using System;
using System.Globalization;
using System.IO;
using System.Net;

namespace ShrlAlgoStudio
{
    internal static class TimeHelper
    {
        public static DateTime GetTrustedTime()
        {
            // 1. 尝试网络时间 (3秒超时)
            try
            {
                var request = WebRequest.Create("http://www.baidu.com"); // 或 microsoft.com
                request.Method = "HEAD";
                request.Timeout = 3000;
                using (var response = request.GetResponse())
                {
                    string dateStr = response.Headers["Date"];
                    if (DateTime.TryParseExact(dateStr, "ddd, dd MMM yyyy HH:mm:ss 'GMT'",
                            CultureInfo.InvariantCulture, DateTimeStyles.AssumeUniversal, out DateTime netTime))
                        return netTime.ToLocalTime();
                }
            }
            catch { }

            // 2. 尝试文件系统痕迹校验 (防断网改时间)
            DateTime localNow = DateTime.Now;
            try
            {
                // 获取系统目录和临时目录的最后修改时间
                DateTime t1 = new DirectoryInfo(Environment.SystemDirectory).LastWriteTime;
                DateTime t2 = new DirectoryInfo(Path.GetTempPath()).LastWriteTime;
                DateTime latestFileTime = t1 > t2 ? t1 : t2;

                // 如果本地时间比系统文件时间还要早超过24小时，判定为作弊
                if (localNow < latestFileTime.AddHours(-24))
                {
                    return latestFileTime; // 强制使用文件时间
                }
            }
            catch { }

            // 3. 兜底
            return localNow;
        }
    }
}