using LiteDB;
using System;
using System.Collections.Concurrent;
using System.IO;
using System.Linq;
using System.Threading.Tasks;

public enum LogLevel { INFO, WARN, DEBUG, ERROR }

public class LogEntry
{
    public int Id { get; set; } // LiteDB 전용
    public DateTime Timestamp { get; set; }
    public LogLevel Level { get; set; }
    public string Message { get; set; }
}

public sealed class AsyncLog : IDisposable
{
    private static AsyncLog _instance;
    private static readonly object _lock = new object();

    private readonly BlockingCollection<LogEntry> _logQueue;
    private readonly BlockingCollection<LogEntry> _errorQueue;
    private readonly Task _logTask;
    private readonly Task _errorTask;

    private StreamWriter _writer;
    private StreamWriter _errorWriter;
    private string _currentDateFolder;

    private LiteDatabase _db;

    public string BaseLogFolder { get; private set; }
    public string LogFileName { get; private set; } = "app.log";
    public string ErrorFileName { get; private set; } = "error.log";
    public bool EnableConsole { get; private set; }

    private static AsyncLog SafeInstance => _instance;

    #region Singleton Init
    public static void Init(string baseLogFolder, bool enableConsole = true)
    {
        if (_instance != null) return;
        lock (_lock)
        {
            if (_instance == null)
            {
                _instance = new AsyncLog(baseLogFolder, enableConsole);
                AppDomain.CurrentDomain.ProcessExit += (s, e) => _instance.Dispose();
            }
        }
    }

    private AsyncLog(string baseLogFolder, bool enableConsole)
    {
        BaseLogFolder = baseLogFolder;
        EnableConsole = enableConsole;

        _logQueue = new BlockingCollection<LogEntry>(new ConcurrentQueue<LogEntry>());
        _errorQueue = new BlockingCollection<LogEntry>(new ConcurrentQueue<LogEntry>());

        _logTask = Task.Run(ProcessLogQueue);
        _errorTask = Task.Run(ProcessErrorQueue);

        Directory.CreateDirectory(BaseLogFolder);
        string dbPath = Path.Combine(BaseLogFolder, "Logs.db");
        _db = new LiteDatabase(dbPath);
    }
    #endregion

    #region Public Logging API (다중 인자 지원)
    public static void I(string message, params object[] args)
        => SafeInstance?.EnqueueLog(LogLevel.INFO, Format(message, args));

    public static void W(string message, params object[] args)
        => SafeInstance?.EnqueueLog(LogLevel.WARN, Format(message, args));

    public static void D(string message, params object[] args)
        => SafeInstance?.EnqueueLog(LogLevel.DEBUG, Format(message, args));

    public static void E(string message, params object[] args)
        => SafeInstance?.EnqueueError(Format(message, args));

    private static string Format(string message, object[] args)
    {
        if (args == null || args.Length == 0) return message;
        try { return string.Format(message, args); }
        catch { return message + " (format error)"; }
    }
    #endregion

    #region Queue Processing
    private void EnqueueLog(LogLevel level, string message)
    {
        var entry = new LogEntry { Timestamp = DateTime.Now, Level = level, Message = message };
        if (EnableConsole) Console.WriteLine($"[{entry.Timestamp:yyyy-MM-dd HH:mm:ss}] [{level}] {message}");
        _logQueue.Add(entry);
    }

    private void EnqueueError(string message)
    {
        var entry = new LogEntry { Timestamp = DateTime.Now, Level = LogLevel.ERROR, Message = message };
        if (EnableConsole) Console.WriteLine($"[{entry.Timestamp:yyyy-MM-dd HH:mm:ss}] [ERROR] {message}");
        _errorQueue.Add(entry);
    }

    private void ProcessLogQueue()
    {
        foreach (var entry in _logQueue.GetConsumingEnumerable())
        {
            try
            {
                string today = DateTime.Now.ToString("yyyy-MM-dd");
                if (_writer == null || _currentDateFolder != today)
                {
                    _writer?.Dispose();
                    _currentDateFolder = today;
                    string todayFolder = Path.Combine(BaseLogFolder, today);
                    Directory.CreateDirectory(todayFolder);
                    string logFilePath = Path.Combine(todayFolder, LogFileName);
                    _writer = new StreamWriter(logFilePath, true) { AutoFlush = true };
                }

                _writer.WriteLine($"[{entry.Timestamp:HH:mm:ss}] [{entry.Level}] {entry.Message}");

                var col = _db.GetCollection<LogEntry>("logs");
                col.Insert(entry);
            }
            catch { }
        }
    }

    private void ProcessErrorQueue()
    {
        foreach (var entry in _errorQueue.GetConsumingEnumerable())
        {
            try
            {
                string today = DateTime.Now.ToString("yyyy-MM-dd");
                if (_errorWriter == null || _currentDateFolder != today)
                {
                    _errorWriter?.Dispose();
                    _currentDateFolder = today;
                    string todayFolder = Path.Combine(BaseLogFolder, today);
                    Directory.CreateDirectory(todayFolder);
                    string errorFilePath = Path.Combine(todayFolder, ErrorFileName);
                    _errorWriter = new StreamWriter(errorFilePath, true) { AutoFlush = true };
                }

                _errorWriter.WriteLine($"[{entry.Timestamp:HH:mm:ss}] [ERROR] {entry.Message}");

                var col = _db.GetCollection<LogEntry>("errors");
                col.Insert(entry);
            }
            catch { }
        }
    }
    #endregion

    #region Dispose
    public void Dispose()
    {
        _logQueue.CompleteAdding();
        _errorQueue.CompleteAdding();
        try { _logTask.Wait(); } catch { }
        try { _errorTask.Wait(); } catch { }
        _writer?.Dispose();
        _errorWriter?.Dispose();
        _logQueue.Dispose();
        _errorQueue.Dispose();
        _db?.Dispose();
    }
    #endregion

    #region Query API
    public static LogEntry[] QueryLogs(DateTime? from = null, DateTime? to = null, LogLevel[] levels = null, bool errorLogs = false)
    {
        if (_instance == null) return Array.Empty<LogEntry>();

        var col = _instance._db.GetCollection<LogEntry>(errorLogs ? "errors" : "logs");
        var query = col.Query();

        if (from.HasValue) query = query.Where(x => x.Timestamp >= from.Value);
        if (to.HasValue) query = query.Where(x => x.Timestamp <= to.Value);
        if (levels != null && levels.Length > 0) query = query.Where(x => levels.Contains(x.Level));

        return query.ToArray();
    }
    #endregion
}
/*
✅ 사용 예제
class Program
{
    static void Main()
    {
        AsyncLog.Init("C:\\Logs", enableConsole: true);

        AsyncLog.I("애플리케이션 시작됨");
        AsyncLog.D("디버그 메시지: 값={0}, 상태={1}", 123, "OK");
        AsyncLog.W("경고 발생: 사용자 {0}, 시도 횟수 {1}", "Alice", 5);
        AsyncLog.E("에러 발생: 코드={0}, 메시지={1}", 500, "Internal Server Error");

        // 로그 조회 (오늘, INFO 레벨만)
        var logs = AsyncLog.QueryLogs(DateTime.Today, DateTime.Today.AddDays(1), new[] { LogLevel.INFO });
        foreach (var log in logs)
        {
            Console.WriteLine($"[조회] {log.Timestamp} {log.Level} {log.Message}");
        }
    }
}
 */