<?php
class Mailer {
    private $db;
    private $smtpEnabled;
    private $smtpHost;
    private $smtpPort;
    private $smtpUsername;
    private $smtpPassword;
    private $smtpEncryption;
    private $fromEmail;
    private $fromName;
    
    public function __construct() {
        $this->db = Database::getInstance();
        $this->loadSettings();
    }
    
    private function loadSettings() {
        $this->smtpEnabled = $this->db->getSetting('smtp_enabled', '0') === '1';
        $this->smtpHost = $this->db->getSetting('smtp_host', '');
        $this->smtpPort = (int)$this->db->getSetting('smtp_port', '587');
        $this->smtpUsername = $this->db->getSetting('smtp_username', '');
        $this->smtpPassword = $this->db->getSetting('smtp_password', '');
        $this->smtpEncryption = $this->db->getSetting('smtp_encryption', 'tls');
        $this->fromEmail = $this->db->getSetting('smtp_from_email', 'noreply@' . $_SERVER['HTTP_HOST']);
        $this->fromName = $this->db->getSetting('smtp_from_name', $this->db->getSetting('app_title', 'UniFi Voucher System'));
    }
    
    public function sendRaw($to, $subject, $plainBody) {
        return $this->send($to, $subject, $plainBody, false);
    }

    public function send($to, $subject, $body, $isHtml = false) {
        // Bis zu 2 Versuche bei vorübergehenden Zustellfehlern (Retry).
        $attempts = 2;
        for ($i = 1; $i <= $attempts; $i++) {
            if (!$this->smtpEnabled || empty($this->smtpHost)) {
                $ok = $this->sendWithPhpMail($to, $subject, $body);
            } else {
                $ok = $this->sendWithSmtp($to, $subject, $body, $isHtml);
            }
            if ($ok) {
                return true;
            }
            if ($i < $attempts) {
                usleep(500000); // 0,5s vor erneutem Versuch
            }
        }
        error_log("Mailer: Zustellung an {$to} nach {$attempts} Versuchen fehlgeschlagen.");
        return false;
    }
    
    private function sendWithPhpMail($to, $subject, $body) {
        $headers = "From: {$this->fromName} <{$this->fromEmail}>\r\n";
        $headers .= "Reply-To: {$this->fromEmail}\r\n";
        $headers .= "Content-Type: text/plain; charset=UTF-8\r\n";
        
        return mail($to, $subject, $body, $headers);
    }
    
    private function sendWithSmtp($to, $subject, $body, $isHtml = false) {
        try {
            // Verbindung aufbauen
            $socket = $this->connectToSmtp();
            
            // EHLO
            $this->smtpCommand($socket, "EHLO " . $_SERVER['HTTP_HOST']);
            
            // STARTTLS wenn nötig
            if ($this->smtpEncryption === 'tls') {
                $this->smtpCommand($socket, "STARTTLS");
                stream_socket_enable_crypto($socket, true, STREAM_CRYPTO_METHOD_TLS_CLIENT);
                $this->smtpCommand($socket, "EHLO " . $_SERVER['HTTP_HOST']);
            }
            
            // AUTH LOGIN
            $this->smtpCommand($socket, "AUTH LOGIN");
            $this->smtpCommand($socket, base64_encode($this->smtpUsername));
            $this->smtpCommand($socket, base64_encode($this->smtpPassword));
            
            // MAIL FROM
            $this->smtpCommand($socket, "MAIL FROM:<{$this->fromEmail}>");
            
            // RCPT TO
            $this->smtpCommand($socket, "RCPT TO:<{$to}>");
            
            // DATA
            $this->smtpCommand($socket, "DATA");
            
            // Headers
            $message = "From: {$this->fromName} <{$this->fromEmail}>\r\n";
            $message .= "To: {$to}\r\n";
            $message .= "Subject: =?UTF-8?B?" . base64_encode($subject) . "?=\r\n";
            $message .= "MIME-Version: 1.0\r\n";
            
            if ($isHtml) {
                $message .= "Content-Type: text/html; charset=UTF-8\r\n";
            } else {
                $message .= "Content-Type: text/plain; charset=UTF-8\r\n";
            }
            
            $message .= "\r\n";
            
            // Body - bei Plain Text Zeilenumbrüche konvertieren
            if (!$isHtml) {
                $body = nl2br($body, false); // Für Plain Text
                $body = str_replace('<br>', "\r\n", $body);
            }
            
            $message .= $body;
            $message .= "\r\n.\r\n";
            
            fwrite($socket, $message);
            $response = fgets($socket);
            
            // QUIT
            $this->smtpCommand($socket, "QUIT");
            fclose($socket);
            
            return strpos($response, '250') === 0;
            
        } catch (Exception $e) {
            error_log("SMTP Error: " . $e->getMessage());
            return false;
        }
    }
    
    private function connectToSmtp() {
        $context = stream_context_create([
            'ssl' => [
                'verify_peer' => false,
                'verify_peer_name' => false,
                'allow_self_signed' => true
            ]
        ]);
        
        if ($this->smtpEncryption === 'ssl') {
            $host = 'ssl://' . $this->smtpHost;
        } else {
            $host = $this->smtpHost;
        }
        
        $socket = stream_socket_client(
            $host . ':' . $this->smtpPort,
            $errno,
            $errstr,
            30,
            STREAM_CLIENT_CONNECT,
            $context
        );
        
        if (!$socket) {
            throw new Exception("SMTP Connection failed: $errstr ($errno)");
        }
        
        // Willkommensnachricht lesen
        fgets($socket);
        
        return $socket;
    }
    
    private function smtpCommand($socket, $command) {
        fwrite($socket, $command . "\r\n");
        $response = fgets($socket);
        
        // Prüfen auf Fehler (4xx oder 5xx)
        if (preg_match('/^[45]/', $response)) {
            throw new Exception("SMTP Error: $response");
        }
        
        return $response;
    }
    
    // Vordefinierte E-Mail-Templates
    /**
     * Legt den Nachrichtentext in ein schlichtes, markentreues HTML-Gerüst.
     * Bewusst Tabellen + Inline-Styles: nur so rendern Outlook & Co. zuverlässig.
     */
    private function brandedHtml(string $title, string $contentHtml, string $footerNote = ''): string
    {
        $accent = $this->db->getSetting('brand_gradient_from', '') ?: '#5b5bd6';
        $accent2 = $this->db->getSetting('brand_gradient_to', '') ?: '#8b5cf6';
        if (!preg_match('/^#[0-9a-fA-F]{6}$/', $accent))  { $accent = '#5b5bd6'; }
        if (!preg_match('/^#[0-9a-fA-F]{6}$/', $accent2)) { $accent2 = '#8b5cf6'; }

        $safeTitle = htmlspecialchars($title, ENT_QUOTES, 'UTF-8');
        $year = date('Y');
        $footer = $footerNote !== '' ? '<div style="margin-top:8px;">' . htmlspecialchars($footerNote, ENT_QUOTES, 'UTF-8') . '</div>' : '';

        return '<!DOCTYPE html><html><head><meta charset="UTF-8">'
            . '<meta name="viewport" content="width=device-width, initial-scale=1.0">'
            . '<title>' . $safeTitle . '</title></head>'
            . '<body style="margin:0;padding:0;background:#f6f7f9;">'
            . '<table role="presentation" width="100%" cellpadding="0" cellspacing="0" style="background:#f6f7f9;padding:28px 12px;">'
            . '<tr><td align="center">'
            . '<table role="presentation" width="600" cellpadding="0" cellspacing="0" style="max-width:600px;width:100%;background:#ffffff;border:1px solid #e5e8ee;border-radius:14px;overflow:hidden;font-family:-apple-system,BlinkMacSystemFont,\'Segoe UI\',Roboto,Helvetica,Arial,sans-serif;">'
            . '<tr><td style="background:' . $accent . ';background-image:linear-gradient(135deg,' . $accent . ' 0%,' . $accent2 . ' 100%);padding:22px 26px;">'
            . '<div style="color:#ffffff;font-size:16px;font-weight:600;letter-spacing:-0.01em;">' . $safeTitle . '</div>'
            . '</td></tr>'
            . '<tr><td style="padding:26px;color:#101625;font-size:15px;line-height:1.6;">' . $contentHtml . '</td></tr>'
            . '<tr><td style="padding:16px 26px;background:#f8f9fb;border-top:1px solid #e5e8ee;color:#6b7280;font-size:12px;">'
            . '&copy; ' . $year . ' ' . $safeTitle . $footer
            . '</td></tr>'
            . '</table></td></tr></table></body></html>';
    }

    /**
     * Voucher-Code als hervorgehobene Karte für die E-Mail.
     */
    private function voucherCardHtml(string $code, string $siteName, $maxUses): string
    {
        return '<table role="presentation" width="100%" cellpadding="0" cellspacing="0" '
            . 'style="margin:18px 0;background:#f8f9fb;border:1px solid #e5e8ee;border-radius:12px;">'
            . '<tr><td align="center" style="padding:22px;">'
            . '<div style="font-size:12px;letter-spacing:.08em;text-transform:uppercase;color:#6b7280;">'
            . htmlspecialchars($siteName, ENT_QUOTES, 'UTF-8') . '</div>'
            . '<div style="margin:10px 0;font-family:Consolas,Menlo,monospace;font-size:28px;font-weight:700;letter-spacing:.12em;color:#101625;">'
            . htmlspecialchars($code, ENT_QUOTES, 'UTF-8') . '</div>'
            . '<div style="font-size:13px;color:#525c6e;">'
            . htmlspecialchars((string)$maxUses, ENT_QUOTES, 'UTF-8') . ' '
            . htmlspecialchars(function_exists('__') ? __('label_devices') : 'Geräte', ENT_QUOTES, 'UTF-8') . '</div>'
            . '</td></tr></table>';
    }

    public function sendVoucherEmail($to, $voucherCode, $siteName, $maxUses) {
        $appTitle = $this->db->getSetting('app_title', 'UniFi Voucher System');
        $instructionHeader = $this->db->getSetting('instruction_header', '');
        $instructionText = $this->db->getSetting('instruction_text', '');
        
        // System-URL aus Einstellungen oder automatisch erkennen
        $systemUrl = $this->db->getSetting('system_url', '');
        if (empty($systemUrl)) {
            $protocol = isset($_SERVER['HTTPS']) && $_SERVER['HTTPS'] === 'on' ? 'https' : 'http';
            $host = $_SERVER['HTTP_HOST'];
            $scriptPath = dirname($_SERVER['SCRIPT_NAME']);
            $scriptPath = $scriptPath === '/' ? '' : $scriptPath;
            $systemUrl = $protocol . '://' . $host . $scriptPath;
        }
        
        // Template aus Datenbank laden
        $subjectTemplate = $this->db->getSetting('email_voucher_subject', '{APP_TITLE} - Ihr WLAN-Zugang');
        $bodyTemplate = $this->db->getSetting('email_voucher_body', "Hallo,\n\nhier ist Ihr WLAN-Zugangscode:\n{VOUCHER_CARD}\n<strong>Maximale Geräte:</strong> {MAX_USES}<br>\n<strong>Standort:</strong> {SITE_NAME}\n\n{INSTRUCTIONS}\n\nViele Grüße\n{APP_TITLE}");
        
        // Anleitung formatieren
        $instructions = '';
        if ($instructionText) {
            $instructions = $instructionHeader . "\n" . $instructionText;
        }
        
        // Platzhalter ersetzen
        $placeholders = [
            '{VOUCHER_CARD}' => $this->voucherCardHtml($voucherCode, (string)$siteName, $maxUses),
            '{VOUCHER_CODE}' => $voucherCode,
            '{SITE_NAME}' => $siteName,
            '{MAX_USES}' => $maxUses,
            '{APP_TITLE}' => $appTitle,
            '{INSTRUCTIONS}' => $instructions,
            '{SYSTEM_URL}' => $systemUrl
        ];

        $subject = str_replace(array_keys($placeholders), array_values($placeholders), $subjectTemplate);

        // Umbrueche der Vorlage vor dem Einsetzen der Platzhalter umwandeln,
        // sonst wuerde das Markup der Voucher-Karte die Erkennung stoeren.
        $isHtml = strip_tags($bodyTemplate) !== $bodyTemplate || strpos($bodyTemplate, '{VOUCHER_CARD}') !== false;
        $template = $isHtml ? $this->textToHtml($bodyTemplate) : $bodyTemplate;
        $body = str_replace(array_keys($placeholders), array_values($placeholders), $template);

        if ($isHtml) {
            $body = $this->brandedHtml($appTitle, $body);
        }

        return $this->send($to, $subject, $body, $isHtml);
    }
    
    public function sendTestEmail($to) {
        $appTitle = $this->db->getSetting('app_title', 'UniFi Voucher System');
        $subject = '[Test] E-Mail-Konfiguration – ' . $appTitle;
        $body = "Dies ist eine Test-E-Mail von {$appTitle}.\n\nDie SMTP-Konfiguration ist korrekt eingerichtet.";
        return $this->send($to, $subject, $body, false);
    }

    public function sendUserNotification($to, $userName, $changes) {
        $appTitle = $this->db->getSetting('app_title', 'UniFi Voucher System');
        
        // System-URL aus Einstellungen oder automatisch erkennen
        $systemUrl = $this->db->getSetting('system_url', '');
        if (empty($systemUrl)) {
            $protocol = isset($_SERVER['HTTPS']) && $_SERVER['HTTPS'] === 'on' ? 'https' : 'http';
            $host = $_SERVER['HTTP_HOST'];
            $scriptPath = dirname($_SERVER['SCRIPT_NAME']);
            $scriptPath = $scriptPath === '/' ? '' : $scriptPath;
            $systemUrl = $protocol . '://' . $host . $scriptPath;
        }
        
        // Template aus Datenbank laden
        $subjectTemplate = $this->db->getSetting('email_user_notification_subject', '{APP_TITLE} - Ihre Berechtigungen wurden geändert');
        $bodyTemplate = $this->db->getSetting('email_user_notification_body', "Hallo {USER_NAME},\n\nEin Administrator hat Ihre Berechtigungen im {APP_TITLE} geändert:\n\n{CHANGES}\n\nSie können sich unter folgender Adresse anmelden:\n{SYSTEM_URL}\n\nMit freundlichen Grüßen\n{APP_TITLE}");
        
        // Änderungen formatieren
        $changesText = '';
        foreach ($changes as $change) {
            $changesText .= "• $change\n";
        }
        
        // Platzhalter ersetzen
        $placeholders = [
            '{USER_NAME}' => $userName,
            '{CHANGES}' => $changesText,
            '{APP_TITLE}' => $appTitle,
            '{SYSTEM_URL}' => $systemUrl
        ];
        
        $subject = str_replace(array_keys($placeholders), array_values($placeholders), $subjectTemplate);

        $isHtml = strip_tags($bodyTemplate) !== $bodyTemplate;
        $template = $isHtml ? $this->textToHtml($bodyTemplate) : $bodyTemplate;
        $body = str_replace(array_keys($placeholders), array_values($placeholders), $template);

        if ($isHtml) {
            $body = $this->brandedHtml($appTitle, $body);
        }

        return $this->send($to, $subject, $body, $isHtml);
    }

    /**
     * Zeilenumbrüche aus dem Vorlagentext in HTML übernehmen, ohne bereits
     * vorhandenes Markup (z. B. aus dem WYSIWYG-Editor) zu zerstören.
     */
    private function textToHtml(string $body): string
    {
        if (preg_match('#<(p|div|ul|ol|h[1-6])[\s>]#i', $body)) {
            return $body;
        }

        return nl2br($body, false);
    }
}