feat(web): config provider — fetch /api/config, default UI language from instance

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

web/src/config/config-context.test.tsx

@@ -0,0 +1,38 @@
+import { expect, test, beforeEach } from "vitest";
+import { screen, waitFor, render } from "@testing-library/react";
+import { QueryClient, QueryClientProvider } from "@tanstack/react-query";
+import i18n, { LOCALE_KEY } from "../i18n";
+import { ConfigProvider, useConfig } from "./config-context";
+
+function Probe() {
+  const config = useConfig();
+  return <span data-testid="lang">{config.default_language}</span>;
+}
+
+function renderProvider() {
+  const qc = new QueryClient({ defaultOptions: { queries: { retry: false } } });
+  return render(
+    <QueryClientProvider client={qc}>
+      <ConfigProvider><Probe /></ConfigProvider>
+    </QueryClientProvider>,
+  );
+}
+
+beforeEach(() => {
+  localStorage.clear();
+  void i18n.changeLanguage("en");
+});
+
+test("exposes config and applies default language when no stored preference", async () => {
+  renderProvider();
+  expect(await screen.findByTestId("lang")).toHaveTextContent("sv");
+  await waitFor(() => expect(i18n.language).toBe("sv"));
+});
+
+test("a stored locale preference wins over the instance default", async () => {
+  localStorage.setItem(LOCALE_KEY, "en");
+  void i18n.changeLanguage("en");
+  renderProvider();
+  await screen.findByTestId("lang");
+  await waitFor(() => expect(i18n.language).toBe("en"));
+});

web/src/config/config-context.tsx

@@ -0,0 +1,44 @@
+import { createContext, useContext, useEffect, type ReactNode } from "react";
+import { useQuery } from "@tanstack/react-query";
+
+import type { components } from "../api/schema";
+import { api } from "../api/client";
+import i18n, { LOCALE_KEY } from "../i18n";
+
+type ConfigView = components["schemas"]["ConfigView"];
+
+const DEFAULTS: ConfigView = {
+  app_name: "Collection Management System",
+  default_language: "sv",
+  default_timezone: "Europe/Stockholm",
+};
+
+const ConfigContext = createContext<ConfigView>(DEFAULTS);
+
+export function useConfig(): ConfigView {
+  return useContext(ConfigContext);
+}
+
+export function ConfigProvider({ children }: { children: ReactNode }) {
+  const { data } = useQuery({
+    queryKey: ["config"],
+    queryFn: async (): Promise<ConfigView> => {
+      const { data, error } = await api.GET("/api/config");
+
+      if (error || !data) throw new Error("failed to load config");
+
+      return data;
+    },
+    staleTime: Infinity,
+  });
+
+  // Default the UI language to the instance default, unless the user has chosen one for
+  // this browser (LangSwitch persists to localStorage[LOCALE_KEY]).
+  useEffect(() => {
+    if (data && !localStorage.getItem(LOCALE_KEY)) {
+      void i18n.changeLanguage(data.default_language);
+    }
+  }, [data]);
+
+  return <ConfigContext.Provider value={data ?? DEFAULTS}>{children}</ConfigContext.Provider>;
+}