using System.Net;
using System.Net.Sockets;
using Flyshot.Runtime.Fanuc.Protocol;

namespace Flyshot.Core.Tests;

/// <summary>
/// 验证 FANUC TCP 10010 状态通道客户端的后台接收与缓存能力。
/// </summary>
public sealed class FanucStateClientTests : IDisposable
{
    private readonly TcpListener _listener;
    private readonly CancellationTokenSource _cts = new();

    /// <summary>
    /// 在随机可用端口启动本地模拟控制器。
    /// </summary>
    public FanucStateClientTests()
    {
        _listener = new TcpListener(IPAddress.Loopback, 0);
        _listener.Start();
    }

    /// <summary>
    /// 获取分配给本地模拟控制器的端口。
    /// </summary>
    private int Port => ((IPEndPoint)_listener.LocalEndpoint).Port;

    /// <summary>
    /// 清理模拟控制器和取消源。
    /// </summary>
    public void Dispose()
    {
        _cts.Cancel();
        _listener.Stop();
        _cts.Dispose();
    }

    /// <summary>
    /// 验证状态客户端可以连接本地模拟控制器。
    /// </summary>
    [Fact]
    public async Task ConnectAsync_ConnectsToLocalListener()
    {
        using var client = new FanucStateClient();
        var acceptTask = _listener.AcceptTcpClientAsync();

        await client.ConnectAsync("127.0.0.1", Port, _cts.Token);

        Assert.True(client.IsConnected);
        await acceptTask.WaitAsync(TimeSpan.FromSeconds(2), _cts.Token);
    }

    /// <summary>
    /// 验证后台循环能正确解析抓包样本状态帧。
    /// </summary>
    [Fact]
    public async Task GetLatestFrame_ReceivesAndParsesCapturedStateFrame()
    {
        using var client = new FanucStateClient();
        var capturedFrame = Convert.FromHexString(
            "646f7a0000005a000000004388a23243f1ed7f43e9de6bc265031ec2b33cc3c278e0153f8742f53c3f128dbc929529bc7861d63cb0184c3c1ca1a7000000000000000000000000000000020000000000000000000000017a6f64");

        var handlerTask = RunStreamingControllerAsync(capturedFrame, _cts.Token);

        await client.ConnectAsync("127.0.0.1", Port, _cts.Token);

        // 给后台循环留出接收和解析的时间。
        await Task.Delay(200, _cts.Token);

        var latest = client.GetLatestFrame();
        Assert.NotNull(latest);
        Assert.Equal(0u, latest.MessageId);
        Assert.Equal(6, latest.Pose.Count);
        Assert.Equal(9, latest.JointOrExtensionValues.Count);
        Assert.Equal([2u, 0u, 0u, 1u], latest.TailWords);

        client.Disconnect();
        await handlerTask.WaitAsync(TimeSpan.FromSeconds(2), _cts.Token);
    }

    /// <summary>
    /// 验证状态客户端在连接前调用 GetLatestFrame 返回 null。
    /// </summary>
    [Fact]
    public void GetLatestFrame_BeforeConnect_ReturnsNull()
    {
        using var client = new FanucStateClient();
        Assert.Null(client.GetLatestFrame());
    }

    /// <summary>
    /// 验证 Disconnect 后最新帧被清空。
    /// </summary>
    [Fact]
    public async Task Disconnect_ClearsLatestFrame()
    {
        using var client = new FanucStateClient();
        var capturedFrame = Convert.FromHexString(
            "646f7a0000005a000000004388a23243f1ed7f43e9de6bc265031ec2b33cc3c278e0153f8742f53c3f128dbc929529bc7861d63cb0184c3c1ca1a7000000000000000000000000000000020000000000000000000000017a6f64");

        var handlerTask = RunStreamingControllerAsync(capturedFrame, _cts.Token);

        await client.ConnectAsync("127.0.0.1", Port, _cts.Token);
        await Task.Delay(200, _cts.Token);
        Assert.NotNull(client.GetLatestFrame());

        client.Disconnect();
        Assert.Null(client.GetLatestFrame());
        await handlerTask.WaitAsync(TimeSpan.FromSeconds(2), _cts.Token);
    }

    /// <summary>
    /// 启动模拟控制器，持续发送状态帧流。
    /// </summary>
    private async Task RunStreamingControllerAsync(byte[] frames, CancellationToken cancellationToken)
    {
        using var controller = await _listener.AcceptTcpClientAsync(cancellationToken);
        await using var stream = controller.GetStream();

        try
        {
            while (!cancellationToken.IsCancellationRequested)
            {
                await stream.WriteAsync(frames, cancellationToken);
                await Task.Delay(50, cancellationToken);
            }
        }
        catch (OperationCanceledException)
        {
            // 正常取消。
        }
        catch (IOException)
        {
            // 客户端断开。
        }
    }
}