@snipsonian/observable-state/es/observer/createStateObserverManager.js

Observable-state snippets (redux-like)

import isArray from '@snipsonian/core/es/is/isArray';
import extendNotificationsToTrigger from './extendNotificationsToTrigger';
export default function createStateObserverManager() {
    let observerCounter = 0;
    const observerMap = {};
    return {
        registerObserver: ({ observerName, notificationsToObserve, onNotify, }) => {
            observerCounter += 1;
            const observer = {
                id: observerCounter,
                observerName,
                notify: onNotify,
            };
            observerMap[observer.id] = Object.assign(Object.assign({}, observer), { notificationsToObserve });
            return observer;
        },
        unRegisterObserver: (observer) => {
            delete observerMap[observer.id];
        },
        notifyObserversOfStateChanges: ({ notificationsToTrigger, triggerParentNotifications, }) => {
            if (isArray(notificationsToTrigger) && notificationsToTrigger.length > 0) {
                const uniqueObserversToNotify = extendNotificationsToTrigger({
                    notificationsToTrigger,
                    triggerParentNotifications,
                })
                    .reduce((accumulator, notificationToTrigger) => {
                    const matchingObservers = Object.values(observerMap)
                        .filter((registeredObserver) => registeredObserver.notificationsToObserve.includes(notificationToTrigger));
                    matchingObservers.forEach((observer) => {
                        const alreadyFoundObserver = accumulator
                            .find((observerToNotify) => observerToNotify.id === observer.id);
                        if (alreadyFoundObserver) {
                            alreadyFoundObserver.notifications.push(notificationToTrigger);
                        }
                        else {
                            accumulator.push(Object.assign(Object.assign({}, observer), { notifications: [notificationToTrigger] }));
                        }
                    });
                    return accumulator;
                }, []);
                if (uniqueObserversToNotify && uniqueObserversToNotify.length > 0) {
                    uniqueObserversToNotify.forEach((observerToNotify) => {
                        observerToNotify.notify({ notifications: observerToNotify.notifications });
                    });
                }
            }
        },
    };
}