features.js

/*eslint-disable no-extra-boolean-cast, no-console */
import Service from '@ember/service';
import { camelize } from '@ember/string';

const FeaturesService = Service.extend({

  init() {
    this._super(...arguments);
    this._flags = Object.create(null);

    this.setUnknownProperty = function(key) {
      throw new Error(`Please use enable/disable to set feature flags. You attempted to set ${key}`);
    };
  },

  setup(flags) {
    this._resetFlags();
    for (let flag in flags) {
      if (flags.hasOwnProperty(flag)) {
        if (!!flags[flag]) {
          this.enable(flag);
        } else {
          this.disable(flag);
        }
      }
    }
  },

  enable(flag) {
    let normalizedFlag = this._normalizeFlag(flag);
    this._flags[normalizedFlag] = true;
    this.notifyPropertyChange(normalizedFlag);
  },

  disable(flag) {
    let normalizedFlag = this._normalizeFlag(flag);
    this._flags[normalizedFlag] = false;
    this.notifyPropertyChange(normalizedFlag);
  },

  isEnabled(feature) {
    let isEnabled = this._featureIsEnabled(feature);
    if (this._logFeatureFlagMissEnabled() && !isEnabled) {
      this._logFeatureFlagMiss(feature);
    }
    return isEnabled;
  },

  _resetFlags() {
    this._flags = Object.create(null);
  },

  _featureIsEnabled(feature) {
    let normalizeFeature = this._normalizeFlag(feature);
    return this._flags[normalizeFeature] || false;
  },

  _logFeatureFlagMissEnabled() {
    return !!this.get('config.LOG_FEATURE_FLAG_MISS');
  },

  _logFeatureFlagMiss(feature) {
    if (console && console.info) {
      console.info('Feature flag off:', feature);
    }
  },

  _normalizeFlag(flag) {
    return camelize(flag);
  },

  unknownProperty(key) {
    return this.isEnabled(key);
  }
});

// Use a native getter instead of a `volatile` computed property since those
// were deprecated as of Ember 3.9. The Object.defineProperty approach (from
// https://github.com/emberjs/ember.js/issues/17709#issuecomment-469941364 is
// used because defining native getters directly on EmberObject-based classes
// is only supported from Ember 3.9 on (https://github.com/emberjs/ember.js/pull/17710)
// and this preserves compatiblity until this addon drops support for older
// Ember versions.
Object.defineProperty(FeaturesService.prototype, 'flags', {
  get() {
    return Object.keys(this._flags);
  }
});

export default FeaturesService;