using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Azimuth;
using Annulus.SweptCollisionDetection;

namespace Lodestone.UnitTests
{
    public class UniverseTests : UnitTestSharp.TestFixture
    {
        public void NegativeStepTime()
        {
            var universe = new Universe();

            CheckThrow(typeof(Exception));
            universe.Step(-1);
        }

        public void ZeroStepTime()
        {
            var universe = new Universe();

            universe.Step(0);
        }

        public void FallingBox()
        {
            var universe = new Universe();

            universe.AddBody(new Body
            {
                Mass = 10,
                MomentOfInertiaRatio = 1,
            });

            universe.Settings.Gravity = new Vector(0, -10);

            for (int t = 0; t < 100; t += 1)
            {
                universe.Step(1);
            }

            CheckEqual(new AffineMatrix(0, new Vector(0, -50000)), universe.Bodies[0].TransformAt(0));
        }

        public void FallingBox_Bounce()
        {
            var universe = new Universe();

            var body = new Body
            {
                Mass = 10,
                MomentOfInertiaRatio = 1,

                Shape = new Annulus.SimplePolygon(new Vector[]
                {
                    new Vector(-10, 0),
                    new Vector(0, -10),
                    new Vector(10, 0),
                    new Vector(0, 10),
                }),
            };

            body.SetMotion(0, new Motion
            {
                InitialPosition = new Vector(0, 110),
            });

            universe.AddBody(body);

            universe.AddBody(new Body
            {
                Shape = new Annulus.SimplePolygon(new Vector[]
                {
                    new Vector(-1000, 0),
                    new Vector(-1000, -10),
                    new Vector(1000, -10),
                    new Vector(1000, 0),
                }),
            });

            universe.Settings.Gravity = new Vector(0, -10);

            Scalar endTime = 10;

            universe.Step(endTime);

            Motion expectedMotion;
            {
                Scalar t = endTime - Math.Sqrt(20);
                Scalar vFinal = Math.Sqrt(2 * 100 * 10); //v_f^2 = 2ad

                expectedMotion = new Motion
                {
                    InitialPosition = new Vector(0, 10 + t * (vFinal - 5 * t)),
                    LinearVelocity = new Vector(0, vFinal - 10 * t),
                    LinearAcceleration = new Vector(0, -10),
                };
            }

            CheckEqual(expectedMotion, universe.Bodies[0].MotionAt(0));
        }
    }
}