using System;
using Paca.Mobile.Core;
using Xunit;

namespace Paca.Tests.Core;

public class AdaptiveBufferScalerGateTests
{
    [Fact]
    public void Gate393_AdaptiveBufferScaler_SelectsGigabitUltra_ForHighThroughput()
    {
        // 80 MB/s
        var speed = 80.0 * 1024 * 1024;
        var profile = AdaptiveBufferScaler.GetAdaptationProfile(speed);

        Assert.Equal(BufferScalingTier.GigabitUltra, profile.CurrentTier);
        Assert.Equal(512 * 1024, profile.BufferSizeBytes);
        Assert.Equal(20 * 1024 * 1024L, profile.RecommendedChunkSizeBytes);
    }

    [Fact]
    public void Gate394_AdaptiveBufferScaler_SelectsMedium_ForModerateSpeed()
    {
        // 5 MB/s
        var speed = 5.0 * 1024 * 1024;
        var profile = AdaptiveBufferScaler.GetAdaptationProfile(speed);

        Assert.Equal(BufferScalingTier.MediumBandwidth, profile.CurrentTier);
        Assert.Equal(32 * 1024, profile.BufferSizeBytes);
        Assert.Equal(5 * 1024 * 1024L, profile.RecommendedChunkSizeBytes);
    }

    [Fact]
    public void Gate395_AdaptiveBufferScaler_SelectsLow_ForSlowConnections()
    {
        // 500 KB/s
        var speed = 500.0 * 1024;
        var profile = AdaptiveBufferScaler.GetAdaptationProfile(speed);

        Assert.Equal(BufferScalingTier.LowBandwidth, profile.CurrentTier);
        Assert.Equal(8 * 1024, profile.BufferSizeBytes);
        Assert.Equal(1 * 1024 * 1024L, profile.RecommendedChunkSizeBytes);
    }

    [Fact]
    public void Gate396_AdaptiveBufferScaler_SmoothsSpeed_WithExponentialMovingAverage()
    {
        var prevAvg = 10.0;
        var newSample = 20.0;
        // With alpha 0.3: 0.3 * 20 + 0.7 * 10 = 6 + 7 = 13.0
        var smoothed = AdaptiveBufferScaler.SmoothSpeedEma(prevAvg, newSample, alpha: 0.3);

        Assert.Equal(13.0, smoothed, 2);
    }
}