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

public class Snake : MonoBehaviour
{
    [Header("Movement Keys")]
    [SerializeField] private KeyCode upKey = KeyCode.W;
    [SerializeField] private KeyCode downKey = KeyCode.S;
    [SerializeField] private KeyCode leftKey = KeyCode.A;
    [SerializeField] private KeyCode rightKey = KeyCode.D;
    [Header("Snake Head")]
    [SerializeField] private Segment.Direction headDirection;
    [Header("Snake Segments")]
    [SerializeField] private Transform snakeSegmentPrefab;
    [SerializeField] private int initialSize = 4;

    private Vector3Int spawnPoint;
    private Vector2 direction = Vector2.right;
    private readonly List<Transform> segments = new List<Transform>();
    private bool moved = true;
    private bool alive = true;

    #region GETTERS
    public Vector2 GetDirection() => direction;
    public List<Transform> GetSegments() => segments;
    public bool Moved() => moved;
    public bool isAlive() => alive;
    #endregion

    private void Awake()
    {
        spawnPoint = new Vector3Int((int)transform.position.x, (int)transform.position.y, 0);
        ResetState();
    }

    private void Update()
    {
        HandleInputs();
    }

    private void FixedUpdate()
    {
        if (!alive) return;

        HandleMovement();
    }

    private void HandleInputs()
    {
        if (!moved) return;

        if (Input.GetKeyDown(upKey) && direction != Vector2.down)
        {
            direction = Vector2.up;
            moved = false;
        }
        else if (Input.GetKeyDown(downKey) && direction != Vector2.up)
        {
            direction = Vector2.down;
            moved = false;
        }
        else if (Input.GetKeyDown(leftKey) && direction != Vector2.right)
        {
            direction = Vector2.left;
            moved = false;
        }
        else if (Input.GetKeyDown(rightKey) && direction != Vector2.left)
        {
            direction = Vector2.right;
            moved = false;
        }
    }

    private void HandleMovement()
    {
        MoveSegments();
        transform.position += (Vector3)direction;
        moved = true;
    }



    public void Grow()
    {
        Transform segment = Instantiate(snakeSegmentPrefab);
        if (segments.Count >= initialSize)
        {
            segment.position = segments[segments.Count - 1].position;
        }
        else
        {
            segment.position = segments[segments.Count - 1].position -

            (Vector3)direction;
        }
        segments.Add(segment);
    }

    private void OnTriggerEnter2D(Collider2D other)
    {
        if (other.CompareTag("Obstacle") || other.CompareTag("Snake"))
        {
            alive = false;
        }
    }

    public  void ResetState()
    {
        for (int i = 1; i < segments.Count; i++)
        {
            Destroy(segments[i].gameObject);
        }

        direction = Segment.DirectionToVector[headDirection];

        segments.Clear();
        segments.Add(transform);
        transform.position = spawnPoint;
        for (int i = 1; i < initialSize; i++)
        {
            Grow();
        }

        alive = true;
        moved = true;
    }

    private void MoveSegments()
    {
        for (int i = segments.Count - 1; i > 0; i--)
        {
            segments[i].position = segments[i - 1].position;
        }
    }
}