using Fleet.Core;
using Fleet.Hosting;
using Monitor.Protocol;

namespace Monitor.Probe.Tests;

public sealed class ProbeTests
{
    [Fact]
    public void ClockEstimator_UsesTheSampleWithTheShortestRoundTrip()
    {
        var clock = new ClockEstimator();
        Assert.False(clock.HasEstimate);

        // Offset 1000 with a 50 ms round trip, offset 5000 with a 2 ms round trip (symmetry assumption is far better here)
        clock.Add(sendUs: 0, agentUs: 25_000 + 1000, receiveUs: 50_000);
        clock.Add(sendUs: 100_000, agentUs: 101_000 + 5000, receiveUs: 102_000);
        Assert.True(clock.HasEstimate);
        Assert.Equal(5000, clock.OffsetUs);

        // Slow samples do not displace the good one
        clock.Add(sendUs: 200_000, agentUs: 300_000, receiveUs: 400_000);
        Assert.Equal(5000, clock.OffsetUs);
    }

    private static string NewDirectory()
    {
        string path = Path.Combine(Path.GetTempPath(), "probe-tests-" + Guid.NewGuid().ToString("N"));
        Directory.CreateDirectory(path);
        return path;
    }

    private static ProbeAgentsResult List(long version, params string[] ids) => new()
    {
        Version = version,
        Agents = [.. ids.Select(id => new AgentEndpoint { AgentId = new NodeId(id), Host = id + ".example", TcpPort = 7443, Spki = "c3BraQ==" })],
    };

    [Fact]
    public void AgentDirectory_StartsFromBootstrap_IgnoresStaleLists_PersistsChanges_AndReloadsThem()
    {
        string directory = NewDirectory();
        try
        {
            var file = new ProbeFile { ProbeId = "prb_x", Bootstrap = [new BootstrapAgent { AgentId = "agt_boot", Host = "boot.example", TcpPort = 7443, Spki = "c3BraQ==" }] };
            var directoryA = new AgentDirectory(new ConfigStore(directory), directory, file, NullNodeLog.Instance);
            int changes = 0;
            directoryA.Changed += () => changes++;
            Assert.Equal(["agt_boot"], directoryA.Agents.Select(a => a.AgentId));

            directoryA.Apply(List(5, "agt_1", "agt_2"));
            Assert.Equal(1, changes);
            Assert.Equal(["agt_1", "agt_2"], directoryA.Agents.Select(a => a.AgentId));

            directoryA.Apply(List(4, "agt_old")); // out-of-order older push
            directoryA.Apply(List(5, "agt_1", "agt_2")); // same version and content
            Assert.Equal(1, changes);
            Assert.Equal(5, directoryA.Version);

            // The next start uses the saved list, not the bootstrap one
            var directoryB = new AgentDirectory(new ConfigStore(directory), directory, file, NullNodeLog.Instance);
            Assert.Equal(["agt_1", "agt_2"], directoryB.Agents.Select(a => a.AgentId));
            Assert.Equal(5, directoryB.Version);
        }
        finally
        {
            Directory.Delete(directory, recursive: true);
        }
    }

    [Fact]
    public void AgentDirectory_FallsBackToBootstrap_WhenTheSavedFileIsCorrupt()
    {
        string directory = NewDirectory();
        try
        {
            new ConfigStore(directory).Write(AgentDirectory.FileName, "{ not json"u8.ToArray());
            var file = new ProbeFile { Bootstrap = [new BootstrapAgent { AgentId = "agt_boot", Host = "h", TcpPort = 1, Spki = "AA==" }] };
            var loaded = new AgentDirectory(new ConfigStore(directory), directory, file, NullNodeLog.Instance);
            Assert.Equal(["agt_boot"], loaded.Agents.Select(a => a.AgentId));
        }
        finally
        {
            Directory.Delete(directory, recursive: true);
        }
    }
}