<?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;
    }

    /**
     * Generate dynamic base64-encoded image containing OTP code using GD library.
     *
     * @param string $otp 4-digit OTP code
     * @return string Base64 encoded PNG image
     */
    public static function generateOtpImageBase64($otp) {
        // 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
        $accentColor = imagecolorallocate($im, 13, 110, 253); // Premium blue
        $noiseColor = imagecolorallocate($im, 200, 210, 220); // Light noise

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

        // Draw some obfuscation lines / background noise
        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);
        }

        // Draw some random dots
        for ($i = 0; $i < 100; $i++) {
            imagesetpixel($im, random_int(0, 300), random_int(0, 100), $noiseColor);
        }

        // Header text (smaller)
        imagestring($im, 3, 20, 15, "Verification Code:", $textColor);
        
        // Large OTP text (using larger font index 5 or custom size if possible)
        // Split OTP and draw characters with varying Y positions and styling to make OCR harder
        $chars = str_split($otp);
        $x = 90;
        foreach ($chars as $char) {
            $y = random_int(35, 45);
            imagestring($im, 5, $x, $y, $char, $accentColor);
            $x += 30;
        }

        // 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);
    }
}