flanders/src/lib/server/serviceDataPolling.ts

import type { Config, ServiceConfig } from '$lib/config';
import type { AsyncServiceHandler, ServiceData, ServiceHandler } from '$lib/services/service';
import { getServiceHandler } from '$lib/services/services';
import { serverConfig } from './config';

export const serviceData: Array<Array<unknown>> = [];

function isPromise(p: any): boolean {
	return typeof p === 'object' && typeof p.then === 'function';
}

async function pollGeneric(upstream: ServiceData, url: string): Promise<ServiceData> {
	upstream.status = undefined;
	return fetch(url)
		.then((resp: Response): ServiceData => {
			upstream.status = resp.ok ? 'online' : 'offline';
			return upstream;
		})
		.catch((error) => {
			console.warn("could not fetch status for '" + url + "': " + error);
			upstream.status = 'offline';
			return upstream;
		});
}

function wrapHandler(handler: ServiceHandler): AsyncServiceHandler {
	return async (config: ServiceConfig): Promise<ServiceData> => {
		const value = handler(config);
		if (isPromise(value) === true) {
			return (value as Promise<ServiceData>)
				.then((data: ServiceData) => {
					if (data.status != undefined) {
						return data;
					}
					return pollGeneric(data, config.url);
				})
				.catch((error) => {
					console.warn("could not resolve service '" + config.url + "': " + error);
					return pollGeneric({}, config.url);
				});
		}
		return pollGeneric(value as ServiceData, config.url);
	};
}

function pollServices() {
	const config: Config = serverConfig();

	for (const [i, group] of config.services.entries()) {
		for (const [j, service] of group.items.entries()) {
			const handler: ServiceHandler =
				getServiceHandler(service.type || '') ||
				(() => {
					return {} as ServiceData;
				});

			wrapHandler(handler)(service).then((data: ServiceData) => {
				serviceData[i][j] = data;
			});
		}
	}
}

export function initializeServiceData() {
	const config = serverConfig();
	serviceData.length = config.services.length;
	for (let i = 0; i < serviceData.length; i++) {
		serviceData[i] = [];
		for (let j = 0; j < config.services[i].items.length; j++) {
			serviceData[i][j] = {};
		}
	}
}

export function initServicePolling() {
	initializeServiceData();
	pollServices();
	setInterval(pollServices, 30000);
}