BodyEditorLoader

package aurelienribon.bodyeditor;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import com.badlogic.gdx.files.FileHandle;
import com.badlogic.gdx.math.Vector2;
import com.badlogic.gdx.physics.box2d.Body;
import com.badlogic.gdx.physics.box2d.CircleShape;
import com.badlogic.gdx.physics.box2d.FixtureDef;
import com.badlogic.gdx.physics.box2d.PolygonShape;
import com.badlogic.gdx.utils.JsonReader;
import com.badlogic.gdx.utils.JsonValue;

/** Loads the collision fixtures defined with the Physics Body Editor application. You only need to give it a body and the
 * corresponding fixture name, and it will attach these fixtures to your body.
 *
 * @author Aurelien Ribon | http://www.aurelienribon.com */
public class BodyEditorLoader {

    // Model
    private final Model model;

    // Reusable stuff
    private final List<Vector2> vectorPool = new ArrayList<Vector2>();
    private final PolygonShape polygonShape = new PolygonShape();
    private final CircleShape circleShape = new CircleShape();
    private final Vector2 vec = new Vector2();

    // -------------------------------------------------------------------------
    // Ctors
    // -------------------------------------------------------------------------

    public BodyEditorLoader(FileHandle file) {
        if(file == null) {
            throw new NullPointerException("file is null");
        }
        model = readJson(file.readString());
    }

    public BodyEditorLoader(String str) {
        if(str == null) {
            throw new NullPointerException("str is null");
        }
        model = readJson(str);
    }

    // -------------------------------------------------------------------------
    // Public API
    // -------------------------------------------------------------------------

    /** Creates and applies the fixtures defined in the editor. The name parameter is used to retrieve the right fixture from the
     * loaded file. <br/>
     * <br/>
     *
     * The body reference point (the red cross in the tool) is by default located at the bottom left corner of the image. This
     * reference point will be put right over the BodyDef position point. Therefore, you should place this reference point
     * carefully to let you place your body in your world easily with its BodyDef.position point. Note that to draw an image at the
     * position of your body, you will need to know this reference point (see {@link #getOrigin(java.lang.String, float)}. <br/>
     * <br/>
     *
     * Also, saved shapes are normalized. As shown in the tool, the width of the image is considered to be always 1 meter. Thus,
     * you need to provide a scale factor so the polygons get resized according to your needs (not every body is 1 meter large in
     * your game, I guess).
     *
     * @param body The Box2d body you want to attach the fixture to.
     * @param name The name of the fixture you want to load.
     * @param fd The fixture parameters to apply to the created body fixture.
     * @param scale The desired scale of the body. The default width is 1. */
    public void attachFixture(Body body, String name, FixtureDef fd, float scale, float scaleX, float scaleY) {
        RigidBodyModel rbModel = model.rigidBodies.get(name);
        if(rbModel == null) {
            throw new RuntimeException("Name '" + name + "' was not found.");
        }

        Vector2 origin = vec.set(rbModel.origin).scl(scale);

        for(int i = 0, n = rbModel.polygons.size(); i < n; i++) {
            PolygonModel polygon = rbModel.polygons.get(i);
            Vector2[] vertices = polygon.buffer;

            for(int ii = 0, nn = vertices.length; ii < nn; ii++) {
                vertices[ii] = newVec().set(polygon.vertices.get(ii)).scl(scale);
                vertices[ii].sub(origin);
                vertices[ii].x *= scaleX;
                vertices[ii].y *= scaleY;
            }

            polygonShape.set(vertices);
            fd.shape = polygonShape;
            body.createFixture(fd);

            for(int ii = 0, nn = vertices.length; ii < nn; ii++) {
                free(vertices[ii]);
            }
        }

        for(int i = 0, n = rbModel.circles.size(); i < n; i++) {
            CircleModel circle = rbModel.circles.get(i);
            Vector2 center = newVec().set(circle.center).scl(scale);
            float radius = circle.radius * scale;

            circleShape.setPosition(center);
            circleShape.setRadius(radius);
            fd.shape = circleShape;
            body.createFixture(fd);

            free(center);
        }
    }

    /** Gets the image path attached to the given name. */
    public String getImagePath(String name) {
        RigidBodyModel rbModel = model.rigidBodies.get(name);
        if(rbModel == null) {
            throw new RuntimeException("Name '" + name + "' was not found.");
        }

        return rbModel.imagePath;
    }

    /** Gets the origin point attached to the given name. Since the point is normalized in [0,1] coordinates, it needs to be scaled
     * to your body size. Warning: this method returns the same Vector2 object each time, so copy it if you need it for later use. */
    public Vector2 getOrigin(String name, float scale) {
        RigidBodyModel rbModel = model.rigidBodies.get(name);
        if(rbModel == null)
            throw new RuntimeException("Name '" + name + "' was not found.");

        return vec.set(rbModel.origin).scl(scale);
    }

    /** <b>For advanced users only.</b> Lets you access the internal model of this loader and modify it. Be aware that any
     * modification is permanent and that you should really know what you are doing. */
    public Model getInternalModel() {
        return model;
    }

    // -------------------------------------------------------------------------
    // Json Models
    // -------------------------------------------------------------------------

    public static class Model {

        public final Map<String, RigidBodyModel> rigidBodies = new HashMap<String, RigidBodyModel>();
    }

    public static class RigidBodyModel {

        public String name;
        public String imagePath;
        public final Vector2 origin = new Vector2();
        public final List<PolygonModel> polygons = new ArrayList<PolygonModel>();
        public final List<CircleModel> circles = new ArrayList<CircleModel>();
    }

    public static class PolygonModel {

        public final List<Vector2> vertices = new ArrayList<Vector2>();
        private Vector2[] buffer; // used to avoid allocation in attachFixture()
    }

    public static class CircleModel {

        public final Vector2 center = new Vector2();
        public float radius;
    }

    // -------------------------------------------------------------------------
    // Json reading process
    // -------------------------------------------------------------------------

    private Model readJson(String str) {
        Model m = new Model();
        JsonValue root = new JsonReader().parse(str);
        JsonValue bodies = root.get("rigidBodies");

        for(JsonValue body = bodies.child(); body != null; body = body.next()) {
            RigidBodyModel rbModel = readRigidBody(body);
            m.rigidBodies.put(rbModel.name, rbModel);
        }

        return m;
    }

    private RigidBodyModel readRigidBody(JsonValue bodyElem) {
        RigidBodyModel rbModel = new RigidBodyModel();
        rbModel.name = bodyElem.getString("name");
        rbModel.imagePath = bodyElem.getString("imagePath");

        JsonValue origin = bodyElem.get("origin");

        rbModel.origin.x = origin.getFloat("x");
        rbModel.origin.y = origin.getFloat("y");

        // polygons
        JsonValue polygons = bodyElem.get("polygons");

        for(JsonValue vertices = polygons.child(); vertices != null; vertices = vertices.next()) {
            PolygonModel polygon = new PolygonModel();
            rbModel.polygons.add(polygon);

            for(JsonValue vertex = vertices.child(); vertex != null; vertex = vertex.next()) {
                polygon.vertices.add(new Vector2(vertex.getFloat("x"), vertex.getFloat("y")));
            }

            polygon.buffer = new Vector2[polygon.vertices.size()];
        }

        // circles
        JsonValue circles = bodyElem.get("circles");

        for(JsonValue circle = circles.child(); circle != null; circle = circle.next()) {
            CircleModel c = new CircleModel();
            rbModel.circles.add(c);

            c.center.x = circle.getFloat("cx");
            c.center.y = circle.getFloat("cy");
            c.radius = circle.getFloat("r");
        }

        return rbModel;
    }

    // -------------------------------------------------------------------------
    // Helpers
    // -------------------------------------------------------------------------

    private Vector2 newVec() {
        return vectorPool.isEmpty() ? new Vector2() : vectorPool.remove(0);
    }

    private void free(Vector2 v) {
        vectorPool.add(v);
    }
}