Fix useMapData debounce loading state

Docs/Tasks.md

@@ -205,7 +205,7 @@ Issues are grouped by category and ordered roughly by severity. Each entry descr
 
 ---
 
-### TASK-011 — No `React.memo` on any heavy component
+### TASK-011 — No `React.memo` on any heavy component (done)
 
 **Where found:** Every component in `frontend/src/components/` — zero uses of `React.memo` exist in the codebase.
 
@@ -222,7 +222,9 @@ Issues are grouped by category and ordered roughly by severity. Each entry descr
 
 ---
 
-### TASK-012 — `useMapData` sets `loading=true` before the debounce fires
+### TASK-012 — `useMapData` sets `loading=true` before the debounce fires (done)
+
+**Where fixed:** `frontend/src/hooks/useMapData.ts`, `frontend/src/hooks/__tests__/useMapData.test.ts`
 
 **Where found:** `frontend/src/hooks/useMapData.ts`, `load` callback — `setLoading(true)` is called at the top of `load`, but the actual fetch is deferred inside a `setTimeout` of 300 ms.
 

frontend/src/hooks/__tests__/useMapData.test.ts

@@ -0,0 +1,78 @@
+import { describe, expect, it, vi, beforeEach } from "vitest";
+import { renderHook, act, waitFor } from "@testing-library/react";
+import type { BansByCountryResponse } from "../../types/map";
+import { useMapData } from "../useMapData";
+import * as api from "../../api/map";
+
+vi.mock("../../api/map");
+
+describe("useMapData", () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+  });
+
+  it("delays loading until the debounced fetch begins", async () => {
+    const fetchMock = vi.mocked(api.fetchBansByCountry);
+    const firstResponse: BansByCountryResponse = {
+      countries: { US: 1 },
+      country_names: { US: "United States" },
+      bans: [],
+      total: 1,
+    };
+    const secondResponse: BansByCountryResponse = {
+      countries: { US: 2 },
+      country_names: { US: "United States" },
+      bans: [],
+      total: 2,
+    };
+
+    let secondResolve: (value: BansByCountryResponse) => void;
+    fetchMock.mockResolvedValueOnce(firstResponse);
+    fetchMock.mockImplementationOnce(
+      () =>
+        new Promise<BansByCountryResponse>((resolve) => {
+          secondResolve = resolve;
+        }),
+    );
+
+    const { result } = renderHook(() => useMapData("24h", "all", "fail2ban"));
+
+    await act(async () => {
+      await new Promise((resolve) => setTimeout(resolve, 310));
+    });
+
+    await waitFor(() => {
+      expect(result.current.loading).toBe(false);
+    });
+
+    expect(fetchMock).toHaveBeenCalledTimes(1);
+
+    act(() => {
+      result.current.refresh();
+    });
+
+    expect(result.current.loading).toBe(false);
+
+    await act(async () => {
+      await new Promise((resolve) => setTimeout(resolve, 100));
+    });
+
+    expect(result.current.loading).toBe(false);
+    expect(fetchMock).toHaveBeenCalledTimes(1);
+
+    await act(async () => {
+      await new Promise((resolve) => setTimeout(resolve, 250));
+    });
+
+    expect(result.current.loading).toBe(true);
+    expect(fetchMock).toHaveBeenCalledTimes(2);
+
+    await act(async () => {
+      secondResolve(secondResponse);
+      await Promise.resolve();
+    });
+
+    expect(result.current.loading).toBe(false);
+    expect(result.current.total).toBe(2);
+  });
+});

frontend/src/hooks/useMapData.ts

@@ -57,11 +57,11 @@ export function useMapData(
     if (debounceRef.current != null) {
       clearTimeout(debounceRef.current);
     }
-    // Show loading immediately so the skeleton / spinner appears.
-    setLoading(true);
     setError(null);
 
     debounceRef.current = setTimeout((): void => {
+      // Show loading only when the fetch is about to start.
+      setLoading(true);
       // Abort any in-flight request from a previous filter selection.
       abortRef.current?.abort();
       abortRef.current = new AbortController();