using System;
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 ActiveEdgeComparerWithRay : IComparer<PolylinePoint> {
        Point pivot;

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

        internal Point IntersectionOfTheRayAndInsertedEdge {
            get { return pointOnTheRay; }
            set { pointOnTheRay = value; }
        }

        int IComparer<PolylinePoint>.Compare(PolylinePoint x, PolylinePoint y) {
            ValidateArg.IsNotNull(x, "x");
            ValidateArg.IsNotNull(y, "y");
            System.Diagnostics.Debug.Assert(IntersectionPointBelongsToTheInsertedEdge(x));
           
            switch (Point.GetTriangleOrientation( IntersectionOfTheRayAndInsertedEdge, y.Point, y.NextOnPolyline.Point)) {
                case TriangleOrientation.Counterclockwise:
                    return -1;
                default:
                    return 1;
            }
        }



        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Performance", "CA1811:AvoidUncalledPrivateCode")]
        private bool IntersectionPointBelongsToTheInsertedEdge(PolylinePoint x) {
            Point a = x.Point - IntersectionOfTheRayAndInsertedEdge;
            Point b = x.NextOnPolyline.Point - IntersectionOfTheRayAndInsertedEdge;
            return Math.Abs(a.X * b.Y - b.X * a.Y) < ApproximateComparer.DistanceEpsilon;
        }

        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2201:DoNotRaiseReservedExceptionTypes")]
        Point IntersectEdgeWithRay(Point source, Point target, Point ray) {
            //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);
            if (!(-ApproximateComparer.Tolerance <= x && x <= 1 + ApproximateComparer.Tolerance))
                throw new Exception();
            if (!result)
                throw new InvalidOperationException();

            return Pivot + y * ray;
        }

        internal Point IntersectEdgeWithRay(PolylinePoint side, Point ray){
            return IntersectEdgeWithRay(side.Point, side.NextOnPolyline.Point, ray);
        }


        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Performance", "CA1811:AvoidUncalledPrivateCode")]
        internal ActiveEdgeComparerWithRay(Point pivot, Point pointOnTheRay) {
            this.pivot = pivot;
            this.pointOnTheRay = pointOnTheRay;
        }

        internal ActiveEdgeComparerWithRay() {}
    }
}