consul/ui/packages/consul-ui/app/components/data-source/index.js

import Component from '@ember/component';
import { inject as service } from '@ember/service';
import { set, get } from '@ember/object';
import { schedule } from '@ember/runloop';

/**
 * Utility function to set, but actually replace if we should replace
 * then call a function on the thing to be replaced (usually a clean up function)
 *
 * @param obj - target object with the property to replace
 * @param prop {string} - property to replace on the target object
 * @param value - value to use for replacement
 * @param destroy {(prev: any, value: any) => any} - teardown function
 */
const replace = function(
  obj,
  prop,
  value,
  destroy = (prev = null, value) => (typeof prev === 'function' ? prev() : null)
) {
  const prev = obj[prop];
  if (prev !== value) {
    destroy(prev, value);
  }
  return set(obj, prop, value);
};

export default Component.extend({
  tagName: '',

  data: service('data-source/service'),
  dom: service('dom'),
  logger: service('logger'),

  onchange: function(e) {},
  onerror: function(e) {},

  loading: 'eager',

  isIntersecting: false,

  init: function() {
    this._super(...arguments);
    this._listeners = this.dom.listeners();
    this._lazyListeners = this.dom.listeners();
    this.guid = this.dom.guid(this);
  },
  willDestroyElement: function() {
    this.actions.close.apply(this);
    this._listeners.remove();
    this._lazyListeners.remove();
    this._super(...arguments);
  },

  didInsertElement: function() {
    this._super(...arguments);
    if (this.loading === 'lazy') {
      this._lazyListeners.add(
        this.dom.isInViewport(this.dom.element(`#${this.guid}`), inViewport => {
          set(this, 'isIntersecting', inViewport);
          if (!this.isIntersecting) {
            this.actions.close.bind(this)();
          } else {
            this.actions.open.bind(this)();
          }
        })
      );
    }
  },
  didReceiveAttrs: function() {
    this._super(...arguments);
    if (this.loading === 'eager') {
      this._lazyListeners.remove();
    }
    if (this.loading === 'eager' || this.isIntersecting) {
      this.actions.open.apply(this, []);
    }
  },
  actions: {
    // keep this argumentless
    open: function() {
      // get a new source and replace the old one, cleaning up as we go
      const source = replace(
        this,
        'source',
        this.data.open(this.src, this, this.open),
        (prev, source) => {
          // Makes sure any previous source (if different) is ALWAYS closed
          this.data.close(prev, this);
        }
      );
      const error = err => {
        try {
          const error = get(err, 'error.errors.firstObject');
          if (get(error || {}, 'status') !== '429') {
            this.onerror(err);
          }
          this.logger.execute(err);
        } catch (err) {
          this.logger.execute(err);
        }
      };
      // set up the listeners (which auto cleanup on component destruction)
      const remove = this._listeners.add(this.source, {
        message: e => {
          try {
            this.onchange(e);
          } catch (err) {
            error(err);
          }
        },
        error: e => {
          error(e);
        },
      });
      replace(this, '_remove', remove);
      // dispatch the current data of the source if we have any
      if (typeof source.getCurrentEvent === 'function') {
        const currentEvent = source.getCurrentEvent();
        if (currentEvent) {
          schedule('afterRender', () => {
            try {
              this.onchange(currentEvent);
            } catch (err) {
              error(err);
            }
          });
        }
      }
    },
    // keep this argumentless
    close: function() {
      if (typeof this.source !== 'undefined') {
        this.data.close(this.source, this);
        replace(this, '_remove', undefined);
        set(this, 'source', undefined);
      }
    },
  },
});