using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Azimuth.UnitTests.RootFinding
{
    public class BisectionTests : UnitTestSharp.TestFixture
    {
        public class Polynomials : UnitTestSharp.TestFixture
        {
            public void Basic()
            {
                Scalar r1 = Azimuth.RootFinding.Bisection.FindRoot(x => x*(x+18)+17, new Interval(-400, -2));
                Scalar r2 = Azimuth.RootFinding.Bisection.FindRoot(x => x * (x + 18) + 17, new Interval(-2, 7000));

                CheckEqual(-17, r1);
                CheckEqual(-1, r2);
            }

            public void DoesNotStraddle()
            {
                CheckThrow(typeof(Exception));
                Scalar r1 = Azimuth.RootFinding.Bisection.FindRoot(x => x * (x + 18) + 17, new Interval(-400, -401));
            }

            public void MultipleRoots()
            {
                // Should give us the minimum root
                Scalar r1 = Azimuth.RootFinding.Bisection.FindRoot(
                    x => (x + 3) * (x - 7) * (x - 4) * (x - 4) * (x - 4) * (x - 4) * (x + 2) * (x - 1) * (x - 3),
                    new Interval(-400, 400));

                var possibleRoots = new List<Scalar>(new Scalar[] { -3, 7, 4, -2, 1, 3 });

                // There's no way to be sure which root the bisection will converge to.
                Check(possibleRoots.Contains(r1));
            }

            public void InfinityBounds()
            {
                CheckThrow(typeof(Exception));
                Scalar r1 = Azimuth.RootFinding.Bisection.FindRoot(
                    x => (x + 3) * (x - 7) * (x - 4) * (x - 4) * (x - 4) * (x - 4) * (x + 2) * (x - 1) * (x - 3),
                    new Interval(Scalar.NegativeInfinity, Scalar.PositiveInfinity));
            }

            public void NonPolynomial()
            {
                var func = new Func<Scalar, Scalar>(x => Math.Exp(x) - 0.5);

                Scalar r1 = Azimuth.RootFinding.Bisection.FindRoot(func, new Interval(-10, 10));

                CheckEqual(Math.Log(0.5), r1);
            }

            public void Singularity()
            {
                var func = new Func<Scalar, Scalar>(x => 1.0 / (x - 1.1));

                Scalar r1 = Azimuth.RootFinding.Bisection.FindRoot(func, new Interval(-10, 10));

                CheckEqual(1.1, r1);
            }
        }
    }
}