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

public class LimitTrailRenderer : MonoBehaviour {

    [SerializeField]
    private float time = 1.0f;
    [SerializeField]
    private float length = 10.0f;

    [SerializeField]
    private LineRenderer[] lineRendererArray = default;

    private List<(float, Vector3)> worldList = new List<(float, Vector3)>();
    private List<Vector3> localList = new List<Vector3>();

    void OnEnable(){
        worldList.Clear();
    }

    void LateUpdate(){
        var deltaTime = Time.deltaTime;
        for(int i = 0; i < worldList.Count; ++i){
            var t = worldList[i];
            t.Item1 += deltaTime;
            worldList[i] = t;
        }
        worldList.Add((0.0f, transform.position));
        while(worldList.Count > 2 && worldList[1].Item1 > time){
            worldList.RemoveAt(0);
        }
        localList.Clear();
        var prev = transform.position;
        var totalLength = 0.0f;
        for(int i = worldList.Count - 1; i >= 0 && totalLength <= length * length; --i){
            var position = worldList[i].Item2;
            totalLength += (position - prev).MagnitudeNotSqrt();
            localList.Add(position);
        }
        if(localList.Count >= 2){
            var l = 0.0f;
            for(int i = 1; i < localList.Count - 1; ++i){
                l += (localList[i - 1] - localList[i]).magnitude;
            }
            if(l > length){
                localList[localList.Count - 1] = localList[localList.Count - 2] + (localList[localList.Count - 1] - localList[localList.Count - 2]) * (length - l) / (Mathf.Sqrt(totalLength) - l);
            }
        }
        var positions = localList.ToArray();
        foreach(var line in lineRendererArray){
            line.positionCount = positions.Length;
            line.SetPositions(positions);
        }
    }

    public void InsertPosition(Vector3 position, float deltaTime){
        worldList.Add((deltaTime, position));
    }

    public void AddPosition(Vector3 value){
        for(int i = 0; i < worldList.Count; ++i){
            var t = worldList[i];
            t.Item2 += value;
            worldList[i] = t;
        }
    }
}