<?php
// Włączenie raportowania błędów dla debugowania
error_reporting(E_ALL);
ini_set('display_errors', 0);
ini_set('log_errors', 1);

header('Content-Type: application/json');
header('Access-Control-Allow-Origin: *');

// Funkcja do zwracania błędów jako JSON
function returnError($message, $code = 500) {
    http_response_code($code);
    echo json_encode([
        'success' => false,
        'error' => $message
    ], JSON_UNESCAPED_UNICODE);
    exit;
}

require_once $_SERVER['DOCUMENT_ROOT'] . '/includes/session_bootstrap.php';

try {
    $pdo = og_session_get_pdo();
    if (!$pdo instanceof PDO) {
        throw new PDOException('Nie udało się zainicjalizować połączenia z bazą danych.');
    }

    // Parametry z requestu
    $page = isset($_GET['page']) ? max(1, (int)$_GET['page']) : 1;
    $limit = isset($_GET['limit']) ? min(100, max(1, (int)$_GET['limit'])) : 50;
    $offset = ($page - 1) * $limit;
    
    // Sortowanie
    $sortBy = isset($_GET['sortBy']) ? $_GET['sortBy'] : 'id';
    $sortOrder = isset($_GET['sortOrder']) && strtoupper($_GET['sortOrder']) === 'DESC' ? 'DESC' : 'ASC';
    
    // Dozwolone kolumny do sortowania (bezpieczeństwo)
    $allowedSortColumns = ['id', 'username', 'email', 'created_at', 'role'];
    if (!in_array($sortBy, $allowedSortColumns)) {
        $sortBy = 'id';
    }
    
    // Filtrowanie
    $filters = [];
    $params = [];
    
    // Filtr po username
    if (isset($_GET['username']) && $_GET['username'] !== '') {
        $filters[] = "u.username LIKE :username";
        $params[':username'] = '%' . $_GET['username'] . '%';
    }
    
    // Filtr po email
    if (isset($_GET['email']) && $_GET['email'] !== '') {
        $filters[] = "u.email LIKE :email";
        $params[':email'] = '%' . $_GET['email'] . '%';
    }
    
    // Filtr po roli
    if (isset($_GET['role']) && $_GET['role'] !== '') {
        $filters[] = "u.role = :role";
        $params[':role'] = $_GET['role'];
    }
    
    // Filtr po statusie weryfikacji
    if (isset($_GET['email_verified'])) {
        $filters[] = "u.email_verified = :email_verified";
        $params[':email_verified'] = (int)$_GET['email_verified'];
    }
    
    // Filtr po dacie rejestracji (od)
    if (isset($_GET['created_from']) && $_GET['created_from'] !== '') {
        $filters[] = "u.created_at >= :created_from";
        $params[':created_from'] = $_GET['created_from'];
    }
    
    // Filtr po dacie rejestracji (do)
    if (isset($_GET['created_to']) && $_GET['created_to'] !== '') {
        $filters[] = "u.created_at <= :created_to";
        $params[':created_to'] = $_GET['created_to'];
    }
    
    // Wyklucz użytkowników z disabled = 1
    $filters[] = "(u.disabled IS NULL OR u.disabled = 0)";
    
    // Budowanie WHERE clause
    $whereClause = '';
    if (count($filters) > 0) {
        $whereClause = 'WHERE ' . implode(' AND ', $filters);
    }
    
    // OPTYMALIZACJA: Fast approximate count z limitem 100k
    // Sprawdzenie czy count jest w cache (ważny 5 minut)
    $cacheKey = 'users_count_' . md5(serialize($params));
    $totalRecords = 0;
    $isApproximate = false;
    
    if (isset($_SESSION[$cacheKey]) && 
        isset($_SESSION[$cacheKey . '_time']) && 
        (time() - $_SESSION[$cacheKey . '_time']) < 300) {
        // Cache hit - użyj zapisanej wartości
        $totalRecords = $_SESSION[$cacheKey];
        $isApproximate = $_SESSION[$cacheKey . '_approx'] ?? false;
    } else {
        // Cache miss - policz z limitem
        // OPTYMALIZACJA: Limit count do 100k dla wydajności
        $countSql = "SELECT COUNT(*) as total FROM (
            SELECT 1 FROM users u $whereClause LIMIT 100000
        ) as limited_count";
        $countStmt = $pdo->prepare($countSql);
        
        try {
            $countStmt->execute($params);
            $totalRecords = $countStmt->fetch(PDO::FETCH_ASSOC)['total'];
            
            // Jeśli osiągnięto limit, sprawdź czy jest więcej
            if ($totalRecords >= 100000) {
                $checkMoreSql = "SELECT EXISTS(
                    SELECT 1 FROM users u $whereClause LIMIT 100001
                ) as has_more";
                $checkStmt = $pdo->prepare($checkMoreSql);
                $checkStmt->execute($params);
                if ($checkStmt->fetch(PDO::FETCH_ASSOC)['has_more']) {
                    $isApproximate = true;
                    $totalRecords = 100000; // Pokazuj 100k+
                }
            }
            
            // Zapisz w cache na 5 minut
            $_SESSION[$cacheKey] = $totalRecords;
            $_SESSION[$cacheKey . '_time'] = time();
            $_SESSION[$cacheKey . '_approx'] = $isApproximate;
            
        } catch (PDOException $e) {
            returnError('Błąd podczas zliczania rekordów: ' . $e->getMessage());
        }
    }
    
    $totalPages = $totalRecords > 0 ? ceil($totalRecords / $limit) : 1;
    
    // Pobieranie użytkowników + podstawowe statystyki salda (lekki LEFT JOIN)
    $sql = "SELECT 
                u.id,
                u.username,
                u.email,
                u.first_name,
                u.last_name,
                u.role,
                u.email_verified,
                u.created_at,
                COALESCE(u.account_suspended, 0) as account_suspended,
                u.suspension_reason,
                u.suspended_until,
                a.username AS suspended_by_username,
                COALESCE(us.balance, 0) as balance,
                COALESCE(us.matches_played, 0) as matches_played,
                COALESCE(us.matches_won, 0) as matches_won,
                COALESCE(us.matches_lost, 0) as matches_lost,
                us.account_status
            FROM users u
            LEFT JOIN user_stats us ON u.id = us.user_id
            LEFT JOIN users a ON a.id = u.suspended_by
            $whereClause
            ORDER BY u.$sortBy $sortOrder
            LIMIT :limit OFFSET :offset";
    
    $stmt = $pdo->prepare($sql);
    
    // Bindowanie parametrów filtrów
    foreach ($params as $key => $value) {
        $stmt->bindValue($key, $value);
    }
    
    // Bindowanie limit i offset
    $stmt->bindValue(':limit', $limit, PDO::PARAM_INT);
    $stmt->bindValue(':offset', $offset, PDO::PARAM_INT);
    
    try {
        $stmt->execute();
        $users = $stmt->fetchAll(PDO::FETCH_ASSOC);
    } catch (PDOException $e) {
        returnError('Błąd podczas pobierania użytkowników: ' . $e->getMessage());
    }
    
    // Formatowanie odpowiedzi
    $response = [
        'success' => true,
        'data' => $users,
        'pagination' => [
            'currentPage' => $page,
            'totalPages' => $totalPages,
            'totalRecords' => (int)$totalRecords,
            'totalRecordsApproximate' => $isApproximate,
            'totalRecordsDisplay' => $isApproximate ? '100,000+' : number_format($totalRecords, 0, ',', ' '),
            'recordsPerPage' => $limit,
            'hasNextPage' => $page < $totalPages,
            'hasPreviousPage' => $page > 1
        ],
        'filters' => [
            'sortBy' => $sortBy,
            'sortOrder' => $sortOrder,
            'appliedFilters' => array_keys($params)
        ]
    ];
    
    echo json_encode($response, JSON_UNESCAPED_UNICODE | JSON_PRETTY_PRINT);
    
} catch (PDOException $e) {
    returnError('Błąd połączenia z bazą danych: ' . $e->getMessage());
} catch (Exception $e) {
    returnError('Nieoczekiwany błąd: ' . $e->getMessage());
}
?>