using Chernobyl.Mathematics.Movement;
using Chernobyl.Mathematics.Vectors;
using NUnit.Framework;

namespace Chernobyl.Mathematics.Geometry
{
    /// <summary>
    /// Tests for <see cref="ILineSegment"/> types.
    /// </summary>
    public abstract class LineSegmentTests
    {
        // Tests:
        // Transform
        //      Two sets of tests: when parented and when not parented.
        //          Position is the center point.
        //          Z axis is in the proper direction.
        //          Z axis scale is the length between point 1 and point 2.

        //-----------------------------------------------------------------
        // Transform Not Parented Tests
        //-----------------------------------------------------------------

        [Test, Description("A test to ensure LineSegment is properly positioned " +
            "at the center of two end points.")]
        public void PositionTest()
        {
            Vector3 expected = new Vector3(2.5f, 0, 0);

            MatrixTransform point1 = new MatrixTransform();
            MatrixTransform point2 = new MatrixTransform();
            point2.Translate(expected.X * 2, 0, 0);

            ILineSegment line = CreateLineSegment(point1, point2);
            
            Assert.AreEqual(expected, line.Position, "The Position is not what was expected.");
        }

        [Test, Description("A test to ensure LineSegment's X axis is properly " +
            "scaled so that its length is the distance between its two end points.")]
        public void ScaleTest()
        {
            Vector3 expected = new Vector3(5, 0, 0);

            MatrixTransform point1 = new MatrixTransform();
            MatrixTransform point2 = new MatrixTransform();
            point2.Translate(expected);

            ILineSegment line = CreateLineSegment(point1, point2);
            
            Assert.AreEqual(expected.X, line.XScale, "The Scale is not what was expected.");
        }

        [Test, Description("A test to ensure LineSegment is properly " +
            "rotated so that its X axis is parallel to the line between its two " +
            "end points.")]
        public void RotationTest()
        {
            Vector3 expectedX = new Vector3(5, 0, 0);

            MatrixTransform point1 = new MatrixTransform();
            MatrixTransform point2 = new MatrixTransform();
            point2.Translate(expectedX);

            ILineSegment line = CreateLineSegment(point1, point2);

            Assert.AreEqual(expectedX, line.WorldMatrix.Column0.Xyz,
                            "The X axis is not what was expectedX.");
            Assert.AreEqual(Vector3.UnitY, line.WorldMatrix.Column1.Xyz,
                            "The Y axis is not what was expectedX.");
            Assert.AreEqual(-Vector3.UnitZ, line.WorldMatrix.Column2.Xyz,
                            "The Z axis is not what was expectedX.");
        }

        /// <summary>
        /// Creates a new <see cref="ILineSegment"/> instance that will be
        /// tested.
        /// </summary>
        /// <param name="point1">The first end point in the line.</param>
        /// <param name="point2">The second end point in the line.</param>
        /// <returns>The <see cref="ILineSegment"/> whose end points are
        /// defined by <paramref name="point1"/> and <paramref name="point2"/>.</returns>
        protected abstract ILineSegment CreateLineSegment(ITransform point1, ITransform point2);
    }
}