using System;
using System.Collections.Generic;
using System.Globalization;
using System.Linq;
using System.Management;
using System.Net;
using System.Reflection;
using System.Security.Cryptography;
using System.Text;
using System.Threading.Tasks;
using Microsoft.Win32;

namespace ShrlAlgoToolkit.Core.Assists
{
    public class LicenseEngine
    {
        // 【重要】替换为你生成的公钥
        private const string PublicKey = @"<RSAKeyValue><Modulus>rd5+EjU6QxaTY/AalU9g6ugAquN0ahJSgeahnf2CrfvUAWFNJ+SH7Qr0RcvOTyAbWfvLWoBDACKaPsg+8nRQcO3EZdFyjJ9oycLNrw38+gSB2+/79Axys/8MHtSXVUw9WN2e9LxeHOQGtcaoSsp+bPGaXswthovQ2CkvBTmCokcAOX6UaR7Av4npaXyEoGCUsZLEiSydMsNbQ+wLsumVg1H2o/cpkO0s4DiJHoF66zUuxA+pYSjSCn5KTUsOemf+gBsob6Sw+7WOToyiOkMdO9Op6esf8yL7DJ1Yd40XaKd5IeLQmEX/b+n1EV2JEkGO0p9q9MQRp6NrEc9LvfMJWQ==</Modulus><Exponent>AQAB</Exponent></RSAKeyValue>";

        private static string RegPath = @$"Software\{Assembly.GetExecutingAssembly().GetName()}\License";

        /// <summary>
        /// 完整验证逻辑
        /// </summary>
        public static (bool isValid, string message) Validate()
        {
            string licenseKey = LoadFromRegistry("Key");
            if (string.IsNullOrEmpty(licenseKey)) return (false, "未找到授权码");

            try
            {
                // 1. RSA 解密/验证逻辑
                // 激活码格式：签名(Base64)|机器码|到期日期
                var parts = licenseKey.Split('|');
                if (parts.Length != 3) return (false, "授权格式非法");

                string signature = parts[0];
                string mCode = parts[1];
                string expiryStr = parts[2];

                // 2. 验证是否是本机的机器码
                if (mCode != GetMachineCode()) return (false, "授权码与本机硬件不匹配");

                // 3. 验证 RSA 签名（确保数据没被篡改）
                if (!VerifySignature($"{mCode}|{expiryStr}", signature)) return (false, "授权签名校验失败");

                // 4. 时间校验
                DateTime expiryDate = DateTime.ParseExact(expiryStr, "yyyyMMdd", CultureInfo.InvariantCulture);
                DateTime now = GetRobustDateTime();

                // 防回滚检查
                DateTime lastRun = GetLastRunTime();
                if (now < lastRun) return (false, "系统时间异常，请检查时钟");
                UpdateLastRunTime(now);

                if (now > expiryDate) return (false, $"授权已于 {expiryDate:yyyy-MM-dd} 到期");

                return (true, "授权有效");
            }
            catch { return (false, "解析授权出错"); }
        }

        private static bool VerifySignature(string data, string signature)
        {
            using (var rsa = new RSACryptoServiceProvider())
            {
                rsa.FromXmlString(PublicKey);
                var formatter = new RSAPKCS1SignatureDeformatter(rsa);
                formatter.SetHashAlgorithm("SHA256");
                byte[] dataBytes = Encoding.UTF8.GetBytes(data);
                using (var sha = SHA256.Create())
                {
                    byte[] hash = sha.ComputeHash(dataBytes);
                    return formatter.VerifySignature(hash, Convert.FromBase64String(signature));
                }
            }
        }

        public static string GetMachineCode()
        {
            // 组合 CPU ID + 硬盘 ID
            string raw = GetHardwareId("Win32_Processor", "ProcessorId") +
                         GetHardwareId("Win32_PhysicalMedia", "SerialNumber");
            using (var sha = SHA256.Create())
            {
                byte[] hash = sha.ComputeHash(Encoding.UTF8.GetBytes(raw));
                return BitConverter.ToString(hash).Replace("-", "").Substring(0, 16);
            }
        }

        private static string GetHardwareId(string wmiClass, string property)
        {
            try
            {
                using (var mc = new ManagementClass(wmiClass))
                    foreach (var mo in mc.GetInstances()) return mo[property]?.ToString().Trim();
            }
            catch { }
            return "UNKNOWN";
        }

        // 获取可靠的时间（网络优先，本地其次）
        private static DateTime GetRobustDateTime()
        {
            try
            {
                var request = WebRequest.Create("http://www.baidu.com");
                request.Timeout = 2000;
                using (var response = request.GetResponse())
                {
                    string dateStr = response.Headers["Date"];
                    return DateTime.ParseExact(dateStr, "ddd, dd MMM yyyy HH:mm:ss 'GMT'", CultureInfo.InvariantCulture, DateTimeStyles.AssumeUniversal);
                }
            }
            catch { return DateTime.Now; }
        }

        #region 注册表操作
        private static DateTime GetLastRunTime()
        {
            string val = LoadFromRegistry("T");
            return string.IsNullOrEmpty(val) ? DateTime.MinValue : new DateTime(long.Parse(val));
        }
        private static void UpdateLastRunTime(DateTime now) => SaveToRegistry("T", now.Ticks.ToString());

        public static void SaveToRegistry(string key, string val)
        {
            using var r = Registry.CurrentUser.CreateSubKey(RegPath);
            r.SetValue(key, val);
        }
        private static string LoadFromRegistry(string key)
        {
            using var r = Registry.CurrentUser.OpenSubKey(RegPath);
            return r?.GetValue(key)?.ToString();
        }
        /// <summary>
        /// 仅移除当前的激活码（重置授权状态，但保留时间戳防止白嫖）
        /// </summary>
        public static void ClearLicenseKey()
        {
            try
            {
                using (var r = Registry.CurrentUser.OpenSubKey(RegPath, true))
                {
                    if (r != null && r.GetValue("Key") != null)
                    {
                        r.DeleteValue("Key");
                    }
                }
            }
            catch (Exception ex)
            {
                Console.WriteLine("移除授权码失败: " + ex.Message);
            }
        }

        /// <summary>
        /// 彻底销毁所有授权痕迹（包括时间戳记录，通常用于卸载）
        /// </summary>
        public static void DestroyAllLicenseData()
        {
            try
            {
                // 第二个参数为 false 表示：如果路径不存在，不抛出异常
                Registry.CurrentUser.DeleteSubKeyTree(RegPath, false);
            }
            catch (Exception ex)
            {
                Console.WriteLine("彻底清理注册表失败: " + ex.Message);
            }
        }
        #endregion
    }
}