<?php
// 通用函数

/**
 * 获取配置值
 */
function getConfig($key, $default = '') {
    global $db;
    $stmt = $db->prepare("SELECT value FROM config WHERE key = ?");
    $stmt->execute([$key]);
    $result = $stmt->fetch(PDO::FETCH_ASSOC);
    return $result ? $result['value'] : $default;
}

/**
 * 更新配置值
 */
function updateConfig($key, $value) {
    global $db;
    $stmt = $db->prepare("INSERT OR REPLACE INTO config (key, value) VALUES (?, ?)");
    return $stmt->execute([$key, $value]);
}

/**
 * 格式化文件大小
 */
function formatFileSize($bytes) {
    if ($bytes >= 1073741824) {
        return number_format($bytes / 1073741824, 2) . ' GB';
    } elseif ($bytes >= 1048576) {
        return number_format($bytes / 1048576, 2) . ' MB';
    } elseif ($bytes >= 1024) {
        return number_format($bytes / 1024, 2) . ' KB';
    } else {
        return $bytes . ' B';
    }
}

/**
 * 检查是否已登录
 */
function isLoggedIn() {
    return isset($_SESSION['admin_logged_in']) && $_SESSION['admin_logged_in'] === true;
}

/**
 * 安全输出 HTML
 */
function e($string) {
    return htmlspecialchars($string, ENT_QUOTES, 'UTF-8');
}