import React, { useState, useEffect } from 'react';

import { usePermission } from '../../contexts/AuthorizationContext';
import NotAuthorizedPage from '../../components/NotAuthorizedPage';
import { useMethod, useServerInformation, useEndpoint } from '../../contexts/ServerContext';
import { downloadJsonAsAFile } from '../../helpers/download';
import { InformationPage } from './InformationPage';

export const InformationRoute = React.memo(function InformationRoute() {
	const canViewStatistics = usePermission('view-statistics');


	const [isLoading, setLoading] = useState(true);
	const [statistics, setStatistics] = useState({});
	const [instances, setInstances] = useState([]);
	const [fetchStatistics, setFetchStatistics] = useState(() => () => ({}));
	const getStatistics = useEndpoint('GET', 'statistics');
	const getInstances = useMethod('instances/get');

	useEffect(() => {
		let didCancel = false;

		const fetchStatistics = async ({ refresh = false } = {}) => {
			setLoading(true);

			try {
				const [statistics, instances] = await Promise.all([
					getStatistics({ refresh }),
					getInstances(),
				]);

				if (didCancel) {
					return;
				}
				setStatistics(statistics);
				setInstances(instances);
			} finally {
				setLoading(false);
			}
		};

		setFetchStatistics(() => fetchStatistics);

		fetchStatistics();

		return () => {
			didCancel = true;
		};
	}, [canViewStatistics, getInstances, getStatistics]);

	const info = useServerInformation();

	const handleClickRefreshButton = () => {
		if (isLoading) {
			return;
		}

		fetchStatistics({ refresh: true });
	};

	const handleClickDownloadInfo = () => {
		if (isLoading) {
			return;
		}
		downloadJsonAsAFile(statistics, 'statistics');
	};

	if (canViewStatistics) {
		return <InformationPage
			canViewStatistics={canViewStatistics}
			isLoading={isLoading}
			info={info}
			statistics={statistics}
			instances={instances}
			onClickRefreshButton={handleClickRefreshButton}
			onClickDownloadInfo={handleClickDownloadInfo}
		/>;
	}
	return <NotAuthorizedPage />;
});

export default InformationRoute;