gistfile1.txt

using System;
using System.Collections.Concurrent;
using System.IO;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

/// <summary>
/// Thread-safe logger for web APIs with buffered writing and daily rotation.
/// The file is only opened during flush, allowing safe moves at the end of the day.
/// </summary>
public class ApiBufferedLogger : IDisposable
{
    private readonly string _folder;
    private readonly ConcurrentQueue<string> _queue = new();
    private readonly Timer _flushTimer;
    private readonly object _flushLock = new();

    public ApiBufferedLogger(string folder, int flushIntervalMs = 1000)
    {
        _folder = folder ?? throw new ArgumentNullException(nameof(folder));
        Directory.CreateDirectory(_folder);

        // Timer triggers flush periodically
        _flushTimer = new Timer(_ => Flush(), null, flushIntervalMs, flushIntervalMs);
    }

    /// <summary>
    /// Adds a log message to the buffer (thread-safe)
    /// </summary>
    public void Log(string message)
    {
        if (message == null) return;
        _queue.Enqueue($"{DateTime.Now:yyyy-MM-dd HH:mm:ss.fff} - {message}");
    }

    /// <summary>
    /// Flushes buffered logs to disk (thread-safe)
    /// </summary>
    public void Flush()
    {
        // Ensure only one flush at a time
        lock (_flushLock)
        {
            if (_queue.IsEmpty) return;

            var sb = new StringBuilder();
            while (_queue.TryDequeue(out var line))
            {
                sb.AppendLine(line);
            }

            string filePath = Path.Combine(_folder, $"log-{DateTime.Now:yyyy-MM-dd}.txt");
            File.AppendAllText(filePath, sb.ToString(), Encoding.UTF8);
        }
    }

    /// <summary>
    /// Dispose flush timer and flush remaining logs
    /// </summary>
    public void Dispose()
    {
        _flushTimer?.Dispose();
        Flush();
    }
}