package org.leverman;

import java.io.File;

import org.jbox2d.collision.AABB;
import org.jbox2d.collision.shapes.PolygonShape;
import org.jbox2d.collision.shapes.Shape;
import org.jbox2d.collision.shapes.ShapeType;
import org.jbox2d.common.Transform;
import org.jbox2d.common.Vec2;
import org.jbox2d.dynamics.Body;
import org.jbox2d.dynamics.BodyDef;
import org.jbox2d.dynamics.BodyType;
import org.jbox2d.dynamics.Fixture;
import org.jbox2d.dynamics.FixtureDef;
import org.jbox2d.dynamics.World;
import org.lwjgl.LWJGLException;
import org.lwjgl.opengl.Display;
import org.lwjgl.opengl.DisplayMode;
import org.lwjgl.opengl.GL11;
import org.lwjgl.util.glu.GLU;

public class Box2D_LWJGL {
    private final String OS = System.getProperty("os.name").toLowerCase();

    final float rad2deg = 180f / (float)Math.PI;
    final float deg2rad = (float)Math.PI / 180f;

    // Window
    int w;
    int h;

    // Delta calculation stuff
    final float framerate = 60.0f;
    final float dt = 1.0f / framerate;
    final float nanoToSecs = 1.0f / 1000000000.0f;
    long last;
    float accum;

    // Fps calculation stuff
    long lastFpsTime;
    int frames;
    double fps;

    // Box2d
    World world;

    public Box2D_LWJGL() {
        w = 800;
        h = 600;
        last = 0;
        accum = 0.0f;
        lastFpsTime = 0;
        frames = 0;
        fps = 0.0;
    }

    public String getNativeName() throws LWJGLException {
        if (OS.indexOf("win") > -1) {
            return "windows";
        } else if (OS.indexOf("linux") > -1) {
            return "linux";
        }
        throw new LWJGLException("Platform '" + OS + "' is not supported!");
    }

    private Body createBox(float x, float y, float angle, float hw, float hh, BodyType type) {
        BodyDef def = new BodyDef();
        def.position.set(x, y);
        def.angle = angle * deg2rad;
        def.type = type;

        PolygonShape shape = new PolygonShape();
        shape.setAsBox(hw, hh);

        FixtureDef fixDef = new FixtureDef();
        fixDef.friction = 1f;
        fixDef.restitution = 0f;
        fixDef.density = 1f;
        fixDef.shape = shape;

        Body body = world.createBody(def);
        body.createFixture(fixDef);
        return body;
    }

    private void init() {
        GL11.glMatrixMode(GL11.GL_MODELVIEW);
        GL11.glClearColor(0f, 0f, 0.2f, 1f);

        GL11.glBlendFunc(GL11.GL_SRC_ALPHA, GL11.GL_ONE_MINUS_SRC_ALPHA);

        world = new World(new Vec2(0f, -10f));
        world.setAllowSleep(true);
        world.setContinuousPhysics(true);

        final float thickness = 0.025f;
        float bottom = -0.5f + thickness;

        createBox(0f, -0.5f, 0f, 1f, thickness, BodyType.STATIC);
        createBox(-0.85f, 0f, 90f, 0.75f, thickness, BodyType.STATIC);
        createBox(0.85f, 0f, 90f, 0.75f, thickness, BodyType.STATIC);

        final float rad = 0.05f;
        final float jr = rad * 0.5f;
        final int count = 100;
        float x = 0f, y = bottom + rad * 2f * 1.1f;
        for (int i = 0; i < count; i++) {
            x = -jr + (float)Math.random() * jr * 2f;
            createBox(x, y, 0f, rad, rad, BodyType.DYNAMIC);
            y += rad * 2f * 1.5f;
        }
    }

    private void update(float dt) {
        world.step(dt, 6, 3);
    }

    private void drawAABB(AABB aabb) {
        float hw = (aabb.upperBound.x - aabb.lowerBound.x) * 0.5f;
        float hh = (aabb.upperBound.y - aabb.lowerBound.y) * 0.5f;
        GL11.glEnable(GL11.GL_BLEND);
        GL11.glColor4f(0f, 1f, 0f, 0.25f);
        GL11.glBegin(GL11.GL_LINE_LOOP);
        GL11.glVertex2f(hw, hh);
        GL11.glVertex2f(-hw, hh);
        GL11.glVertex2f(-hw, -hh);
        GL11.glVertex2f(hw, -hh);
        GL11.glEnd();
        GL11.glDisable(GL11.GL_BLEND);
    }

    private void drawShape(Shape shape) {
        if (shape.getType().equals(ShapeType.POLYGON)) {
            PolygonShape polyShape = (PolygonShape) shape;
            int vertexCount = polyShape.getVertexCount();
            Vec2[] vertices = polyShape.getVertices();
            GL11.glColor3f(1f, 1f, 1f);
            GL11.glBegin(GL11.GL_LINE_LOOP);
            for (int i = 0; i < vertexCount; i++) {
                GL11.glVertex2f(vertices[i].x, vertices[i].y);
            }
            GL11.glEnd();
        }
    }

    private void draw(){
        GL11.glLoadIdentity();
        GLU.gluPerspective(45f, (float)Display.getWidth()/Display.getHeight(), 0.1f, 100f);
        GL11.glTranslatef(0f, 0f, -2f);

        GL11.glClear(GL11.GL_COLOR_BUFFER_BIT | GL11.GL_DEPTH_BUFFER_BIT);

        // Bodies
        Body body = world.getBodyList();
        while (body != null) {
            Transform transform = body.getTransform();
            GL11.glPushMatrix();
            GL11.glTranslatef(transform.p.x, transform.p.y, 0f);
            GL11.glRotatef(transform.q.getAngle() * rad2deg, 0f, 0f, 1f);
            Fixture fixture = body.getFixtureList();
            while (fixture != null) {
                drawShape(fixture.getShape());
                fixture = fixture.m_next;
            }
            GL11.glPopMatrix();
            body = body.m_next;
        }

        // AABBs
        body = world.getBodyList();
        while (body != null) {
            Transform transform = body.getTransform();
            GL11.glPushMatrix();
            GL11.glTranslatef(transform.p.x, transform.p.y, 0f);
            Fixture fixture = body.getFixtureList();
            while (fixture != null) {
                AABB aabb = fixture.getAABB(0);
                drawAABB(aabb);
                fixture = fixture.m_next;
            }
            GL11.glPopMatrix();
            body = body.m_next;
        }
    }

    private void tick() {
        // Fps
        long curFpsTime = System.currentTimeMillis();
        frames++;
        if (curFpsTime > lastFpsTime + 1000) {
            fps = frames * 1000 / (curFpsTime - lastFpsTime);
            Display.setTitle("Game - " + String.format("%3.2f fps", fps));
            lastFpsTime = curFpsTime;
            frames = 0;
        }

        // Delta time
        long now = System.nanoTime();
        float delta = (now - last) * nanoToSecs;
        if (delta > 0.25f) {
            delta = 0.25f;
        }
        last = now;

        // Accumulate delta time
        accum += dt;
        while (!Display.isCloseRequested() && accum >= dt) {
            update(dt);
            accum -= dt;
        }

        // Draw frame
        draw();
    }

    public void run() throws LWJGLException {
        System.setProperty("org.lwjgl.librarypath", new File("lib/lwjgl-2.9.1/native/" + getNativeName()).getAbsolutePath());

        try {
            Display.setDisplayMode(new DisplayMode(w,h));
            Display.create();
        } catch (LWJGLException e) {
            throw e;
        }

        init();

        while (!Display.isCloseRequested()) {
            tick();
            Display.update();
            Display.sync(60);
        }

        Display.destroy();
    }

    public static void main(String[] args) throws Exception {
        Box2D_LWJGL app = new Box2D_LWJGL();
        app.run();
    }
}