using System.Threading.Channels;
using CoreAgent.WebSocketTransport.Interfaces;

namespace CoreAgent.WebSocketTransport.Services;

/// <summary>
/// 基于 Channel 的消息通道实现
/// 提供线程安全的消息队列操作
/// </summary>
/// <typeparam name="T">消息类型</typeparam>
public class ChannelMessageChannel<T> : IMessageChannel<T>
{
    private readonly Channel<T> _channel;
    private readonly ChannelWriter<T> _writer;
    private readonly ChannelReader<T> _reader;
    private volatile bool _disposed;
    private readonly object _disposeLock = new object();

    public int Capacity { get; }
    public int Count => _channel.Reader.Count;
    public bool IsCompleted => _channel.Reader.Completion.IsCompleted;

    /// <summary>
    /// 构造函数
    /// </summary>
    /// <param name="capacity">通道容量</param>
    /// <param name="fullMode">队列满时的处理模式</param>
    public ChannelMessageChannel(int capacity, BoundedChannelFullMode fullMode = BoundedChannelFullMode.DropOldest)
    {
        if (capacity <= 0)
            throw new ArgumentOutOfRangeException(nameof(capacity), "容量必须大于0");

        Capacity = capacity;
        
        var options = new BoundedChannelOptions(capacity)
        {
            SingleWriter = false,  // 允许多个写入者
            SingleReader = true,   // 只允许一个读取者
            FullMode = fullMode,
            AllowSynchronousContinuations = false
        };
        
        _channel = Channel.CreateBounded<T>(options);
        _writer = _channel.Writer;
        _reader = _channel.Reader;
    }

    /// <summary>
    /// 异步写入消息
    /// </summary>
    public ValueTask WriteAsync(T message, CancellationToken cancellationToken = default)
    {
        ThrowIfDisposed();
        
        if (message == null)
            throw new ArgumentNullException(nameof(message));
            
        return _writer.WriteAsync(message, cancellationToken);
    }

    /// <summary>
    /// 尝试写入消息（非阻塞）
    /// </summary>
    public bool TryWrite(T message)
    {
        ThrowIfDisposed();
        
        if (message == null)
            throw new ArgumentNullException(nameof(message));
            
        return _writer.TryWrite(message);
    }

    /// <summary>
    /// 异步读取消息
    /// </summary>
    public ValueTask<T> ReadAsync(CancellationToken cancellationToken = default)
    {
        ThrowIfDisposed();
        return _reader.ReadAsync(cancellationToken);
    }

    /// <summary>
    /// 尝试读取消息（非阻塞）
    /// </summary>
    public bool TryRead(out T message)
    {
        ThrowIfDisposed();
        return _reader.TryRead(out message);
    }

    /// <summary>
    /// 等待消息可读
    /// </summary>
    public ValueTask<bool> WaitToReadAsync(CancellationToken cancellationToken = default)
    {
        ThrowIfDisposed();
        return _reader.WaitToReadAsync(cancellationToken);
    }

    /// <summary>
    /// 完成通道，不再接受新消息
    /// </summary>
    public void Complete()
    {
        ThrowIfDisposed();
        
        try
        {
            _writer.Complete();
        }
        catch (InvalidOperationException)
        {
            // 通道可能已经完成，忽略异常
        }
    }

    /// <summary>
    /// 清空队列中的所有消息
    /// </summary>
    public void Clear()
    {
        ThrowIfDisposed();
        
        try
        {
            // 读取并丢弃所有消息，直到队列为空
            while (_reader.TryRead(out _))
            {
                // 继续读取直到没有更多消息
            }
        }
        catch (InvalidOperationException)
        {
            // 通道可能已完成，忽略异常
        }
    }

    /// <summary>
    /// 释放资源
    /// </summary>
    public void Dispose()
    {
        lock (_disposeLock)
        {
            if (!_disposed)
            {
                _disposed = true;
                
                try
                {
                    // 完成写入器
                    if (!_writer.TryComplete())
                    {
                        _writer.Complete();
                    }
                }
                catch (InvalidOperationException)
                {
                    // 忽略已完成的异常
                }
                catch (Exception)
                {
                    // 记录其他异常但不抛出
                }
                
                GC.SuppressFinalize(this);
            }
        }
    }

    /// <summary>
    /// 检查是否已释放
    /// </summary>
    private void ThrowIfDisposed()
    {
        if (_disposed)
        {
            throw new ObjectDisposedException(nameof(ChannelMessageChannel<T>));
        }
    }
}