using System;
using Annulus.BezierCurves;
using Annulus.CSG;
using Azimuth;

namespace Annulus.UnitTests.CSG
{
    public class BoundaryMergesTests : UnitTestSharp.TestFixture
    {
        // A box under a pointed arch, whose tight curvature at the top grows a branch back into the shape.
        public static QuadraticBezierCurve[] Arch(Scalar height, Scalar apexControlX)
        {
            return new QuadraticBezierCurve[]
            {
                DiskQueryTests.Line(new Vector(-2, 0), new Vector(2, 0)),
                DiskQueryTests.Line(new Vector(2, 0), new Vector(2, height)),
                DiskQueryTests.Piece(new Vector(2, height), new Vector(apexControlX, height + 6),
                    new Vector(-2, height)),
                DiskQueryTests.Line(new Vector(-2, height), new Vector(-2, 0)),
            };
        }

        public static int BranchInterval(BoundaryLabelling labelling)
        {
            for (int i = 0; i < labelling.Intervals.Length; ++i)
            {
                if (labelling.Intervals[i].Own == 2 && labelling.Intervals[i].Across == 2)
                {
                    return i;
                }
            }

            throw new InvalidOperationException("The arch has no branch into its own top piece.");
        }

        public class AddPieceTests : UnitTestSharp.TestFixture
        {
            public static BoundaryRegion Empty()
            {
                return new BoundaryRegion { First = -1, Second = -1 };
            }

            public void FirstPiece_FillsBothSlots()
            {
                BoundaryRegion label = Empty();

                BoundaryMerges.AddPiece(ref label, 4);

                CheckEqual(4, label.First);
                CheckEqual(4, label.Second);
            }

            public void RepeatedPiece_ChangesNothing()
            {
                BoundaryRegion label = Empty();
                BoundaryMerges.AddPiece(ref label, 4);

                BoundaryMerges.AddPiece(ref label, 4);

                CheckEqual(4, label.First);
                CheckEqual(4, label.Second);
            }

            public void SecondPieceBelowTheFirst_GoesInFront()
            {
                BoundaryRegion label = Empty();
                BoundaryMerges.AddPiece(ref label, 4);

                BoundaryMerges.AddPiece(ref label, 2);

                CheckEqual(2, label.First);
                CheckEqual(4, label.Second);
            }

            public void SecondPieceAboveTheFirst_GoesBehind()
            {
                BoundaryRegion label = Empty();
                BoundaryMerges.AddPiece(ref label, 2);

                BoundaryMerges.AddPiece(ref label, 4);

                CheckEqual(2, label.First);
                CheckEqual(4, label.Second);
            }

            public void EitherOfTwoPiecesAddedAgain_ChangesNothing()
            {
                BoundaryRegion label = Empty();
                BoundaryMerges.AddPiece(ref label, 2);
                BoundaryMerges.AddPiece(ref label, 4);

                BoundaryMerges.AddPiece(ref label, 4);
                BoundaryMerges.AddPiece(ref label, 2);

                CheckEqual(2, label.First);
                CheckEqual(4, label.Second);
            }

            public void ThirdPiece_Throws()
            {
                BoundaryRegion label = Empty();
                BoundaryMerges.AddPiece(ref label, 2);
                BoundaryMerges.AddPiece(ref label, 4);

                CheckThrow(typeof(InvalidOperationException));
                BoundaryMerges.AddPiece(ref label, 7);
            }
        }

        public class BuildTests : UnitTestSharp.TestFixture
        {
            public void TightLens_JoinsItsSingleCandidateWedgesAndEverythingBetweenThemIntoOneRegion()
            {
                BoundaryLabelling labelling = new BoundaryLabelling(DiskQueryTests.Lens(bulge: 2));

                CheckEqual(1, labelling.Regions.Length);
                CheckEqual(0, labelling.Regions[0].First);
                CheckEqual(1, labelling.Regions[0].Second);
                foreach (BoundaryCut cut in labelling.Cuts)
                {
                    CheckFalse(cut.IsLive);
                }
            }

            public void SingleCandidateRegionsWhoseNeighboursDoNotNameItsPiece_StayAsTheyAre()
            {
                BoundaryLabelling labelling = new BoundaryLabelling(BoundaryLabellingTests.CircleArcs(4));

                CheckEqual(4, labelling.Regions.Length);
                for (int i = 0; i < 4; ++i)
                {
                    CheckEqual(i, labelling.Regions[i].First);
                    CheckEqual(i, labelling.Regions[i].Second);
                }
            }

            public void BranchBetweenTwoRegionsWithTheSamePieces_JoinsThemAllIntoOne()
            {
                BoundaryLabelling labelling = new BoundaryLabelling(Arch(height: 2, apexControlX: 0));
                int branch = BranchInterval(labelling);
                int count = labelling.Intervals.Length;

                int before = labelling.Intervals[(branch + count - 1) % count].Region;
                int after = labelling.Intervals[(branch + 1) % count].Region;

                CheckEqual(5, labelling.Regions.Length);
                CheckEqual(before, labelling.Intervals[branch].Region);
                CheckEqual(after, labelling.Intervals[branch].Region);
            }

            public void BranchBetweenTwoDifferentRegions_JoinsTheOneMetFirstWhenBothAreEquallyCheap()
            {
                BoundaryLabelling labelling = new BoundaryLabelling(Arch(height: 6, apexControlX: 0));
                int branch = BranchInterval(labelling);
                int count = labelling.Intervals.Length;
                int before = labelling.Intervals[(branch + count - 1) % count].Region;
                int after = labelling.Intervals[(branch + 1) % count].Region;

                CheckEqual(5, labelling.Regions.Length);
                CheckEqual(before, labelling.Intervals[branch].Region);
                CheckTrue(before != after);
            }
        }
    }
}