From 9f7e1cf7baba8b46e3d5c0cc88182968082cb14a Mon Sep 17 00:00:00 2001
From: Alexandre Tuleu <alexandre.tuleu.2005@polytechnique.org>
Date: Tue, 26 Sep 2023 10:50:54 +0200
Subject: [PATCH] Adds an api to get asynchronous update events.

---
 src/lib/server/dataPolling.ts     | 73 +++++++++++++++++++++++++++++++
 src/routes/api/updates/+server.ts | 27 ++++++++++++
 vite.config.ts                    |  3 +-
 3 files changed, 102 insertions(+), 1 deletion(-)
 create mode 100644 src/lib/server/dataPolling.ts
 create mode 100644 src/routes/api/updates/+server.ts

diff --git a/src/lib/server/dataPolling.ts b/src/lib/server/dataPolling.ts
new file mode 100644
index 0000000..4d1f68c
--- /dev/null
+++ b/src/lib/server/dataPolling.ts
@@ -0,0 +1,73 @@
+import type { ServiceData, ServicePoller } from '$lib/services/service';
+import { getServiceRecord } from '$lib/services/services';
+import { readable, type Readable } from 'svelte/store';
+import { serverConfig } from './config';
+
+type MayAsyncServiceData = ServiceData | Promise<ServiceData>;
+
+let serviceData: MayAsyncServiceData[][] | undefined = undefined;
+
+function forEachService(
+	fn: (group: number, item: number, pollResult: Promise<ServiceData>) => void
+): MayAsyncServiceData[][] {
+	const config = serverConfig();
+
+	if (serviceData == undefined) {
+		serviceData = [];
+	}
+
+	for (const [idxGroup, group] of config.services.entries()) {
+		if (serviceData[group] == undefined) {
+			serviceData[group] = [];
+		}
+
+		for (const [idxItem, service] of group.items.entries()) {
+			const poller: ServicePoller = getServiceRecord(service.type || '').poll;
+			fn(idxGroup, idxItem, poller(service));
+		}
+	}
+	return serviceData;
+}
+
+export function getCurrentServiceData(): MayAsyncServiceData[][] {
+	if (serviceData != undefined) {
+		return serviceData;
+	}
+
+	return forEachService((group: number, item: number, pollResult: Promise<ServiceData>) => {
+		(serviceData as MayAsyncServiceData[][])[group][item] = pollResult.then(
+			(data: ServiceData) => {
+				(serviceData as MayAsyncServiceData[][])[group][item] = data;
+				return data;
+			}
+		);
+	});
+}
+
+export interface ServiceDataEvent {
+	group: number;
+	item: number;
+	data: ServiceData;
+}
+
+const pollInterval = 30000;
+
+export const serviceDataEvents = readable<ServiceDataEvent>(undefined, (set) => {
+	console.debug('starting ServiceData polling loop every ' + pollInterval / 1000 + 's');
+	const timer = setInterval(() => {
+		forEachService((group: number, item: number, result: Promise<ServiceData>) => {
+			(serviceData as MayAsyncServiceData[][])[group][item] = result.then(
+				(data: ServiceData) => {
+					(serviceData as MayAsyncServiceData[][])[group][item] = data;
+					set({ group, item, data });
+					return data;
+				}
+			);
+		});
+	}, pollInterval);
+
+	return () => {
+		console.debug('stopping ServiceData polling loop');
+		clearInterval(timer);
+	};
+});
diff --git a/src/routes/api/updates/+server.ts b/src/routes/api/updates/+server.ts
new file mode 100644
index 0000000..66c9079
--- /dev/null
+++ b/src/routes/api/updates/+server.ts
@@ -0,0 +1,27 @@
+import { serviceDataEvents } from '$lib/server/dataPolling';
+import type { RequestHandler } from '@sveltejs/kit';
+import type { Unsubscriber } from 'svelte/store';
+
+export const GET: RequestHandler = () => {
+	let unsubscribe: Unsubscriber | undefined = undefined;
+	const stream = new ReadableStream({
+		start: (controller) => {
+			console.debug('ServiceDataEvent stream started');
+			unsubscribe = serviceDataEvents.subscribe((event) => {
+				const data = `event:message\ndata:${JSON.stringify(event)}\n\n`;
+				controller.enqueue(data);
+			});
+		},
+		cancel: (reason) => {
+			console.debug('ServiceDataEvent stream canceled: ', reason);
+			if (unsubscribe != undefined) {
+				unsubscribe();
+			}
+		}
+	});
+	return new Response(stream, {
+		headers: {
+			'Content-Type': 'text/event-stream'
+		}
+	});
+};
diff --git a/vite.config.ts b/vite.config.ts
index 1329e84..3cc9a1d 100644
--- a/vite.config.ts
+++ b/vite.config.ts
@@ -8,5 +8,6 @@ export default defineConfig({
 		include: ['src/**/*.{test,spec}.{js,ts}']
 	},
 
-	build: { target: 'esnext' }
+	build: { target: 'esnext' },
+	logLevel: 'info'
 });