refactor(hooks): rewrite usePagination hook

* replace `isLoadingInitialData` with `isLoading` & `isRefreshing`
* rename `fallbackData` prop to `fallback`
* replace `setSize` return with a `loadMore` callback
* add tests

4 files changed, 233 insertions, 119 deletions

diff --git a/src/utils/hooks/use-pagination.tsx b/src/utils/hooks/use-pagination.tsx
deleted file mode 100644
index 706e656..0000000
--- a/src/utils/hooks/use-pagination.tsx
+++ /dev/null
@@ -1,119 +0,0 @@
-import useSWRInfinite, { SWRInfiniteKeyLoader } from 'swr/infinite';
-import {
-  type EdgesResponse,
-  type GraphQLEdgesInput,
-  type Search,
-} from '../../types';
-
-export type UsePaginationProps<T> = {
-  /**
-   * The initial data.
-   */
-  fallbackData: EdgesResponse<T>[];
-  /**
-   * A function to fetch more data.
-   */
-  fetcher: (props: GraphQLEdgesInput & Search) => Promise<EdgesResponse<T>>;
-  /**
-   * The number of results per page.
-   */
-  perPage: number;
-  /**
-   * An optional search string.
-   */
-  search?: string;
-};
-
-export type UsePaginationReturn<T> = {
-  /**
-   * The data from the API.
-   */
-  data?: EdgesResponse<T>[];
-  /**
-   * An error thrown by fetcher.
-   */
-  error: any;
-  /**
-   * Determine if there's more data to fetch.
-   */
-  hasNextPage?: boolean;
-  /**
-   * Determine if the initial data is loading.
-   */
-  isLoadingInitialData: boolean;
-  /**
-   * Determine if more data is currently loading.
-   */
-  isLoadingMore?: boolean;
-  /**
-   * Determine if the data is refreshing.
-   */
-  isRefreshing?: boolean;
-  /**
-   * Determine if there's a request or revalidation loading.
-   */
-  isValidating: boolean;
-  /**
-   * Set the number of pages that need to be fetched.
-   */
-  setSize: (
-    size: number | ((_size: number) => number)
-  ) => Promise<EdgesResponse<T>[] | undefined>;
-};
-
-/**
- * Handle data fetching with pagination.
- *
- * This hook is a wrapper of `useSWRInfinite` hook.
- *
- * @param {UsePaginationProps} props - The pagination configuration.
- * @returns {UsePaginationReturn} An object with pagination data and helpers.
- */
-export const usePagination = <T extends object>({
-  fallbackData,
-  fetcher,
-  perPage,
-  search,
-}: UsePaginationProps<T>): UsePaginationReturn<T> => {
-  const getKey: SWRInfiniteKeyLoader = (
-    pageIndex: number,
-    previousData: EdgesResponse<T>
-  ): (GraphQLEdgesInput & Search) | null => {
-    // Reached the end.
-    if (previousData && !previousData.edges.length) return null;
-
-    // Fetch data using this parameters.
-    return pageIndex === 0
-      ? { first: perPage, search }
-      : {
-          first: perPage,
-          after: previousData.pageInfo.endCursor,
-          search,
-        };
-  };
-
-  const { data, error, isValidating, size, setSize } = useSWRInfinite(
-    getKey,
-    fetcher,
-    { fallbackData }
-  );
-
-  const isLoadingInitialData = !data && !error;
-  const isLoadingMore =
-    isLoadingInitialData ||
-    (size > 0 && data && typeof data[size - 1] === 'undefined');
-  const isRefreshing = isValidating && data && data.length === size;
-  const hasNextPage =
-    data && data.length > 0 && data[data.length - 1].pageInfo.hasNextPage;
-
-  return {
-    data,
-    error,
-    hasNextPage,
-    isLoadingInitialData,
-    isLoadingMore,
-    isRefreshing,
-    isValidating,
-    setSize,
-  };
-};
diff --git a/src/utils/hooks/use-pagination/index.ts b/src/utils/hooks/use-pagination/index.ts
new file mode 100644
index 0000000..a372577
--- /dev/null
+++ b/src/utils/hooks/use-pagination/index.ts
@@ -0,0 +1 @@
+export * from './use-pagination';
diff --git a/src/utils/hooks/use-pagination/use-pagination.test.ts b/src/utils/hooks/use-pagination/use-pagination.test.ts
new file mode 100644
index 0000000..20cb37e
--- /dev/null
+++ b/src/utils/hooks/use-pagination/use-pagination.test.ts
@@ -0,0 +1,96 @@
+import { beforeEach, describe, expect, it, jest } from '@jest/globals';
+import { act, renderHook, waitFor } from '@testing-library/react';
+import { getConnection } from '../../../../tests/utils/graphql';
+import type { EdgesResponse, GraphQLEdgesInput, Search } from '../../../types';
+import { usePagination } from './use-pagination';
+
+type Data = {
+  id: number;
+  title: string;
+};
+
+describe('usePagination', () => {
+  const data: Data[] = [
+    { id: 1, title: 'illo sequi nihil' },
+    { id: 2, title: 'atque et magni' },
+    { id: 3, title: 'cupiditate ut sit' },
+    { id: 4, title: 'aut rerum quisquam' },
+    { id: 5, title: 'et ea officia' },
+    { id: 6, title: 'ratione eos numquam' },
+    { id: 7, title: 'repellat quos et' },
+  ];
+  const fetcher = jest.fn(
+    async ({
+      after,
+      first,
+      search,
+    }: GraphQLEdgesInput & Search): Promise<EdgesResponse<Data>> => {
+      const filteredData = search
+        ? data.filter((d) => d.title.includes(search))
+        : data;
+
+      return Promise.resolve(
+        getConnection({ after, first, data: filteredData })
+      );
+    }
+  );
+
+  beforeEach(() => {
+    jest.clearAllMocks();
+  });
+
+  it('can use a fetcher to retrieve data from a GraphQL API', async () => {
+    /* We should use this statement because of async nature but with waitFor
+     * the number of assertion in inaccurate... */
+    // eslint-disable-next-line @typescript-eslint/no-magic-numbers
+    //expect.assertions(6);
+
+    expect(fetcher).not.toHaveBeenCalled();
+
+    const perPage = 10;
+    const { result } = renderHook(() =>
+      usePagination({
+        fetcher,
+        perPage,
+      })
+    );
+
+    await waitFor(() => {
+      // `data.length` is lower than `perPage` so 1 page.
+      expect(result.current.data?.length).toBe(1);
+    });
+    expect(result.current.data?.[0].edges.length).toBe(data.length);
+    expect(result.current.hasNextPage).toBe(false);
+    expect(fetcher).toHaveBeenCalledTimes(1);
+    expect(fetcher).toHaveBeenCalledWith({ first: perPage });
+  });
+
+  it('can retrieve more data from the GraphQL API', async () => {
+    /* We should use this statement because of async nature but with waitFor
+     * the number of assertion in inaccurate... */
+    // eslint-disable-next-line @typescript-eslint/no-magic-numbers
+    //expect.assertions(7);
+
+    const perPage = 5;
+    const { result } = renderHook(() =>
+      usePagination({
+        fetcher,
+        perPage,
+      })
+    );
+
+    await waitFor(() => {
+      expect(result.current.data?.length).toBe(1);
+    });
+    expect(result.current.data?.[0].edges.length).toBe(perPage);
+    expect(result.current.hasNextPage).toBe(true);
+    expect(fetcher).toHaveBeenCalledTimes(1);
+
+    await act(async () => {
+      await result.current.loadMore();
+    });
+
+    expect(result.current.data?.length).toBe(2);
+    expect(result.current.data?.[1].edges.length).toBe(data.length - perPage);
+  });
+});
diff --git a/src/utils/hooks/use-pagination/use-pagination.ts b/src/utils/hooks/use-pagination/use-pagination.ts
new file mode 100644
index 0000000..4df521b
--- /dev/null
+++ b/src/utils/hooks/use-pagination/use-pagination.ts
@@ -0,0 +1,136 @@
+import { useCallback } from 'react';
+import useSWRInfinite, { type SWRInfiniteKeyLoader } from 'swr/infinite';
+import type {
+  EdgesResponse,
+  GraphQLEdgesInput,
+  Maybe,
+  Nullable,
+  Search,
+} from '../../../types';
+
+export type UsePaginationConfig<T> = {
+  /**
+   * The initial data.
+   */
+  fallback?: EdgesResponse<T>[];
+  /**
+   * A function to fetch more data.
+   */
+  fetcher: (props: GraphQLEdgesInput & Search) => Promise<EdgesResponse<T>>;
+  /**
+   * The number of results per page.
+   */
+  perPage: number;
+  /**
+   * An optional search string.
+   */
+  searchQuery?: string;
+};
+
+export type UsePaginationReturn<T> = {
+  /**
+   * The data from the API.
+   */
+  data: Maybe<EdgesResponse<T>[]>;
+  /**
+   * An error thrown by fetcher.
+   */
+  error: unknown;
+  /**
+   * Determine if there's more data to fetch.
+   */
+  hasNextPage: Maybe<boolean>;
+  /**
+   * Determine if there is some data.
+   */
+  isEmpty: boolean;
+  /**
+   * Determine if there is some errors.
+   */
+  isError: boolean;
+  /**
+   * Determine if there is an ongoing request and no loaded data.
+   */
+  isLoading: boolean;
+  /**
+   * Determine if more data is currently loading.
+   */
+  isLoadingMore: boolean;
+  /**
+   * Determine if the data is refreshing.
+   */
+  isRefreshing: boolean;
+  /**
+   * Determine if there's a request or revalidation loading.
+   */
+  isValidating: boolean;
+  /**
+   * A callback function to load more data.
+   */
+  loadMore: () => Promise<void>;
+  /**
+   * Determine the number of pages that will be fetched and returned.
+   */
+  size: number;
+};
+
+/**
+ * Handle data fetching with pagination.
+ *
+ * This hook is a wrapper of `useSWRInfinite` hook.
+ *
+ * @param {UsePaginationConfig<T>} props - The pagination configuration.
+ * @returns {UsePaginationReturn} An object with pagination data and helpers.
+ */
+export const usePagination = <T>({
+  fallback,
+  fetcher,
+  perPage,
+  searchQuery,
+}: UsePaginationConfig<T>): UsePaginationReturn<T> => {
+  const getKey: SWRInfiniteKeyLoader<EdgesResponse<T>> = useCallback(
+    (pageIndex, previousPageData): Nullable<GraphQLEdgesInput & Search> => {
+      if (previousPageData && !previousPageData.edges.length) return null;
+
+      return {
+        first: perPage,
+        after:
+          pageIndex === 0 ? undefined : previousPageData?.pageInfo.endCursor,
+        search: searchQuery,
+      };
+    },
+    [perPage, searchQuery]
+  );
+
+  const { data, error, isLoading, isValidating, setSize, size } =
+    useSWRInfinite(getKey, fetcher, { fallbackData: fallback });
+
+  const loadMore = useCallback(async () => {
+    await setSize((prevSize) => prevSize + 1);
+  }, [setSize]);
+
+  const hasNextPage =
+    data && data.length > 0 && data[data.length - 1].pageInfo.hasNextPage;
+
+  const isLoadingMore = data
+    ? isLoading || (size > 0 && typeof data[size - 1] === 'undefined')
+    : false;
+
+  const isEmpty = data?.[0]?.edges.length === 0;
+
+  const isRefreshing = data ? isValidating && data.length === size : false;
+
+  return {
+    data,
+    error,
+    hasNextPage,
+    isEmpty,
+    isError: !!error,
+    isLoading,
+    isLoadingMore,
+    isRefreshing,
+    isValidating,
+    loadMore,
+    size,
+  };
+};