using System.Runtime.InteropServices;
using System.Text;
using Serilog;

namespace ServerLib.Utils;

/// <summary>
///     크래시 핸들러 (Windows / Linux 공통)
///     Register() 를 Program.cs 최상단에서 한 번 호출.
///
///     덤프 생성은 CLR 환경변수로 처리 (스택 언와인드 전에 찍힘):
///       DOTNET_DbgEnableMiniDump=1
///       DOTNET_DbgMiniDumpType=4
///       DOTNET_DbgMiniDumpName=crashes/crash_%p_%t.dmp
///
///     생성 파일 (crashes/ 폴더):
///       crash_YYYY-MM-DD_HH-mm-ss.log  ← 항상 생성
///       crash_%p_%t.dmp                ← CLR이 직접 생성 (정확한 크래시 위치)
/// </summary>
public static class CrashDumpHandler
{
    private const string CRASH_DIR = "crashes";
    private static int registered;

    public static void Register()
    {
        // 중복 등록 방지
        if (Interlocked.Exchange(ref registered, 1) != 0)
        {
            return;
        }

        AppDomain.CurrentDomain.UnhandledException += OnUnhandledException;
        TaskScheduler.UnobservedTaskException      += OnUnobservedTaskException;

        Log.Information("[CrashDump] 핸들러 등록 완료 (CrashDir={Dir})", Path.GetFullPath(CRASH_DIR));
    }

    private static void OnUnhandledException(object sender, UnhandledExceptionEventArgs e)
    {
        Exception? ex = e.ExceptionObject as Exception;
        string tag = $"[CrashDump] UnhandledException (IsTerminating={e.IsTerminating})";
        WriteCrash(tag, ex);
    }

    private static void OnUnobservedTaskException(object? sender, UnobservedTaskExceptionEventArgs e)
    {
        e.SetObserved(); // 프로세스 종료 방지
        string tag = "[CrashDump] UnobservedTaskException";
        WriteCrash(tag, e.Exception);
    }

    private static void WriteCrash(string tag, Exception? ex)
    {
        try
        {
            Directory.CreateDirectory(CRASH_DIR);

            string timestamp = DateTime.Now.ToString("yyyy-MM-dd_HH-mm-ss");
            string logPath = Path.Combine(CRASH_DIR, $"crash_{timestamp}.log");

            WriteCrashLog(logPath, ex);
            Log.Fatal("{Tag} → {Log}", tag, logPath);
        }
        catch (Exception writeEx)
        {
            Log.Error(writeEx, "[CrashDump] 로그 저장 실패");
        }
        finally
        {
            Log.CloseAndFlush();
        }
    }

    private static void WriteCrashLog(string path, Exception? ex)
    {
        StringBuilder sb = new();
        sb.AppendLine("═══════════════════════════════════════════════════");
        sb.AppendLine($"  CRASH REPORT  {DateTime.Now:yyyy-MM-dd HH:mm:ss}");
        sb.AppendLine("═══════════════════════════════════════════════════");
        sb.AppendLine();

        sb.AppendLine("[Environment]");
        sb.AppendLine($"  OS         : {RuntimeInformation.OSDescription}");
        sb.AppendLine($"  Runtime    : {RuntimeInformation.FrameworkDescription}");
        sb.AppendLine($"  PID        : {Environment.ProcessId}");
        sb.AppendLine($"  WorkDir    : {Environment.CurrentDirectory}");
        sb.AppendLine($"  MachineName: {Environment.MachineName}");
        sb.AppendLine();

        sb.AppendLine("[Thread]");
        sb.AppendLine($"  ThreadId : {Environment.CurrentManagedThreadId}");
        sb.AppendLine();

        sb.AppendLine("[Exception]");
        if (ex is null)
        {
            sb.AppendLine("  (예외 객체 없음)");
        }
        else
        {
            AppendException(sb, ex, 0);
        }

        File.WriteAllText(path, sb.ToString(), Encoding.UTF8);
    }

    private static void AppendException(StringBuilder sb, Exception ex, int depth)
    {
        string indent = new(' ', depth * 2);
        sb.AppendLine($"{indent}  Type    : {ex.GetType().FullName}");
        sb.AppendLine($"{indent}  Message : {ex.Message}");
        sb.AppendLine($"{indent}  Source  : {ex.Source}");
        sb.AppendLine();
        sb.AppendLine($"{indent}  StackTrace:");

        if (ex.StackTrace is not null)
        {
            foreach (string line in ex.StackTrace.Split('\n'))
            {
                sb.AppendLine($"{indent}    {line.TrimEnd()}");
            }
        }

        if (ex is AggregateException agg)
        {
            foreach (Exception inner in agg.InnerExceptions)
            {
                sb.AppendLine();
                sb.AppendLine($"{indent}  [InnerException]");
                AppendException(sb, inner, depth + 1);
            }
        }
        else if (ex.InnerException is not null)
        {
            sb.AppendLine();
            sb.AppendLine($"{indent}  [InnerException]");
            AppendException(sb, ex.InnerException, depth + 1);
        }
    }
}