aretherecookies-mobile/js/streams/ImagesStream.js

//@flow
import { Map, Set } from 'immutable';
import { ReplaySubject } from 'rxjs';
import ImageRecord, { buildImageRecord } from '../records/ImageRecord';
import type { ImageRaw } from '../records/ImageRecord';

const observable: ReplaySubject<ImageRecord> = new ReplaySubject();

export function emit(val: ?ImageRaw) {
	observable.next(val);
}

// force our observable to emit an initial empty map so that food items will load
emit(null);

export default observable.scan((imagesByFoodItemId: Map<string, ImageRecord>, image: ImageRaw) => {
	if (!image || !image.food_item_id) {
		return imagesByFoodItemId;
	}

	return imagesByFoodItemId.update(image.food_item_id, ({ images = Set() } = {}) => {
		return {
			id: image.food_item_id,
			images: images.add(buildImageRecord(image)),
		};
	});
}, new Map());