import {Camera} from '@avocado/topdown';

import {Trait} from '../trait';

export class Followed extends Trait {

  static defaultParams() {
    return {
      viewSize: [320, 180],
    }
  }

  initialize() {
    const camera = new Camera();
    camera.viewSize = this.params.get('viewSize').toJS();
    this._camera = camera;
    this.updatePosition();
    this.onRoomSizeChanged();
  }

  get camera() {
    return this._camera;
  }

  onRoomSizeChanged() {
    if (!this.entity.is('roomed')) {
      return;
    }
    this._camera.areaSize = this.entity.room.size;
  }

  updatePosition() {
    if (!this.entity.is('positioned')) {
      return;
    }
    this._camera.position = this.entity.position;
  }

  listeners() {
    return {

      // TODO won't catch initial room size changes.
      addedToRoom: () => {
        this.onRoomSizeChanged();
        this.entity.room.on('sizeChanged', this.onRoomSizeChanged, this);
      },

      removedFromRoom: (room) => {
        room.off('sizeChanged', this.onRoomSizeChanged);
      },

      traitAdded: (type) => {
        if (-1 === [
          'positioned',
          'followed',
        ].indexOf(type)) {
          return;
        }
        this.updatePosition();
      },

    }
  }

  tick(elapsed) {
    this.updatePosition();
    this._camera.tick(elapsed);
  }

}