using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Diagnostics.CodeAnalysis;
using System.Drawing;
using System.Globalization;
using System.IO;
using System.Linq;
using System.Net;
using System.Net.Http;
using System.Runtime.InteropServices;
using System.Security.Cryptography;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using System.Windows.Forms;
using Aliyun.OSS;
using Aliyun.OSS.Common;
using Newtonsoft.Json;
using Newtonsoft.Json.Linq;

using System.Collections.Concurrent;
using System.Diagnostics;
using System.Configuration;

namespace CheckDownload
{
    public partial class Update : Form
    {
        // MD5文件名称
        private const string Md5File = "md5.json";
        // 阿里云OSS访问地址
        private const string OssEndpoint = "oss-cn-hongkong.aliyuncs.com";
        // 阿里云OSS存储空间名称
        private const string OssBucketName = "suwin-oss";
        // 阿里云OSS访问密钥ID
        private const string OssAccessKeyId = "LTAI5tCwRcL5LUgyHB2j7w82";
        // 阿里云OSS访问密钥Secret
        private const string OssAccessKeySecret = "7ClQns3wz6psmIp9T2OfuEn3tpzrCK";
        // 123盘鉴权密钥
        private const string OneDriveAuthKey = "6SwdpWdSJuJRSh";
        // 123盘UID
        private const string OneDriveUid = "1826795402";
        // 123盘路径（不包含域名）- 修改此处即可同时生效于主备域名
        private const string OneDrivePath = "/1826795402/KeyAuth";
        // 123盘主域名
        private const string OneDriveMainDomain = "vip.123pan.cn";
        // 123盘备用域名
        private const string OneDriveBackupDomain = "vip.123yx.com";
        // 123盘鉴权有效时间（秒）
        private const int OneDriveAuthTimeout = 600;
        // 下载流超时时间（毫秒）
        private const int DownloadStreamTimeoutMs = 60000;

        // 网络优化: 静态HttpClient实例，避免套接字耗尽
        private static readonly HttpClient _httpClient = new HttpClient { Timeout = TimeSpan.FromSeconds(20) };
        // OSS客户端：仅初始化一次，避免频繁创建导致内存占用过高
        private static readonly ClientConfiguration _ossClientConfig = new ClientConfiguration
        {
            ConnectionTimeout = 20000, // 20 seconds
            MaxErrorRetry = 0
        };
        private static readonly OssClient _ossClient = new OssClient(OssEndpoint, OssAccessKeyId, OssAccessKeySecret, _ossClientConfig);
        // 网络优化: 备用DNS服务列表，提高解析成功率
        private static readonly List<string> _dnsServers = new List<string> { "223.5.5.5", "119.29.29.29" };
        // 最大并发下载数量
        private static readonly int MaxConcurrentDownloads = int.TryParse(ConfigurationManager.AppSettings["MaxConcurrentDownloads"], out var mcd) ? mcd : 4;
        // 最大下载重试次数
        private static readonly int MaxDownloadRetries = int.TryParse(ConfigurationManager.AppSettings["MaxDownloadRetries"], out var mdr) ? mdr : 2;
        // 用于存储下载的文件数据
        private Dictionary<string, string> _downloadedFiles = new Dictionary<string, string>();
        // 已完成的下载数量
        private int _completedCount = 0;
        // 总下载数量
        private int _totalCount = 0;
        // 已下载总字节数
        private long _totalDownloadedBytes = 0;
        // 下载总计时器
        private Stopwatch _overallStopwatch;
        // 已下载速度字节数
        private long _speedDownloadedBytes = 0;
        // 更新计数显示（线程安全）
        private void UpdateCountBox(int completed, int total)
        {
            string text = total > 0 ? $"{completed}/{total}" : "";
            if (this.InvokeRequired)
            {
                this.Invoke((MethodInvoker)delegate { Count_Box.Text = text; });
            }
            else
            {
                Count_Box.Text = text;
            }
        }
        // 更新文件大小和速度显示（线程安全）
        private void UpdateSizeBox(string text)
        {
            if (this.InvokeRequired)
            {
                this.Invoke((MethodInvoker)delegate { Size_Box.Text = text; });
            }
            else
            {
                Size_Box.Text = text;
            }
        }
        // 累计已下载字节并更新Size_Box
        private void AddDownloadedBytes(long bytes, bool countForSpeed)
        {
            long total = Interlocked.Add(ref _totalDownloadedBytes, bytes);
            if (countForSpeed)
            {
                Interlocked.Add(ref _speedDownloadedBytes, bytes);
            }

            if (_overallStopwatch == null) return;

            double mbTotal = total / 1024.0 / 1024.0;
            double mbSpeed = (_speedDownloadedBytes / 1024.0 / 1024.0) / Math.Max(0.1, _overallStopwatch.Elapsed.TotalSeconds);
            UpdateSizeBox($"{mbTotal:F1}MB/{mbSpeed:F1}MB/s");
        }
        // 临时文件夹路径
        private string _tempDirectory;
        // 基准目录路径（用于文件更新的目标目录）
        private string _baseDirectory;

        /// <summary>
        /// 初始化窗体
        /// </summary>
        public Update()
        {
            InitializeComponent();
            ConfigureProgressBar();
            InitializeTempDirectory();
        }

        /// <summary>
        /// 配置进度条的基本属性
        /// </summary>
        private void ConfigureProgressBar()
        {
            Update_Pro.Minimum = 0;
            Update_Pro.Maximum = 100;
            Update_Pro.Value = 0;
            Update_Pro.Step = 1;
        }

        /// <summary>
        /// 更新进度条的值（线程安全）
        /// </summary>
        /// <param name="percentage">进度百分比</param>
        private void UpdateProgressValue(int percentage)
        {
            if (percentage < 0) percentage = 0;
            if (percentage > 100) percentage = 100;

            if (this.InvokeRequired)
            {
                this.Invoke((MethodInvoker)delegate
                {
                    Update_Pro.Value = Math.Min(Math.Max(percentage, Update_Pro.Minimum), Update_Pro.Maximum);
                });
            }
            else
            {
                Update_Pro.Value = Math.Min(Math.Max(percentage, Update_Pro.Minimum), Update_Pro.Maximum);
            }
        }

        /// <summary>
        /// 更新状态显示文本（线程安全）
        /// </summary>
        /// <param name="message">状态消息</param>
        private void UpdateStatus(string message)
        {
            if (this.InvokeRequired)
            {
                this.Invoke((MethodInvoker)delegate { Status_Box.Text = message; });
            }
            else
            {
                Status_Box.Text = message;
            }
        }

        /// <summary>
        /// 窗体加载事件处理，启动更新流程
        /// </summary>
        public async void Update_Load(object sender, EventArgs e)
        {
            PositionFormToBottomRight();
            try
            {
                await UpdateFile();
            }
            finally
            {
            }
        }

        /// <summary>
        /// 将窗体定位到屏幕右下角
        /// </summary>
        private void PositionFormToBottomRight()
        {
            Rectangle workingArea = Screen.GetWorkingArea(this);
            this.Location = new Point(workingArea.Right - this.Width, workingArea.Bottom - this.Height);
        }

        /// <summary>
        /// 主要的文件更新流程
        /// </summary>
        private async Task UpdateFile()
        {
            try
            {
                CleanupNewFiles();
                UpdateStatus("下载MD5...");
                string tempFilePath = Path.Combine(_tempDirectory, Md5File);
                // 使用新的带123盘的下载方法
                if (!await DownloadMd5FileWithFallback(Md5File, tempFilePath))
                {
                    UpdateStatus("MD5下载失败");
                    await Task.Delay(3000);
                    this.Close();
                    return;
                }
                var onlineData = ReadOnlineMd5File(tempFilePath);
                if (!ValidateOnlineData(onlineData.Version, onlineData.Md5, onlineData.Data))
                {
                    UpdateStatus("MD5文件无效");
                    await Task.Delay(3000);
                    this.Close();
                    return;
                }

                // 基于md5.json内容智能检测基准目录
                InitializeBaseDirectoryFromMd5Data(onlineData.Data);

                UpdateStatus("比较文件...");
                var compareResult = CompareMd5Data(onlineData.Data);
                if (compareResult.Count == 0)
                {
                    UpdateProgressValue(100);
                    UpdateCountBox(0, 0);
                    UpdateSizeBox("");
                    
                    // 无需更新时清理临时文件夹
                    CleanupTempDirectory();
                    UpdateStatus("无需更新");
                    await Task.Delay(2000);
                    this.Close();
                    return;
                }

                UpdateStatus("下载文件...");
                // 根据路径长度排序，优先下载小文件/浅层文件，可加其它排序规则
                var orderedFileList = compareResult.OrderBy(k => k.Key.Length)
                                               .ToDictionary(k => k.Key, v => v.Value);

                _totalCount = orderedFileList.Count;
                _completedCount = 0;
                _totalDownloadedBytes = 0;
                _speedDownloadedBytes = 0;
                _overallStopwatch = Stopwatch.StartNew();
                UpdateSizeBox("0MB/0MB/s");
                UpdateCountBox(_completedCount, _totalCount);
                _downloadedFiles.Clear();
                var failedFiles = new ConcurrentDictionary<string, string>();

                await PerformDownloads(orderedFileList, failedFiles);

                if (!failedFiles.IsEmpty)
                {
                    UpdateStatus($"重试 {failedFiles.Count} 个失败文件...");
                    var stillFailing = await RetryFailedFilesAsync(new Dictionary<string, string>(failedFiles));
                    if (stillFailing.Any())
                    {
                        UpdateStatus($"{stillFailing.Count} 个文件重试失败");
                    }
                }

                if (_completedCount == 0 && orderedFileList.Count > 0)
                {
                     throw new Exception("全部文件下载失败");
                }
                
                await VerifyAndSaveAllFiles();

                // 校验和保存成功后清理临时目录
                CleanupTempDirectory();

                // 显示完成状态并退出
                UpdateStatus("更新完成");
                UpdateCountBox(0, 0);
                UpdateSizeBox("");
                await Task.Delay(3000);
                this.Close();
                return;
            }
            catch (Exception ex)
            {
                UpdateStatus($"更新失败: {ex.Message.Split(new[] { '\r', '\n' }, StringSplitOptions.RemoveEmptyEntries).FirstOrDefault()}");
                await Task.Delay(3000);
                this.Close();
            }
        }

        /// <summary>
        /// 清理旧的更新文件，删除所有.new后缀的临时文件
        /// </summary>
        private void CleanupNewFiles()
        {
            try
            {
                var newFiles = Directory.GetFiles(_baseDirectory, "*.new", SearchOption.AllDirectories);
                if (newFiles.Length > 0)
                {
                    UpdateStatus("清理旧文件...");
                    foreach (var file in newFiles)
                    {
                        try
                        {
                            File.Delete(file);
                        }
                        catch
                        {
                        }
                    }
                }
            }
            catch
            {
            }
        }

        /// <summary>
        /// 读取在线MD5文件并解析JSON内容，提取版本信息和文件清单数据
        /// </summary>
        /// <param name="filePath">MD5文件的本地路径</param>
        /// <returns>包含版本号、MD5值和文件数据的元组</returns>
        private (string Version, string Md5, JObject Data) ReadOnlineMd5File(string filePath)
        {
            try
            {
                using (var reader = new StreamReader(filePath))
                {
                    string json = reader.ReadToEnd();
                    var parsed = JObject.Parse(json);
                    string version = parsed["version"]?.ToString();
                    var data = (JObject)parsed["data"];
                    string jsonMd5 = CalculateMD5(json);
                    return (version, jsonMd5, data);
                }
            }
            catch (OssException)
            {
                UpdateStatus("读取MD5失败");
                return (null, null, null);
            }
            catch (JsonException)
            {
                UpdateStatus("读取MD5失败");
                return (null, null, null);
            }
        }

        /// <summary>
        /// 验证在线MD5数据的完整性和有效性
        /// </summary>
        /// <param name="version">版本号字符串</param>
        /// <param name="md5">文件的MD5哈希值</param>
        /// <param name="data">包含文件信息的JSON对象</param>
        /// <returns>如果所有必需字段都有效则返回true，否则返回false</returns>
        private bool ValidateOnlineData(string version, string md5, JObject data)
        {
            if (string.IsNullOrEmpty(version) || string.IsNullOrEmpty(md5) || data == null)
            {
                UpdateStatus("MD5文件无效");
                return false;
            }
            return true;
        }

        /// <summary>
        /// 递归比较本地文件和在线MD5数据，识别需要更新的文件
        /// </summary>
        /// <param name="onlineData">在线文件清单的JSON数据</param>
        /// <param name="currentPath">当前递归路径，用于构建完整的文件路径</param>
        /// <returns>包含需要更新的文件路径和对应MD5值的字典</returns>
        private Dictionary<string, string> CompareMd5Data(JObject onlineData, string currentPath = "")
        {
            var differences = new Dictionary<string, string>();

            foreach (var onlineProperty in onlineData.Properties())
            {
                string key = onlineProperty.Name;
                JToken onlineValue = onlineProperty.Value;
                
                string relativePath = string.IsNullOrEmpty(currentPath) ? key : Path.Combine(currentPath, key);
                string localFullPath = Path.Combine(_baseDirectory, relativePath);

                if (onlineValue.Type == JTokenType.String)
                {
                    string expectedMd5 = onlineValue.ToString();
                    if (!File.Exists(localFullPath))
                    {
                        if (!differences.ContainsKey(relativePath))
                        {
                            differences[relativePath] = expectedMd5;
                        }
                    }
                    else
                    {
                        string localMd5 = CalculateMD5FromFile(localFullPath);
                        if (!localMd5.Equals(expectedMd5, StringComparison.OrdinalIgnoreCase))
                        {
                            if (!differences.ContainsKey(relativePath))
                            {
                                differences[relativePath] = expectedMd5;
                            }
                        }
                    }
                }
                else if (onlineValue.Type == JTokenType.Object)
                {
                    var subDifferences = CompareMd5Data((JObject)onlineValue, relativePath);
                    foreach (var diff in subDifferences)
                    {
                        if (!differences.ContainsKey(diff.Key))
                        {
                            differences[diff.Key] = diff.Value;
                        }
                    }
                }
            }
            return differences;
        }

        /// <summary>
        /// 批量下载文件列表并进行MD5验证，支持重试机制
        /// </summary>
        /// <param name="fileList">包含文件路径和期望MD5值的字典</param>
        private async Task DownloadAndVerifyFiles(Dictionary<string, string> fileList)
        {
            _totalCount = fileList.Count;
            _completedCount = 0;
            _totalDownloadedBytes = 0;
            _speedDownloadedBytes = 0;
            _overallStopwatch = Stopwatch.StartNew();
            UpdateSizeBox("0MB/0MB/s");
            UpdateCountBox(_completedCount, _totalCount);
            _downloadedFiles.Clear();
            var failedFiles = new ConcurrentDictionary<string, string>();

            await PerformDownloads(fileList, failedFiles);

            if (!failedFiles.IsEmpty)
            {
                UpdateStatus($"重试 {failedFiles.Count} 个失败文件...");
                var stillFailing = await RetryFailedFilesAsync(new Dictionary<string, string>(failedFiles));
                if (stillFailing.Any())
                {
                    UpdateStatus($"{stillFailing.Count} 个文件重试失败");
                }
            }

            if (_completedCount == 0 && fileList.Count > 0)
            {
                 throw new Exception("所有文件下载失败。");
            }
            
            await VerifyAndSaveAllFiles();
        }

        /// <summary>
        /// 使用信号量控制并发数量，执行多个文件的并发下载任务
        /// </summary>
        /// <param name="filesToDownload">包含文件路径和MD5值的下载任务字典</param>
        /// <param name="failedDownloads">用于收集下载失败文件的线程安全集合</param>
        private async Task PerformDownloads(IDictionary<string, string> filesToDownload, ConcurrentDictionary<string, string> failedDownloads)
        {
            var semaphore = new SemaphoreSlim(MaxConcurrentDownloads);
            var downloadTasks = filesToDownload.Select(async (file) =>
            {
                await semaphore.WaitAsync();
                try
                {
                    bool success = await AttemptDownloadAsync(file.Key, file.Value);
                    if (success)
                    {
                        lock (_downloadedFiles)
                        {
                            _downloadedFiles[file.Key] = file.Value;
                        }
                        Interlocked.Increment(ref _completedCount);
                        
                        int progress = (int)((double)_completedCount / _totalCount * 95);
                        UpdateProgressValue(progress);
                        
                        UpdateStatus($"下载: {Path.GetFileName(file.Key)}");
                        UpdateCountBox(_completedCount, _totalCount);
                    }
                    else
                    {
                        failedDownloads.TryAdd(file.Key, file.Value);
                    }
                }
                finally
                {
                    semaphore.Release();
                }
            });
            await Task.WhenAll(downloadTasks);
        }
        
        /// <summary>
        /// 尝试从多个数据源下载单个文件，优先使用123盘，OSS作为备用
        /// </summary>
        /// <param name="filePath">文件的相对路径</param>
        /// <param name="expectedMd5">文件的期望MD5值，用于验证完整性</param>
        /// <returns>下载成功返回true，否则返回false</returns>
        private async Task<bool> AttemptDownloadAsync(string filePath, string expectedMd5)
        {
            string tempFilePath = Path.Combine(_tempDirectory, filePath);
            string fileName = Path.GetFileName(filePath);
            long downloadedBytes = 0;

            try
            {
                if (await CheckExistingTempFile(tempFilePath, expectedMd5, fileName))
                {
                    // 已存在临时文件
                    downloadedBytes = new FileInfo(tempFilePath).Length;
                    AddDownloadedBytes(downloadedBytes, false);
                    return true;
                }

                UpdateStatus($"下载: {fileName}");
                UpdateCountBox(_completedCount + 1, _totalCount);
                if (await DownloadFileFromOneDrive(filePath, expectedMd5, tempFilePath))
                {
                    downloadedBytes = new FileInfo(tempFilePath).Length;
                    AddDownloadedBytes(downloadedBytes, true);
                    return true;
                }
                
                UpdateStatus($"下载: {fileName}");
                UpdateCountBox(_completedCount + 1, _totalCount);
                string ossKey = $"File/{expectedMd5}";
                
                var obj = _ossClient.GetObject(OssBucketName, ossKey);
                
                string tempDir = Path.GetDirectoryName(tempFilePath);
                if (!Directory.Exists(tempDir))
                {
                    Directory.CreateDirectory(tempDir);
                }

                using (var fileStream = File.Create(tempFilePath))
                {
                    using (var cts = new CancellationTokenSource(DownloadStreamTimeoutMs))
                    {
                        await obj.Content.CopyToAsync(fileStream, 81920, cts.Token);
                    }
                }
                downloadedBytes = new FileInfo(tempFilePath).Length;
                AddDownloadedBytes(downloadedBytes, true);
                return true;
            }
            catch (Exception ex) when (ex is OssException || ex is WebException || ex is OperationCanceledException)
            {
                UpdateStatus($"下载: {fileName}");
                UpdateCountBox(_completedCount + 1, _totalCount);
                string ossKey = $"File/{expectedMd5}";
                bool ok = await DownloadFileWithFallback(ossKey, tempFilePath);
                if (ok)
                {
                    try
                    {
                        downloadedBytes = new FileInfo(tempFilePath).Length;
                        AddDownloadedBytes(downloadedBytes, true);
                    }
                    catch
                    {
                        // File might not be accessible for a moment after download
                    }
                }
                return ok;
            }
            catch
            {
                UpdateStatus($"下载异常: {fileName}");
                return false;
            }
        }

        /// <summary>
        /// 检查临时目录中是否已存在完整的文件，通过MD5验证文件完整性
        /// </summary>
        /// <param name="tempFilePath">临时文件的完整路径</param>
        /// <param name="expectedMd5">文件的期望MD5哈希值</param>
        /// <param name="fileName">文件名，用于状态显示</param>
        /// <returns>如果文件存在且MD5匹配返回true，否则返回false</returns>
        private async Task<bool> CheckExistingTempFile(string tempFilePath, string expectedMd5, string fileName)
        {
            try
            {
                if (!File.Exists(tempFilePath))
                {
                    return false;
                }

                UpdateStatus($"检查: {fileName}");
                
                string actualMd5 = await Task.Run(() => CalculateMD5FromFile(tempFilePath));
                
                if (actualMd5.Equals(expectedMd5, StringComparison.OrdinalIgnoreCase))
                {
                    UpdateStatus($"跳过: {fileName}");
                    return true;
                }
                else
                {
                    UpdateStatus($"重下载: {fileName}");
                    File.Delete(tempFilePath);
                    return false;
                }
            }
            catch (Exception ex)
            {
                UpdateStatus($"检查出错: {fileName}");
                try
                {
                    if (File.Exists(tempFilePath))
                    {
                        File.Delete(tempFilePath);
                    }
                }
                catch
                {
                }
                return false;
            }
        }

        /// <summary>
        /// 从123盘下载文件，先尝试主域名，失败后自动切换到备用域名
        /// </summary>
        /// <param name="baseUrl">123盘的基础URL地址</param>
        /// <param name="fileName">要下载的文件名</param>
        /// <param name="localPath">文件保存的本地路径</param>
        /// <returns>下载成功返回true，两个域名都失败则返回false</returns>
        private async Task<bool> DownloadFromOneDrive(string baseUrl, string fileName, string localPath)
        {
            try
            {
                UpdateStatus($"123盘下载: {fileName}");
                
                string authUrl = GenerateAuthUrl($"http://{OneDriveMainDomain}{OneDrivePath}", fileName);
                
                UpdateStatus("123盘主域...");
                
                var request = new HttpRequestMessage(HttpMethod.Get, authUrl) { Version = HttpVersion.Version11 };
                request.Headers.Add("User-Agent", "CheckDownload/1.0");
                
                using (var response = await _httpClient.SendAsync(request, HttpCompletionOption.ResponseHeadersRead))
                {
                    response.EnsureSuccessStatusCode();
                    string localDir = Path.GetDirectoryName(localPath);
                    if (!Directory.Exists(localDir))
                    {
                        Directory.CreateDirectory(localDir);
                    }

                    using (var remote = await response.Content.ReadAsStreamAsync())
                    using (var localFile = File.Create(localPath))
                    {
                        using (var cts = new CancellationTokenSource(DownloadStreamTimeoutMs))
                        {
                            await remote.CopyToAsync(localFile, 81920, cts.Token);
                        }
                    }
                    
                    UpdateStatus($"主域成功: {fileName}");
                    return true;
                }
            }
            catch
            {
                UpdateStatus("主域失败, 转备用...");
            }

            try
            {
                UpdateStatus($"123盘备用下载: {fileName}");
                
                string authUrl = GenerateAuthUrl($"http://{OneDriveBackupDomain}{OneDrivePath}", fileName);
                
                UpdateStatus("123盘备用域...");
                
                var request = new HttpRequestMessage(HttpMethod.Get, authUrl) { Version = HttpVersion.Version11 };
                request.Headers.Add("User-Agent", "CheckDownload/1.0");
                
                using (var response = await _httpClient.SendAsync(request, HttpCompletionOption.ResponseHeadersRead))
                {
                    response.EnsureSuccessStatusCode();
                    string localDir = Path.GetDirectoryName(localPath);
                    if (!Directory.Exists(localDir))
                    {
                        Directory.CreateDirectory(localDir);
                    }

                    using (var remote = await response.Content.ReadAsStreamAsync())
                    using (var localFile = File.Create(localPath))
                    {
                        using (var cts = new CancellationTokenSource(DownloadStreamTimeoutMs))
                        {
                            await remote.CopyToAsync(localFile, 81920, cts.Token);
                        }
                    }
                    
                    UpdateStatus($"备用域成功: {fileName}");
                    return true;
                }
            }
            catch
            {
                UpdateStatus($"备用域失败: {fileName}");
                return false;
            }
        }

        /// <summary>
        /// 根据文件MD5从123盘下载文件，使用主备域名双重保障
        /// </summary>
        /// <param name="filePath">文件的相对路径（仅用于日志显示）</param>
        /// <param name="expectedMd5">文件的MD5值，用于构建123盘存储路径</param>
        /// <param name="localPath">文件保存的本地完整路径</param>
        /// <returns>下载成功返回true，两个域名都失败则返回false</returns>
        private async Task<bool> DownloadFileFromOneDrive(string filePath, string expectedMd5, string localPath)
        {
            string fileName = $"File/{expectedMd5}";
            
            try
            {
                string authUrl = GenerateAuthUrl($"http://{OneDriveMainDomain}{OneDrivePath}", fileName);
                
                var request = new HttpRequestMessage(HttpMethod.Get, authUrl) { Version = HttpVersion.Version11 };
                request.Headers.Add("User-Agent", "CheckDownload/1.0");
                
                using (var response = await _httpClient.SendAsync(request, HttpCompletionOption.ResponseHeadersRead))
                {
                    response.EnsureSuccessStatusCode();
                    string localDir = Path.GetDirectoryName(localPath);
                    if (!Directory.Exists(localDir))
                    {
                        Directory.CreateDirectory(localDir);
                    }

                    using (var remote = await response.Content.ReadAsStreamAsync())
                    using (var localFile = File.Create(localPath))
                    {
                        using (var cts = new CancellationTokenSource(DownloadStreamTimeoutMs))
                        {
                            await remote.CopyToAsync(localFile, 81920, cts.Token);
                        }
                    }
                    
                    return true;
                }
            }
            catch (Exception ex)
            {
            }

            try
            {
                string authUrl = GenerateAuthUrl($"http://{OneDriveBackupDomain}{OneDrivePath}", fileName);
                
                var request = new HttpRequestMessage(HttpMethod.Get, authUrl) { Version = HttpVersion.Version11 };
                request.Headers.Add("User-Agent", "CheckDownload/1.0");
                
                using (var response = await _httpClient.SendAsync(request, HttpCompletionOption.ResponseHeadersRead))
                {
                    response.EnsureSuccessStatusCode();
                    string localDir = Path.GetDirectoryName(localPath);
                    if (!Directory.Exists(localDir))
                    {
                        Directory.CreateDirectory(localDir);
                    }

                    using (var remote = await response.Content.ReadAsStreamAsync())
                    using (var localFile = File.Create(localPath))
                    {
                        using (var cts = new CancellationTokenSource(DownloadStreamTimeoutMs))
                        {
                            await remote.CopyToAsync(localFile, 81920, cts.Token);
                        }
                    }
                    
                    return true;
                }
            }
            catch
            {
                return false;
            }
        }

        /// <summary>
        /// 对下载失败的文件进行重试，最多重试指定次数
        /// </summary>
        /// <param name="failedFiles">包含失败文件路径和MD5值的字典</param>
        /// <returns>重试后仍然失败的文件字典</returns>
        private async Task<Dictionary<string, string>> RetryFailedFilesAsync(Dictionary<string, string> failedFiles)
        {
            var filesToRetry = new Dictionary<string, string>(failedFiles);

            for (int i = 0; i < MaxDownloadRetries && filesToRetry.Any(); i++)
            {
                UpdateStatus($"重试 {i + 1}/{MaxDownloadRetries}, 剩{filesToRetry.Count}个");
                var failedThisRound = new ConcurrentDictionary<string, string>();
                
                await PerformDownloads(filesToRetry, failedThisRound);
                
                filesToRetry = new Dictionary<string, string>(failedThisRound);

                if (filesToRetry.Any() && i < MaxDownloadRetries - 1)
                {
                    UpdateStatus("等待3秒后重试");
                    await Task.Delay(3000);
                }
            }

            return filesToRetry;
        }

        /// <summary>
        /// 使用多个DNS服务器解析域名获取IP地址列表，提高解析成功率
        /// </summary>
        /// <param name="domain">要解析的目标域名</param>
        /// <returns>解析成功的IP地址列表，解析失败返回空列表</returns>
        private async Task<List<string>> GetIpAddressesForDomain(string domain)
        {
            foreach (var dnsServer in _dnsServers)
            {
                try
                {
                    var requestUri = $"http://{dnsServer}/resolve?name={domain}&type=1&short=1";
                    var request = new HttpRequestMessage(HttpMethod.Get, requestUri) { Version = HttpVersion.Version11 };
                    request.Headers.Add("User-Agent", "CheckDownload/1.0");
                    request.Headers.Host = dnsServer;

                    var response = await _httpClient.SendAsync(request);
                    response.EnsureSuccessStatusCode();

                    string responseBody = await response.Content.ReadAsStringAsync();
                    var ips = JsonConvert.DeserializeObject<List<string>>(responseBody);
                    if (ips != null && ips.Any())
                    {
                        UpdateStatus($"DNS解析成功: {dnsServer}");
                        return ips;
                    }
                }
                catch
                {
                    UpdateStatus($"DNS解析失败: {dnsServer}");
                    await Task.Delay(500);
                }
            }

            UpdateStatus("所有DNS解析失败");
            return new List<string>();
        }
        
        /// <summary>
        /// 验证所有下载文件的MD5完整性并保存到目标位置，处理文件占用情况
        /// </summary>
        private async Task VerifyAndSaveAllFiles()
        {
            UpdateStatus("校验文件...");
            var failedFiles = new ConcurrentBag<string>();
            var filesForScripting = new ConcurrentBag<(string original, string newFile)>();

            int totalFiles = _downloadedFiles.Count;
            int completed = 0;
            var semaphore = new SemaphoreSlim(Environment.ProcessorCount);

            var tasks = _downloadedFiles.Select(async item =>
            {
                await semaphore.WaitAsync();
                try
                {
                    string relativePath = item.Key;
                    string expectedMd5 = item.Value;
                    string tempFilePath = Path.Combine(_tempDirectory, relativePath);

                    string actualMd5 = CalculateMD5FromFile(tempFilePath);
                    if (actualMd5 != expectedMd5.ToLower())
                    {
                        failedFiles.Add(relativePath);
                        return;
                    }

                    string localPath = Path.Combine(_baseDirectory, relativePath);
                    string localDir = Path.GetDirectoryName(localPath);
                    if (!Directory.Exists(localDir))
                    {
                        Directory.CreateDirectory(localDir);
                    }

                    if (!await TryMoveFileAsync(tempFilePath, localPath))
                    {
                        string backupPath = localPath + ".new";
                        File.Move(tempFilePath, backupPath);
                        filesForScripting.Add((localPath, backupPath));
                    }

                }
                finally
                {
                    int done = Interlocked.Increment(ref completed);
                    int percentage = 95 + (int)(done * 5.0 / totalFiles);
                    UpdateProgressValue(Math.Min(100, percentage));
                    semaphore.Release();
                }
            });

            await Task.WhenAll(tasks);

            if (filesForScripting.Any())
            {
                CreateReplaceScriptForAll(filesForScripting.ToList());
            }

            foreach (var failed in failedFiles)
            {
                _downloadedFiles.Remove(failed);
            }

            if (failedFiles.Count > 0)
            {
                throw new Exception($"{failedFiles.Count}个文件校验失败");
            }
            else
            {
                UpdateStatus("校验保存成功");
                UpdateProgressValue(100);
            }
        }
        
        /// <summary>
        /// 尝试将文件从临时位置移动到目标位置（异步），若文件被占用则等待一秒后重试一次
        /// </summary>
        /// <param name="sourcePath">源文件的完整路径</param>
        /// <param name="targetPath">目标文件的完整路径</param>
        /// <returns>移动成功返回true，失败返回false</returns>
        private async Task<bool> TryMoveFileAsync(string sourcePath, string targetPath)
        {
            try
            {
                File.Move(sourcePath, targetPath);
                return true;
            }
            catch (IOException)
            {
                UpdateStatus("文件占用，解锁中...");

                try
                {
                    await Task.Delay(1000);

                    File.Move(sourcePath, targetPath);
                    UpdateStatus("解锁并更新成功");
                    return true;
                }
                catch
                {
                    UpdateStatus("文件仍被占用");
                    return false;
                }
            }
            catch (Exception ex)
            {
                UpdateStatus("移动文件出错");
                return false;
            }
        }
        
        /// <summary>
        /// 为被占用文件创建批处理脚本，在程序退出后自动完成文件替换
        /// </summary>
        /// <param name="files">包含原始文件路径和新文件路径的元组列表</param>
        private void CreateReplaceScriptForAll(List<(string original, string newFile)> files)
        {
            if (!files.Any()) return;

            try
            {
                string batchFilePath = Path.Combine(_baseDirectory, "update_files.bat");
                string processId = Process.GetCurrentProcess().Id.ToString();

                var batchContent = new StringBuilder();
                batchContent.AppendLine("@echo off");
                batchContent.AppendLine("chcp 65001 > nul");
                batchContent.AppendLine(":check_process");
                batchContent.AppendLine($"tasklist /FI \"PID eq {processId}\" 2>NUL | find /I \"{processId}\" >NUL");
                batchContent.AppendLine("if %ERRORLEVEL% == 0 (");
                batchContent.AppendLine("    timeout /t 1 /nobreak > NUL");
                batchContent.AppendLine("    goto check_process");
                batchContent.AppendLine(")");
                batchContent.AppendLine("timeout /t 2 /nobreak > NUL");

                foreach (var file in files)
                {
                    batchContent.AppendLine($"del \"{file.original}\" /f /q");
                    batchContent.AppendLine($"move \"{file.newFile}\" \"{file.original}\"");
                }

                batchContent.AppendLine("del \"%~f0\" /f /q");
                batchContent.AppendLine("exit");
                
                File.WriteAllText(batchFilePath, batchContent.ToString(), new UTF8Encoding(false));
                
                var startInfo = new ProcessStartInfo
                {
                    FileName = "cmd.exe",
                    Arguments = $"/c \"{batchFilePath}\"",
                    CreateNoWindow = true,
                    UseShellExecute = false,
                    WindowStyle = ProcessWindowStyle.Hidden
                };
                Process.Start(startInfo);
            }
            catch
            {
                UpdateStatus("创建脚本出错");
            }
        }

        /// <summary>
        /// 初始化程序使用的临时目录，用于存储下载过程中的临时文件
        /// </summary>
        private void InitializeTempDirectory()
        {
            try
            {
                _tempDirectory = Path.Combine(
                    Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData),
                    "Temp",
                    "CheckDownload"
                );

                if (!Directory.Exists(_tempDirectory))
                {
                    Directory.CreateDirectory(_tempDirectory);
                }
            }
            catch
            {
                UpdateStatus("初始化Temp失败");
            }
        }

        /// <summary>
        /// 计算字符串的MD5哈希值，返回32位小写十六进制字符串
        /// </summary>
        /// <param name="input">要计算哈希值的字符串</param>
        /// <returns>32位小写十六进制MD5哈希值</returns>
        private string CalculateMD5(string input)
        {
            using (var md5 = MD5.Create())
            {
                byte[] inputBytes = Encoding.UTF8.GetBytes(input);
                byte[] hashBytes = md5.ComputeHash(inputBytes);
                return BitConverter.ToString(hashBytes).Replace("-", "").ToLowerInvariant();
            }
        }

        /// <summary>
        /// 计算字节数组的MD5哈希值，返回32位小写十六进制字符串
        /// </summary>
        /// <param name="data">要计算哈希值的字节数组</param>
        /// <returns>32位小写十六进制MD5哈希值</returns>
        private string CalculateMD5(byte[] data)
        {
            using (var md5 = MD5.Create())
            {
                byte[] hashBytes = md5.ComputeHash(data);
                return BitConverter.ToString(hashBytes).Replace("-", "").ToLowerInvariant();
            }
        }

        /// <summary>
        /// 从阿里云OSS下载文件，包含SDK直连和IP直连两种备用方案
        /// </summary>
        /// <param name="ossKey">OSS对象的存储键值</param>
        /// <param name="localPath">文件保存的本地路径</param>
        /// <returns>下载成功返回true，所有方案都失败返回false</returns>
        private async Task<bool> DownloadFileWithFallback(string ossKey, string localPath)
        {
            try
            {
                var obj = _ossClient.GetObject(OssBucketName, ossKey);
                string localDir = Path.GetDirectoryName(localPath);
                if (!Directory.Exists(localDir))
                {
                    Directory.CreateDirectory(localDir);
                }
                using (var fileStream = File.Create(localPath))
                {
                    using (var cts = new CancellationTokenSource(DownloadStreamTimeoutMs))
                    {
                        await obj.Content.CopyToAsync(fileStream, 81920, cts.Token);
                    }
                }
                return true;
            }
            catch (OssException)
            {
                UpdateStatus("主下载失败，转备用...");
            }
            catch (WebException)
            {
                UpdateStatus("主下载失败，转备用...");
            }
            catch (IOException)
            {
                UpdateStatus("主下载失败，转备用...");
            }
            catch (OperationCanceledException)
            {
                UpdateStatus("主下载失败，转备用...");
            }

            var domain = new Uri("https://" + OssEndpoint).Host;
            List<string> ips = await GetIpAddressesForDomain(domain);
            if (ips == null || ips.Count == 0)
            {
                UpdateStatus($"无法获取IP地址");
                return false;
            }

            var req = new GeneratePresignedUriRequest(OssBucketName, ossKey, SignHttpMethod.Get)
            {
                Expiration = DateTime.Now.AddMinutes(10)
            };
            var signedUrl = _ossClient.GeneratePresignedUri(req).ToString();
            var signedUri = new Uri(signedUrl);

            foreach (var ip in ips)
            {
                try
                {
                    var ipUrl = signedUrl.Replace(signedUri.Host, ip);
                    
                    var request = new HttpRequestMessage(HttpMethod.Get, ipUrl) { Version = HttpVersion.Version11 };
                    request.Headers.Host = signedUri.Host;
                    using (var response = await _httpClient.SendAsync(request, HttpCompletionOption.ResponseHeadersRead))
                    {
                        response.EnsureSuccessStatusCode();
                        string localDir = Path.GetDirectoryName(localPath);
                        if (!Directory.Exists(localDir))
                        {
                            Directory.CreateDirectory(localDir);
                        }

                        using (var remote = await response.Content.ReadAsStreamAsync())
                        using (var localFile = File.Create(localPath))
                        {
                            using (var cts = new CancellationTokenSource(DownloadStreamTimeoutMs))
                            {
                                await remote.CopyToAsync(localFile, 81920, cts.Token);
                            }
                        }
                    }
                    return true;
                }
                catch (HttpRequestException)
                {
                    UpdateStatus($"IP下载失败: {ip}");
                }
                catch (OperationCanceledException)
                {
                    UpdateStatus($"IP下载失败: {ip}");
                }
            }
            return false;
        }

        /// <summary>
        /// 生成基于当前UTC时间的Unix时间戳，并添加指定的秒数偏移
        /// </summary>
        /// <param name="number">要在当前时间戳基础上增加的秒数</param>
        /// <returns>Unix时间戳（秒）</returns>
        private long GenerateTimestamp(int number)
        {
            return (long)(DateTime.UtcNow.Subtract(new DateTime(1970, 1, 1))).TotalSeconds + number;
        }

        /// <summary>
        /// 使用指定数字作为随机种子生成确定性的32位UUID字符串
        /// </summary>
        /// <param name="number">用作随机种子的数字</param>
        /// <returns>不含连字符的32位UUID字符串</returns>
        private string GenerateUUID(int number)
        {
            var random = new Random(number);
            var guid = new byte[16];
            random.NextBytes(guid);
            
            guid[7] = (byte)((guid[7] & 0x0F) | 0x40);
            guid[8] = (byte)((guid[8] & 0x3F) | 0x80);
            
            var resultGuid = new Guid(guid);
            return resultGuid.ToString("N").Replace("-", "");
        }

        /// <summary>
        /// 计算字符串的MD5哈希值，用于123盘鉴权签名生成
        /// </summary>
        /// <param name="input">要计算哈希值的输入字符串</param>
        /// <returns>32位小写十六进制MD5哈希值</returns>
        private string GenerateMD5(string input)
        {
            using (var md5 = MD5.Create())
            {
                byte[] inputBytes = Encoding.UTF8.GetBytes(input);
                byte[] hashBytes = md5.ComputeHash(inputBytes);
                return BitConverter.ToString(hashBytes).Replace("-", "").ToLowerInvariant();
            }
        }

        /// <summary>
        /// 为123盘文件访问生成带有时间戳和签名验证的鉴权URL
        /// </summary>
        /// <param name="url">123盘的基础访问URL</param>
        /// <param name="file">要访问的文件名或路径</param>
        /// <returns>包含鉴权参数的完整访问URL</returns>
        private string GenerateAuthUrl(string url, string file)
        {
            try
            {
                long timestamp = GenerateTimestamp(OneDriveAuthTimeout);
                
                string rand = GenerateUUID(16);
                
                string pathPart = ExtractPathFromUrl(url);
                
                string fullUrl = $"{url}/{file}";
                
                string signString = $"/{pathPart}/{file}-{timestamp}-{rand}-{OneDriveUid}-{OneDriveAuthKey}";
                
                string signature = GenerateMD5(signString);
                
                string authUrl = $"{fullUrl}?auth_key={timestamp}-{rand}-{OneDriveUid}-{signature}";
                
                return authUrl;
            }
            catch
            {
                UpdateStatus("生成AuthUrl失败");
                return $"{url}/{file}";
            }
        }

        /// <summary>
        /// 从完整URL中解析并提取域名后的路径部分，用于生成123盘签名
        /// </summary>
        /// <param name="url">要解析的完整URL地址</param>
        /// <returns>去除域名和协议后的路径字符串</returns>
        private string ExtractPathFromUrl(string url)
        {
            string pathPart = "";
            try
            {
                var uri = new Uri(url);
                pathPart = uri.AbsolutePath.TrimStart('/');
                
                if (string.IsNullOrEmpty(pathPart))
                {
                    string basePattern = $"{uri.Scheme}://{uri.Host}";
                    if (url.StartsWith(basePattern))
                    {
                        pathPart = url.Substring(basePattern.Length).TrimStart('/');
                    }
                }
            }
            catch
            {
                int protocolIndex = url.IndexOf("://");
                if (protocolIndex > 0)
                {
                    int domainEndIndex = url.IndexOf('/', protocolIndex + 3);
                    if (domainEndIndex > 0)
                    {
                        pathPart = url.Substring(domainEndIndex + 1);
                    }
                }
            }
            return pathPart;
        }

        /// <summary>
        /// 下载MD5配置文件，优先使用123盘，失败后切换到阿里云OSS备用方案
        /// </summary>
        /// <param name="fileName">MD5配置文件名</param>
        /// <param name="localPath">文件保存的本地路径</param>
        /// <returns>下载成功返回true，所有方案都失败返回false</returns>
        private async Task<bool> DownloadMd5FileWithFallback(string fileName, string localPath)
        {
            try
            {
                UpdateStatus("123盘下载MD5...");
                if (await DownloadFromOneDrive($"http://{OneDriveMainDomain}{OneDrivePath}", fileName, localPath))
                {
                    return true;
                }
                
                UpdateStatus("123盘失败，转OSS...");
                return await DownloadFileWithFallback(fileName, localPath);
            }
            catch (Exception ex)
            {
                UpdateStatus("所有下载方式均失败");
                return false;
            }
        }

        /// <summary>
        /// 清理程序使用的临时目录，删除所有下载过程中产生的临时文件
        /// </summary>
        private void CleanupTempDirectory()
        {
            try
            {
                string tempPath = Path.Combine(
                    Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData),
                    "Temp",
                    "CheckDownload"
                );

                if (Directory.Exists(tempPath))
                {
                    UpdateStatus("清理Temp...");
                    Directory.Delete(tempPath, true);
                }
            }
            catch (Exception ex)
            {
            }
        }

        /// <summary>
        /// 通过分析md5.json文件内容智能确定项目基准目录，用于正确定位文件更新路径
        /// </summary>
        /// <param name="data">md5.json文件中的数据对象</param>
        private void InitializeBaseDirectoryFromMd5Data(JObject data)
        {
            try
            {
                string currentProgramName = Path.GetFileName(Application.ExecutablePath);
                
                string programPathInMd5 = FindFileInMd5Data(data, currentProgramName);
                
                if (!string.IsNullOrEmpty(programPathInMd5))
                {
                    string programDirInMd5 = Path.GetDirectoryName(programPathInMd5);
                    if (string.IsNullOrEmpty(programDirInMd5))
                    {
                        programDirInMd5 = "";
                    }
                    
                    string currentProgramDir = Application.StartupPath;
                    
                    if (string.IsNullOrEmpty(programDirInMd5))
                    {
                        _baseDirectory = currentProgramDir;
                    }
                    else
                    {
                        _baseDirectory = FindProjectBaseDirectory(currentProgramDir, programDirInMd5);
                    }
                }
                else
                {
                    _baseDirectory = Application.StartupPath;
                }
            }
            catch (Exception ex)
            {
                _baseDirectory = Application.StartupPath;
            }
        }

        /// <summary>
        /// 在md5.json的数据结构中递归搜索指定的文件名
        /// </summary>
        /// <param name="data">md5.json解析后的JSON对象</param>
        /// <param name="fileName">要搜索的目标文件名</param>
        /// <param name="currentPath">当前递归的路径，用于构建完整路径</param>
        /// <returns>找到的文件在md5.json中的完整相对路径，未找到返回null</returns>
        private string FindFileInMd5Data(JObject data, string fileName, string currentPath = "")
        {
            foreach (var property in data.Properties())
            {
                string key = property.Name;
                JToken value = property.Value;
                
                string fullPath = string.IsNullOrEmpty(currentPath) ? key : Path.Combine(currentPath, key);
                
                if (value.Type == JTokenType.String)
                {
                    if (string.Equals(key, fileName, StringComparison.OrdinalIgnoreCase))
                    {
                        return fullPath;
                    }
                }
                else if (value.Type == JTokenType.Object)
                {
                    string result = FindFileInMd5Data((JObject)value, fileName, fullPath);
                    if (!string.IsNullOrEmpty(result))
                    {
                        return result;
                    }
                }
            }
            return null;
        }

        /// <summary>
        /// 通过分析程序在md5.json中的相对路径，向上递归查找项目根目录
        /// </summary>
        /// <param name="currentDir">当前程序运行的目录</param>
        /// <param name="expectedRelativePath">程序在md5.json中的相对路径</param>
        /// <returns>项目的基准目录路径</returns>
        private string FindProjectBaseDirectory(string currentDir, string expectedRelativePath)
        {
            try
            {
                string[] expectedDirs = expectedRelativePath.Split(new char[] { Path.DirectorySeparatorChar, Path.AltDirectorySeparatorChar }, 
                    StringSplitOptions.RemoveEmptyEntries);
                
                string checkDir = currentDir;
                
                for (int i = 0; i < expectedDirs.Length; i++)
                {
                    string parentDir = Directory.GetParent(checkDir)?.FullName;
                    if (string.IsNullOrEmpty(parentDir))
                    {
                        break;
                    }
                    
                    string currentDirName = Path.GetFileName(checkDir);
                    string expectedDirName = expectedDirs[expectedDirs.Length - 1 - i];
                    
                    if (string.Equals(currentDirName, expectedDirName, StringComparison.OrdinalIgnoreCase))
                    {
                        if (i == expectedDirs.Length - 1)
                        {
                            return parentDir;
                        }
                        checkDir = parentDir;
                    }
                    else
                    {
                        break;
                    }
                }
                
                return currentDir;
            }
            catch
            {
                return currentDir;
            }
        }

        /// <summary>
        /// 使用文件流计算指定文件的 MD5 哈希值（32 位小写十六进制）。
        /// </summary>
        /// <param name="filePath">要计算 MD5 的文件完整路径</param>
        /// <returns>32 位小写十六进制 MD5 字符串</returns>
        private string CalculateMD5FromFile(string filePath)
        {
            using (var fs = File.OpenRead(filePath))
            using (var md5 = MD5.Create())
            {
                var hashBytes = md5.ComputeHash(fs);
                return BitConverter.ToString(hashBytes).Replace("-", string.Empty).ToLowerInvariant();
            }
        }
    }
}