using System.Collections;
using System.Collections.Generic;
using System.Linq;
using UnityEngine;

public class PlanoConvexLens : OpticalSurface2D
{
    public float LensRadius = 1.0f;
    public float CurveRadius = 1.0f;
    public int SamplesCount = 10;
    public float Height = 0.1f;

    // Start is called before the first frame update
    void Start()
    {
        
    }

    // Update is called once per frame
    void Update()
    {
        
    }

    private RaycastMath.RaycastResult2D[] _raycasts;

    public override bool Raycast(Ray2D ray, ref RaycastMath.RaycastResult2D result) {
        if(_raycasts == null) {
            _raycasts = new RaycastMath.RaycastResult2D[4];
        }

        var localSpaceRay = ray;
        localSpaceRay.origin = transform.InverseTransformPoint(localSpaceRay.origin);
        localSpaceRay.direction = transform.InverseTransformVector(localSpaceRay.direction).normalized;

        //cs = as + bs
        //bs = cs - as


        float h = Mathf.Sqrt(CurveRadius * CurveRadius - LensRadius * LensRadius);


        var sphereCastRay = localSpaceRay;
        sphereCastRay.origin += Vector2.up *  (Mathf.Sign(CurveRadius) * h - Height);

        int raycastsCount = 0;

        bool curveIntersected = RaycastMath.RaycastCircle(sphereCastRay, Mathf.Abs( CurveRadius), ref _raycasts[raycastsCount]);
        if (curveIntersected) {
            _raycasts[raycastsCount].Point += Vector2.down * Mathf.Sign(CurveRadius) * (h);

            if(CurveRadius >= 0) {
                if (_raycasts[raycastsCount].Point.y < 0) {
                    curveIntersected = false;
                } else {
                    _raycasts[raycastsCount].Point += Vector2.up * Height;
                    raycastsCount++;
                }
            } else {
                if (_raycasts[raycastsCount].Point.y > 0) {
                    curveIntersected = false;
                } else {
                    _raycasts[raycastsCount].Point += Vector2.up * Height;
                    _raycasts[raycastsCount].Normal = -_raycasts[raycastsCount].Normal;
                    raycastsCount++;
                }
            }
           
        }


        Vector2 leftHitPoint = Vector2.zero;
        if(Height > 0.0f && RaycastMath.RayLineSegmentIntersection(localSpaceRay.origin, localSpaceRay.direction, new Vector2(-LensRadius, 0), new Vector2(-LensRadius, Height), ref leftHitPoint)) {
            _raycasts[raycastsCount].Normal = Vector2.left;
            _raycasts[raycastsCount].Point = leftHitPoint;
            raycastsCount++;
        }

        Vector2 rightHitPoint = Vector2.zero;
        if(Height > 0.0f && RaycastMath.RayLineSegmentIntersection(localSpaceRay.origin, localSpaceRay.direction, new Vector2(LensRadius, 0), new Vector2(LensRadius, Height), ref rightHitPoint)) {
            _raycasts[raycastsCount].Normal = Vector2.right;
            _raycasts[raycastsCount].Point = rightHitPoint;
            raycastsCount++;
        }

        Vector2 bottomHitPoint = Vector2.zero;
        if(LensRadius > 0.0f && RaycastMath.RayLineSegmentIntersection(localSpaceRay.origin, localSpaceRay.direction, new Vector2(-LensRadius, 0), new Vector2(LensRadius, 0), ref bottomHitPoint)) {
            _raycasts[raycastsCount].Normal = Vector2.down;
            _raycasts[raycastsCount].Point = bottomHitPoint;
            raycastsCount++;
        }


        if(raycastsCount == 0) {
            return false;
        }

        result = _raycasts.Take(raycastsCount).OrderBy(x => Vector2.Distance(x.Point, localSpaceRay.origin)).First();

        result.Point = transform.TransformPoint(result.Point);
        result.Normal = transform.InverseTransformVector(result.Normal).normalized;

        return true;
    }

    private void OnValidate() {

        if(CurveRadius > 0 && CurveRadius < LensRadius) {
            CurveRadius = LensRadius;   
        }

        if (CurveRadius < 0 && CurveRadius > -LensRadius) {
            CurveRadius = -LensRadius;
        }

        var points = RadialCurve(LensRadius, CurveRadius, SamplesCount);
        if(points.Length < 2) {
            return;
        }

        Shape = new Line[points.Length - 1 + 3];

        for(int i = 0; i < points.Length - 1; i++) {
            Shape[i] = new Line() { P1 = points[i] + Vector2.up * Height, P2 = points[i + 1] + Vector2.up * Height };
        }

        Vector2 p1 = new Vector2(-LensRadius, Height);
        Vector2 p2 = new Vector2(-LensRadius, 0);
        Vector2 p3 = new Vector2(LensRadius, 0);
        Vector2 p4 = new Vector2(LensRadius, Height);

        Shape[Shape.Length - 3] = new Line() { P1 = p1, P2 = p2 };
        Shape[Shape.Length - 2] = new Line() { P1 = p2, P2 = p3 };
        Shape[Shape.Length - 1] = new Line() { P1 = p3, P2 = p4 };
    }


    public static Vector2[] RadialCurve(float lenseRadius, float curveRadius, int samplesCount) {


        //r*r = x*x + h*h
        //h*h = r*r - x*x

        Vector2[] result = new Vector2[samplesCount];

        float h = Mathf.Sqrt(curveRadius * curveRadius - lenseRadius * lenseRadius);

        float dx = (-2.0f * lenseRadius) / (samplesCount - 1);

        for (int i = 0; i < samplesCount; i++) {
            float x2 = lenseRadius + dx * i;
            float h2 = Mathf.Sqrt(curveRadius * curveRadius - x2 * x2);

         
            result[i] = new Vector2(x2, Mathf.Sign(curveRadius) *  (h2 - h));
       
            
        }

        return result;
    }
}