package lecture16;

import com.jme3.app.SimpleApplication;
import com.jme3.light.DirectionalLight;
import com.jme3.material.Material;
import com.jme3.math.ColorRGBA;
import com.jme3.math.Vector3f;
import com.jme3.scene.Geometry;
import com.jme3.scene.shape.Sphere;

public class Example05 extends SimpleApplication {
    // world constants

    final float g = 9.8f;
    final Vector3f gravity = new Vector3f(0, -g, 0);
    final float b = 0.9f;
    // distance to travel
    final float distance = 100f;
    // how fast along the x axis. Play with this value!
    final float vx = 20f;
    final float m = 1f; // mass
    final float eps = 1f; // error
    float step = 50f; // iteration steps
    //Geometries
    Geometry bullet;
    Geometry target;
    Vector3f velocity = new Vector3f(0, 0, 0);
    Vector3f force = new Vector3f(0, 0, 0);
    Vector3f oldVelocity = new Vector3f(0, 0, 0);
    Vector3f acceleration = new Vector3f(0, 0, 0);
    boolean overshot = false;

    private Geometry makeBall(ColorRGBA color) {
        Material mat = new Material(assetManager, "Common/MatDefs/Light/Lighting.j3md");
        mat.setBoolean("UseMaterialColors", true);
        mat.setColor("Ambient", color);
        mat.setColor("Diffuse", color);

        Sphere s = new Sphere(60, 60, 1.5f);
        Geometry geom = new Geometry("Sphere", s);
        geom.setMaterial(mat);
        return geom;
    }

    public void simpleInitApp() {
        DirectionalLight sun = new DirectionalLight();
        sun.setDirection(new Vector3f(-10, 2, -2).normalize());
        sun.setColor(ColorRGBA.White);
        rootNode.addLight(sun);

        bullet = makeBall(ColorRGBA.Blue);
        rootNode.attachChild(bullet);

        target = makeBall(ColorRGBA.Red);
        rootNode.attachChild(target);

        target.move(distance, 0, 0);


        float vy = (g * distance) / (2 * vx);
        velocity = new Vector3f(vx, vy, 0);

        oldVelocity = velocity;

        cam.setLocation(new Vector3f(distance + 50, 0, 15));
        cam.lookAt(new Vector3f(3 * distance / 4f, 0, 0), Vector3f.UNIT_Y);


    }

    @Override
    public void simpleUpdate(float tpf) {
        boolean relaunch = false;
        if (bullet.getLocalTranslation().getY() >= 0) {
            // Linear drag for added fun
            force = velocity.mult(-b);
            acceleration = gravity.add(force.divide(m));
            velocity = velocity.add(acceleration.mult(tpf));

            bullet.move(velocity.mult(tpf));
        } else {
            if (bullet.getLocalTranslation().length() + eps < distance) {
                if (overshot) {
                    step = step / 2f;
                }
                velocity = oldVelocity.add(step, 0, 0);
                relaunch = true;
            } else if (bullet.getLocalTranslation().length() - eps > distance) {
                if (!overshot) {
                    step = step / 2f;
                }
                velocity = oldVelocity.subtract(step, 0, 0);
                relaunch = true;
            }

            if (relaunch) {
                oldVelocity = velocity;
                bullet.setLocalTranslation(0, 0, 0);
            }
        }


    }

    public static void main(String[] args) {
        Example05 app = new Example05();
        app.start();
    }
}