using System;
using System.Diagnostics;
using System.IO;
using System.Runtime.InteropServices;
using System.Threading;
using System.Threading.Tasks;
using XP.Common.Dump.Configs;
using XP.Common.Dump.Interfaces;
using XP.Common.Dump.Native;
using XP.Common.Logging.Interfaces;

namespace XP.Common.Dump.Implementations
{
    /// <summary>
    /// Dump 文件管理服务实现，负责 Dump 生成、崩溃事件订阅、定时调度和清理
    /// Dump file management service implementation, handles dump generation, crash event subscription, scheduled tasks and cleanup
    /// </summary>
    public class DumpService : IDumpService
    {
        private readonly DumpConfig _config;
        private readonly ILoggerService _logger;
        private readonly DumpCleaner _cleaner;
        private Timer? _scheduledTimer;
        private Timer? _cleanupTimer;
        private bool _isStarted;
        private bool _disposed;

        /// <summary>
        /// 默认存储路径 | Default storage path
        /// </summary>
        private const string DefaultStoragePath = @"D:\XplorePlane\Dump";

        public DumpService(DumpConfig config, ILoggerService logger)
        {
            _config = config ?? throw new ArgumentNullException(nameof(config));
            _logger = logger?.ForModule<DumpService>() ?? throw new ArgumentNullException(nameof(logger));
            _cleaner = new DumpCleaner(config, logger);
        }

        /// <summary>
        /// 生成 Dump 文件名（纯函数）| Generate dump file name (pure function)
        /// 格式：XplorePlane_{yyyyMMdd_HHmm}_{TriggerType}.dmp
        /// </summary>
        /// <param name="triggerType">触发类型 | Trigger type</param>
        /// <param name="timestamp">时间戳 | Timestamp</param>
        /// <returns>文件名 | File name</returns>
        internal static string GenerateFileName(DumpTriggerType triggerType, DateTime timestamp)
        {
            return $"XplorePlane_{timestamp:yyyyMMdd_HHmm}_{triggerType}.dmp";
        }

        /// <summary>
        /// 验证 Mini Dump 文件大小是否在限制范围内 | Validate Mini Dump file size is within limit
        /// </summary>
        /// <param name="fileSizeBytes">文件大小（字节）| File size in bytes</param>
        /// <param name="sizeLimitMB">大小限制（MB）| Size limit in MB</param>
        /// <returns>true 表示在限制内 | true if within limit</returns>
        internal static bool ValidateFileSize(long fileSizeBytes, long sizeLimitMB)
        {
            return fileSizeBytes <= sizeLimitMB * 1024 * 1024;
        }

        /// <summary>
        /// 写入 Dump 文件的核心方法 | Core method to write dump file
        /// </summary>
        /// <param name="triggerType">触发类型 | Trigger type</param>
        /// <param name="isMiniDump">是否为 Mini Dump | Whether it is a Mini Dump</param>
        /// <returns>生成的文件完整路径，失败返回 null | Full path of generated file, null on failure</returns>
        private string? WriteDump(DumpTriggerType triggerType, bool isMiniDump)
        {
            try
            {
                // 非手动触发请求 Full Dump 时，降级为 Mini Dump | Downgrade to Mini Dump for non-manual Full Dump requests
                if (!isMiniDump && triggerType != DumpTriggerType.Manual)
                {
                    _logger.Warn("非手动触发不允许生成 Full Dump，已降级为 Mini Dump：{TriggerType} | Non-manual trigger cannot generate Full Dump, downgraded to Mini Dump: {TriggerType}", triggerType);
                    isMiniDump = true;
                }

                var fileName = GenerateFileName(triggerType, DateTime.Now);
                var filePath = Path.Combine(_config.StoragePath, fileName);

                // 确定 Dump 类型标志 | Determine dump type flags
                uint dumpType = isMiniDump
                    ? (uint)(MiniDumpType.MiniDumpWithDataSegs | MiniDumpType.MiniDumpWithHandleData | MiniDumpType.MiniDumpWithThreadInfo)
                    : (uint)MiniDumpType.MiniDumpWithFullMemory;

                var process = Process.GetCurrentProcess();

                using (var fileStream = new FileStream(filePath, FileMode.Create, FileAccess.ReadWrite, FileShare.None))
                {
                    bool success = NativeMethods.MiniDumpWriteDump(
                        process.Handle,
                        (uint)process.Id,
                        fileStream.SafeFileHandle,
                        dumpType,
                        IntPtr.Zero,
                        IntPtr.Zero,
                        IntPtr.Zero);

                    if (!success)
                    {
                        var errorCode = Marshal.GetLastWin32Error();
                        _logger.Error(null!, "MiniDumpWriteDump 调用失败，错误码：{ErrorCode} | MiniDumpWriteDump failed, error code: {ErrorCode}", errorCode);
                        // 清理失败的文件 | Clean up failed file
                        try { File.Delete(filePath); } catch { }
                        return null;
                    }
                }

                // Mini Dump 文件大小检查 | Mini Dump file size check
                if (isMiniDump)
                {
                    var fileInfo = new FileInfo(filePath);
                    if (!ValidateFileSize(fileInfo.Length, _config.MiniDumpSizeLimitMB))
                    {
                        _logger.Warn("Mini Dump 文件超过大小限制（{SizeMB}MB），已删除：{FilePath} | Mini Dump file exceeds size limit ({SizeMB}MB), deleted: {FilePath}",
                            _config.MiniDumpSizeLimitMB, filePath);
                        File.Delete(filePath);
                        return null;
                    }
                }

                var dumpTypeStr = isMiniDump ? "Mini" : "Full";
                _logger.Info("Dump 文件已生成：{FilePath}，触发类型：{TriggerType}，Dump 类型：{DumpType} | Dump file generated: {FilePath}, trigger: {TriggerType}, type: {DumpType}",
                    filePath, triggerType, dumpTypeStr);

                return filePath;
            }
            catch (IOException ex)
            {
                _logger.Error(ex, "Dump 文件写入失败：{Message} | Dump file write failed: {Message}", ex.Message);
                return null;
            }
            catch (UnauthorizedAccessException ex)
            {
                _logger.Error(ex, "Dump 文件写入权限不足：{Message} | Dump file write permission denied: {Message}", ex.Message);
                return null;
            }
            catch (Exception ex)
            {
                _logger.Error(ex, "Dump 文件生成异常：{Message} | Dump file generation error: {Message}", ex.Message);
                return null;
            }
        }

        #region 手动触发方法 | Manual trigger methods

        /// <inheritdoc />
        public string? CreateMiniDump()
        {
            _logger.Info("手动触发 Mini Dump 生成 | Manually triggering Mini Dump generation");
            var filePath = WriteDump(DumpTriggerType.Manual, isMiniDump: true);
            if (filePath != null)
            {
                _logger.Info("手动 Mini Dump 已生成：{FilePath} | Manual Mini Dump generated: {FilePath}", filePath);
            }
            return filePath;
        }

        /// <inheritdoc />
        public string? CreateFullDump()
        {
            _logger.Info("手动触发 Full Dump 生成 | Manually triggering Full Dump generation");
            var filePath = WriteDump(DumpTriggerType.Manual, isMiniDump: false);
            if (filePath != null)
            {
                _logger.Info("手动 Full Dump 已生成：{FilePath} | Manual Full Dump generated: {FilePath}", filePath);
            }
            return filePath;
        }

        #endregion

        #region 生命周期管理 | Lifecycle management

        /// <inheritdoc />
        public void Start()
        {
            if (_isStarted) return;

            _logger.Info("Dump 服务启动中 | Dump service starting");

            // 确保存储目录存在 | Ensure storage directory exists
            EnsureStorageDirectory();

            // 订阅崩溃事件 | Subscribe to crash events
            AppDomain.CurrentDomain.UnhandledException += OnUnhandledException;
            TaskScheduler.UnobservedTaskException += OnUnobservedTaskException;

            // 启动定时 Dump 计时器 | Start scheduled dump timer
            if (_config.EnableScheduledDump)
            {
                var intervalMs = _config.ScheduledIntervalMinutes * 60 * 1000;
                _scheduledTimer = new Timer(OnScheduledDumpCallback, null, intervalMs, intervalMs);
                _logger.Info("定时 Dump 已启用，间隔：{Interval} 分钟 | Scheduled dump enabled, interval: {Interval} minutes", _config.ScheduledIntervalMinutes);
            }

            // 启动每日清理计时器（每24小时执行一次）| Start daily cleanup timer (every 24 hours)
            var dailyMs = 24 * 60 * 60 * 1000;
            _cleanupTimer = new Timer(OnCleanupCallback, null, dailyMs, dailyMs);

            // 立即执行一次清理 | Execute cleanup immediately
            _cleaner.CleanExpiredFiles();

            _isStarted = true;
            _logger.Info("Dump 服务已启动 | Dump service started");
        }

        /// <inheritdoc />
        public void Stop()
        {
            if (!_isStarted) return;

            _logger.Info("Dump 服务停止中 | Dump service stopping");

            // 取消事件订阅 | Unsubscribe from events
            AppDomain.CurrentDomain.UnhandledException -= OnUnhandledException;
            TaskScheduler.UnobservedTaskException -= OnUnobservedTaskException;

            // 停止所有计时器 | Stop all timers
            _scheduledTimer?.Change(Timeout.Infinite, Timeout.Infinite);
            _cleanupTimer?.Change(Timeout.Infinite, Timeout.Infinite);

            _isStarted = false;
            _logger.Info("Dump 服务已停止 | Dump service stopped");
        }

        /// <inheritdoc />
        public void Dispose()
        {
            if (_disposed) return;

            Stop();

            _scheduledTimer?.Dispose();
            _scheduledTimer = null;

            _cleanupTimer?.Dispose();
            _cleanupTimer = null;

            _disposed = true;
        }

        #endregion

        #region 内部方法 | Internal methods

        /// <summary>
        /// 确保存储目录存在，不存在则创建，创建失败回退默认路径
        /// Ensure storage directory exists, create if not, fallback to default on failure
        /// </summary>
        private void EnsureStorageDirectory()
        {
            try
            {
                if (!Directory.Exists(_config.StoragePath))
                {
                    Directory.CreateDirectory(_config.StoragePath);
                    _logger.Info("已创建存储目录：{Path} | Created storage directory: {Path}", _config.StoragePath);
                }
            }
            catch (Exception ex)
            {
                _logger.Error(ex, "存储目录创建失败：{Path}，回退到默认路径 | Storage directory creation failed: {Path}, falling back to default", _config.StoragePath);
                _config.StoragePath = DefaultStoragePath;

                try
                {
                    if (!Directory.Exists(DefaultStoragePath))
                    {
                        Directory.CreateDirectory(DefaultStoragePath);
                        _logger.Info("已创建默认存储目录：{Path} | Created default storage directory: {Path}", DefaultStoragePath);
                    }
                }
                catch (Exception fallbackEx)
                {
                    _logger.Fatal(fallbackEx, "默认存储目录创建也失败：{Path} | Default storage directory creation also failed: {Path}", DefaultStoragePath);
                }
            }
        }

        /// <summary>
        /// 未处理异常回调 | Unhandled exception callback
        /// </summary>
        private void OnUnhandledException(object sender, UnhandledExceptionEventArgs e)
        {
            _logger.Info("检测到未处理异常，正在生成崩溃 Dump | Unhandled exception detected, generating crash dump");
            WriteDump(DumpTriggerType.Crash, isMiniDump: true);
        }

        /// <summary>
        /// 未观察到的 Task 异常回调 | Unobserved task exception callback
        /// </summary>
        private void OnUnobservedTaskException(object? sender, UnobservedTaskExceptionEventArgs e)
        {
            _logger.Info("检测到未观察的 Task 异常，正在生成崩溃 Dump | Unobserved task exception detected, generating crash dump");
            WriteDump(DumpTriggerType.Crash, isMiniDump: true);
        }

        /// <summary>
        /// 定时 Dump 回调 | Scheduled dump callback
        /// </summary>
        private void OnScheduledDumpCallback(object? state)
        {
            _logger.Debug("定时 Dump 触发 | Scheduled dump triggered");
            WriteDump(DumpTriggerType.Scheduled, isMiniDump: true);
        }

        /// <summary>
        /// 清理回调 | Cleanup callback
        /// </summary>
        private void OnCleanupCallback(object? state)
        {
            _logger.Debug("定时清理触发 | Scheduled cleanup triggered");
            _cleaner.CleanExpiredFiles();
        }

        #endregion
    }
}