using VoiceCat.Server.Transport;
using Voicecat.V1;

namespace VoiceCat.Tests;

public class PacketLossTrackerTests
{
    [Fact]
    public void FastModeReportsWindowedLossAndCapsExtremeValues()
    {
        var clock = new ManualClock();
        var tracker = new PacketLossTracker(clock);
        Assert.Null(tracker.Observe(0, 1, PacketLossMode.PacketLossAutoFast));
        for (ulong sequence = 1; sequence <= 100; sequence++)
            if (sequence % 10 != 0) Assert.Null(tracker.Observe(sequence, 1, PacketLossMode.PacketLossAutoFast));
        clock.Advance(TimeSpan.FromSeconds(3));

        PacketLossSample sample = Assert.IsType<PacketLossSample>(tracker.Observe(101, 1, PacketLossMode.PacketLossAutoFast));
        Assert.Equal(10U, sample.MeasuredPercent);
        Assert.Equal(10U, sample.AppliedPercent);

        tracker = new(clock);
        Assert.Null(tracker.Observe(0, 1, PacketLossMode.PacketLossAutoFast));
        clock.Advance(TimeSpan.FromSeconds(3));
        sample = Assert.IsType<PacketLossSample>(tracker.Observe(100, 1, PacketLossMode.PacketLossAutoFast));
        Assert.Equal(99U, sample.MeasuredPercent);
        Assert.Equal(30U, sample.AppliedPercent);
    }

    [Fact]
    public void ReorderingDoesNotCountAsLossAndStableModeWaitsForItsWindow()
    {
        var clock = new ManualClock();
        var tracker = new PacketLossTracker(clock);
        tracker.Observe(0, 1, PacketLossMode.PacketLossAutoStable);
        tracker.Observe(2, 1, PacketLossMode.PacketLossAutoStable);
        tracker.Observe(1, 1, PacketLossMode.PacketLossAutoStable);
        for (ulong sequence = 3; sequence <= 30; sequence++) tracker.Observe(sequence, 1, PacketLossMode.PacketLossAutoStable);
        clock.Advance(TimeSpan.FromSeconds(29));
        Assert.Null(tracker.Observe(31, 1, PacketLossMode.PacketLossAutoStable));
        clock.Advance(TimeSpan.FromSeconds(1));
        PacketLossSample sample = Assert.IsType<PacketLossSample>(tracker.Observe(32, 1, PacketLossMode.PacketLossAutoStable));
        Assert.Equal(0U, sample.MeasuredPercent);
    }

    [Fact]
    public void ManualModeAndChannelChangesResetMeasurement()
    {
        var clock = new ManualClock();
        var tracker = new PacketLossTracker(clock);
        tracker.Observe(0, 1, PacketLossMode.PacketLossAutoFast);
        clock.Advance(TimeSpan.FromSeconds(3));
        Assert.Null(tracker.Observe(100, 2, PacketLossMode.PacketLossAutoFast));
        Assert.Null(tracker.Observe(101, 2, PacketLossMode.PacketLossManual));
    }

    private sealed class ManualClock : TimeProvider
    {
        private long timestamp;
        public override long TimestampFrequency => 1_000;
        public override long GetTimestamp() => timestamp;
        internal void Advance(TimeSpan duration) => timestamp += (long)duration.TotalMilliseconds;
    }
}