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

public class Snake : MonoBehaviour
{
    // Current Movement Direction
    // (by default it moves to the right)
    Vector2 dir = Vector2.right;

    List<Transform> tail = new List<Transform>();

    // Did the snake eat something?
    bool ate = false;

    // Tail Prefab
    public GameObject tailPrefab;

    public Action OnLose;

    // Use this for initialization
    void Start()
    {

        // Move the Snake every 300ms
        InvokeRepeating("Move", 0.3f, 0.3f);
    }

    void OnTriggerEnter2D(Collider2D coll)
    {
        // Food?
        if (coll.name.StartsWith("food"))
        {
            // Get longer in next Move call
            ate = true;

            // Remove the Food
            Destroy(coll.gameObject);
        }
        // Collided with Tail or Border
        else
        {
            OnLose();
        }
    }

    void Update()
    {
        // Move in a new Direction?
        if (Input.GetKey(KeyCode.RightArrow))
            dir = Vector2.right;
        else if (Input.GetKey(KeyCode.DownArrow))
            dir = -Vector2.up;    // '-up' means 'down'
        else if (Input.GetKey(KeyCode.LeftArrow))
            dir = -Vector2.right; // '-right' means 'left'
        else if (Input.GetKey(KeyCode.UpArrow))
            dir = Vector2.up;
    }

    void Move()
    {
        // Move head into new direction
        Vector2 v = transform.position;

        transform.Translate(dir);

        if (ate)
        {
            // Load Prefab into the world
            GameObject g = (GameObject)Instantiate(tailPrefab,
                                                  v,
                                                  Quaternion.identity);

            // Keep track of it in our tail list
            tail.Insert(0, g.transform);

            // Reset the flag
            ate = false;
        }
        // Do we have a Tail?
        else if (tail.Count > 0)
        {
            // Move last Tail Element to where the Head was
            tail.Last().position = v;

            // Add to front of list, remove from the back
            tail.Insert(0, tail.Last());
            tail.RemoveAt(tail.Count - 1);
        }
    }
}

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