using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace WindowsFormsApplication6
{
    public partial class Form1 : Form
    {
        public enum Direction
        { Up, Down, Left, Right };
        public Random rand = new Random();
        private int x, y, SnakeLength;
        private Direction direction;
        private bool FoodExists;
        Graphics g;
        Rectangle foodfield = new Rectangle();
        List<Rectangle> snake = new List<Rectangle>();

        public Form1()
        {
            InitializeComponent();
            direction = Direction.Down;
            snake.Add(new Rectangle(1, 0, 20, 20));
            snake.Add(new Rectangle(21, 0, 20, 20));
            snake.Add(new Rectangle(41, 0, 20, 20));
            SnakeLength = 3;
            g = CreateGraphics();
            DrawSnake();
        }

        private void Form1_KeyDown(object sender, KeyEventArgs e)
        {
            if(e.KeyCode==Keys.Down)
            {
                direction = Direction.Down;
            }
            if (e.KeyCode == Keys.Up)
            {
                direction = Direction.Up;
            }
            if (e.KeyCode == Keys.Right)
            {
                direction = Direction.Right;
            }
            if (e.KeyCode == Keys.Left)
            {
                direction = Direction.Left;
            }
        }

        private void timer1_Tick(object sender, EventArgs e)
        {
            Refresh();
            timer1.Enabled = false;
            switch (direction)
            {
                case (Direction.Down):
                    {
                        y = 20;
                        x = 0;
                        break;
                    }
                case (Direction.Up):
                    {
                        y = -20;
                        x = 0;
                        break;
                    }
                case (Direction.Right):
                    {
                        y = 0;
                        x = 20;
                        break;
                    }
                case (Direction.Left):
                    {
                        y = 0;
                        x = -20;
                        break;
                    }
            }
            Rectangle Prev = snake[0];
            Rectangle Next;
            for (int i = 0; i < snake.Count - 1; i++)
            {

                if (i == 0)
                {

                    snake[i] = new Rectangle(snake[i].X + x, snake[i].Y + y, 20, 20);
                }
                if (!(snake[i + 1].IsEmpty))
                {
                    Next = snake[i + 1];
                    snake[i + 1] = Prev;
                    Prev=Next;
                }
            }
            if (snake[0]==foodfield)
            {
                snake.Add(foodfield);
                SnakeLength++;
                FoodExists = false;
            }
            if ((snake[0].X < 0 || snake[0].X > 510 || snake[0].Y < 0 || snake[0].Y > 700) || EatItSelf())
            {
                MessageBox.Show("Игра закончена\n Длина змейки равна: " + SnakeLength.ToString());
                Close();
                return;
            }
            DrawSnake();
            timer1.Enabled = true;
        }
        private void DrawSnake()
        {
            for (int i = 0; i < snake.Count; i++)
            {
                if (i == 0)
                    g.FillRectangle(Brushes.Red, snake[i]);
                else
                    g.FillRectangle(Brushes.Gray, snake[i]);
                g.DrawRectangle(Pens.Green, snake[i]);
            }
        }
        private bool EatItSelf()
        {
            int count = 0;
            foreach (Rectangle a in snake)
                if (a == snake[0]) count++;
            if (count > 1 && foodfield != snake[0])
                return true;
            else
                return false;
        }
    }
}