MoShiro/backend/agent/tests/MoShiro.Agent.Tests/LinkStateTests.cs

using System.Collections.Concurrent;
using System.Net.Sockets;
using System.Security.Authentication;
using Fleet.Core;
using Fleet.Link;
using MoShiro.Protocol;

namespace MoShiro.Agent.Tests;

public sealed class LinkStateTests
{
    [Fact]
    public void QuicRedialBackoff_StaysShort_AndRestartsAfterReset()
    {
        var backoff = new QuicRedialBackoff();
        int[] seconds = [1, 2, 3, 5, 5, 5];
        Assert.Equal(seconds, seconds.Select(_ => (int)backoff.Next().TotalSeconds));

        backoff.Reset();

        Assert.Equal(TimeSpan.FromSeconds(1), backoff.Next());
        TimeSpan jittered = new QuicRedialBackoff().Next(new Random(1));
        Assert.InRange(jittered.TotalSeconds, 0.8, 1.2);
    }

    public static TheoryData<Exception, string> Faults => new()
    {
        { new OperationCanceledException(), "timeout" },
        { new SocketException((int)SocketError.ConnectionRefused), "refused" },
        { new SocketException((int)SocketError.HostNotFound), "dns" },
        { new IOException("reset", new SocketException((int)SocketError.ConnectionReset)), "reset" },
        { new AuthenticationException("bad certificate"), "tls" },
        { new InvalidOperationException("peer authentication failed: unauthorized"), "auth" },
        { new ControlSilentException("no frames"), "silent" },
        { new IOException("closed"), "closed" },
    };

    [Theory]
    [MemberData(nameof(Faults))]
    public void LinkFaults_ClassifyTheFailureAndKeepThePhase(Exception exception, string kind)
    {
        LinkFault fault = LinkFaults.From(exception, "tls");

        Assert.Equal(kind, fault.Kind);
        Assert.Equal("tls", fault.Phase);
    }

    [Fact]
    public void ControlStatus_LogsEveryTransition_AndReportsTheFaultWhileInBackoff()
    {
        var log = new CaptureLog();
        var status = new LinkStatus("agt_1", "ipv4", TimeProvider.System, log);

        status.SetControl(ControlState.Dialing);
        status.SetControl(ControlState.Authenticating);
        status.SetControl(ControlState.Syncing);
        status.SetControl(ControlState.Up);
        status.SetControl(ControlState.Backoff, new LinkFault { Phase = "control_session", Kind = "silent" }, attempt: 1, retryIn: TimeSpan.FromSeconds(1));

        Assert.Equal(["authenticating", "syncing", "up", "backoff"], log.Items.Select(x => (string)x["to"]!));
        LinkHealth health = status.Snapshot(new Outbox(1 << 10), 0, null);
        Assert.Equal(ControlState.Backoff, health.Control.State);
        Assert.Equal("silent", health.Control.LastError?.Kind);
        Assert.InRange(health.Control.RetryInMs ?? -1, 1, 1000);

        status.SetControl(ControlState.Up);
        Assert.Null(status.Snapshot(new Outbox(1 << 10), 0, null).Control.LastError);
    }

    [Fact]
    public void QuicStatus_LogsOnlyTheEdgesOfAnOutage_NotEveryRedial()
    {
        var log = new CaptureLog();
        var status = new LinkStatus("agt_1", "ipv4", TimeProvider.System, log);
        var fault = new LinkFault { Phase = "quic_handshake", Kind = "timeout" };

        status.SetQuic(QuicState.Connecting);
        status.SetQuic(QuicState.Ready);
        status.SetQuic(QuicState.Retrying, fault, 1, TimeSpan.FromSeconds(1));
        for (int attempt = 1; attempt <= 5; attempt++)
        {
            status.SetQuic(QuicState.Connecting, attempt: attempt);
            status.SetQuic(QuicState.Retrying, fault, attempt + 1, TimeSpan.FromSeconds(5));
        }

        status.SetQuic(QuicState.Connecting, attempt: 6);
        status.SetQuic(QuicState.Ready);

        Assert.Equal(["ready", "retrying", "ready"], log.Items.Select(x => (string)x["to"]!));
        Assert.NotNull(log.Items[^1]["down_ms"]);
        Assert.True(status.Ready is false);
        status.SetControl(ControlState.Up);
        Assert.True(status.Ready);
    }

    private sealed class CaptureLog : INodeLog
    {
        private readonly ConcurrentQueue<Dictionary<string, object?>> _items = new();

        public IReadOnlyList<Dictionary<string, object?>> Items => [.. _items];

        public void Write(NodeLogLevel level, string message, params (string Key, object? Value)[] fields)
        {
            if (message == "link state")
            {
                _items.Enqueue(fields.ToDictionary(x => x.Key, x => x.Value));
            }
        }
    }
}