using OpenTK.Mathematics;
using System.Windows.Forms;

namespace Yw.WinFrmUI.Hydro
{
    /// <summary>
    /// 射线
    /// </summary>
    internal class Ray3
    {
        /// <summary>
        /// 
        /// </summary>
        public Ray3() { }

        /// <summary>
        /// 
        /// </summary>
        public Ray3(Vector3 origin, Vector3 direction)
        {
            Origin = origin;
            Direction = direction.Normalized();//确保归一化
        }

        /// <summary>
        /// 原点
        /// </summary>
        public Vector3 Origin { get; set; }

        /// <summary>
        /// 方向
        /// </summary>
        public Vector3 Direction { get; set; }

        /// <summary>
        /// 检测射线是否与点相交（基于容差）
        /// </summary>
        /// <param name="point">目标点</param>
        /// <param name="epsilon">容差阈值（点与射线的最大允许距离 默认 0.01f）</param>
        /// <param name="maxDistance">最大有效距离（射线方向上的范围 默认 Float.MaxValue）</param>
        /// <param name="distance">输出相交距离</param>
        /// <returns>是否相交</returns>
        public bool IntersectsPoint
            (
                Vector3 point,
                float epsilon,
                float maxDistance,
                out float distance
            )
        {
            // 计算从起点到目标点的向量
            Vector3 originToPoint = point - Origin;

            // 计算点在射线方向上的投影长度（参数t）
            float t = Vector3.Dot(originToPoint, Direction);

            // 如果t为负数或超过最大距离，说明点在射线反方向或超出范围
            if (t < 0 || t > maxDistance)
            {
                distance = float.NaN;
                return false;
            }

            // 计算投影点位置
            Vector3 projectedPoint = Origin + Direction * t;

            // 计算实际点与投影点的距离（最短距离）
            float pointDistance = Vector3.Distance(point, projectedPoint);

            // 判断是否在容差范围内
            if (pointDistance <= epsilon)
            {
                distance = t; // 返回射线起点到投影点的距离（若Direction是单位向量，t即实际距离）
                return true;
            }

            distance = float.NaN;
            return false;
        }


        /// <summary>
        /// 检测射线是否与线段相交
        /// </summary>
        /// <param name="start">线段开始点</param>
        /// <param name="end">线段结束点</param>
        /// <param name="epsilon">误差（包含线段的半径）</param>
        /// <param name="maxDistance">射线方向的最大有效距离</param>
        /// <param name="distance">输出射线起点到交点的距离</param>
        /// <returns>是否相交</returns>
        public bool IntersectsLine
            (
                Vector3 segStart,
                Vector3 segEnd,
                float epsilon,
                float maxDistance,
                out float distance
            )
        {
            distance = float.MaxValue;
            Vector3 ab = segEnd - segStart;
            Vector3 ao = Origin - segStart;
            Vector3 n = Vector3.Cross(ab, Direction);
            float denom = n.Length * n.Length;

            if (Math.Abs(denom) < 1e-8)
            {
                return false;
            }

            Vector3 q = Vector3.Cross(ao, Direction);
            float s = Vector3.Dot(q, n) / denom;

            if (s < 0 || s > 1)
            {
                return false;
            }

            Vector3 closestPointOnSegment = segStart + Vector3.Multiply(ab, s);
            Vector3 v = closestPointOnSegment - Origin;
            float t = Vector3.Dot(v, Direction);

            if (t < 0)
            {
                return false;
            }

            Vector3 intersectionPoint = Origin + Vector3.Multiply(Direction, t);
            double distanceToSegment = (intersectionPoint - closestPointOnSegment).Length;

            if (distanceToSegment > epsilon)
            {
                return false;
            }

            distance = t;
            return true;
        }




    }
}