aistudio-wpf-diagram/AIStudio.Wpf.DiagramDesigner/Geometrys/LineBase.cs

namespace AIStudio.Wpf.DiagramDesigner.Geometrys
{
    public struct LineBase
    {
        public LineBase(PointBase start, PointBase end)
        {
            Start = start;
            End = end;
        }

        public PointBase Start { get; }
        public PointBase End { get; }

        public PointBase? GetIntersection(LineBase line)
        {
            var pt1Dir = new PointBase(End.X - Start.X, End.Y - Start.Y);
            var pt2Dir = new PointBase(line.End.X - line.Start.X, line.End.Y - line.Start.Y);
            var det = (pt1Dir.X * pt2Dir.Y) - (pt1Dir.Y * pt2Dir.X);
            var deltaPt = new PointBase(line.Start.X - Start.X, line.Start.Y - Start.Y);
            var alpha = (deltaPt.X * pt2Dir.Y) - (deltaPt.Y * pt2Dir.X);
            var beta = (deltaPt.X * pt1Dir.Y) - (deltaPt.Y * pt1Dir.X);

            if (det == 0 || alpha * det < 0 || beta * det < 0)
                return null;

            if (det > 0)
            {
                if (alpha > det || beta > det)
                    return null;

            }
            else
            {
                if (alpha < det || beta < det)
                    return null;
            }

            return new PointBase(Start.X + (alpha * pt1Dir.X / det), Start.Y + (alpha * pt1Dir.Y / det));
        }

        public override string ToString() => $"Line from {Start} to {End}";
    }
}