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


public class TailingLine : MonoBehaviour
{
    [System.Serializable]
    public class LinePointInfo
    {
        public Vector3 pos;
        public Vector3 rotion;
        public Vector3 dir;
    }

    public AnimationCurve offQuanZhong;

    public float quanZhong=5;
    public float disStrength=0.5f;
    // public float addTime;
    public Transform rootTran;
    public int count;
    public float maxDis;
    private LineRenderer _lineRenderer;

    public List<LinePointInfo> _linePointInfo = new List<LinePointInfo>();

    protected float minDis;


    private void Awake()
    {
        _linePointInfo.Clear();
        _lineRenderer = GetComponent<LineRenderer>();
        Init();
    }

    private void Init()
    {
        minDis = maxDis / count;
        // Vector3 startPos = rootTran.position;
        Vector3 startRot = rootTran.rotation.eulerAngles;
        _lineRenderer.positionCount = count;
        for (int i = 0; i < count; i++)
        {
            LinePointInfo linePointInfo = new LinePointInfo();
            Vector3 pos = rootTran.transform.TransformPoint(new Vector3(0, 0, minDis * i * -1));
            linePointInfo.pos = pos;
            linePointInfo.rotion = startRot;
            linePointInfo.dir = rootTran.transform.forward;
            _lineRenderer.SetPosition(i, linePointInfo.pos);
            _linePointInfo.Add(linePointInfo);
        }
    }

    void Start()
    {
    }


    // Update is called once per frame
    void Update()
    {
        LinePointInfo linePointInfo = _linePointInfo[0];
        linePointInfo.pos = rootTran.position;
        linePointInfo.rotion = rootTran.rotation.eulerAngles;
        linePointInfo.dir = rootTran.transform.forward;
        _lineRenderer.SetPosition(0, linePointInfo.pos);
        // float at = (1 - addTime) / _linePointInfo.Count;

        int m = 2;
        int c = _linePointInfo.Count - m;
        float quanZhongWidget = 1.0f / c;
        for (int i = 1; i < _linePointInfo.Count; i++)
        {
            float w = i * 1.0f / _linePointInfo.Count;
            float at = offQuanZhong.Evaluate(w);
            if (at <= 0)
            {
                at = 0.01f;
            }

            LinePointInfo point = _linePointInfo[i];
            LinePointInfo lasetPoint = _linePointInfo[i - 1];
            Vector3 dir = lasetPoint.pos - point.pos;
            float md = dir.magnitude;
            if (md < minDis)
            {
                md = minDis;
            }
            else
            {
                md = Mathf.Lerp(md, minDis, at*disStrength);
            }

            if (m == i)
            {
                var sin = Mathf.Sin(Time.time);
                var cos = Mathf.Cos(Time.time);
                Quaternion quaternion = Quaternion.Euler(sin * quanZhong, cos * quanZhong, 0);
                dir = quaternion * dir;
            }

            Vector3 newDir = Vector3.Lerp(dir.normalized, lasetPoint.dir, at).normalized;
            point.pos = lasetPoint.pos + (newDir * (md * -1));
            point.dir = newDir;
            _lineRenderer.SetPosition(i, point.pos);
        }
    }
}