import {Engine, Events, World as MatterWorld} from 'matter-js';

import {Body} from './body';
import {AbstractWorld} from '../abstract/world';

export class World extends AbstractWorld {

  constructor() {
    super();
    const world = MatterWorld.create({
      gravity: {
        x: 0,
        y: 0,
        scale: 0,
      },
    });
    this.engine = Engine.create({
      world,
    });
    this.handleCollisions('collisionStart');
    this.handleCollisions('collisionEnd');
    this.lastElapsed = undefined;
  }

  addBody(body) {
    MatterWorld.add(this.engine.world, body.matterBody);
  }

  createBody(shape) {
    return new Body(shape);
  }

  handleCollisions(eventName) {
    Events.on(this.engine, eventName, (event) => {
      event.pairs.forEach((pair) => {
        const {bodyA, bodyB} = pair;
        const entityA = this.entities.get(Body.lookupBody(bodyA));
        const entityB = this.entities.get(Body.lookupBody(bodyB));
        if (entityA && entityB) {
          entityA.emit(eventName, entityB);
          entityB.emit(eventName, entityA);
        }
      });
    });
  }

  removeBody(body) {
    super.removeBody(body);
    MatterWorld.remove(this.engine.world, body.matterBody);
  }

  tick(elapsed) {
    // Milliseconds.
    elapsed = elapsed * 1000;
    const correction = this.lastElapsed ? elapsed / this.lastElapsed : 1;
    // Update simulation.
    Engine.update(this.engine, elapsed, correction)
    this.lastElapsed = elapsed;
    // Propagate.
    super.tick(elapsed);
  }

}