// -------- Demo object oriented design ----------

// Try to rely as litle as possible on the global space, i will turn messy quick
Scene ActiveScene;


// used for setting up the staring logic of the game
void setup(){
    ActiveScene = new SpaceScene();
}

// the game loop
void draw(){
    ActiveScene.Update();
    ActiveScene.Draw();
}

// base class for all scenes
public abstract class Scene{

    // when a scene gets constructed, it will request the assets to be loaded
    public Scene(){
        LoadAssets();
    }

    // the shell of a function responsible for loading assets into the scene.
    protected abstract void LoadAssets();
    // the shell of a function responsible for updating all objects in the scene
    public abstract void Update();
    // the shell of a function responsible for drawing all objects in the scene
    public abstract void Draw();
}

public class SpaceScene{
    private PImage _asteroidImage;
    private Asteroid _asteroid;

    // construct the space scene
    public SpaceScene(){
        super();

        _asteroid = new Asteroid(_asteroidImage,200,200,10,10);
    }

    // load al the assets in the space scene
    protected void LoadAssets(){
        _asteroidImage = loadImage("asteroid.png");
    }

    // update all logic related to the space scene
    public void Update(){
        _asteroid.Update();
    }

    // draw all objects in the space scene
    public void Draw(){
        // draw the background of the scene to prevent ghosting
        background(0);

        _asteroid.Draw();
    }
}


// base class for all game objects
public abstract class GameObject{

    // the current location of the game object
    public PVector Position;
    public PVector Size;

    // the sprite of the gameobject
    protected PImage _sprite;

    // constructors for the base class
    public GameObject(PImage sprite, PVector position, PVector size){
        Position = position
        Size = size;
        _sprite = sprite;
    }

    // overloaded constructor to give more options of configuring the object
    public GameObject(PImage sprite, float x, float y, float width, float height){
        Position = new PVector(x,y);
        Size = new PVector(width,height);
        _sprite = sprite;
    }

    // declare functions for the subclasses

    // execute the game logic of the game object
    public abstract void Update();

    // draw the current game object
    public virtual void Draw(){
        image(_sprite,Position.x, Position.y,Size.x,Size.y)
    };
}

// sub class that inherits from GameObject
public class Asteroid extends GameObject{

    // constructors for the base class
    public GameObject(PImage sprite, PVector position, PVector size){
        super(sprite, position, size);
    }

    // overloaded constructor to give more options of configuring the object
    public GameObject(PImage sprite, float x, float y, float width, float height){
        super(sprite, x, y, width, height);
    }

    // object specific logic update
    public void Update{
        Position.y += 10;
    }

    // draw is missing, as the base class has already defined basic behavior
    // you can make your own draw logic by overriding the method
}

/*
* References:
* PVector - https://processing.org/reference/PVector.html
* java keywords - https://www.w3schools.com/java/java_ref_keywords.asp
* inheritance - https://www.w3schools.com/java/ref_keyword_extends.asp
* polymorphism - https://www.w3schools.com/java/java_polymorphism.asp
*/