Add retried fetch and connection check

plugin/src/services/sync-service.ts

@@ -11,7 +11,12 @@ import type {
 	VaultUpdateId,
 } from "src/database/document-metadata";
 import { Logger } from "src/tracing/logger.js";
+import { retriedFetch } from "src/utils/retried-fetch.js";
 
+export interface CheckConnectionResult {
+	isSuccessful: boolean;
+	message: string;
+}
 export class SyncService {
 	private client: Client<paths>;
 
@@ -272,9 +277,32 @@ export class SyncService {
 		return response.data;
 	}
 
+	public async checkConnection(): Promise<CheckConnectionResult> {
+		try {
+			const result = await this.ping();
+			if (result.isAuthenticated) {
+				return {
+					isSuccessful: true,
+					message: `Successfully connected to server (version: ${result.serverVersion}) and authenticated.`,
+				};
+			}
+
+			return {
+				isSuccessful: false,
+				message: `Successfully connected to server (version: ${result.serverVersion}) but failed to authenticate.`,
+			};
+		} catch (e) {
+			return {
+				isSuccessful: false,
+				message: `Failed to connect to server: ${e}`,
+			};
+		}
+	}
+
 	private createClient(settings: SyncSettings): void {
 		this.client = createClient<paths>({
 			baseUrl: settings.remoteUri,
+			fetch: retriedFetch,
 		});
 	}
 }

plugin/src/utils/retried-fetch.ts

@@ -0,0 +1,41 @@
+import * as fetchRetryFactory from "fetch-retry";
+import { Logger } from "src/tracing/logger";
+
+const fetchWithRetry = fetchRetryFactory.default(fetch);
+
+export async function retriedFetch(
+	input: RequestInfo | URL,
+	init: RequestInit = {}
+): Promise<Response> {
+	return fetchWithRetry(input, {
+		...init,
+		retryOn: function (attempt, error, response) {
+			// retry on any network error, or 4xx or 5xx status codes
+			if (error !== null || !response || response.status >= 500) {
+				Logger.getInstance().warn(
+					`Retrying fetch attempt ${attempt} for ${getUrlFromInput(
+						input
+					)}`
+				);
+
+				return true;
+			}
+			return false;
+		},
+		retries: 6,
+		retryDelay: function (attempt) {
+			Logger;
+			return Math.pow(1.5, attempt) * 500;
+		},
+	});
+}
+
+function getUrlFromInput(input: RequestInfo | URL): string {
+	if (input instanceof URL) {
+		return input.href;
+	}
+	if (typeof input === "string") {
+		return input;
+	}
+	return input.url;
+}