using System.Collections.Generic;
using Microsoft.Msagl.Core.Geometry;
using Microsoft.Msagl.Core.Geometry.Curves;
using Microsoft.Msagl.Core;

namespace Microsoft.Msagl.Routing.Visibility {
      internal class ActiveDiagonalComparerWithRay: IComparer<Diagonal> {

          Point pointOnTheRay;

          [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Performance", "CA1811:AvoidUncalledPrivateCode")]
          internal Point PointOnTangentAndInsertedDiagonal {
              get { return pointOnTheRay; }
              set { pointOnTheRay = value; }
          }

          public int Compare(Diagonal x, Diagonal y) {
              ValidateArg.IsNotNull(x, "x");
              ValidateArg.IsNotNull(y, "y");
              System.Diagnostics.Debug.Assert(BelongsToTheDiagonal(PointOnTangentAndInsertedDiagonal, x.Start, x.End));
              if (x.Start != y.Start)
                  switch (Point.GetTriangleOrientation(PointOnTangentAndInsertedDiagonal, y.Start, y.End)) {
                      case TriangleOrientation.Counterclockwise:
                          return -1;
                      default:
                          return 1;
                  } else {
                  return 0;
              }
          }

          [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Performance", "CA1811:AvoidUncalledPrivateCode")]
          static bool BelongsToTheDiagonal(Point IntersectionOfTheRayAndInsertedEdge, Point start, Point end) {
              return ApproximateComparer.Close(IntersectionOfTheRayAndInsertedEdge, Point.ClosestPointAtLineSegment(IntersectionOfTheRayAndInsertedEdge, start, end));
          }

          [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Performance", "CA1811:AvoidUncalledPrivateCode")]
          static internal Point IntersectDiagonalWithRay(Point pivot, Point pointOnRay, Diagonal diagonal ) {
              Point ray=pointOnRay-pivot;
              Point source=diagonal.Start;
              Point target = diagonal.End;
              //let x(t-s)+s is on the ray, then for some y we x(t-s)+s=y*ray+pivot, or x(t-s)-y*ray=pivot-s
              double x, y;
              bool result = LinearSystem2.Solve(target.X - source.X, -ray.X, pivot.X - source.X, target.Y - source.Y, -ray.Y, pivot.Y - source.Y, out x, out y);
          
              System.Diagnostics.Debug.Assert(result && -ApproximateComparer.Tolerance <= x && x <= 1 + ApproximateComparer.Tolerance);
              
              return pivot + y * ray;
          }

      }
}