using System.Collections.Generic;
using UnityEngine;

public class Game : MonoBehaviour
{
    public float speed;
    public float updateTimer; //Timer interval at which snake position is updated
    char direction; //[U]p, [D]own, [R]ight, [L]eft]

    public GameObject food;
    public GameObject part;
    List<GameObject> snake;

    void Start ()
    {
        direction = 'R';

        snake = new List<GameObject>();
        part = Instantiate(part, new Vector3(0, 0, 0), part.transform.rotation, gameObject.transform);
        snake.Add(part);

        SpawnFood();
        InvokeRepeating("Move", 0, 0.1f);
    }

	void Update ()
    {
        GetInput();

        if (Mathf.Abs(snake[0].transform.position.x - food.transform.position.x) < 1
            && Mathf.Abs(snake[0].transform.position.y - food.transform.position.y) < 1)
                Eat();


        Die();
    }

    void Move()
    {
        Vector2 nextPos = new Vector2();

        switch (direction)
        {
            case 'U':
                nextPos = new Vector2(snake[0].transform.position.x, snake[0].transform.position.y + 1);
                break;
            case 'R':
                nextPos = new Vector2(snake[0].transform.position.x + 1, snake[0].transform.position.y);
                break;
            case 'D':
                nextPos = new Vector2(snake[0].transform.position.x, snake[0].transform.position.y - 1);
                break;
            case 'L':
                nextPos = new Vector2(snake[0].transform.position.x - 1, snake[0].transform.position.y);
                break;
        }

        for (int i = snake.Count - 1; i > 0; i--)
            snake[i].transform.position = snake[i - 1].transform.position;

        snake[0].transform.position = nextPos;
    }

    void GetInput()
    {
        if (Input.GetKeyDown(KeyCode.D) && direction != 'L')
            direction = 'R';
        if (Input.GetKeyDown(KeyCode.A) && direction != 'R')
            direction = 'L';
        if (Input.GetKeyDown(KeyCode.W) && direction != 'D')
            direction = 'U';
        if (Input.GetKeyDown(KeyCode.S) && direction != 'U')
            direction = 'D';
    }

    void Eat()
    {

        snake.Add(Instantiate(part, transform));
        SpawnFood();
    }

    void SpawnFood()
    {
        food.transform.position = new Vector3(Random.Range(-20, 20), Random.Range(-11, 12), food.transform.position.z);
    }

    void Die()
    {
        //Borders
        if (snake[0].transform.position.x < -21.5f ||
            snake[0].transform.position.x > 21.5 ||
            snake[0].transform.position.y < -12 ||
            snake[0].transform.position.y > 12)
                Destroy(gameObject);
    }
}