import { prop, computed } from 'frptools';

import { Watcher } from './watcher.js';
import { pouchDocArrayComparator } from './comparators.js';

// LiveArray is a subscribable property function that always returns the db results that match the provided selector and calls subscribers when the results change.
export function LiveArray(db, selector, mapper) {
	const _watcher = Watcher(db, selector);
	let changeSub = null;
	let _mapper = mapper || (doc => doc);

	const ready = prop(false);
	const data = prop({ docs: [] });
	const docs = computed(r => r.docs.map(_mapper), [data], pouchDocArrayComparator);

	const cleanup = () => {
		docs.unsubscribeAll();
		ready.unsubscribeAll();
		if (changeSub) {
			changeSub();
			changeSub = null;
		}
		data({ docs: [] });
	};

	const refresh = async function refresh(...args) {
		data(await db.find({ selector }));
	};

	docs.ready = ready;
	docs.cleanup = cleanup;
	docs.selector = selector;
	docs.db = db;

	refresh().then(() => {
		changeSub = _watcher(refresh);
		ready(true);
	});
	return docs;
}