using System.Net.Sockets;
using System.Security.Authentication;
using MoShiro.Protocol;

namespace MoShiro.Agent;

/// <summary>控制连接在已建立之后停止应答：对端不认这个会话了，或者线路中断超过了空闲上限。</summary>
public sealed class ControlSilentException(string message) : IOException(message);

/// <summary>把连接各阶段的异常归类成上报给面板的 <see cref="LinkFault"/>：失败发生在哪个阶段、属于哪一类。</summary>
public static class LinkFaults
{
    private const int MaxMessage = 200;

    public static LinkFault From(Exception ex, string phase)
    {
        Exception inner = ex is AggregateException { InnerExceptions.Count: 1 } aggregate ? aggregate.InnerExceptions[0] : ex;
        string kind = inner switch
        {
            ControlSilentException => "silent",
            OperationCanceledException or TimeoutException => "timeout",
            AuthenticationException => "tls",
            SocketException socket => Kind(socket.SocketErrorCode),
            IOException { InnerException: SocketException socket } => Kind(socket.SocketErrorCode),
            InvalidOperationException invalid when invalid.Message.Contains("authentication", StringComparison.OrdinalIgnoreCase)
                || invalid.Message.Contains("challenge", StringComparison.OrdinalIgnoreCase) => "auth",
            IOException => "closed",
            _ => "other",
        };
        string message = kind == "timeout" && inner is OperationCanceledException ? $"{phase} did not finish in time" : inner.Message;
        return new LinkFault { Phase = phase, Kind = kind, Message = message.Length > MaxMessage ? message[..MaxMessage] : message };
    }

    public static LinkFault Closed(string phase, string message) => new() { Phase = phase, Kind = "closed", Message = message };

    private static string Kind(SocketError error) => error switch
    {
        SocketError.ConnectionRefused => "refused",
        SocketError.ConnectionReset or SocketError.ConnectionAborted => "reset",
        SocketError.HostNotFound or SocketError.NoData or SocketError.TryAgain => "dns",
        SocketError.TimedOut => "timeout",
        _ => "other",
    };
}