portfolio/packages/frptools/src/container.js

import { id, registerSubscriptions, registerFire } from './util.js';

export function container(store, hash) {
	let subscribers = [];
	let id = hash(store);

	const containerMethods = {
		subscribe: registerSubscriptions(subscribers),
		fire: registerFire(subscribers),
		unsubscribeAll: () => {
			subscribers = [];
		}
	};

	function checkUpdate(target) {
		const newId = hash(target);
		if (id !== newId) {
			id = newId;
			containerMethods.fire(target);
		}
	}

	const p = new Proxy(store, {
		apply: (target, context, args) => {
			return target;
		},
		get: (target, name) => {
			if (name in containerMethods) {
				return containerMethods[name];
			}
			if (name === '_') {
				return target;
			}
			const thing = target[name];
			if (typeof thing === 'function') {
				return (...args) => {
					const ret = target[name](...args);
					checkUpdate(target);
					return ret;
				};
			}
			return thing;
		},
		set: (target, name, newVal) => {
			if (name in containerMethods) {
				throw new ReferenceError(`Cannot set ${name} in ${target}`);
			}
			target[name] = newVal;
			checkUpdate(target);

			return newVal;
		}
	});

	return p;
}