using System;
using System.Reflection;
using System.Security.Cryptography;
using System.Text;
using Microsoft.Win32;

namespace ShrlAlgoStudio
{
    internal class LicenseManager
    {
        // 【重要】替换为你生成的公钥
        public static 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>
        /// 校验结果枚举
        /// </summary>
        public enum AuthStatus { Valid, Expired, HardwareMismatch, TimeTampered, InvalidSignature, NoLicense }
        /// <summary>
        /// 核心验证方法
        /// </summary>
        public static (AuthStatus status, string msg) Validate()
        {
            string licenseKey = LoadReg("Key");
            if (string.IsNullOrEmpty(licenseKey)) return (AuthStatus.NoLicense, "未激活");

            try
            {
                // 格式：签名|机器码|发码日期|过期日期
                var parts = licenseKey.Split('|');
                if (parts.Length != 4) return (AuthStatus.InvalidSignature, "授权格式错误");

                string signature = parts[0];
                string mCode = parts[1];
                string issueDateStr = parts[2];
                string expiryDateStr = parts[3];

                // 1. 硬件校验
                if (mCode != HardwareInfo.GetMachineCode())
                    return (AuthStatus.HardwareMismatch, "机器码不匹配，请联系管理员");

                // 2. RSA 签名校验 (防止篡改日期)
                string dataVerify = $"{mCode}|{issueDateStr}|{expiryDateStr}";
                if (!VerifyRSA(dataVerify, signature))
                    return (AuthStatus.InvalidSignature, "非法授权 (签名无效)");

                // 3. 时间逻辑校验
                DateTime issueDate = DateTime.ParseExact(issueDateStr, "yyyyMMdd", null);
                DateTime expiryDate = DateTime.ParseExact(expiryDateStr, "yyyyMMdd", null);
                DateTime now = TimeHelper.GetTrustedTime(); // 获取可信时间

                // 3.1 检查是否早于发码日期 (防极度回滚)
                if (now < issueDate)
                    return (AuthStatus.TimeTampered, "系统时间异常：早于授权发码时间");

                // 3.2 检查上次运行记录 T (防短期回滚)
                long lastRunTicks = 0;
                long.TryParse(LoadReg("T"), out lastRunTicks);
                if (lastRunTicks > 0)
                {
                    DateTime lastRun = new DateTime(lastRunTicks);
                    // 允许1小时的误差
                    if (now < lastRun.AddHours(-1))
                        return (AuthStatus.TimeTampered, "系统时间异常：检测到时间倒流");
                }

                // 3.3 检查过期
                if (now.Date > expiryDate.Date)
                    return (AuthStatus.Expired, $"授权已于 {expiryDate:yyyy-MM-dd} 到期");

                // --- 验证通过 ---
                SaveReg("T", now.Ticks.ToString()); // 更新痕迹
                return (AuthStatus.Valid, $"授权有效，到期时间为{expiryDate:yyyy-MM-dd}");
            }
            catch
            {
                return (AuthStatus.InvalidSignature, "授权解析异常");
            }
        }

        // 保存激活码
        public static void Activate(string keyInput)
        {
            SaveReg("Key", keyInput);
        }

        // RSA 验签辅助
        private static bool VerifyRSA(string data, string signature)
        {
            try
            {
                using (var rsa = new RSACryptoServiceProvider())
                {
                    rsa.FromXmlString(PublicKey);
                    var formatter = new RSAPKCS1SignatureDeformatter(rsa);
                    formatter.SetHashAlgorithm("SHA256");
                    byte[] dataBytes = Encoding.UTF8.GetBytes(data);
                    byte[] signBytes = Convert.FromBase64String(signature);
                    using (var sha = SHA256.Create())
                    {
                        return formatter.VerifySignature(sha.ComputeHash(dataBytes), signBytes);
                    }
                }
            }
            catch { return false; }
        }

        #region 注册表底层
        private static void SaveReg(string key, string val)
        {
            using (var r = Registry.CurrentUser.CreateSubKey(RegPath)) r.SetValue(key, val);
        }
        private static string LoadReg(string key)
        {
            using (var r = Registry.CurrentUser.OpenSubKey(RegPath)) return r?.GetValue(key)?.ToString();
        }
        public static void RemoveLicense()
        {
            using (var r = Registry.CurrentUser.OpenSubKey(RegPath, true)) r?.DeleteValue("Key", false);
        }
        #endregion
    }
}