using System.Collections.Generic;
using UnityEngine;

namespace Core.Utility
{
    /// <summary>
    /// 贝塞尔曲线
    /// </summary>
    public class BesselPath
    {
        public List<Vector3> PosList;

        private List<float> _time = new List<float>();

        public void SetPos(List<Vector3> PosList)
        {
            this.PosList = PosList;

            List<float> allbs = new List<float>();
            float allb = 0;
            for (int i = 0; i < PosList.Count; i += 3)
            {
                if (i + 3 > PosList.Count)
                {
                    break;
                }

                Vector3 p1 = PosList[i];
                Vector3 p2 = PosList[i + 1];
                Vector3 p3 = PosList[i + 2];
                float b = GetPathCount(p1, p2, p3, 100);
                allb += b;
                allbs.Add(b);
            }
            _time.Clear();
            float allt = 0;
            for (int i = 0; i < allbs.Count; i++)
            {
                float currt = allbs[i] / allb;
                allt+=currt;
                _time.Add(allt);
              
            }
        }

        private float GetPathCount(Vector3 p1, Vector3 p2, Vector3 p3, int count)
        {
            float step = 1f / count;
            Vector3 startPos = p1;
            float d = 0;
            for (int i = 1; i < count; i++)
            {
                float t = i * count;
                Vector3 a = Vector3.Lerp(p1, p2, t);
                Vector3 b = Vector3.Lerp(a, p3, t);
                d += Vector3.Distance(startPos, b);
                startPos = b;
            }


            return d;
        }

        public float GetPathCount(int count)
        {
            float step = 1f / count;
            Vector3 startPos = GetValue(0);
            float d = 0;
            for (int i = 1; i < count; i++)
            {
                Vector3 currPos = GetValue(step * i);
                d += Vector3.Distance(startPos, currPos);
            }

            return d;
        }

        public Vector3 GetValue(float t)
        {
            int startIndex = 0;
            float allt = 0;
            float startt = 0;
            
            for (int i = 0; i < _time.Count; i++)
            {
                if (t < _time[i])
                {
                    startIndex = i * 3;
                    allt = _time[i];
                    if (i > 0)
                    {
                        allt= _time[i] - _time[i - 1];
                        startt= _time[i - 1];
                    }

                    break;
                }
            }
            
            float t1 = (t - startt) / allt;
            if (t1 > 1)
            {
                t1 = 1;
            }
            if (t1 < 0)
            {
                t1 = 0;
            }
            
            
            Vector3 a = PosList[startIndex];
            Vector3 p2 = PosList[startIndex + 1];
            Vector3 p3 = PosList[startIndex + 2];
            Vector3 b = Vector3.Lerp(a, p2, t1);
            Vector3 c = Vector3.Lerp(b, p3, t1);

            return c;
        }
    }
}