fix: use descriptive error messages

app/server/headscale/api-client.ts

@@ -1,8 +1,132 @@
 import { readFile } from 'node:fs/promises';
+import { data } from 'react-router';
 import { Agent, Dispatcher, request } from 'undici';
+import { errors } from 'undici';
 import log from '~/utils/log';
 import ResponseError from './api-error';
 
+function isNodeNetworkError(error: unknown): error is NodeJS.ErrnoException {
+	const keys = Object.keys(error as Record<string, unknown>);
+	return (
+		typeof error === 'object' &&
+		error !== null &&
+		keys.includes('code') &&
+		keys.includes('errno')
+	);
+}
+
+function friendlyError(givenError: unknown) {
+	let error: unknown = givenError;
+	if (error instanceof AggregateError) {
+		error = error.errors[0];
+	}
+
+	switch (true) {
+		case error instanceof errors.BodyTimeoutError:
+		case error instanceof errors.ConnectTimeoutError:
+		case error instanceof errors.HeadersTimeoutError:
+			return data('Timed out waiting for a response from the Headscale API', {
+				statusText: 'Request Timeout',
+				status: 408,
+			});
+
+		case error instanceof errors.SocketError:
+		case error instanceof errors.SecureProxyConnectionError:
+		case error instanceof errors.ClientClosedError:
+		case error instanceof errors.ClientDestroyedError:
+		case error instanceof errors.RequestAbortedError:
+			return data('The Headscale API is not reachable', {
+				statusText: 'Service Unavailable',
+				status: 503,
+			});
+
+		case error instanceof errors.InvalidArgumentError:
+		case error instanceof errors.InvalidReturnValueError:
+		case error instanceof errors.NotSupportedError:
+			return data('Unable to make a request (this is most likely a bug)', {
+				statusText: 'Internal Server Error',
+				status: 500,
+			});
+
+		case error instanceof errors.HeadersOverflowError:
+		case error instanceof errors.RequestContentLengthMismatchError:
+		case error instanceof errors.ResponseContentLengthMismatchError:
+		case error instanceof errors.ResponseExceededMaxSizeError:
+			return data('The Headscale API returned a malformed response', {
+				statusText: 'Bad Gateway',
+				status: 502,
+			});
+
+		case isNodeNetworkError(error):
+			if (error.code === 'ECONNREFUSED') {
+				return data('The Headscale API is not reachable', {
+					statusText: 'Service Unavailable',
+					status: 503,
+				});
+			}
+
+			if (error.code === 'ENOTFOUND') {
+				return data('The Headscale API is not reachable', {
+					statusText: 'Service Unavailable',
+					status: 503,
+				});
+			}
+
+			if (error.code === 'EAI_AGAIN') {
+				return data('The Headscale API is not reachable', {
+					statusText: 'Service Unavailable',
+					status: 503,
+				});
+			}
+
+			if (error.code === 'ETIMEDOUT') {
+				return data('Timed out waiting for a response from the Headscale API', {
+					statusText: 'Request Timeout',
+					status: 408,
+				});
+			}
+
+			if (error.code === 'ECONNRESET') {
+				return data('The Headscale API is not reachable', {
+					statusText: 'Service Unavailable',
+					status: 503,
+				});
+			}
+
+			if (error.code === 'EPIPE') {
+				return data('The Headscale API is not reachable', {
+					statusText: 'Service Unavailable',
+					status: 503,
+				});
+			}
+
+			if (error.code === 'ENETUNREACH') {
+				return data('The Headscale API is not reachable', {
+					statusText: 'Service Unavailable',
+					status: 503,
+				});
+			}
+
+			if (error.code === 'ENETRESET') {
+				return data('The Headscale API is not reachable', {
+					statusText: 'Service Unavailable',
+					status: 503,
+				});
+			}
+
+			return data('The Headscale API is not reachable', {
+				statusText: 'Service Unavailable',
+				status: 503,
+			});
+
+		default:
+			return data((error as Error).message ?? 'An unknown error occurred', {
+				statusText: 'Internal Server Error',
+				status: 500,
+			});
+	}
+}
+
 export async function createApiClient(base: string, certPath?: string) {
 	if (!certPath) {
 		return new ApiClient(new Agent(), base);
@@ -37,21 +161,34 @@ export class ApiClient {
 		const method = options?.method ?? 'GET';
 		log.debug('api', '%s %s', method, url);
 
-		return await request(new URL(url, this.base), {
-			dispatcher: this.agent,
-			headers: {
-				...options?.headers,
-				Accept: 'application/json',
-				'User-Agent': `Headplane/${__VERSION__}`,
-			},
-			body: options?.body,
-			method,
-		});
+		try {
+			const res = await request(new URL(url, this.base), {
+				dispatcher: this.agent,
+				headers: {
+					...options?.headers,
+					Accept: 'application/json',
+					'User-Agent': `Headplane/${__VERSION__}`,
+				},
+				body: options?.body,
+				method,
+			});
+
+			return res;
+		} catch (error: unknown) {
+			throw friendlyError(error);
+		}
 	}
 
 	async healthcheck() {
 		try {
-			const res = await this.defaultFetch('/health');
+			const res = await request(new URL('/health', this.base), {
+				dispatcher: this.agent,
+				headers: {
+					Accept: 'application/json',
+					'User-Agent': `Headplane/${__VERSION__}`,
+				},
+			});
+
 			return res.statusCode === 200;
 		} catch (error) {
 			log.debug('api', 'Healthcheck failed %o', error);