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


public class GameManager : MonoBehaviour
{
 List<Transform> bodyList = new List<Transform>();//身體位置的列表
 private float speed = 2f;//移動速度
 public GameObject bodyObj;//用來生成的身體對象
 List<Transform> bodyCreatePostion = new List<Transform>();//身體部分的transfrom 列表
 private float TransOffset=1f;//位置間隔
 private List<Vector2> mapAddress=new List<Vector2>();//前進目標在地圖上的位置，
 public Transform firstBody;//第一個身體部件的transfrom
 const int row = 100;//地圖寬
 const int col = 100;//地圖高
 int step=1;//步伐
 int x=0, z=0;//記錄x和z軸的移動量

 // Start is called before the first frame update
 public Vector3[,] map = new Vector3[row, col];//地圖
 // Start is called before the first frame update
 void Start()
 {
  
  for (int i = 0; i < row; i++)//生成地圖
  {
   for (int j = 0; j < col; j++)
   {
    map[i, j] = new Vector3(i, 1.5f, j);
   }
  }
  transform.position =map[0,0];將當前位置設為原點
  mapAddress.Add(new Vector2(1,0));//增加第一個目標
  bodyList.Add(transform);//刷新第一個頭和一個身體的transform
  bodyList.Add(firstBody);
  mapAddress.Add(new Vector2(0,0));
 }

 // Update is called once per frame
 void Update()
 {
  for (int i = 0; i < row - 1; i++)
  {
   for (int j = 0; j < col - 1; j++)//繪制地圖格子
   {
    Debug.DrawLine(map[i, j], map[i + 1, j], Color.red);
    Debug.DrawLine(map[i, j], map[i, j + 1], Color.red);
   }
  }
  if (Input.anyKeyDown)//有任何鍵按下
  {
   if (Input.GetKeyDown(KeyCode.W) && z != -step)//上
   {
    z = step;
    x = 0;


   }
   if (Input.GetKeyDown(KeyCode.S) && z != step)//下
   {
    z = -step;
    x = 0;
    
   
   }
   if (Input.GetKeyDown(KeyCode.A) && x != step)//左
   {
    x = -step;
    z = 0;

   
   }
   if (Input.GetKeyDown(KeyCode.D) && x != -step)//右
   {
    x = step;
    z = 0;
   
    
   }
   

  }
  Move();


 }
 private void Move()//移動
 {


  if (Vector3.Distance(bodyList[0].position, map[(int)mapAddress[0].x + x, (int)mapAddress[0].y + z]) < 0.7f)//當前坐標和目標位置的距離小于0.5f
  {
   
   for (int i = mapAddress.Count - 1; i > 0; i--)//刷新后一個的目標為前一個的目標
   {
    mapAddress[i] = mapAddress[i-1];
   }
   
   mapAddress[0] = new Vector2(mapAddress[0].x + x, mapAddress[0].y + z);//刷新第一個目標的位置

  }
  else
  {
   for (int i = bodyList.Count - 1; i > 0; i--)//移動
   {
    bodyList[i].position = Vector3.MoveTowards(bodyList[i].position,
              map[(int)mapAddress[i - 1].x, (int)mapAddress[i - 1].y], Time.deltaTime * speed);

   }
   bodyList[0].position = Vector3.MoveTowards(transform.position,
             map[(int)mapAddress[0].x + x, (int)mapAddress[0].y + z], Time.deltaTime * speed);
  }
 }

 private void OnCollisionEnter(Collision collision)//碰撞到了食物就增加身體長度
 {

  if (collision.collider.tag == "Food")
  {
   
   Destroy(collision.collider.gameObject);
   GameObject tmpGameObject=new GameObject();
   Vector2 tmpVec = new Vector2();
   
   tmpGameObject = Instantiate(bodyObj, map[(int)mapAddress[mapAddress.Count - 1].x+x, (int)mapAddress[mapAddress.Count - 1].y +z], Quaternion.identity);//生成body物體
   tmpVec = new Vector2(mapAddress[mapAddress.Count - 1].x+x, mapAddress[mapAddress.Count - 1].y +z);
   //增加身體的transform和目標向量
   bodyList.Add(tmpGameObject.transform);
   mapAddress.Add(tmpVec);
  }
  
 }
}