'Genericise' errors ready for +error.svelte upgrade to handle known errors

src/lib/owlClient.ts

@@ -1,5 +1,6 @@
 import { OwlBoardClient, ValidationError, ApiError } from '@owlboard/owlboard-ts';
 import { browser, dev } from '$app/environment';
+import { error } from '@sveltejs/kit';
 
 // Import the runes containing the API Key config Here...
 
@@ -18,6 +19,46 @@ export const OwlClient = new OwlBoardClient(
 	// API Key Here when ready!!!
 );
 
-export function ThrowApiError(e: any): void {}
+export function ThrowApiError(e: unknown): never {
+	// Handle Request failure
+	if (e instanceof TypeError && e.message === 'Failed to fetch') {
+		throw error(503, {
+			message: 'Unable to connect to the OwlBoard server',
+			name: 'NETWORK_ERROR',
+			code: 'NETWORK_UNREACHABLE'
+		});
+	}
+
+	// Map ApiError 'code' values
+	if (e instanceof ApiError) {
+		let status = 500;
+		if (e.code === 'AUTH') {
+			status = 401;
+		} else if (e.code === 'NOT_FOUND') {
+			status = 404;
+		} else if (e.code === 'RATE_LIMIT') {
+			status = 421;
+		} else if (e.code === 'NETWORK_DISCONNECTED') {
+			status = 503;
+		} else if (e.code === 'VALIDATION') {
+			status = 400;
+		}
+
+		throw error(status, {
+			message: e.message || 'An operational error has occurred',
+			name: e.name || 'API_ERROR',
+			code: e.code || 'UNKNOWN_API_ERROR'
+		});
+	}
+
+	// Fallback for other error kind
+	const genericMessage = e instanceof Error ? e.message : 'An unexpected error occurred.';
+	throw error(500, {
+		message: genericMessage,
+		name: 'CRITICAL_ERROR',
+		code: 'INTERNAL_ERROR',
+		msg: 'UNHANDLED_EXCEPTION'
+	});
+}
 
 export { ValidationError, ApiError };