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

public static class BezierCurve
{
    // 新增路径生成方法
    public static Vector3[] GenerateBezierPath(Vector3[] controlPoints, int segments = 20)
    {
        Vector3[] path = new Vector3[segments + 1];

        for (int i = 0; i <= segments; i++)
        {
            float t = i / (float)segments;
            switch (controlPoints.Length)
            {
                case 2:
                    path[i] = LineBezier(controlPoints[0], controlPoints[1], t);
                    break;
                case 3:
                    path[i] = QuadraticBezier(controlPoints, t);
                    break;
                case 4:
                    path[i] = CubicBezier(controlPoints, t);
                    break;
                default:  // 处理n阶情况
                    path[i] = BezierInterpolation(controlPoints, t);
                    break;
            }
        }

        return path;
    }

    // 一阶贝塞尔（线性插值）
    public static Vector3 LineBezier(Vector3 p0, Vector3 p1, float t)
    {
        return Vector3.Lerp(p0, p1, t);
    }

    // 二阶贝塞尔曲线
    public static Vector3 QuadraticBezier(Vector3[] points, float t)
    {
        if (points.Length != 3) Debug.LogError("需要3个控制点");

        float u = 1 - t;
        return
            u * u * points[0] +
            2 * u * t * points[1] +
            t * t * points[2];
    }

    // 三阶贝塞尔曲线
    public static Vector3 CubicBezier(Vector3[] points, float t)
    {
        if (points.Length != 4) Debug.LogError("需要4个控制点");

        float u = 1 - t;
        return
            u * u * u * points[0] +
            3 * u * u * t * points[1] +
            3 * u * t * t * points[2] +
            t * t * t * points[3];
    }
    
    // n阶贝塞尔曲线（通用实现）
    public static Vector3 BezierInterpolation(Vector3[] points, float t)
    {
        if (points.Length < 2)
        {
            Debug.LogError("至少需要2个控制点");
            return Vector3.zero;
        }
    
        Vector3[] temp = new Vector3[points.Length];
        points.CopyTo(temp, 0);
    
        // 德卡斯特里奥算法递推
        for (int k = 1; k < points.Length; k++)
        {
            for (int i = 0; i < points.Length - k; i++)
            {
                temp[i] = Vector3.Lerp(temp[i], temp[i + 1], t);
            }
        }
        return temp[0];
    }
}