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 SnakeWinForm1b
{

    public struct Point
    { 
        public int x, y;
        public Point(int x, int y)
        {
            this.x = x;
            this.y = y;
        }
    }

    public partial class Form1 : Form
    {
        public enum Direction { Left, Right, Up, Down};

        int positionX = 0;
        int positionY = 0;
        int width = 16;
        int height = 16;
        int speed = 16;

        Direction direction = Direction.Right;

        Queue<Point> snake = new Queue<Point>();

        Point newHead, head;

        Point food;

        Random randomNumber = new Random();

        List<Point> obstacles = new List<Point>() { 
            new Point(20, 20),
            new Point(10, 20),
            new Point(20, 10)
        };

        bool gameRunning = true;
        public Form1()
        {
            InitializeComponent();

            for (int i = 0; i < 5; i++) {
                snake.Enqueue(new Point(i, 0));
            }

            food = new Point(
                randomNumber.Next(0, pbGame.Size.Width / speed),
                randomNumber.Next(0, pbGame.Size.Height / speed));

            timer1.Interval = 100;
            timer1.Tick += UpdateScreen;
            timer1.Start();
        }

        private void UpdateScreen(object sender, EventArgs e)
        {
            if (gameRunning)
            {
                pbGame.Invalidate();
            }
            else 
            {
                lblGamaeOver.Text = "Game Over! Press Esc to exit!";
                lblGamaeOver.Visible = true;
            }
        }

        private void pbGame_Paint(object sender, PaintEventArgs e)
        {
            Graphics canvas = e.Graphics;

            Point segment;

            head = snake.Last();

            switch (direction) { 
                case Direction.Right :
                    // if (positionX >= pbGame.Size.Width / speed) positionX = 0;
                    // else positionX++;
                    if (head.x >= pbGame.Size.Width / speed) newHead = new Point(0, head.y);
                    else newHead = new Point(head.x + 1, head.y);
                    break;
                case Direction.Left:
                    // if (positionX <= 0) positionX = pbGame.Size.Width / speed;
                    // else positionX--;
                    if (head.x <= 0) newHead = new Point(pbGame.Size.Width / speed, head.y);
                    else newHead = new Point(head.x - 1, head.y);
                    break;
                case Direction.Up:
                    // if (positionY <= 0) positionY = pbGame.Size.Height / speed;
                    // else positionY--;
                    if (head.y <= 0) newHead = new Point(head.x, pbGame.Size.Height / speed);
                    else newHead = new Point(head.x, head.y - 1);
                    break;
                case Direction.Down:
                    // if (positionY >= pbGame.Size.Height / speed) positionY = 0;
                    // else positionY++;
                    if (head.y >= pbGame.Size.Height / speed) newHead = new Point(head.x, 0);
                    else newHead = new Point(head.x, head.y + 1);
                    break;
            }

            snake.Enqueue(newHead);

            // obstacle collision
            if (obstacles.Contains(newHead)) gameRunning = false;

            // food collision
            if (newHead.x == food.x && newHead.y == food.y)
            {
                // generate new food
                do{
                    food = new Point(
                        randomNumber.Next(0, pbGame.Size.Width / speed),
                        randomNumber.Next(0, pbGame.Size.Height / speed));
                } while(snake.Contains(food));
            }
            else 
            {
                snake.Dequeue();
            }

            // render obstacles
            foreach (Point obstacle in obstacles) {
                canvas.FillEllipse(Brushes.Blue,
                    new Rectangle(obstacle.x * speed, obstacle.y * speed, width, height));                
            }

            // render food
            canvas.FillEllipse(Brushes.Green,
                new Rectangle(food.x * speed, food.y * speed, width, height));

            // render snake
            for (int i = 0; i < snake.Count; i++)
            {
                segment = snake.ElementAt(i);

                if (i == snake.Count - 1)
                {
                    canvas.FillEllipse(Brushes.Black,
                        new Rectangle(segment.x * speed, segment.y * speed, width, height));
                }
                else 
                {
                    canvas.FillEllipse(Brushes.Red,
                        new Rectangle(segment.x * speed, segment.y * speed, width, height));
                }
            }

            // canvas.FillEllipse(Brushes.Red,
            //    new Rectangle(positionX * speed, positionY * speed, width, height));
        }

        private void Form1_KeyDown(object sender, KeyEventArgs e)
        {
            switch (e.KeyCode)
            {
                case Keys.Right:
                    // positionX++;
                    direction = Direction.Right;
                    break;
                case Keys.Left:
                    // positionX--;
                    direction = Direction.Left;
                    break;
                case Keys.Up:
                    // positionY--;
                    direction = Direction.Up;
                    break;
                case Keys.Down:
                    // positionY++;
                    direction = Direction.Down;
                    break;
                case Keys.Escape:
                    Application.Exit();
                    break;
            }
        }
    }
}