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

public class SnakeController : MonoBehaviour
{
    public float movingInterval = 0.2f;
    public Vector2 curDirection = Vector3.right;
    public List<Vector2> tail = new List<Vector2>();
    public List<Transform> snakePieces = new List<Transform>();
    public GameObject snakePiecePrefab;
    public int startingLength = 3;

    public Vector2 fieldSize= new Vector2(160,90);
    float moveTimer;

    float topEdge => transform.position.y + fieldSize.y /2f;
    float botEdge => transform.position.y -fieldSize.y /2f;
    float leftEdge =>transform.position.x-fieldSize.x/2f;
    float rightEdge => transform.position.x + fieldSize.x/2f;
    

    void Start(){
        tail = new List<Vector2>();
        for(int i=0; i < startingLength; i++){
            Vector3 pos = (Vector2)transform.position-(Vector2.right * i); 
            tail.Add(pos);
            GameObject newPiece = Instantiate(snakePiecePrefab,pos, Quaternion.identity );
            snakePieces.Add(newPiece.transform);
        }
    }

    void Update()
    {
        Move();
        
        if(Input.GetKeyDown(KeyCode.RightArrow)){            
            ChangeDir(Vector2.right);
        }else if(Input.GetKeyDown(KeyCode.LeftArrow)){
            ChangeDir(-Vector2.right);
        }else if(Input.GetKeyDown(KeyCode.UpArrow)){
            ChangeDir(Vector2.up);
        }else if(Input.GetKeyDown(KeyCode.DownArrow)){
            ChangeDir(-Vector2.up);
        }

        if(Input.GetKeyDown(KeyCode.Space)){
            queueNewPiece=true;
        }
    }

    void ChangeDir(Vector2 newDir){
        if(curDirection == -newDir){
            return;
        }

        curDirection = newDir;
    }

    bool queueNewPiece = false;

    void Move(){
        if(moveTimer > 0){
            moveTimer-=Time.deltaTime;
        }else{
            moveTimer = movingInterval;
            Vector2 curPosition = tail[0];
            Vector2 lastPosition = tail[tail.Count-1];

            for(int i=tail.Count-1; i>0; i--){
                tail[i] = tail[i-1];
                snakePieces[i].position = tail[i];
            }

            if(queueNewPiece){
                tail.Add(lastPosition);
                GameObject newPiece = Instantiate(snakePiecePrefab,lastPosition, Quaternion.identity );
                snakePieces.Add(newPiece.transform);

                queueNewPiece=false;
            }

            tail[0] = curPosition + curDirection;
            
            if(tail[0].x > rightEdge){
                tail[0]= new Vector2(leftEdge,tail[0].y);
            }else if(tail[0].x <leftEdge){
                tail[0]= new Vector2(rightEdge,tail[0].y);
            }

            

            if(tail[0].y > topEdge){
                tail[0] = new Vector2(tail[0].x, botEdge);
            }else if(tail[0].y < botEdge){
                tail[0] = new Vector2(tail[0].x, topEdge);
            }
            snakePieces[0].position = tail[0];
        }
    }
    
    private void OnDrawGizmos() {
        Gizmos.DrawWireCube(transform.position, new Vector3(fieldSize.x,fieldSize.y));
    }

}