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

namespace FastRngTests.Double.Distributions
{
    [ExcludeFromCodeCoverage]
    public class ExponentialLa5
    {
        [Test]
        [Category(TestCategories.COVER)]
        [Category(TestCategories.NORMAL)]
        public async Task TestExponentialDistribution01()
        {
            using var rng = new MultiThreadedRng();
            var dist = new FastRng.Double.Distributions.ExponentialLa5(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(1.0002177398625).Within(0.05));
            Assert.That(result[1], Is.EqualTo(0.951436545064811).Within(0.05));
            Assert.That(result[2], Is.EqualTo(0.905034437210948).Within(0.05));
            
            Assert.That(result[21], Is.EqualTo(0.35001394450853).Within(0.05));
            Assert.That(result[22], Is.EqualTo(0.332943563002074).Within(0.05));
            Assert.That(result[23], Is.EqualTo(0.31670571382568).Within(0.05));
            
            Assert.That(result[50], Is.EqualTo(0.082102871800213).Within(0.01));
            
            Assert.That(result[75], Is.EqualTo(0.023522866606758).Within(0.01));
            Assert.That(result[85], Is.EqualTo(0.014267339801329).Within(0.01));
            Assert.That(result[90], Is.EqualTo(0.011111415409621).Within(0.01));
            
            Assert.That(result[97], Is.EqualTo(0.007830082099077).Within(0.008));
            Assert.That(result[98], Is.EqualTo(0.007448204488898).Within(0.008));
            Assert.That(result[99], Is.EqualTo(0.007084951269538).Within(0.008));
        }
        
        [Test]
        [Category(TestCategories.COVER)]
        [Category(TestCategories.NORMAL)]
        public async Task TestExponentialGeneratorWithRange01()
        {
            using var rng = new MultiThreadedRng();
            var dist = new FastRng.Double.Distributions.ExponentialLa5(rng);
            var samples = new double[1_000];
            for (var n = 0; n < samples.Length; n++)
                samples[n] = await dist.NextNumber(-1.0, 1.0);
            
            Assert.That(samples.Min(), Is.GreaterThanOrEqualTo(-1.0), "Min out of range");
            Assert.That(samples.Max(), Is.LessThanOrEqualTo(1.0), "Max out of range");
        }
        
        [Test]
        [Category(TestCategories.COVER)]
        [Category(TestCategories.NORMAL)]
        public async Task TestExponentialGeneratorWithRange02()
        {
            using var rng = new MultiThreadedRng();
            var dist = new FastRng.Double.Distributions.ExponentialLa5(rng);
            var samples = new double[1_000];
            for (var n = 0; n < samples.Length; n++)
                samples[n] = await dist.NextNumber(0.0, 1.0);
            
            Assert.That(samples.Min(), Is.GreaterThanOrEqualTo(0.0), "Min is out of range");
            Assert.That(samples.Max(), Is.LessThanOrEqualTo(1.0), "Max is out of range");
        }

        [Test]
        [Category(TestCategories.COVER)]
        [Category(TestCategories.NORMAL)]
        public void NoRandomNumberGenerator01()
        {
            Assert.Throws<ArgumentNullException>(() => new FastRng.Double.Distributions.ExponentialLa5(null));
        }
    }
}