using System;
using System.IO;
using System.Threading.Tasks;
using Microsoft.Win32;

namespace KSTools.Licensing
{
    /// <summary>
    /// KSTools 授權管理器
    /// 提供完整的授權管理功能，包括授權儲存、驗證、快取等
    /// </summary>
    public class LicenseManager
    {
        private const string REGISTRY_KEY_PATH = @"HKEY_CURRENT_USER\Software\KSTools\RevitPlugin";
        private const string LICENSE_CODE_KEY = "LicenseCode";
        private const string LICENSE_CACHE_KEY = "LicenseCache";
        private const string LAST_VALIDATION_KEY = "LastValidation";
        private const int VALIDATION_CACHE_HOURS = 1; // 快取驗證結果1小時
        
        private readonly ApiClient _apiClient;
        private readonly string _hardwareId;
        
        /// <summary>
        /// 初始化授權管理器
        /// </summary>
        /// <param name="apiBaseUrl">API 基礎 URL</param>
        public LicenseManager(string apiBaseUrl = null)
        {
            _apiClient = new ApiClient(apiBaseUrl);
            _hardwareId = HardwareFingerprint.GetHardwareId();
        }
        
        /// <summary>
        /// 取得當前硬體指紋ID
        /// </summary>
        /// <returns>硬體指紋ID</returns>
        public string GetHardwareId()
        {
            return _hardwareId;
        }
        
        /// <summary>
        /// 取得硬體資訊摘要
        /// </summary>
        /// <returns>硬體資訊</returns>
        public string GetHardwareInfo()
        {
            return HardwareFingerprint.GetHardwareInfo();
        }
        
        /// <summary>
        /// 啟用授權並儲存到本地
        /// </summary>
        /// <param name="licenseCode">授權碼</param>
        /// <returns>啟用結果</returns>
        public async Task<ActivationResult> ActivateLicenseAsync(string licenseCode)
        {
            try
            {
                var result = await _apiClient.ActivateLicenseAsync(licenseCode, _hardwareId);
                
                if (result.Success)
                {
                    // 儲存授權碼到註冊表
                    StoreLicenseCode(licenseCode);
                    
                    // 儲存快取資訊
                    StoreLicenseCache(result);
                    
                    // 記錄最後驗證時間
                    StoreLastValidation();
                }
                
                return result;
            }
            catch (Exception ex)
            {
                return new ActivationResult
                {
                    Success = false,
                    Message = $"啟用過程發生錯誤: {ex.Message}"
                };
            }
        }
        
        /// <summary>
        /// 驗證授權 (使用快取機制)
        /// </summary>
        /// <param name="forceOnlineCheck">是否強制進行線上檢查</param>
        /// <returns>驗證結果</returns>
        public async Task<ValidationResult> ValidateLicenseAsync(bool forceOnlineCheck = false)
        {
            try
            {
                string licenseCode = GetStoredLicenseCode();
                
                if (string.IsNullOrEmpty(licenseCode))
                {
                    return new ValidationResult
                    {
                        Valid = false,
                        Message = "尚未啟用授權，請先輸入授權碼"
                    };
                }
                
                // 如果不強制線上檢查，先嘗試使用快取
                if (!forceOnlineCheck)
                {
                    var cachedResult = GetCachedValidation();
                    if (cachedResult != null)
                    {
                        return cachedResult;
                    }
                }
                
                // 進行線上驗證
                var result = await _apiClient.ValidateLicenseAsync(licenseCode, _hardwareId);
                
                if (result.Valid)
                {
                    // 更新快取
                    StoreLicenseCache(new ActivationResult
                    {
                        Success = true,
                        Message = result.Message,
                        ExpiresAt = result.ExpiresAt,
                        UserName = result.UserName,
                        HardwareId = result.HardwareId
                    });
                    
                    StoreLastValidation();
                }
                else
                {
                    // 驗證失敗，清除快取
                    ClearLicenseCache();
                }
                
                return result;
            }
            catch (Exception ex)
            {
                // 網路錯誤時，嘗試使用快取的驗證結果
                var cachedResult = GetCachedValidation();
                if (cachedResult != null)
                {
                    cachedResult.Message += " (離線模式)";
                    return cachedResult;
                }
                
                return new ValidationResult
                {
                    Valid = false,
                    Message = $"驗證過程發生錯誤: {ex.Message}"
                };
            }
        }
        
        /// <summary>
        /// 檢查是否已有有效授權 (快速檢查)
        /// </summary>
        /// <returns>是否有有效授權</returns>
        public bool HasValidLicense()
        {
            try
            {
                string licenseCode = GetStoredLicenseCode();
                if (string.IsNullOrEmpty(licenseCode))
                    return false;
                
                var cachedResult = GetCachedValidation();
                return cachedResult?.Valid == true;
            }
            catch
            {
                return false;
            }
        }
        
        /// <summary>
        /// 取得授權資訊
        /// </summary>
        /// <returns>授權資訊，如果沒有授權則返回 null</returns>
        public LicenseInfo GetLicenseInfo()
        {
            try
            {
                string licenseCode = GetStoredLicenseCode();
                if (string.IsNullOrEmpty(licenseCode))
                    return null;
                
                var cachedData = GetRegistryValue(LICENSE_CACHE_KEY);
                if (!string.IsNullOrEmpty(cachedData))
                {
                    var parts = cachedData.Split('|');
                    if (parts.Length >= 4)
                    {
                        return new LicenseInfo
                        {
                            LicenseCode = licenseCode,
                            UserName = parts[0],
                            ExpiresAt = DateTime.TryParse(parts[1], out var expires) ? expires : (DateTime?)null,
                            HardwareId = parts[2],
                            LastValidation = DateTime.TryParse(parts[3], out var lastVal) ? lastVal : (DateTime?)null
                        };
                    }
                }
                
                return new LicenseInfo
                {
                    LicenseCode = licenseCode,
                    HardwareId = _hardwareId
                };
            }
            catch
            {
                return null;
            }
        }
        
        /// <summary>
        /// 清除儲存的授權資訊
        /// </summary>
        public void ClearLicense()
        {
            try
            {
                Registry.SetValue(REGISTRY_KEY_PATH, LICENSE_CODE_KEY, "");
                ClearLicenseCache();
            }
            catch
            {
                // 忽略錯誤
            }
        }
        
        /// <summary>
        /// 測試 API 連接
        /// </summary>
        /// <returns>是否連接成功</returns>
        public async Task<bool> TestApiConnectionAsync()
        {
            return await _apiClient.TestConnectionAsync();
        }
        
        #region 私有方法
        
        /// <summary>
        /// 儲存授權碼到註冊表
        /// </summary>
        /// <param name="licenseCode">授權碼</param>
        private void StoreLicenseCode(string licenseCode)
        {
            Registry.SetValue(REGISTRY_KEY_PATH, LICENSE_CODE_KEY, licenseCode);
        }
        
        /// <summary>
        /// 從註冊表取得授權碼
        /// </summary>
        /// <returns>授權碼</returns>
        private string GetStoredLicenseCode()
        {
            return GetRegistryValue(LICENSE_CODE_KEY);
        }
        
        /// <summary>
        /// 儲存授權快取資訊
        /// </summary>
        /// <param name="result">啟用或驗證結果</param>
        private void StoreLicenseCache(ActivationResult result)
        {
            string cacheData = $"{result.UserName}|{result.ExpiresAt}|{result.HardwareId}|{DateTime.Now}";
            Registry.SetValue(REGISTRY_KEY_PATH, LICENSE_CACHE_KEY, cacheData);
        }
        
        /// <summary>
        /// 記錄最後驗證時間
        /// </summary>
        private void StoreLastValidation()
        {
            Registry.SetValue(REGISTRY_KEY_PATH, LAST_VALIDATION_KEY, DateTime.Now.ToString());
        }
        
        /// <summary>
        /// 取得快取的驗證結果
        /// </summary>
        /// <returns>驗證結果，如果快取無效則返回 null</returns>
        private ValidationResult GetCachedValidation()
        {
            try
            {
                string lastValidationStr = GetRegistryValue(LAST_VALIDATION_KEY);
                if (string.IsNullOrEmpty(lastValidationStr))
                    return null;
                
                if (!DateTime.TryParse(lastValidationStr, out var lastValidation))
                    return null;
                
                // 檢查快取是否過期
                if (DateTime.Now - lastValidation > TimeSpan.FromHours(VALIDATION_CACHE_HOURS))
                    return null;
                
                string cacheData = GetRegistryValue(LICENSE_CACHE_KEY);
                if (string.IsNullOrEmpty(cacheData))
                    return null;
                
                var parts = cacheData.Split('|');
                if (parts.Length < 4)
                    return null;
                
                DateTime.TryParse(parts[1], out var expiresAt);
                
                // 檢查是否已過期
                if (expiresAt > DateTime.MinValue && expiresAt < DateTime.Now)
                {
                    return new ValidationResult
                    {
                        Valid = false,
                        Message = "授權已過期"
                    };
                }
                
                return new ValidationResult
                {
                    Valid = true,
                    Message = "授權有效 (快取)",
                    ExpiresAt = expiresAt > DateTime.MinValue ? expiresAt : (DateTime?)null,
                    UserName = parts[0],
                    HardwareId = parts[2]
                };
            }
            catch
            {
                return null;
            }
        }
        
        /// <summary>
        /// 清除授權快取
        /// </summary>
        private void ClearLicenseCache()
        {
            try
            {
                Registry.SetValue(REGISTRY_KEY_PATH, LICENSE_CACHE_KEY, "");
                Registry.SetValue(REGISTRY_KEY_PATH, LAST_VALIDATION_KEY, "");
            }
            catch
            {
                // 忽略錯誤
            }
        }
        
        /// <summary>
        /// 從註冊表取得值
        /// </summary>
        /// <param name="keyName">鍵名</param>
        /// <returns>值</returns>
        private string GetRegistryValue(string keyName)
        {
            try
            {
                return Registry.GetValue(REGISTRY_KEY_PATH, keyName, "")?.ToString() ?? "";
            }
            catch
            {
                return "";
            }
        }
        
        #endregion
    }
    
    /// <summary>
    /// 授權資訊
    /// </summary>
    public class LicenseInfo
    {
        /// <summary>
        /// 授權碼
        /// </summary>
        public string LicenseCode { get; set; }
        
        /// <summary>
        /// 用戶名稱
        /// </summary>
        public string UserName { get; set; }
        
        /// <summary>
        /// 到期時間
        /// </summary>
        public DateTime? ExpiresAt { get; set; }
        
        /// <summary>
        /// 硬體指紋ID
        /// </summary>
        public string HardwareId { get; set; }
        
        /// <summary>
        /// 最後驗證時間
        /// </summary>
        public DateTime? LastValidation { get; set; }
        
        /// <summary>
        /// 是否即將到期 (7天內)
        /// </summary>
        public bool IsExpiringSoon => ExpiresAt.HasValue && ExpiresAt.Value.Subtract(DateTime.Now).TotalDays <= 7;
        
        /// <summary>
        /// 剩餘天數
        /// </summary>
        public int DaysRemaining => ExpiresAt.HasValue ? Math.Max(0, (int)ExpiresAt.Value.Subtract(DateTime.Now).TotalDays) : 0;
    }
}