using System;
using System.Diagnostics.CodeAnalysis;
using System.Linq;
using System.Threading.Tasks;
using FastRng;
using NUnit.Framework;

namespace FastRngTests.Distributions;

[ExcludeFromCodeCoverage]
public class ChiSquareK4
{
    [Test]
    [Category(TestCategories.COVER)]
    [Category(TestCategories.NORMAL)]
    public async Task TestChiSquareDistribution01()
    {
        using var rng = new MultiThreadedRng();
        var dist = new FastRng.Distributions.ChiSquareK4(rng);
        var fqa = new FrequencyAnalysis();

        for (var n = 0; n < 100_000; n++)
            fqa.CountThis(await dist.NextNumber());

        var result = fqa.NormalizeAndPlotEvents(TestContext.WriteLine);

        Assert.That(result[0], Is.EqualTo(0.016417705906679f).Within(0.02f));
        Assert.That(result[1], Is.EqualTo(0.032671644513723f).Within(0.02f));
        Assert.That(result[2], Is.EqualTo(0.048763041010352f).Within(0.02f));
            
        Assert.That(result[21], Is.EqualTo(0.32518779111264f).Within(0.05f));
        Assert.That(result[22], Is.EqualTo(0.338273451612642f).Within(0.05f));
        Assert.That(result[23], Is.EqualTo(0.351220492939994f).Within(0.05f));
            
        Assert.That(result[50], Is.EqualTo(0.65209223303425f).Within(0.08f));
            
        Assert.That(result[75], Is.EqualTo(0.857562207152294f).Within(0.099f));
        Assert.That(result[85], Is.EqualTo(0.923072405412387f).Within(0.099f));
        Assert.That(result[90], Is.EqualTo(0.952623623874265f).Within(0.099f));
            
        Assert.That(result[97], Is.EqualTo(0.990616879396201f).Within(0.099f));
        Assert.That(result[98], Is.EqualTo(0.995734077068522f).Within(0.099f));
        Assert.That(result[99], Is.EqualTo(1.00077558852585f).Within(0.1f));
    }
        
    [Test]
    [Category(TestCategories.COVER)]
    [Category(TestCategories.NORMAL)]
    public async Task TestChiSquareGeneratorWithRange01()
    {
        using var rng = new MultiThreadedRng();
        var dist = new FastRng.Distributions.ChiSquareK4(rng);
        var samples = new float[1_000];
        for (var n = 0; n < samples.Length; n++)
            samples[n] = await dist.NextNumber(-1.0f, 1.0f);
            
        Assert.That(samples.Min(), Is.GreaterThanOrEqualTo(-1.0f), "Min out of range");
        Assert.That(samples.Max(), Is.LessThanOrEqualTo(1.0f), "Max out of range");
    }
        
    [Test]
    [Category(TestCategories.COVER)]
    [Category(TestCategories.NORMAL)]
    public async Task TestChiSquareGeneratorWithRange02()
    {
        using var rng = new MultiThreadedRng();
        var dist = new FastRng.Distributions.ChiSquareK4(rng);
        var samples = new float[1_000];
        for (var n = 0; n < samples.Length; n++)
            samples[n] = await dist.NextNumber(0.0f, 1.0f);
            
        Assert.That(samples.Min(), Is.GreaterThanOrEqualTo(0.0f), "Min is out of range");
        Assert.That(samples.Max(), Is.LessThanOrEqualTo(1.0f), "Max is out of range");
    }

    [Test]
    [Category(TestCategories.COVER)]
    [Category(TestCategories.NORMAL)]
    public void NoRandomNumberGenerator01()
    {
        Assert.Throws<ArgumentNullException>(() => new FastRng.Distributions.ChiSquareK4(null));
    }
}