using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Linq;
using Serilog.Core;
using Serilog.Events;

namespace XP.Common.Logging.ViewModels
{
    /// <summary>
    /// Serilog 自定义 Sink，将日志事件转发到 RealTimeLogViewerViewModel，并维护环形缓冲区
    /// Custom Serilog Sink that forwards log events and maintains a ring buffer for history
    /// </summary>
    public class RealTimeLogSink : ILogEventSink
    {
        private const int BufferCapacity = 500;
        private readonly ConcurrentQueue<LogEvent> _buffer = new();

        /// <summary>
        /// 全局单例实例 | Global singleton instance
        /// </summary>
        public static RealTimeLogSink Instance { get; } = new();

        /// <summary>
        /// 日志事件到达时触发 | Fired when a log event arrives
        /// </summary>
        public event Action<LogEvent>? LogEventReceived;

        public void Emit(LogEvent logEvent)
        {
            // 入队缓冲区 | Enqueue to buffer
            _buffer.Enqueue(logEvent);
            while (_buffer.Count > BufferCapacity)
            {
                _buffer.TryDequeue(out _);
            }

            LogEventReceived?.Invoke(logEvent);
        }

        /// <summary>
        /// 获取缓冲区中的历史日志快照 | Get a snapshot of buffered history logs
        /// </summary>
        public List<LogEvent> GetBufferedHistory()
        {
            return _buffer.ToList();
        }
    }
}