trc-client-core/src/utils/AsyncStateReducer.js

The core of the TRC Client

import {Map} from 'immutable';

const initialState = Map();

//
// AsyncStateReducer
//
// Keeps fetching and error state in a global redux property "async", which is an immutable.js Map
// It tracks state on actions ending with _FETCH, _ERROR or _RECEIVE
// Variables are uppercase snakes and match the consts for fetch and error
// XXX_FETCH is a boolean indicating if that action is currently requesting info (or undefined before any actions have been dispatched)
// XXX_ERROR is either { status, message } if an error has occured, or is null otherwise
// ^ really only useful for ensuring that a complete list of objects has been received when using ordered maps for collections. You won't know whether your list is complete or partial without this
//
// e.g. state.async.LEARNING_PLAN_FETCH
//

export default function AsyncStateReducer(state = initialState, action) {

	const { type } = action;

	if(!type) {
		return state;
	}

	const actionName = type.replace(/(_FETCH|_ERROR|_RECEIVE)$/g,'');

	if(/_FETCH$/g.test(type)) {
		return state
			.set(actionName + '_FETCH', true)
			.set(actionName + '_ERROR', null);
	}

	if(/_ERROR$/g.test(type)) {
		const { status, message } = action.payload;
		return state
			.set(actionName + '_FETCH', false)
			.set(actionName + '_ERROR', { status, message });
	}

	if(/_RECEIVE$/g.test(type)) {
		return state
			.set(actionName + '_FETCH', false)
			.set(actionName + '_ERROR', null);
	}

	return state;
}