using System;

namespace HandyControl.Expression.Drawing
{
    internal class RandomEngine
    {
        private double? _anotherSample;

        private Random _random;

        public RandomEngine(long seed) => Initialize(seed);

        private double Gaussian()
        {
            double num;
            double num2;
            double num3;
            if (_anotherSample.HasValue)
            {
                var num4 = _anotherSample.Value;
                _anotherSample = null;
                return num4;
            }

            do
            {
                num2 = 2.0 * Uniform() - 1.0;
                num3 = 2.0 * Uniform() - 1.0;
                num = num2 * num2 + num3 * num3;
            } while (num >= 1.0);

            var num5 = Math.Sqrt(-2.0 * Math.Log(num) / num);
            _anotherSample = num2 * num5;
            return num3 * num5;
        }

        private void Initialize(long seed) => _random = new Random((int) seed);

        public double NextGaussian(double mean, double variance) => Gaussian() * variance + mean;

        public double NextUniform(double min, double max) => Uniform() * (max - min) + min;

        private double Uniform() => _random.NextDouble();
    }
}
