $mail->addAttachment($att['path'], $att['filename'], $att['mime']);
                }

                if (!$mail->send()) {
                    Bootstrap::log('mail', 'Versand an Admin fehlgeschlagen: ' . $recipient . ' - ' . $mail->getErrorInfo());
                }
            } catch (\Throwable $e) {
                Bootstrap::log('mail', 'Versand an Admin fehlgeschlagen: ' . $recipient . ' - ' . $e->getMessage());
            }
        }
    }

    /** @param array<string, mixed> $submission */
    private function sendApplicantMail(array $submission, ?string $minorSignaturePdf): void
    {
        $email = (string) ($submission['email'] ?? '');
        if ($email === '') {
            return;
        }

        $isMinorSubmission = $this->isMinorSubmission($submission);
        $subject = (string) ($this->mailConfig['subjects']['applicant'] ?? 'Bestätigung Mitgliedsantrag');
        $htmlBody = $this->renderApplicantHtml($submission, $isMinorSubmission);
        $textBody = $this->renderApplicantText($submission, $isMinorSubmission);

        try {
            $mail = $this->createMailBuilder();
            $mail->setTo($email)
                ->setSubject($subject)
                ->setHtmlBody($htmlBody)
                ->setTextBody($textBody);

            if ($minorSignaturePdf !== null && is_file($minorSignaturePdf)) {
                $mail->addAttachment($minorSignaturePdf, 'Einverstaendniserklaerung-Minderjaehrige.pdf', 'application/pdf');
            }

            if (!$mail->send()) {
                Bootstrap::log('mail', 'Versand an Antragsteller fehlgeschlagen: ' . $email . ' - ' . $mail->getErrorInfo());
            }
        } catch (\Throwable $e) {
            Bootstrap::log('mail', 'Versand an Antragsteller fehlgeschlagen: ' . $email . ' - ' . $e->getMessage());
        }
    }

    // ---------------------------------------------------------------
    // Mail builder
    // ---------------------------------------------------------------

    private function createMailBuilder(): MimeMailBuilder
    {
        $from = (string) ($this->mailConfig['from'] ?? 'no-reply@example.org');
        $fromName = (string) ($this->mailConfig['from_name'] ?? '');

        return (new MimeMailBuilder())->setFrom($from, $fromName);
    }

    // ---------------------------------------------------------------
    // Admin email rendering
    // ---------------------------------------------------------------

    /** @param array<string, mixed> $submission */
    private function renderAdminHtml(array $submission, bool $isMinorSubmission = false, ?string $uploadWarning = null): string
    {
        $steps = $this->formatter->formatSteps($submission);
        $uploads = $this->formatter->formatUploads($submission);

        $h = '<!DOCTYPE html><html><head><meta charset="UTF-8"></head><body style="font-family:Arial,sans-serif;color:#333;max-width:700px;margin:0 auto">';
        $h .= '<h2 style="color:#c0392b">Neuer Mitgliedsantrag</h2>';
        $h .= '<p>Eingereicht: ' . $this->esc($this->formatTimestamp($submission)) . '<br>';
        $h .= 'E-Mail: ' . $this->esc((string) ($submission['email'] ?? '')) . '</p>';
        if ($isMinorSubmission) {
            $h .= $this->renderMinorAdminNoticeHtml();
        }
        if ($uploadWarning !== null && $uploadWarning !== '') {
            $h .= '<div style="background:#fff3cd;border:1px solid #f0c36d;padding:10px 12px;margin:12px 0">'
                . '<strong>Hinweis zu Anhängen:</strong> ' . nl2br($this->esc($uploadWarning))
                . '</div>';
        }

        foreach ($steps as $step) {
            $h .= '<h3 style="border-bottom:2px solid #c0392b;padding-bottom:4px">' . $this->esc($step['title']) . '</h3>';
            $h .= '<table style="width:100%;border-collapse:collapse">';
            foreach ($step['fields'] as $field) {
                $h .= '<tr><td style="padding:4px 8px;border-bottom:1px solid #eee;font-weight:bold;vertical-align:top;width:40%">'
                    . $this->esc($field['label']) . '</td>';
                $h .= '<td style="padding:4px 8px;border-bottom:1px solid #eee;vertical-align:top">'
                    . nl2br($this->esc($field['value'])) . '</td></tr>';
            }
            $h .= '</table>';
        }

        if ($uploads !== []) {
            $h .= '<h3 style="border-bottom:2px solid #c0392b;padding-bottom:4px">Hochgeladene Dateien</h3><ul>';
            foreach ($uploads as $group) {
                foreach ($group['files'] as $name) {
                    $h .= '<li><strong>' . $this->esc($group['label']) . ':</strong> ' . $this->esc($name) . '</li>';
                }
            }
            $h .= '</ul>';
        }

        $h .= '</body></html>';
        return $h;
    }

    /** @param array<string, mixed> $submission */
    private function renderAdminText(array $submission, bool $isMinorSubmission = false, ?string $uploadWarning = null): string
    {
        $steps = $this->formatter->formatSteps($submission);
        $uploads = $this->formatter->formatUploads($submission);

        $t = "NEUER MITGLIEDSANTRAG\n";
        $t .= 'Eingereicht: ' . $this->formatTimestamp($submission) . "\n";
        $t .= 'E-Mail: ' . (string) ($submission['email'] ?? '') . "\n\n";
        if ($isMinorSubmission) {
            $t .= $this->renderMinorAdminNoticeText() . "\n\n";
        }
        if ($uploadWarning !== null && $uploadWarning !== '') {
            $t .= "HINWEIS ZU ANHÄNGEN\n";
            $t .= $uploadWarning . "\n\n";
        }

        foreach ($steps as $step) {
            $t .= strtoupper($step['title']) . "\n" . str_repeat('-', 40) . "\n";
            foreach ($step['fields'] as $field) {
                $t .= $field['label'] . ': ' . $field['value'] . "\n";
            }
            $t .= "\n";
        }

        if ($uploads !== []) {
            $t .= "HOCHGELADENE DATEIEN\n" . str_repeat('-', 40) . "\n";
            foreach ($uploads as $group) {
                foreach ($group['files'] as $name) {
                    $t .= '- ' . $group['label'] . ': ' . $name . "\n";
                }
            }
        }

        return $t;
    }

    // ---------------------------------------------------------------
    // Applicant email rendering
    // ---------------------------------------------------------------

    /** @param array<string, mixed> $submission */
    private function renderApplicantHtml(array $submission, bool $isMinorSubmission = false): string
    {
        $steps = $this->formatter->formatSteps($submission);
        $uploads = $this->formatter->formatUploads($submission);

        $h = '<!DOCTYPE html><html><head><meta charset="UTF-8"></head><body style="font-family:Arial,sans-serif;color:#333;max-width:700px;margin:0 auto">';
        $h .= '<h2 style="color:#c0392b">Vielen Dank für Ihren Mitgliedsantrag!</h2>';
        $h .= '<p>Ihre Daten wurden erfolgreich übermittelt. Nachfolgend finden Sie eine Zusammenfassung.</p>';
        if ($isMinorSubmission) {
            $h .= '<p><strong>Hinweis für Minderjährige:</strong> '
                . 'Das angehängte Formular ist auszudrucken, von Antragsteller/in und Erziehungsberechtigten zu unterschreiben '
                . 'und persönlich einzureichen.</p>';
        }

        foreach ($steps as $step) {
            $h .= '<h3>' . $this->esc($step['title']) . '</h3>';
            $h .= '<table style="width:100%;border-collapse:collapse">';
            foreach ($step['fields'] as $field) {
                $h .= '<tr><td style="padding:3px 6px;border-bottom:1px solid #eee;font-weight:bold;vertical-align:top;width:40%">'
                    . $this->esc($field['label']) . '</td>';
                $h .= '<td style="padding:3px 6px;border-bottom:1px solid #eee;vertical-align:top">'
                    . nl2br($this->esc($field['value'])) . '</td></tr>';
            }
            $h .= '</table>';
        }

        if ($uploads !== []) {
            $h .= '<h3>Hochgeladene Dateien</h3><ul>';
            foreach ($uploads as $group) {
                foreach ($group['files'] as $name) {
                    $h .= '<li>' . $this->esc($group['label']) . ': ' . $this->esc($name) . '</li>';
                }
            }
            $h .= '</ul>';
        }

        $h .= '<p style="color:#888;font-size:0.9em">Bei Rückfragen kontaktieren Sie bitte den Verein.</p>';
        $h .= '</body></html>';
        return $h;
    }

    /** @param array<string, mixed> $submission */
    private function renderApplicantText(array $submission, bool $isMinorSubmission = false): string
    {
        $steps = $this->formatter->formatSteps($submission);
        $uploads = $this->formatter->formatUploads($submission);

        $t = "Vielen Dank für Ihren Mitgliedsantrag!\n\n";
        $t .= "Ihre Daten wurden erfolgreich übermittelt. Nachfolgend finden Sie eine Zusammenfassung.\n\n";
        if ($isMinorSubmission) {
            $t .= "Hinweis für Minderjährige: Das angehängte Formular ist auszudrucken, von Antragsteller/in und "
                . "Erziehungsberechtigten zu unterschreiben und persönlich einzureichen.\n\n";
        }

        foreach ($steps as $step) {
            $t .= strtoupper($step['title']) . "\n";
            foreach ($step['fields'] as $field) {
                $t .= $field['label'] . ': ' . $field['value'] . "\n";
            }
            $t .= "\n";
        }

        if ($uploads !== []) {
            $t .= "HOCHGELADENE DATEIEN\n";
            foreach ($uploads as $group) {
                foreach ($group['files'] as $name) {
                    $t .= '- ' . $group['label'] . ': ' . $name . "\n";
                }
            }
            $t .= "\n";
        }

        $t .= "Bei Rückfragen kontaktieren Sie bitte den Verein.\n";
        return $t;
    }

    // ---------------------------------------------------------------
    // Utilities
    // ---------------------------------------------------------------

    /** @param array<string, mixed> $submission */
    private function formatTimestamp(array $submission): string
    {
        $ts = (string) ($submission['submitted_at'] ?? '');
        $parsed = strtotime($ts);
        return $parsed !== false ? date('d.m.Y H:i', $parsed) : $ts;
    }

    private function esc(string $value): string
    {
        return htmlspecialchars($value, ENT_QUOTES | ENT_SUBSTITUTE, 'UTF-8');
    }

    private function renderMinorAdminNoticeHtml(): string
    {
        return '<div style="background:#fff3cd;border:1px solid #f0c36d;padding:10px 12px;margin:12px 0">'
            . '<strong>Wichtiger Hinweis (Minderjährig):</strong> '
            . 'Die Unterschrift eines Erziehungsberechtigten liegt digital noch nicht vor. '
            . 'Bitte die Bearbeitung erst nach Eingang des handschriftlich unterschriebenen Formulars fortsetzen.'
            . '</div>';
    }

    private function renderMinorAdminNoticeText(): string
    {
        return "WICHTIGER HINWEIS (MINDERJÄHRIG)\n"
            . 'Die Unterschrift eines Erziehungsberechtigten liegt digital noch nicht vor. '
            . 'Bitte die Bearbeitung erst nach Eingang des handschriftlich unterschriebenen Formulars fortsetzen.';
    }

    /**
     * @param array<string, mixed> $submission
     * @return array{
     *   attachments: array<int, array{path: string, filename: string, mime: string}>,
     *   nachweise_skipped: bool,
     *   nachweise_total_bytes: int
     * }
     */
    private function collectAdminUploadAttachments(array $submission): array
    {
        $uploads = (array) ($submission['uploads'] ?? []);
        $uploadFields = $this->schema->getUploadFields();
        $attachments = [];
        $nachweiseAttachments = [];
        $nachweiseTotalBytes = 0;

        foreach ($uploadFields as $fieldKey => $_fieldDef) {
            $files = $uploads[$fieldKey] ?? [];
            if (!is_array($files)) {
                continue;
            }

            foreach ($files as $file) {
                if (!is_array($file)) {
                    continue;
                }

                $resolved = $this->resolveUploadAttachment($submission, $file);
                if ($resolved === null) {
                    continue;
                }

                $entry = [
                    'path' => $resolved['path'],
                    'filename' => $resolved['filename'],
                    'mime' => $resolved['mime'],
                ];

                if ($fieldKey === self::NACHWEISE_FIELD_KEY) {
                    $nachweiseAttachments[] = $entry;
                    $nachweiseTotalBytes += $resolved['size'];
                    continue;
                }

                $attachments[] = $entry;
            }
        }

        $nachweiseSkipped = $nachweiseTotalBytes > self::NACHWEISE_MAX_ATTACHMENT_BYTES;
        if (!$nachweiseSkipped) {
            $attachments = array_merge($attachments, $nachweiseAttachments);
        }

        return [
            'attachments' => $attachments,
            'nachweise_skipped' => $nachweiseSkipped,
            'nachweise_total_bytes' => $nachweiseTotalBytes,
        ];
    }

    /**
     * @param array<string, mixed> $submission
     * @param array<string, mixed> $file
     * @return array{path: string, filename: string, mime: string, size: int}|null
     */
    private function resolveUploadAttachment(array $submission, array $file): ?array
    {
        $path = $this->resolveSubmissionUploadPath($submission, $file);
        if ($path === null || !is_file($path)) {
            return null;
        }

        $filename = trim((string) ($file['original_filename'] ?? basename($path)));
        if ($filename === '') {
            $filename = basename($path);
        }

        $mime = trim((string) ($file['mime'] ?? ''));
        if ($mime === '') {
            $detected = @mime_content_type($path);
            $mime = is_string($detected) && $detected !== '' ? $detected : 'application/octet-stream';
        }

        $size = (int) ($file['size'] ?? 0);
        if ($size <= 0) {
            $size = (int) (filesize($path) ?: 0);
        }

        return [
            'path' => $path,
            'filename' => $filename,
            'mime' => $mime,
            'size' => $size,
        ];
    }

    /**
     * @param array<string, mixed> $submission
     * @param array<string, mixed> $file
     */
    private function resolveSubmissionUploadPath(array $submission, array $file): ?string
    {
        $baseUploads = rtrim((string) ($this->appConfig['storage']['uploads'] ?? ''), '/');
        if ($baseUploads === '') {
            return null;
        }

        $relativePath = str_replace(['..', '\\'], '', (string) ($file['relative_path'] ?? ''));
        if ($relativePath !== '') {
            $candidate = $baseUploads . '/' . ltrim($relativePath, '/');
            if (is_file($candidate)) {
                return $candidate;
            }
        }

        $storedDir = str_replace(['..', '\\'], '', (string) ($file['stored_dir'] ?? ''));
        $storedFilename = str_replace(['..', '\\'], '', (string) ($file['stored_filename'] ?? ''));
        if ($storedDir === '' || $storedFilename === '') {
            return null;
        }

        $storedDir = ltrim($storedDir, '/');
        $candidates = [$baseUploads . '/' . $storedDir . '/' . $storedFilename];
        $appKey = trim((string) ($submission['application_key'] ?? ''));

        if ($appKey !== '' && !str_starts_with($storedDir, $appKey . '/')) {
            $candidates[] = $baseUploads . '/' . $appKey . '/' . $storedDir . '/' . $storedFilename;
        }

        foreach ($candidates as $candidate) {
            if (is_file($candidate)) {
                return $candidate;
            }
        }

        return null;
    }

    private function buildNachweiseOversizeWarning(int $totalBytes): string
    {
        $totalMb = $this->formatMegabytes($totalBytes);
        $limitMb = $this->formatMegabytes(self::NACHWEISE_MAX_ATTACHMENT_BYTES);

        return 'Die Qualifikationsnachweise wurden nicht als E-Mail-Anhang versendet, weil die Gesamtgröße mit '
            . $totalMb . ' MB das Limit von ' . $limitMb . ' MB überschreitet. '
            . 'Bitte laden Sie diese Dateien über die Admin-Seite herunter.';
    }

    private function formatMegabytes(int $bytes): string
    {
        return number_format(max(0, $bytes) / 1024 / 1024, 1, ',', '.');
    }

    /** @param array<string, mixed> $submission */
    private function isMinorSubmission(array $submission): bool
    {
        if (array_key_exists('is_minor_submission', $submission)) {
            return (bool) $submission['is_minor_submission'];
        }

        $formData = (array) ($submission['form_data'] ?? []);
        return $this->deriveIsMinorFromBirthdate((string) ($formData['geburtsdatum'] ?? ''));
    }

    private function deriveIsMinorFromBirthdate(string $birthdate): bool
    {
        $birthdate = trim($birthdate);
        if ($birthdate === '') {
            return false;
        }

        $date = \DateTimeImmutable::createFromFormat('!Y-m-d', $birthdate);
        if (!$date || $date->format('Y-m-d') !== $birthdate) {
            return false;
        }

        $today = new \DateTimeImmutable('today');
        if ($date > $today) {
            return false;
        }

        return $date->diff($today)->y < 18;
    }

    private function renderOtpText(string $code, int $ttlSeconds): string
    {
        $configured = (string) ($this->mailConfig['otp']['text_template'] ?? '');
        $template = trim($configured);
        if ($template === '') {
            $template = "Ihr Sicherheitscode lautet: {{code}}\nDer Code ist {{ttl_minutes}} Minuten gültig.";
        }

        return $this->replaceOtpTemplateVars($template, $code, $ttlSeconds, false);
    }

    private function renderOtpHtml(string $code, int $ttlSeconds): string
    {
        $configured = (string) ($this->mailConfig['otp']['html_template'] ?? '');
        $template = trim($configured);
        if ($template === '') {
            $template = '<p>Ihr Sicherheitscode lautet: <strong>{{code}}</strong></p><p>Der Code ist {{ttl_minutes}} Minuten gültig.</p>';
        }

        return $this->replaceOtpTemplateVars($template, $code, $ttlSeconds, true);
    }

    private function replaceOtpTemplateVars(string $template, string $code, int $ttlSeconds, bool $htmlContext): string
    {
        $minutes = (string) max(1, (int) ceil($ttlSeconds / 60));
        $projectName = (string) ($this->appConfig['project_name'] ?? 'Mitgliedsantrag');
        $safeCode = trim($code);
        $safeProjectName = trim($projectName);
        if ($htmlContext) {
            $safeCode = $this->esc($safeCode);
            $safeProjectName = $this->esc($safeProjectName);
        }

        return strtr($template, [
            '{{code}}' => $safeCode,
            '{{ttl_seconds}}' => (string) max(1, $ttlSeconds),
            '{{ttl_minutes}}' => $minutes,
            '{{project_name}}' => $safeProjectName,
        ]);
    }
}