FastRng/FastRng/Distributions/Uniform.cs

using System;
using System.Numerics;
using System.Threading;

namespace FastRng.Distributions;

public sealed class Uniform<TNum> : IDistribution<TNum> where TNum : IFloatingPointIeee754<TNum>
{
    private readonly IRandom<TNum> rng;
        
    public Uniform(IRandom<TNum> rng)
    {
        this.rng = rng ?? throw new ArgumentNullException(nameof(rng), "An IRandom<TNum> implementation is needed.");
    }

    public TNum GetDistributedValue(CancellationToken token = default) => this.rng.GetUniform(token);
        
    public uint NextNumber(uint rangeStart, uint rangeEnd, CancellationToken cancel = default)
    {
        // Swap the values if the range start is greater than the range end:
        if (rangeStart > rangeEnd)
            (rangeStart, rangeEnd) = (rangeEnd, rangeStart);

        var range = rangeEnd - rangeStart;
        var distributedValue = this.GetDistributedValue(cancel);
        return (uint) ((float.CreateChecked(distributedValue) * range) + rangeStart);
    }

    public ulong NextNumber(ulong rangeStart, ulong rangeEnd, CancellationToken cancel = default)
    {
        // Swap the values if the range start is greater than the range end:
        if (rangeStart > rangeEnd)
            (rangeStart, rangeEnd) = (rangeEnd, rangeStart);

        var range = rangeEnd - rangeStart;
        var distributedValue = this.GetDistributedValue(cancel);
        return (ulong) ((double.CreateChecked(distributedValue) * range) + rangeStart);
    }

    public TNum NextNumber(TNum rangeStart, TNum rangeEnd, CancellationToken cancel = default)
    {
        // Swap the values if the range start is greater than the range end:
        if (rangeStart > rangeEnd)
            (rangeStart, rangeEnd) = (rangeEnd, rangeStart);

        var range = rangeEnd - rangeStart;
        var distributedValue = this.GetDistributedValue(cancel);
        return (distributedValue * range) + rangeStart;
    }

    public TNum NextNumber(CancellationToken cancel = default) => this.NextNumber(TNum.Zero,  TNum.One, cancel);
        
    public bool HasDecisionBeenMade(TNum above, TNum below, CancellationToken cancel = default)
    {
        var number = this.NextNumber(cancel);
        return number > above && number < below;
    }
}