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

class GAME : Game
{
    class SPRITE
    {
        public Vector2 pos;
        public Texture2D tex;
        public bool colliding(SPRITE other)
        { 
            Rectangle this_rect = new Rectangle(
                (int)this.pos.X, (int)this.pos.Y, this.tex.Width, this.tex.Height);
            Rectangle other_rect = new Rectangle(
                (int)other.pos.X, (int)other.pos.Y, other.tex.Width, other.tex.Height);
            return this_rect.Intersects(other_rect);
        }
        public virtual void update() { }
        public virtual void collide(SPRITE other) { }
        public void draw(SpriteBatch sprite_batch) { sprite_batch.Draw(tex, pos, Color.White); }
    }
    class PLAYER : SPRITE
    {
        public PLAYER() { tex = player_tex; }
        public override void update()
        {
            float speed = 10;
            if (keyboard.IsKeyDown(Keys.Up)) this.pos.Y -= speed;
            if (keyboard.IsKeyDown(Keys.Down)) this.pos.Y += speed;
            if (keyboard.IsKeyDown(Keys.Left)) this.pos.X -= speed;
            if (keyboard.IsKeyDown(Keys.Right)) this.pos.X += speed;
            if (keyboard.IsKeyDown(Keys.Space) &&
                !last_keyboard.IsKeyDown(Keys.Space))
            {
                BULLET bullet = new BULLET();
                bullet.pos = this.pos + new Vector2(50, 0);
                sprites.Add(bullet);
            }
        }
    }
    class BULLET : SPRITE
    {
        public BULLET() { tex = bullet_tex; }
        public override void update() { this.pos.X += 20; }
        public override void collide(SPRITE enemy) // SPRITE waaa
        {
            if (enemy.GetType() != typeof(ENEMY)) return; // waaa
            enemy.tex = explosion_tex;
        }
    }
    class ENEMY : SPRITE
    {
        public ENEMY() { tex = enemy_tex; }
        public override void collide(SPRITE player) // SPRITE waaa
        {
            if (player.GetType() != typeof(PLAYER)) return; // waaa
            player.tex = explosion_tex; 
        }
    }
    static Texture2D player_tex, bullet_tex, enemy_tex, explosion_tex;
    static List<SPRITE> sprites = new List<SPRITE>();
    static Random random = new Random();
    static KeyboardState keyboard, last_keyboard;
    static void Main() { new GAME().Run(); }
    GAME()
    {
        GraphicsDeviceManager graphics = new GraphicsDeviceManager(this);
        graphics.PreferredBackBufferWidth = 1280;
        graphics.PreferredBackBufferHeight = 720;
        graphics.ApplyChanges();
        IsMouseVisible = true;
    }
    protected override void LoadContent()
    {
        player_tex = Texture2D.FromFile(GraphicsDevice, "player.png");
        bullet_tex = Texture2D.FromFile(GraphicsDevice, "bullet.png");
        enemy_tex = Texture2D.FromFile(GraphicsDevice, "enemy.png");
        explosion_tex = Texture2D.FromFile(GraphicsDevice, "explosion.png");
        for (int i = 0; i < 10; i++)
        {
            ENEMY enemy = new ENEMY();
            enemy.pos = new Vector2(random.Next(600, 1200), random.Next(720));
            sprites.Add(enemy);
        }
        PLAYER player = new PLAYER();
        player.pos = new Vector2(100, 360);
        sprites.Add(player);
        base.LoadContent();
    }
    protected override void Update(GameTime gameTime)
    {
        last_keyboard = keyboard; keyboard = Keyboard.GetState();
        for (int i = 0; i < sprites.Count; i++)
            sprites[i].update();
        for (int i = 0; i < sprites.Count; i++)
            for (int j = i + 1; j < sprites.Count; j++)
                if (sprites[i].colliding(sprites[j]))
                {
                    sprites[i].collide(sprites[j]); // how do i make these two lines trigger 
                    sprites[j].collide(sprites[i]); // the derived classes' ver instead of SPRITE?
                }
        base.Update(gameTime);
    }
    protected override void Draw(GameTime gameTime)
    {
        GraphicsDevice.Clear(Color.CornflowerBlue);
        SpriteBatch sprite_batch = new SpriteBatch(GraphicsDevice);
        sprite_batch.Begin();
        for (int i = 0; i < sprites.Count; i++)
            sprites[i].draw(sprite_batch);
        sprite_batch.End();
        base.Draw(gameTime);
    }
}