nabeh/backend/app/Models/WhatsAppSession.php

<?php

namespace App\Models;

use App\Core\Security;
use App\Core\Database;
use App\Core\Cache;

/**
 * WhatsAppSession Model
 * Handles the whatsapp_sessions table with encryption for phone and QR code,
 * Redis caching of connected sessions, and Round-Robin distribution for outbound messages.
 */
class WhatsAppSession extends BaseModel
{
    protected static string $table = 'whatsapp_sessions';

    /**
     * Clear cached connected sessions for a company
     */
    public static function clearSessionsCache(int $companyId): void
    {
        Cache::delete("connected_sessions:company_{$companyId}");
    }

    /**
     * Get all active connected sessions for a company (cached via Redis if available)
     */
    public static function getConnectedSessionsForCompany(int $companyId): array
    {
        $cacheKey = "connected_sessions:company_{$companyId}";
        $cached = Cache::get($cacheKey);
        if ($cached !== null && is_array($cached)) {
            return $cached;
        }

        $sessions = Database::select(
            "SELECT * FROM " . static::$table . " WHERE company_id = ? AND status = 'connected' ORDER BY id ASC",
            [$companyId]
        );

        foreach ($sessions as &$session) {
            $session['phone'] = $session['phone'] ? Security::decrypt($session['phone']) : null;
            $session['qr_code'] = $session['qr_code'] ? Security::decrypt($session['qr_code']) : null;
        }

        Cache::set($cacheKey, $sessions, 3000); // Cache for 50 minutes
        return $sessions;
    }

    /**
     * Get next connected session using Round-Robin strategy via Redis
     */
    public static function getRoundRobinSession(int $companyId): ?array
    {
        $connectedSessions = static::getConnectedSessionsForCompany($companyId);

        if (empty($connectedSessions)) {
            // Fallback to legacy single session if no connected sessions are found
            return static::findByCompany($companyId, false);
        }

        $count = count($connectedSessions);
        if ($count === 1) {
            return $connectedSessions[0];
        }

        $rrKey = "rr_index:company_{$companyId}";
        $currentIndex = Cache::get($rrKey);
        if ($currentIndex === null || !is_numeric($currentIndex)) {
            $currentIndex = 0;
        } else {
            $currentIndex = (int)$currentIndex;
        }

        $selectedIndex = $currentIndex % $count;
        $nextIndex = ($selectedIndex + 1) % $count;

        Cache::set($rrKey, $nextIndex, 86400);

        return $connectedSessions[$selectedIndex];
    }

    /**
     * Get the session for a specific company (defaults to Round-Robin among connected sessions)
     */
    public static function findByCompany(int $companyId, bool $useRoundRobin = true)
    {
        if ($useRoundRobin) {
            $session = static::getRoundRobinSession($companyId);
            if ($session) {
                return $session;
            }
        }

        $session = Database::selectOne(
            "SELECT * FROM " . static::$table . " WHERE company_id = ? LIMIT 1",
            [$companyId]
        );

        if ($session) {
            $session['phone'] = $session['phone'] ? Security::decrypt($session['phone']) : null;
            $session['qr_code'] = $session['qr_code'] ? Security::decrypt($session['qr_code']) : null;
        }

        return $session;
    }

    /**
     * Find secure session by ID
     */
    public static function findSecure(int $id)
    {
        $session = Database::selectOne(
            "SELECT * FROM " . static::$table . " WHERE id = ? LIMIT 1",
            [$id]
        );

        if ($session) {
            $session['phone'] = $session['phone'] ? Security::decrypt($session['phone']) : null;
            $session['qr_code'] = $session['qr_code'] ? Security::decrypt($session['qr_code']) : null;
        }

        return $session;
    }

    /**
     * Get all WhatsApp sessions for a company
     */
    public static function findAllByCompany(int $companyId): array
    {
        $sessions = Database::select(
            "SELECT * FROM " . static::$table . " WHERE company_id = ? ORDER BY id ASC",
            [$companyId]
        );

        foreach ($sessions as &$session) {
            $session['phone'] = $session['phone'] ? Security::decrypt($session['phone']) : null;
            $session['qr_code'] = $session['qr_code'] ? Security::decrypt($session['qr_code']) : null;
        }

        return $sessions;
    }

    /**
     * Get a session by session_key (used by webhooks)
     */
    public static function findBySessionKey(string $sessionKey)
    {
        $session = Database::selectOne(
            "SELECT * FROM " . static::$table . " WHERE session_key = ? LIMIT 1",
            [$sessionKey]
        );

        if ($session) {
            $session['phone'] = $session['phone'] ? Security::decrypt($session['phone']) : null;
            $session['qr_code'] = $session['qr_code'] ? Security::decrypt($session['qr_code']) : null;
        }

        return $session;
    }

    /**
     * Find session by phone number (useful to prevent duplicates across companies)
     */
    public static function findByPhone(string $phone)
    {
        $phoneHash = Security::blindIndex($phone);
        $session = Database::selectOne(
            "SELECT * FROM " . static::$table . " WHERE phone_hash = ? LIMIT 1",
            [$phoneHash]
        );

        if ($session) {
            $session['phone'] = $session['phone'] ? Security::decrypt($session['phone']) : null;
            $session['qr_code'] = $session['qr_code'] ? Security::decrypt($session['qr_code']) : null;
        }

        return $session;
    }

    /**
     * Create or retrieve a new session for a company
     */
    public static function findOrCreate(int $companyId, string $name = 'Main WhatsApp')
    {
        $session = static::findByCompany($companyId, false);
        if ($session) {
            return $session;
        }

        $sessionKey = 'cmp_' . $companyId . '_' . bin2hex(random_bytes(4));

        $id = static::create([
            'company_id' => $companyId,
            'name' => $name,
            'session_key' => $sessionKey,
            'status' => 'disconnected'
        ]);

        static::clearSessionsCache($companyId);
        return static::findByCompany($companyId, false);
    }

    /**
     * Update session state securely and clear Redis cache
     */
    public static function updateState(int $id, array $data)
    {
        if (isset($data['phone'])) {
            $data['phone_hash'] = Security::blindIndex($data['phone']);
            $data['phone'] = Security::encrypt($data['phone']);
        }

        if (isset($data['qr_code'])) {
            $data['qr_code'] = Security::encrypt($data['qr_code']);
        }

        $session = Database::selectOne("SELECT company_id FROM " . static::$table . " WHERE id = ? LIMIT 1", [$id]);
        $result = static::update($id, $data);

        if ($session && !empty($session['company_id'])) {
            static::clearSessionsCache((int)$session['company_id']);
        }

        return $result;
    }
}