aretherecookies-mobile/js/streams/QuantityStream.js

//@flow
import { ReplaySubject } from 'rxjs';
import type { QuantityResponse, QuantityFragment } from '../constants/QuantityConstants';
import { Map } from 'immutable';

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

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

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

export default observable.scan(
	(quantitiesByProductId: Map<string, QuantityFragment>, quantity?: QuantityResponse) => {
		if (!quantity) {
			return quantitiesByProductId;
		}

		return quantitiesByProductId.set(quantity.food_item_id, {
			quantity: quantity.quantity,
			lastupdated: quantity.date,
		});
	},
	new Map()
);