<?php
/**
 * WhatsApp Gateway Client Helper
 */

class WhatsAppClient {
    private static $gatewayUrl;
    private static $secret;
    private static $sessionKey;

    private static function init() {
        if (!self::$gatewayUrl) {
            self::$gatewayUrl = rtrim(defined('WHATSAPP_GATEWAY_URL') ? WHATSAPP_GATEWAY_URL : 'http://localhost:3732', '/');
            self::$secret = defined('WHATSAPP_WEBHOOK_SECRET') ? WHATSAPP_WEBHOOK_SECRET : '';
            self::$sessionKey = defined('WHATSAPP_SESSION_KEY') ? WHATSAPP_SESSION_KEY : 'otp_session';
        }
    }

    /**
     * Check if a phone number is registered on WhatsApp.
     *
     * @param string $phone Phone number in E.164 format (e.g. +96279XXXXXXXX)
     * @return bool True if registered, false otherwise
     */
    public static function isAvailable($phone) {
        self::init();
        
        $cleanPhone = preg_replace('/[^\d]/', '', $phone); // Strip '+' and other non-digits

        $payload = json_encode([
            'session_key' => self::$sessionKey,
            'phone' => $cleanPhone
        ]);

        $ch = curl_init(self::$gatewayUrl . '/api/contacts/check');
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
        curl_setopt($ch, CURLOPT_POST, true);
        curl_setopt($ch, CURLOPT_POSTFIELDS, $payload);
        curl_setopt($ch, CURLOPT_HTTPHEADER, [
            'Content-Type: application/json',
            'X-Webhook-Secret: ' . self::$secret
        ]);
        curl_setopt($ch, CURLOPT_TIMEOUT, 5);
        $response = curl_exec($ch);
        $httpCode = curl_getinfo($ch, CURLINFO_HTTP_CODE);
        curl_close($ch);

        if ($httpCode === 200 && $response) {
            $data = json_decode($response, true);
            if (isset($data['status']) && $data['status'] === 'success') {
                return isset($data['data']['exists']) && $data['data']['exists'] === true;
            }
        }
        return false;
    }

    /**
     * Send OTP message via WhatsApp Gateway.
     *
     * @param string $phone Destination phone number
     * @param string $message Message text
     * @param string|null $imageBase64 Optional base64 image data
     * @return bool True if successfully sent
     */
    public static function sendMessage($phone, $message, $imageBase64 = null) {
        self::init();

        $cleanPhone = preg_replace('/[^\d]/', '', $phone);

        $payloadData = [
            'session_key' => self::$sessionKey,
            'phone' => $cleanPhone,
            'message' => $message
        ];

        if ($imageBase64) {
            $payloadData['image'] = $imageBase64;
        }

        $payload = json_encode($payloadData);

        $ch = curl_init(self::$gatewayUrl . '/api/messages/send');
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
        curl_setopt($ch, CURLOPT_POST, true);
        curl_setopt($ch, CURLOPT_POSTFIELDS, $payload);
        curl_setopt($ch, CURLOPT_HTTPHEADER, [
            'Content-Type: application/json',
            'X-Webhook-Secret: ' . self::$secret
        ]);
        curl_setopt($ch, CURLOPT_TIMEOUT, 10);
        $response = curl_exec($ch);
        $httpCode = curl_getinfo($ch, CURLINFO_HTTP_CODE);
        curl_close($ch);

        if ($httpCode === 200 && $response) {
            $data = json_decode($response, true);
            return isset($data['status']) && $data['status'] === 'success';
        }
        return false;
    }

    /**
     * Ensure the TTF fonts exist in the backend/fonts directory.
     * If they don't, try to download them.
     */
    private static function ensureFontsExist() {
        $fontDir = __DIR__ . '/../fonts';
        if (!is_dir($fontDir)) {
            @mkdir($fontDir, 0755, true);
        }
        $fontDir = realpath($fontDir);

        if (!$fontDir) {
            return;
        }

        // Use Fontsource dedicated jsDelivr CDN endpoint for direct TTF files
        $fonts = [
            'Roboto-Bold.ttf' => 'https://cdn.jsdelivr.net/fontsource/fonts/roboto@latest/latin-700-normal.ttf',
            'Lora-Bold.ttf' => 'https://cdn.jsdelivr.net/fontsource/fonts/lora@latest/latin-700-normal.ttf',
            'Cairo-Bold.ttf' => 'https://cdn.jsdelivr.net/fontsource/fonts/cairo@latest/arabic-700-normal.ttf'
        ];

        foreach ($fonts as $filename => $url) {
            $path = $fontDir . '/' . $filename;
            
            // Validate if file exists and starts with valid TTF signatures
            $isValid = false;
            if (file_exists($path) && filesize($path) > 20000) {
                $fp = @fopen($path, 'rb');
                if ($fp) {
                    $sig = fread($fp, 4);
                    fclose($fp);
                    // Match TTF signatures: 0x00010000, 'OTTO', 'true'
                    if ($sig === "\x00\x01\x00\x00" || $sig === "OTTO" || $sig === "true") {
                        $isValid = true;
                    }
                }
            }

            if (!$isValid) {
                @unlink($path); // Delete invalid/corrupted file
                
                // Try file_get_contents first
                $content = @file_get_contents($url);
                if ($content !== false && strlen($content) > 20000) {
                    @file_put_contents($path, $content);
                } elseif (function_exists('curl_init')) {
                    $ch = curl_init($url);
                    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
                    curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true);
                    curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
                    curl_setopt($ch, CURLOPT_TIMEOUT, 15);
                    $content = curl_exec($ch);
                    curl_close($ch);
                    if ($content && strlen($content) > 20000) {
                        @file_put_contents($path, $content);
                    }
                }
            }
        }
    }

    /**
     * Generate dynamic base64-encoded image containing OTP code using GD library.
     *
     * @param string $otp 3-digit OTP code
     * @return string Base64 encoded PNG image
     */
    public static function generateOtpImageBase64($otp) {
        // Ensure fonts exist (downloads them if missing)
        self::ensureFontsExist();

        // Create a 300x100 image
        $im = imagecreatetruecolor(300, 100);
        if (!$im) {
            return '';
        }

        // Colors
        $bgColor = imagecolorallocate($im, 240, 244, 248); // Soft grey-blue
        $textColor = imagecolorallocate($im, 33, 37, 41);   // Dark charcoal
        $noiseColor = imagecolorallocate($im, 200, 210, 220); // Light noise
        $otpFg = imagecolorallocate($im, 13, 110, 253);      // Royal blue for OTP

        // Fill background
        imagefill($im, 0, 0, $bgColor);

        // --- 1. Check if TTF is available and fonts are loaded ---
        $useTtf = false;
        $availableFonts = [];
        $arabicFont = '';
        if (function_exists('imagettftext')) {
            $fontDir = realpath(__DIR__ . '/../fonts');
            if ($fontDir) {
                if (file_exists($fontDir . '/Roboto-Bold.ttf') && @filesize($fontDir . '/Roboto-Bold.ttf') > 20000) {
                    $availableFonts[] = $fontDir . '/Roboto-Bold.ttf';
                }
                if (file_exists($fontDir . '/Lora-Bold.ttf') && @filesize($fontDir . '/Lora-Bold.ttf') > 20000) {
                    $availableFonts[] = $fontDir . '/Lora-Bold.ttf';
                }
                if (file_exists($fontDir . '/Cairo-Bold.ttf') && @filesize($fontDir . '/Cairo-Bold.ttf') > 20000) {
                    $arabicFont = $fontDir . '/Cairo-Bold.ttf';
                    // We can also use Cairo for drawing OTP digits for extra variety!
                    $availableFonts[] = $fontDir . '/Cairo-Bold.ttf';
                }
                if (!empty($availableFonts)) {
                    $useTtf = true;
                }
            }
        }

        $chars = str_split($otp);

        if ($useTtf) {
            // Render smooth OTP using TTF fonts
            // Center the text block roughly. A 3-digit OTP with size 30px needs ~120px width.
            $startX = random_int(85, 115);
            $yBase = 65; // Baseline of TTF text
            
            foreach ($chars as $char) {
                // Alternating / random font selection per digit
                $fontFile = $availableFonts[array_rand($availableFonts)];
                $angle = random_int(-15, 15); // Dynamic tilts to thwart OCR
                $size = random_int(28, 34);   // Dynamic size
                $yOffset = random_int(-6, 6); // Vertical jitter
                
                // Draw character
                imagettftext($im, $size, $angle, $startX, $yBase + $yOffset, $otpFg, $fontFile, $char);
                $startX += 42; // Spacing to next char (larger spacing to handle angle/size variations)
            }
        } else {
            // Fallback: draw scaled bitmap fonts if TTF not supported
            $otpWidth = 45; // 3 chars * 15px width roughly
            $otpHeight = 20;
            $otpIm = imagecreatetruecolor($otpWidth, $otpHeight);
            $otpBg = imagecolorallocate($otpIm, 240, 244, 248);
            $otpFgTemp = imagecolorallocate($otpIm, 13, 110, 253);
            imagefill($otpIm, 0, 0, $otpBg);
            
            $x = 2;
            foreach ($chars as $char) {
                $y = random_int(0, 5); // Slight vertical jitter
                imagestring($otpIm, 5, $x, $y, $char, $otpFgTemp);
                $x += 14;
            }

            // Scale it up by 3x onto the main image
            $scale = 3;
            $dstWidth = $otpWidth * $scale;
            $dstHeight = $otpHeight * $scale;
            
            $dstX = random_int(80, 140);
            $dstY = random_int(30, 40);
            
            imagecopyresampled($im, $otpIm, $dstX, $dstY, 0, 0, $dstWidth, $dstHeight, $otpWidth, $otpHeight);
            imagedestroy($otpIm);
        }

        // --- 2. Add Background Noise (Lines & Dots) ---
        for ($i = 0; $i < 6; $i++) {
            imageline($im, random_int(0, 300), random_int(0, 100), random_int(0, 300), random_int(0, 100), $noiseColor);
        }
        for ($i = 0; $i < 100; $i++) {
            imagesetpixel($im, random_int(0, 300), random_int(0, 100), $noiseColor);
        }

        // --- 3. Draw Random Header Label with Variable Font ---
        $labels = [
            // English labels of varying word count
            ['text' => 'Verification Code:', 'lang' => 'en'],
            ['text' => 'Your OTP:', 'lang' => 'en'],
            ['text' => 'Security Key:', 'lang' => 'en'],
            ['text' => 'Access Number:', 'lang' => 'en'],
            ['text' => 'Auth Code:', 'lang' => 'en'],
            ['text' => 'Login Pin:', 'lang' => 'en'],
            ['text' => 'Secret Key:', 'lang' => 'en'],
            ['text' => 'Your Number:', 'lang' => 'en'],
            ['text' => 'One Time Pass:', 'lang' => 'en'],
            ['text' => 'Code:', 'lang' => 'en'],
            ['text' => 'App Verification PIN:', 'lang' => 'en'],
            ['text' => 'System Access Key:', 'lang' => 'en'],
            ['text' => 'Dynamic Access PIN:', 'lang' => 'en'],
            ['text' => 'Secure Verification Code:', 'lang' => 'en'],
            ['text' => 'Account Code:', 'lang' => 'en'],
            ['text' => 'Secure Passcode:', 'lang' => 'en'],
            
            // Pre-shaped Arabic labels (written RTL for GD engine)
            ['text' => 'ﻖﻘﺤﺘﻠﺎ ﺰﻣﺮ', 'lang' => 'ar'], // رمز التحقق
            ['text' => 'ﻥﺎﻣﺃﻟﺍ ﺩﻮﻛ', 'lang' => 'ar'],  // كود الأمان
            ['text' => 'ﺪﻴﻜﺃﺘﻠﺍ ﺰﻣﺮ', 'lang' => 'ar'], // رمز التأكيد
            ['text' => 'ﻒﻳﺮﻌﺘﻟﺍ ﻢﻗﺭ', 'lang' => 'ar']  // رقم التعريف
        ];
        
        $selectedLabel = $labels[array_rand($labels)];
        $label = $selectedLabel['text'];
        
        if ($useTtf) {
            // Select font: Cairo-Bold for Arabic, random for English
            $labelFont = ($selectedLabel['lang'] === 'ar' && $arabicFont) 
                ? $arabicFont 
                : $availableFonts[array_rand($availableFonts)];
            
            // Draw smooth TTF label (y=28 is baseline position, roughly equivalent to y=10 box)
            $size = ($selectedLabel['lang'] === 'ar') ? 14 : 12; // Adjust size for Arabic readability
            imagettftext($im, $size, 0, 20, 28, $textColor, $labelFont, $label);
        } else {
            // Fallback: draw using built-in font (convert Arabic to English fallback to avoid garbage text)
            $fallbackLabel = $label;
            if ($selectedLabel['lang'] === 'ar') {
                $fallbackLabel = 'Verification Code:';
            }
            $labelFont = random_int(3, 5);
            imagestring($im, $labelFont, 20, 10, $fallbackLabel, $textColor);
        }

        // Draw a bounding border
        imagerectangle($im, 0, 0, 299, 99, $noiseColor);

        // Capture output
        ob_start();
        imagepng($im);
        $imageData = ob_get_clean();
        imagedestroy($im);

        return base64_encode($imageData);
    }
}