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

namespace BF
{
    public class DrawBezierLine : MonoBehaviour
    {
        public LineRenderer lineRender;
        private Vector3 _startPoint = Vector3.zero;
        private Vector3 _endPoint = Vector3.zero;
        private Vector3 _controlPoint1 = Vector3.zero;
        private Vector3 _controlPoint2 = Vector3.zero;
        // 曲线上的路径点数量，值越大，取得的路径点越多，曲线越平滑
        private int drawPointCount = 30;
        private bool isDraw = false;
        private bool useCubicBezier = true;
        public void SetStartPoint(float x, float y, float z)
        {
            _startPoint = new Vector3(x, y, z);
        }

        public void SetEndPoint(float x, float y, float z)
        {
            _endPoint = new Vector3(x, y, z);
        }

        public void SetControlPoint1(float x, float y, float z)
        {
            _controlPoint1 = new Vector3(x, y, z);
        }

        public void SetControlPoint2(float x, float y, float z)
        {
            _controlPoint2 = new Vector3(x, y, z);
        }

        public void SetDrawPointCount(int count)
        {
            drawPointCount = count;
        }

        public void DrawLine()
        {
            isDraw = true;
        }

        public void ClearLine()
        {
            isDraw = false;
            lineRender.positionCount = 0;
        }

        public Vector3[] GetPathList()
        {
            Vector3[] positions = new Vector3[lineRender.positionCount];
            lineRender.GetPositions(positions);
            return positions;
        }

        public void SetUseCubicBezier(bool use)
        {
            useCubicBezier = use;
        }

        void Update()
        {
            if (!isDraw)
            {
                return;
            }
            isDraw = false;
            if (drawPointCount <= 0)
            {
                return;
            }
            lineRender.positionCount = drawPointCount;
            lineRender.SetPosition(0, _startPoint);
            for (int i = 1; i < drawPointCount; i++)
            {
                var t = (i + 1) / (float)drawPointCount;
                if (useCubicBezier)
                {
                    var pathPoint = GetPointInCubicBezierCurve(t, _startPoint, _controlPoint1, _controlPoint2, _endPoint);//使用贝塞尔曲线的公式取得t时的路径点
                    lineRender.SetPosition(i, pathPoint);
                }
                else
                {
                    var pathPoint = GetBezierPoint(t, _startPoint, _controlPoint1, _endPoint);//使用贝塞尔曲线的公式取得t时的路径点
                    lineRender.SetPosition(i, pathPoint);
                }
            }
        }

        /// <param name="t">0到1的值，0获取曲线的起点，1获得曲线的终点</param>
        /// <param name="start">曲线的起始位置</param>
        /// <param name="center">决定曲线形状的控制点</param>
        /// <param name="end">曲线的终点</param>
        public static Vector3 GetBezierPoint(float t, Vector3 start, Vector3 controlPoint, Vector3 end)
        {
            return (1 - t) * (1 - t) * start + 2 * t * (1 - t) * controlPoint + t * t * end;
        }

        public Vector3 GetPointInCubicBezierCurve(float t, Vector3 startPoint, Vector3 controlPoint1, Vector3 controlPoint2, Vector3 endPoint)
        {
            var A = startPoint * (Mathf.Pow(-t, 3) + 3 * Mathf.Pow(t, 2) - 3 * t + 1);
            var B = controlPoint1 * (3 * Mathf.Pow(t, 3) - 6 * Mathf.Pow(t, 2) + 3 * t);
            var C = controlPoint2 * (-3 * Mathf.Pow(t, 3) + 3 * Mathf.Pow(t, 2));
            var D = endPoint * (Mathf.Pow(t, 3));
            return A + B + C + D;
        }
    }
}