using System;
using UnitTestSharp;

namespace Azimuth.UnitTests
{
    public class ViewProjectionTests : TestFixture
    {
        public class CtorTests : TestFixture
        {
            public void StraightDown_AssignsTheCoefficients()
            {
                var projection = new ViewProjection(yawTurns: 0, pitchTurns: 0.25);

                CheckEqual(1, projection.XToScreenX);
                CheckEqual(0, projection.YToScreenX);
                CheckEqual(0, projection.XToScreenY);
                CheckEqual(1, projection.YToScreenY);
                CheckEqual(0, projection.AltitudeToScreenY);
                CheckEqual(0, projection.XToDepth);
                CheckEqual(0, projection.YToDepth);
                CheckEqual(-1, projection.AltitudeToDepth);
            }

            public void SideOn_AssignsTheCoefficients()
            {
                var projection = new ViewProjection(yawTurns: 0.25, pitchTurns: 0);

                CheckEqual(0, projection.XToScreenX);
                CheckEqual(-1, projection.YToScreenX);
                CheckEqual(0, projection.XToScreenY);
                CheckEqual(0, projection.YToScreenY);
                CheckEqual(1, projection.AltitudeToScreenY);
                CheckEqual(1, projection.XToDepth);
                CheckEqual(0, projection.YToDepth);
                CheckEqual(0, projection.AltitudeToDepth);
            }

            public void PitchesAtTheEnds_AreAllowed()
            {
                new ViewProjection(yawTurns: 0, pitchTurns: 0);
                new ViewProjection(yawTurns: 0, pitchTurns: 0.25);
            }

            public void AnyFiniteYaw_IsAllowed()
            {
                new ViewProjection(yawTurns: -3.5, pitchTurns: 0.1);
                new ViewProjection(yawTurns: 12, pitchTurns: 0.1);
            }

            public void NaNYaw_Throws()
            {
                CheckThrow(typeof(ArgumentOutOfRangeException));
                new ViewProjection(yawTurns: double.NaN, pitchTurns: 0.1);
            }

            public void InfiniteYaw_Throws()
            {
                CheckThrow(typeof(ArgumentOutOfRangeException));
                new ViewProjection(yawTurns: double.PositiveInfinity, pitchTurns: 0.1);
            }

            public void NaNPitch_Throws()
            {
                CheckThrow(typeof(ArgumentOutOfRangeException));
                new ViewProjection(yawTurns: 0, pitchTurns: double.NaN);
            }

            public void NegativePitch_Throws()
            {
                CheckThrow(typeof(ArgumentOutOfRangeException));
                new ViewProjection(yawTurns: 0, pitchTurns: -0.01);
            }

            public void PitchBeyondStraightDown_Throws()
            {
                CheckThrow(typeof(ArgumentOutOfRangeException));
                new ViewProjection(yawTurns: 0, pitchTurns: 0.26);
            }
        }

        public class ProjectTests : TestFixture
        {
            public void TheOrigin_LandsOnTheOrigin()
            {
                CheckEqual(new Vector(0, 0), ViewProjection.Isometric.Project(new Vector3(0, 0, 0)));
            }

            public void YawZeroAndPitchZero_KeepsGroundXAndTakesAltitudeForUp()
            {
                var projection = new ViewProjection(yawTurns: 0, pitchTurns: 0);

                CheckEqual(new Vector(1, 3), projection.Project(new Vector3(1, 2, 3)));
            }

            public void APositiveYaw_TurnsTheGroundCounterClockwise()
            {
                var projection = new ViewProjection(yawTurns: 0.25, pitchTurns: 0.25);

                CheckEqual(new Vector(0, 1), projection.Project(new Vector3(1, 0, 0)));
                CheckEqual(new Vector(-1, 0), projection.Project(new Vector3(0, 1, 0)));
            }

            public void ANegativeYaw_TurnsTheGroundClockwise()
            {
                var projection = new ViewProjection(yawTurns: -0.25, pitchTurns: 0.25);

                CheckEqual(new Vector(0, -1), projection.Project(new Vector3(1, 0, 0)));
            }

            public void TopDown_IgnoresAltitude()
            {
                CheckEqual(new Vector(3, 4), ViewProjection.TopDown.Project(new Vector3(3, 4, 5)));
                CheckEqual(new Vector(3, 4), ViewProjection.TopDown.Project(new Vector3(3, 4, -5)));
            }

            public void Isometric_GroundXGoesRightAndUp()
            {
                CheckEqual(
                    new Vector(0.707106781187, 0.408248290464), ViewProjection.Isometric.Project(new Vector3(1, 0, 0)));
            }

            public void Isometric_GroundYGoesLeftAndUp()
            {
                CheckEqual(
                    new Vector(-0.707106781187, 0.408248290464),
                    ViewProjection.Isometric.Project(new Vector3(0, 1, 0)));
            }

            public void Isometric_AltitudeGoesStraightUp()
            {
                CheckEqual(new Vector(0, 0.816496580928), ViewProjection.Isometric.Project(new Vector3(0, 0, 1)));
            }

            public void Isometric_AGroundDiagonalIsAsTallAsAnAltitudeStep()
            {
                CheckEqual(new Vector(0, 0.816496580928), ViewProjection.Isometric.Project(new Vector3(1, 1, 0)));
            }

            public void Dimetric2To1_GroundXIsTwiceAsWideAsItIsTall()
            {
                CheckEqual(
                    new Vector(0.707106781187, 0.353553390593),
                    ViewProjection.Dimetric2To1.Project(new Vector3(1, 0, 0)));
            }

            public void Dimetric2To1_TheTwoGroundDiagonalsLieOnTheScreenAxes()
            {
                CheckEqual(new Vector(0, 0.707106781187), ViewProjection.Dimetric2To1.Project(new Vector3(1, 1, 0)));
                CheckEqual(new Vector(1.414213562373, 0), ViewProjection.Dimetric2To1.Project(new Vector3(1, -1, 0)));
            }

            public void Dimetric2To1_AltitudeGoesStraightUp()
            {
                CheckEqual(new Vector(0, 0.866025403784), ViewProjection.Dimetric2To1.Project(new Vector3(0, 0, 1)));
            }

            public void ScalesLinearlyWithThePosition()
            {
                CheckEqual(
                    new Vector(2.121320343560, 3.674234614176), ViewProjection.Isometric.Project(new Vector3(3, 0, 3)));
            }
        }

        public class TryUnprojectTests : TestFixture
        {
            public void TopDown_ReadsTheScreenAsTheGround()
            {
                bool found = ViewProjection.TopDown.TryUnproject(new Vector(3, 4), 0, out Vector3 position);

                CheckTrue(found);
                CheckEqual(new Vector3(3, 4, 0), position);
            }

            public void TopDown_KeepsTheAltitudeAsGiven()
            {
                ViewProjection.TopDown.TryUnproject(new Vector(3, 4), 7, out Vector3 position);

                CheckEqual(new Vector3(3, 4, 7), position);
            }

            public void Dimetric2To1_FindsTheGroundPositionThatProjectedThere()
            {
                var ground = new Vector3(5, -2, 0);
                Vector screen = ViewProjection.Dimetric2To1.Project(ground);

                bool found = ViewProjection.Dimetric2To1.TryUnproject(screen, 0, out Vector3 position);

                CheckTrue(found);
                CheckEqual(ground, position);
            }

            public void Dimetric2To1_AtAnAltitude_FindsThePositionAtThatAltitude()
            {
                var raised = new Vector3(5, -2, 3);
                Vector screen = ViewProjection.Dimetric2To1.Project(raised);

                ViewProjection.Dimetric2To1.TryUnproject(screen, 3, out Vector3 position);

                CheckEqual(raised, position);
            }

            public void Isometric_FindsTheGroundPositionThatProjectedThere()
            {
                var ground = new Vector3(-4, 6, 0);

                Vector screen = ViewProjection.Isometric.Project(ground);

                ViewProjection.Isometric.TryUnproject(screen, 0, out Vector3 position);

                CheckEqual(ground, position);
            }

            public void ATurnedView_FindsTheGroundPositionThatProjectedThere()
            {
                var projection = new ViewProjection(yawTurns: 0.3, pitchTurns: 0.1);
                var ground = new Vector3(2, 9, 0);

                projection.TryUnproject(projection.Project(ground), 0, out Vector3 position);

                CheckEqual(ground, position);
            }

            public void SideOn_FindsNothing()
            {
                var projection = new ViewProjection(yawTurns: 0, pitchTurns: 0);

                bool found = projection.TryUnproject(new Vector(1, 2), 0, out Vector3 position);

                CheckFalse(found);
                CheckEqual(new Vector3(0, 0, 0), position);
            }
        }

        public class DepthTests : TestFixture
        {
            public void TheOrigin_IsAtZeroDepth()
            {
                CheckEqual(0, ViewProjection.Isometric.Depth(new Vector3(0, 0, 0)));
            }

            public void SideOn_IsGroundXAlone()
            {
                var projection = new ViewProjection(yawTurns: 0.25, pitchTurns: 0);

                CheckEqual(1, projection.Depth(new Vector3(1, 7, 7)));
            }

            public void TopDown_HigherIsNearerTheCamera()
            {
                CheckEqual(-5, ViewProjection.TopDown.Depth(new Vector3(3, 4, 5)));
                CheckEqual(5, ViewProjection.TopDown.Depth(new Vector3(3, 4, -5)));
            }

            public void Dimetric2To1_FartherAlongGroundYIsFartherAway()
            {
                CheckEqual(0.612372435696, ViewProjection.Dimetric2To1.Depth(new Vector3(0, 1, 0)));
            }

            public void Isometric_AltitudeBringsItNearer()
            {
                CheckEqual(-0.577350269190, ViewProjection.Isometric.Depth(new Vector3(0, 0, 1)));
            }
        }

        public class PresetTests : TestFixture
        {
            public void TopDown_IsAStraightDownPitch()
            {
                CheckEqual(new ViewProjection(yawTurns: 0, pitchTurns: 0.25).Project(new Vector3(3, 4, 5)),
                    ViewProjection.TopDown.Project(new Vector3(3, 4, 5)));
            }

            public void Dimetric2To1_IsAThirtyDegreePitchAtFortyFiveDegreesYaw()
            {
                var projection = new ViewProjection(yawTurns: 0.125, pitchTurns: 30.0 / 360);

                CheckEqual(projection.Project(new Vector3(3, 4, 5)),
                    ViewProjection.Dimetric2To1.Project(new Vector3(3, 4, 5)));
            }
        }
    }
}