Fixing bug where pagination would show an extra link that would load no results.

app/src/hooks/customHooks.js

@@ -139,7 +139,7 @@ const calculateTotalPages = (total, limit) => {
     if (!total || !limit || total < limit) {
         return 1;
     }
-    return Math.round(total / limit) + 1;
+    return Math.ceil(total / limit);
 }
 
 export const useRecurringTimeout = (callback, delay) => {

app/src/hooks/customHooks.test.js

@@ -0,0 +1,113 @@
+import React from 'react';
+import {act, renderHook} from '@testing-library/react';
+import {render, screen} from '@testing-library/react';
+import {usePages} from './customHooks';
+import {QueryContext} from '../contexts/contexts';
+import {Paginator} from '../components/Common';
+
+// Build a wrapper that provides a controlled QueryContext so usePages can read
+// `o` and `l` from searchParams without a real router.
+const makeWrapper = (initialParams = {}) => {
+    const params = new URLSearchParams(initialParams);
+    const Wrapper = ({children}) => {
+        const [searchParams, setSearchParams] = React.useState(params);
+
+        const updateQuery = (newParams) => {
+            const next = new URLSearchParams(searchParams.toString());
+            Object.entries(newParams).forEach(([k, v]) => {
+                if (v === null || v === undefined) {
+                    next.delete(k);
+                } else {
+                    next.set(k, String(v));
+                }
+            });
+            setSearchParams(next);
+        };
+
+        return (
+            <QueryContext.Provider value={{searchParams, updateQuery, getLocationStr: () => '/'}}>
+                {children}
+            </QueryContext.Provider>
+        );
+    };
+    return Wrapper;
+};
+
+// Mock Media so Paginator renders both mobile + tablet variants synchronously.
+jest.mock('../contexts/contexts', () => {
+    const actual = jest.requireActual('../contexts/contexts');
+    return {
+        ...actual,
+        Media: ({children}) => <>{children}</>,
+    };
+});
+
+describe('usePages.setTotal -> totalPages', () => {
+    // These cases describe the contract: how many pages should the Paginator
+    // render given a total result count and a per-page limit?
+    const cases = [
+        // [total, limit, expectedPages, label]
+        [0, 24, 1, 'no results -> 1 page'],
+        [1, 24, 1, 'fewer than one page'],
+        [23, 24, 1, 'just under one page'],
+        [24, 24, 1, 'exactly one page (BUG: reports 2)'],
+        [25, 24, 2, 'one full page plus one'],
+        [47, 24, 2, 'just under two pages'],
+        [48, 24, 2, 'exactly two pages (BUG: reports 3)'],
+        [49, 24, 3, 'just over two pages'],
+        [72, 24, 3, 'exactly three pages (BUG: reports 4)'],
+        [100, 24, 5, 'partial last page'],
+        [144, 24, 6, 'exactly six pages (BUG: reports 7)'],
+    ];
+
+    test.each(cases)('total=%i limit=%i -> %i pages (%s)', (total, limit, expected) => {
+        const wrapper = makeWrapper({l: String(limit)});
+        const {result} = renderHook(() => usePages(limit), {wrapper});
+
+        act(() => {
+            result.current.setTotal(total);
+        });
+
+        expect(result.current.totalPages).toBe(expected);
+    });
+
+    test('the last reported page yields an offset within total (no empty trailing page)', () => {
+        // This is the user-visible symptom: clicking the last page link should
+        // produce an offset that the API can still satisfy.  When totalPages is
+        // off-by-one, the last page maps to offset === total (or > total) and
+        // the API returns zero rows.
+        const total = 48;
+        const limit = 24;
+        const wrapper = makeWrapper({l: String(limit)});
+        const {result} = renderHook(() => usePages(limit), {wrapper});
+
+        act(() => {
+            result.current.setTotal(total);
+        });
+
+        act(() => {
+            result.current.setPage(result.current.totalPages);
+        });
+
+        // setPage stores (page - 1) * limit as `o` in the query.
+        const lastOffset = (result.current.totalPages - 1) * limit;
+        expect(lastOffset).toBeLessThan(total);
+    });
+});
+
+describe('Paginator rendering', () => {
+    test('renders exactly totalPages numbered page links (no phantom trailing link)', () => {
+        // 48 results at 24 per page -> 2 pages.  If totalPages is 3, semantic-ui
+        // will render an extra "3" link that fetches an empty page.
+        render(
+            <Paginator activePage={1} totalPages={2} onPageChange={() => {}}/>
+        );
+
+        // Semantic UI renders page numbers as <a> elements with the page text.
+        // Tablet + mobile variants both render here because Media is mocked to
+        // pass children through, so each numeric page appears at least once.
+        expect(screen.queryAllByText('1').length).toBeGreaterThan(0);
+        expect(screen.queryAllByText('2').length).toBeGreaterThan(0);
+        expect(screen.queryByText('3')).toBeNull();
+    });
+});