gistfile1.txt

import Component from '@ember/component';
import { inject } from '@ember/service';
import { computed, get, set } from '@ember/object';
import { task } from 'ember-concurrency';
import { assert } from '@ember/debug';

export default Component.extend({

  mapService: inject('components/map'),

  mapZoomLevel: computed.alias('mapService.mapZoomLevel'),

  _startZoomLevel: undefined,  // <- ideally, I would like to avoid having to set this property

  actions: {
    zoom(zoomLevelStep) {
      assert(Number.isInteger(zoomLevelStep), 'zoomLevelStep must be an integer.');

      // HACK: the call to `map.setExtent` will update the map zoom level value
      // and fire the `zoom-end` event prior to the resolution of the deffered returned
      // by `map.setExtent`. Because of this, we can't rely on the zoom level to
      // be correct when we are calculating the target zoom level so we need to store
      // the starting zoom level to be used in this calculation.
      if (!get(this, '_zoomInTask.isRunning') && !get(this, '_zoomOutTask.isRunning')) {
        set(this, '_startZoomLevel', get(this, 'mapZoomLevel'));
      }

      if (zoomLevelStep > 0) {
        get(this, '_zoomInTask').perform(zoomLevelStep + zoomLevelStep * (get(this, '_zoomInTask.concurrency') - get(this, '_zoomOutTask.concurrency')));
      } else {
        get(this, '_zoomOutTask').perform(zoomLevelStep + zoomLevelStep * (get(this, '_zoomOutTask.concurrency') - get(this, '_zoomInTask.concurrency')));
      }
    },
  },

  _zoomInTask: task(function* (zoomLevelDelta) {
    yield this._zoom(zoomLevelDelta);
  }),

  _zoomOutTask: task(function* (zoomLevelDelta) {
    yield this._zoom(zoomLevelDelta);
  }),

  _zoom(zoomLevelDelta) {
    const targetZoomLevel = get(this, '_startZoomLevel') + zoomLevelDelta;
    
    // resolves after the zooming animation has completed. subsequent calls will
    // cancel any in progress animation and immediately resume the animation to the
    // target zoom level.
    return get(this, 'mapService').setZoomLevel(targetZoomLevel).then(() => {
      this._cancelInProgressZoomTasks();
    });
  },

  _cancelInProgressZoomTasks() {
    get(this, '_zoomInTask').cancelAll();
    get(this, '_zoomOutTask').cancelAll();
  }

});