Physics Engine (#4)

[rbdr/sumo] / lib / factories / sumo.js

import { Bodies, Constraint } from 'matter-js';
import { Entity } from '@serpentity/serpentity';

import AngleComponent from '../components/angle';
import BodyComponent from '../components/body';
import CoupledEntitiesComponent from '../components/coupled_entities';
import PositionComponent from '@serpentity/components.position';
import PixiContainerComponent from '../components/pixi_container';
import PixiFactory from '../factories/pixi';

const internals = {
  kNoEntityError: 'Entity Not Found: This method requires entityA and entityB to be set in the config.',
  kEntityHasNoBodyError: 'Entity Has No Body: This method requires entities have a BodyComponent.'
};

/**
 * Factory object that contains many methods to create prefab entities.
 *
 * @type object
 * @name SumoFactory
 */
export default {

  /**
   * Creates a sumo entity and adds it to the engine. Can override
   * position in the config object
   *
   * @function createSumo
   * @memberof SumoFactory
   * @param {external:Serpentity} [engine] the serpentity engine to attach
   * to. If not sent, it will not be attached.
   * @param {object} [config] the config to override the entity, accepts
   * the key `position` as an object with an x and y property.
   * @return {external:Serpentity.Entity} the created entity
   */
  createSumo(engine, config = {}) {

    const entity = new Entity();

    // POSITION

    entity.addComponent(new PositionComponent(config.position));
    const position = entity.getComponent(PositionComponent);

    entity.addComponent(new AngleComponent(config.angle));
    const angle = entity.getComponent(AngleComponent);

    // RENDERING

    const radius = 25;

    const container = config.container || {
      container: PixiFactory.createSumo({ radius })
    };
    container.container.position.x = position.x;
    container.container.position.y = position.y;
    container.container.rotation = angle.angle;
    entity.addComponent(new PixiContainerComponent(container));

    // PHYSICS

    const frictionAir = 0.00001;
    const friction = 0.00001;
    const restitution = 0.9;
    const density = 0.5;

    const body = Bodies.circle(position.x, position.y, radius, {
      angle: angle.angle,
      density,
      frictionAir,
      friction,
      restitution
    });
    entity.addComponent(new BodyComponent({ body }));

    if (engine) {
      engine.addEntity(entity);
    }

    return entity;
  },

  /**
   * Creates a rubber band entity and adds it to the engine.
   *
   * @function createRubberBand
   * @memberof SumoFactory
   * @param {external:Serpentity} [engine] the serpentity engine to attach
   * to. If not sent, it will not be attached.
   * @param {object} [config] the config to override the entity, it
   * must include entityA and entityB which will be tied by it. If they
   * are not sent or don't have a physics body, this will throw.
   * @return {external:Serpentity.Entity} the created entity
   */
  createRubberBand(engine, config = {}) {

    const entity = new Entity();

    if (!config.entityA || !config.entityB) {
      throw new Error(internals.kNoEntityError);
    }

    if (!config.entityA.hasComponent(BodyComponent) || !config.entityB.hasComponent(BodyComponent)) {
      throw new Error(internals.kEntityHasNoBodyError);
    }

    // RENDERING

    const container = config.container || {
      container: PixiFactory.createEmptyGraphic()
    };
    entity.addComponent(new PixiContainerComponent(container));

    // PHYSICS

    const bodyA = config.entityA.getComponent(BodyComponent).body;
    const bodyB = config.entityB.getComponent(BodyComponent).body;
    const damping = 0.01;
    const length = 100;
    const stiffness = 0.0001;
    const angularStiffness = 0.0001;

    const body = Constraint.create({
      bodyA,
      bodyB,
      damping,
      length,
      stiffness,
      angularStiffness
    });
    entity.addComponent(new BodyComponent({ body }));

    entity.addComponent(new CoupledEntitiesComponent({
      coupledEntities: [config.entityA, config.entityB]
    }));

    if (engine) {
      engine.addEntity(entity);
    }

    return entity;
  }
};