using System;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Graphics;
using Microsoft.Xna.Framework.Input;

namespace SnakeMonoGame;

public class Game1 : Game
{
    private GraphicsDeviceManager _graphics;
    private SpriteBatch _spriteBatch;
    private KeyboardState _previousKeyboardState;
    private int w = 15;
    private int h = 15;
    private int scale;
    private int xoff;
    private bool paused = false;

    public Snake Snake;

    public Game1()
    {
        _graphics = new GraphicsDeviceManager(this);

        Content.RootDirectory = "Content";
        IsMouseVisible = true;
    }

    protected override void Initialize()
    {
        Window.Title = "SnakeMonoGame   -   Press Space to Pause   -   Esc to Quit";
        Snake = new Snake(w, h);

        scale = (int)Window.ClientBounds.Height / h;
        xoff = (int)(Window.ClientBounds.Width - (w * scale)) / 2;

        base.Initialize();
    }

    protected override void LoadContent()
    {
        _spriteBatch = new SpriteBatch(GraphicsDevice);
    }

    protected override void Update(GameTime gameTime)
    {
        Input();
        if (!paused) { Snake.Update(); }

        base.Update(gameTime);
    }

    protected override void Draw(GameTime gameTime)
    {
        Color DarkGray = new Color(0.2f, 0.2f, 0.2f);
        GraphicsDevice.Clear(Color.Black);

        _spriteBatch.Begin();
        Primitives2D.FillRectangle(_spriteBatch, new Rectangle(xoff + 0, 0, scale * w, scale * h), DarkGray);

        Primitives2D.FillRectangle(_spriteBatch, new Rectangle(xoff + Calc(Snake.Food.X), Calc(Snake.Food.Y), scale, scale), Color.DarkRed);
        Primitives2D.DrawRectangle(_spriteBatch, new Rectangle(xoff + Calc(Snake.Food.X), Calc(Snake.Food.Y), scale, scale), DarkGray, 2f);
        foreach (Point p in Snake.Segments)
        {
            Primitives2D.FillRectangle(_spriteBatch, new Rectangle(xoff + Calc(p.X), Calc(p.Y), scale, scale), Color.Gray);
            Primitives2D.DrawRectangle(_spriteBatch, new Rectangle(xoff + Calc(p.X), Calc(p.Y), scale, scale), DarkGray, 2f);
        }
        _spriteBatch.End();

        base.Draw(gameTime);
    }

    private void Input()
    {
        KeyboardState keyboardState = Keyboard.GetState();

        if (KeyPress(keyboardState, Keys.Escape)) { Exit(); }
        if (KeyPress(keyboardState, Keys.Space)) { paused = !paused; }

        if (!paused)
        {
            Snake.AddDirection(KeyPress(keyboardState, Keys.Up)    || KeyPress(keyboardState, Keys.W) ? "UpArrow"    : "");
            Snake.AddDirection(KeyPress(keyboardState, Keys.Down)  || KeyPress(keyboardState, Keys.S) ? "DownArrow"  : "");
            Snake.AddDirection(KeyPress(keyboardState, Keys.Left)  || KeyPress(keyboardState, Keys.A) ? "LeftArrow"  : "");
            Snake.AddDirection(KeyPress(keyboardState, Keys.Right) || KeyPress(keyboardState, Keys.D) ? "RightArrow" : "");
        }

        _previousKeyboardState = keyboardState;
    }

    private int Calc(int Value) { return Value * this.scale; }
    private bool KeyPress(KeyboardState keyboardState, Keys key) { return keyboardState.IsKeyDown(key) && _previousKeyboardState.IsKeyUp(key); }
}