using System;
using System.Collections.Generic;

using UnityEngine;

using NUnit.Framework;

namespace Framework.Geometry.Lines.Fitting {

	/// <summary>Unit tests for the 2D line segment fitting algorithms</summary>
	[TestFixture]
	public static class Segment2FitterTest {

		/// <summary>
		///   Verifies that attempting to fit a segment to no points results in a zero-length
		///   segment at the center of the coordinate system
		/// </summary>
		[Test]
		public static void NoPointsResultInDefaultLine() {
			var noPoints = new Vector2[0];
			Segment2 fittedSegment = Segment2Fitter.Fit(noPoints);

			Assert.That(fittedSegment.From, Is.EqualTo(Vector2.zero));
			Assert.That(fittedSegment.To, Is.EqualTo(Vector2.zero));
		}

		/// <summary>
		///   Verifies that fitting a segment to a single point produces a zero-length segment
		/// </summary>
		[Test]
		public static void SinglePointResultsInZeroLengthLine() {
			var singlePoint = new Vector2[] { new Vector2(1.2f, 3.4f) };
			Segment2 fittedSegment = Segment2Fitter.Fit(singlePoint);

			Assert.That(fittedSegment.From, Is.EqualTo(singlePoint[0]));
			Assert.That(fittedSegment.To, Is.EqualTo(singlePoint[0]));
		}

		/// <summary>
		///   Verifies that fitting a bunch of points all on top of each other produces
		///   a zero-length line segment
		/// </summary>
		[Test]
		public static void ClumpedPointsResultInZeroLengthSegment() {
			var clumpedPoints = new Vector2[] {
				new Vector2(1.2f, 3.4f),
				new Vector2(1.2f, 3.4f),
				new Vector2(1.2f, 3.4f),
				new Vector2(1.2f, 3.4f)
			};
			Segment2 fittedSegment = Segment2Fitter.Fit(clumpedPoints);

			Assert.That(fittedSegment.From, Is.EqualTo(clumpedPoints[0]));
			Assert.That(fittedSegment.To, Is.EqualTo(clumpedPoints[0]));
		}

		/// <summary>
		///   Verifies that fitting a line segment to a series in a flat row builds
		///   a horizontal line segment
		/// </summary>
		[Test]
		public static void FlatHorizontalSegmentCanBeFitted() {
			var horizontalPoints = new Vector2[] {
				new Vector2(4.0f, 5.0f),
				new Vector2(9.0f, 5.0f),
				new Vector2(14.0f, 5.0f),
				new Vector2(21.0f, 5.0f)
			};
			Segment2 fittedSegment = Segment2Fitter.Fit(horizontalPoints);

			Assert.That(fittedSegment.From, Is.EqualTo(horizontalPoints[0]));
			Assert.That(fittedSegment.To, Is.EqualTo(horizontalPoints[3]));
		}

		/// <summary>
		///   Verifies that fitting a line segment to a series in a flat column builds
		///   a vertical line segment
		/// </summary>
		[Test]
		public static void FlatVerticalSegmentCanBeFitted() {
			var verticalPoints = new Vector2[] {
				new Vector2(5.0f, 4.0f),
				new Vector2(5.0f, 9.0f),
				new Vector2(5.0f, 14.0f),
				new Vector2(5.0f, 21.0f)
			};
			Segment2 fittedSegment = Segment2Fitter.Fit(verticalPoints);

			Assert.That(fittedSegment.From, Is.EqualTo(verticalPoints[0]));
			Assert.That(fittedSegment.To, Is.EqualTo(verticalPoints[3]));
		}

		/// <summary>
		///   Verifies that the fitted segment's direction matches the general direction
		///   of the points it is fitted to
		/// </summary>
		[Test]
		public static void SegmentDirectionMatchesPointOrder() {
			var points = new Vector2[] {
				new Vector2(-5.0f, 5.0f),
				new Vector2(5.0f, 2.5f), new Vector2(10.0f, 7.5f),
				new Vector2(5.0f, 7.5f), new Vector2(10.0f, 2.5f),
				new Vector2(15.0f, 5.0f)
			};
			Segment2 fittedSegment = Segment2Fitter.Fit(points);

			Assert.That(fittedSegment.From, Is.EqualTo(new Vector2(-5.0f, 5.0f)));
			Assert.That(fittedSegment.To, Is.EqualTo(new Vector2(15.0f, 5.0f)));

			var reversePoints = new List<Vector2>(points);
			reversePoints.Reverse();
			fittedSegment = Segment2Fitter.Fit(reversePoints);

			Assert.That(fittedSegment.From, Is.EqualTo(new Vector2(15.0f, 5.0f)));
			Assert.That(fittedSegment.To, Is.EqualTo(new Vector2(-5.0f, 5.0f)));
		}

	}

} // namespace Framework.Geometry.Lines.Fitting