feat: introduce InfiniteScroll component (#2)

Author: isqua

src/Component/Component.scss renamed to src/components/Component/Component.scss

@@ -8,4 +8,4 @@ export default {
 } as Meta;
 
 export const Playground: Story<ComponentProps> = (args) => <Component {...args} />;
-Playground.storyName = 'Component';
+Playground.storyName = 'Components/Component';

src/Component/Component.tsx renamed to src/components/Component/Component.tsx

@@ -0,0 +1,12 @@
+@use '../variables';
+
+$block: '.#{variables.$ns}infinite-scroll';
+
+#{$block} {
+    &__loader {
+        width: 100%;
+        padding: 60px 0 20px;
+        display: flex;
+        justify-content: center;
+    }
+}

src/Component/__stories__/Component.stories.tsx renamed to src/components/Component/__stories__/Component.stories.tsx

@@ -0,0 +1,70 @@
+import React, {useState, useRef, useEffect} from 'react';
+import {Loader} from '@gravity-ui/uikit';
+
+import {block} from '../utils/cn';
+import {useIntersection} from './hooks/useIntersection';
+
+import './InfiniteScroll.scss';
+
+export interface InfiniteScrollProps {
+    /** When called shows loader and wait till the promise is fulfilled to hide loader */
+    onActivate: () => Promise<void>;
+    /** Turn off activation */
+    disabled: boolean;
+    children: React.ReactNode;
+    /** Custom loader */
+    loader?: React.ReactNode;
+}
+
+const b = block('infinite-scroll');
+
+export const InfiniteScroll: React.FC<InfiniteScrollProps> = ({
+    onActivate,
+    disabled,
+    children,
+    loader,
+}) => {
+    const [isActive, setIsActive] = useState(false);
+    const [bottomRef, setBottomRef] = useState<HTMLDivElement | null>(null);
+    const mounted = useRef(false);
+    const isBottomVisible = useIntersection(bottomRef);
+
+    useEffect(() => {
+        mounted.current = true;
+
+        return () => {
+            mounted.current = false;
+        };
+    }, []);
+
+    useEffect(() => {
+        const handleFetchData = async () => {
+            setIsActive(true);
+            await onActivate();
+
+            if (mounted.current) {
+                setIsActive(false);
+            }
+        };
+
+        if (isBottomVisible && !isActive && !disabled) {
+            handleFetchData();
+        }
+    }, [isBottomVisible, onActivate, isActive, disabled]);
+
+    const renderedLoader = loader || (
+        <div className={b('loader')}>
+            <Loader size="l" />
+        </div>
+    );
+
+    return (
+        <>
+            {children}
+
+            {isActive && renderedLoader}
+
+            <div className={b('intersector')} ref={setBottomRef} />
+        </>
+    );
+};

src/Component/__tests__/Component.test.ts renamed to src/components/Component/__tests__/Component.test.ts

@@ -0,0 +1,24 @@
+## InfiniteScroll
+
+The component is useful for creating infinite lists like Social Network Feed, or events history. It renders its children. If you scroll it to the bottom, it will show a loader and call an `onActivate` callback. When all the data is loaded and there is no need to load more, pass the `disabled={true}` property.
+
+### InfiniteScroll PropTypes
+
+| Property   | Type                  | Required | Default               | Description                                                                    |
+| :--------- | :-------------------- | :------: | :-------------------- | :----------------------------------------------------------------------------- |
+| onActivate | `() => Promise<void>` |  `true`  |                       | When called shows loader and wait till the promise is fulfilled to hide loader |
+| disabled   | `Boolean`             |  `true`  |                       | Turn off activation                                                            |
+| loader     | `ReactNode`           | `false`  | `<Loader size="l" />` | Custom loader component                                                        |
+
+### Example
+
+```jsx
+const {data, fetchNextPage} = useFeedQuery();
+const isAllPostsShown = data.posts.length === data.total;
+
+<InfiniteScroll onActivate={fetchNextPage} disabled={isAllPostsShown}>
+  {data.posts.map((post) => (
+    <Post key={post.id} post={post} />
+  ))}
+</InfiniteScroll>;
+```

src/Component/index.ts renamed to src/components/Component/index.ts

@@ -0,0 +1,12 @@
+import React from 'react';
+import {InfiniteScroll} from '../InfiniteScroll';
+import {InfiniteScrollShowcase} from './InfiniteScrollShowcase';
+import type {Meta, Story} from '@storybook/react';
+
+export default {
+    title: 'Components/InfiniteScroll',
+    component: InfiniteScroll,
+} as Meta;
+
+export const Playground: Story = () => <InfiniteScrollShowcase />;
+Playground.storyName = 'InfiniteScroll';

src/components/InfiniteScroll/InfiniteScroll.scss

@@ -0,0 +1,26 @@
+import React from 'react';
+
+import {InfiniteScroll} from '../InfiniteScroll';
+import {emailsList, delay} from './utils';
+
+export function InfiniteScrollShowcase() {
+    const [emails, setEmails] = React.useState<string[]>([]);
+    const [page, setPage] = React.useState<number>(0);
+    const isAllEmailsShown = emails.length >= emailsList.length;
+
+    const fetchData = async () => {
+        await delay(3000);
+        setPage(page + 1);
+        setEmails(emailsList.slice(0, (page + 1) * 10));
+    };
+
+    return (
+        <InfiniteScroll onActivate={fetchData} disabled={isAllEmailsShown}>
+            {emails.map((email, index) => (
+                <li key={index} style={{lineHeight: '90px', fontSize: '54px'}}>
+                    {email}
+                </li>
+            ))}
+        </InfiniteScroll>
+    );
+}

src/components/InfiniteScroll/InfiniteScroll.tsx

@@ -0,0 +1,39 @@
+export function delay(ms: number): Promise<void> {
+    return new Promise((resolve) => setTimeout(resolve, ms));
+}
+
+export const emailsList = [
+    'bdbrn@msn.com',
+    'chlim@yahoo.ca',
+    'tjensen@gmail.com',
+    'morain@mac.com',
+    'arachne@aol.com',
+    'cfhsoft@att.net',
+    'empathy@att.net',
+    'goldberg@outlook.com',
+    'jsnover@yahoo.ca',
+    'carreras@gmail.com',
+    'tubajon@att.net',
+    'gbacon@gmail.com',
+    'dialworld@verizon.net',
+    'fglock@sbcglobal.net',
+    'jane.smith@testfed.com',
+    'terjesa@att.net',
+    'tsuruta@optonline.net',
+    'pkplex@yahoo.ca',
+    'storerm@verizon.net',
+    'overbom@aol.com',
+    'rande@yahoo.ca',
+    'crowemojo@msn.com',
+    'tristan@yahoo.com',
+    'ducasse@comcast.net',
+    'tsuruta@mac.com',
+    'kostas@mac.com',
+    'rcwil@outlook.com',
+    'msloan@aol.com',
+    'sarahs@icloud.com',
+    'srour@aol.com',
+    'rnelson@me.com',
+    'mcnihil@live.com',
+    'treeves@me.com',
+];

src/components/InfiniteScroll/README.md

@@ -0,0 +1,19 @@
+import {useState, useEffect} from 'react';
+
+export const useIntersection = (element: Element | null, options?: IntersectionObserverInit) => {
+    const [isVisible, setState] = useState(false);
+
+    useEffect(() => {
+        const observer = new IntersectionObserver(([entry]) => {
+            setState(entry.isIntersecting);
+        }, options);
+
+        if (element) {
+            observer.observe(element);
+        }
+
+        return () => (element === null ? undefined : observer.unobserve(element));
+    }, [element, options]);
+
+    return isVisible;
+};

src/components/InfiniteScroll/__stories__/InfiniteScroll.stories.tsx

@@ -0,0 +1 @@
+export * from './InfiniteScroll';

src/components/InfiniteScroll/__stories__/InfiniteScrollShowcase.tsx

@@ -1,3 +1,4 @@
 export * from './AdaptiveTabs';
+export * from './InfiniteScroll';
 
 export {Lang, configure} from './utils/configure';