feat(new-ui): add image prefetch in new ui

lib/static/modules/utils/imageEntity.ts

@@ -0,0 +1,54 @@
+import {ImageEntity, ImageEntityCommitted, ImageEntityError, ImageEntityFail, ImageEntityStaged, ImageEntitySuccess, ImageEntityUpdated} from '../../new-ui/types/store';
+
+function preloadImage(url: string): HTMLElement {
+    const link = document.createElement('link');
+
+    link.rel = 'preload';
+    link.as = 'image';
+    link.href = url;
+    link.onload;
+
+    document.head.appendChild(link);
+
+    return link;
+}
+
+function hasExpectedImage(image: ImageEntity): image is ImageEntityFail | ImageEntitySuccess | ImageEntityUpdated {
+    return Object.hasOwn(image, 'expectedImg');
+}
+
+function hasActualImage(image: ImageEntity): image is ImageEntityFail | ImageEntityCommitted | ImageEntityError | ImageEntityStaged {
+    return Object.hasOwn(image, 'actualImg');
+}
+
+function hasDiffImage(image: ImageEntity): image is ImageEntityFail {
+    return Object.hasOwn(image, 'diffImg');
+}
+
+function hasRefImage(image: ImageEntity): image is ImageEntityFail {
+    return Object.hasOwn(image, 'refImg');
+}
+
+export function preloadImageEntity(image: ImageEntity): () => void {
+    const elements: HTMLElement[] = [];
+
+    if (hasExpectedImage(image)) {
+        elements.push(preloadImage(image.expectedImg.path));
+    }
+
+    if (hasActualImage(image)) {
+        elements.push(preloadImage(image.actualImg.path));
+    }
+
+    if (hasDiffImage(image)) {
+        elements.push(preloadImage(image.diffImg.path));
+    }
+
+    if (hasRefImage(image)) {
+        elements.push(preloadImage(image.refImg.path));
+    }
+
+    return (): void => {
+        elements.forEach(element => element.remove());
+    };
+}

lib/static/modules/utils/index.js

@@ -160,6 +160,10 @@ export function parseKeyToGroupTestsBy(key) {
     return [groupSection, groupKey];
 }
 
+/** @deprecated - this is just not working.
+ * @link https://stackoverflow.com/questions/3646036/preloading-images-with-javascript
+ * @see preloadImage from lib/static/modules/utils/imageEntity.ts instead
+ */
 export function preloadImage(url) {
     new Image().src = url;
 }

lib/static/new-ui/components/SuiteTitle/index.tsx

@@ -49,9 +49,9 @@ export function SuiteTitle(props: SuiteTitlePropsInternal): ReactNode {
         </div>
         <div className={styles.paginationContainer}>
             <span className={styles.counter}>{props.index === -1 ? '–' : props.index + 1}/{props.totalItems}</span>
-            <Button view={'flat'} disabled={props.index <= 0} onClick={props.onPrevious}><Icon
+            <Button qa='suite-prev' view={'flat'} disabled={props.index <= 0} onClick={props.onPrevious}><Icon
                 data={ChevronUp}/></Button>
-            <Button view={'flat'} disabled={props.index < 0 || props.index === props.totalItems - 1} onClick={props.onNext}><Icon
+            <Button qa='suite-next' view={'flat'} disabled={props.index < 0 || props.index === props.totalItems - 1} onClick={props.onNext}><Icon
                 data={ChevronDown}/></Button>
         </div>
     </div>;

lib/static/new-ui/features/visual-checks/components/VisualChecksPage/index.tsx

@@ -1,14 +1,15 @@
 import {ArrowUturnCcwLeft, Check} from '@gravity-ui/icons';
 import {Button, Divider, Icon, Select} from '@gravity-ui/uikit';
 import classNames from 'classnames';
-import React, {ReactNode} from 'react';
+import React, {ReactNode, useEffect, useRef} from 'react';
 import {useDispatch, useSelector} from 'react-redux';
 
 import {SplitViewLayout} from '@/static/new-ui/components/SplitViewLayout';
 import {UiCard} from '@/static/new-ui/components/Card/UiCard';
 import {
     getCurrentImage,
     getCurrentNamedImage,
+    getImagesByNamedImageIds,
     getVisibleNamedImageIds
 } from '@/static/new-ui/features/visual-checks/selectors';
 import {SuiteTitle} from '@/static/new-ui/components/SuiteTitle';
@@ -28,6 +29,36 @@ import {
 } from '@/static/new-ui/features/visual-checks/components/VisualChecksPage/AssertViewResultSkeleton';
 import {thunkAcceptImages, thunkRevertImages} from '@/static/modules/actions/screenshots';
 import {useAnalytics} from '@/static/new-ui/hooks/useAnalytics';
+import {preloadImageEntity} from '../../../../../modules/utils/imageEntity';
+
+export const PRELOAD_IMAGES_COUNT = 3;
+
+const usePreloadImages = (
+    currentNamedImageIndex: number,
+    visibleNamedImageIds: string[]): void => {
+    const preloaded = useRef<Record<string, () => void | undefined>>({});
+
+    const namedImageIdsToPreload: string[] = visibleNamedImageIds.slice(
+        Math.max(0, currentNamedImageIndex - 1 - PRELOAD_IMAGES_COUNT),
+        Math.min(visibleNamedImageIds.length, currentNamedImageIndex + 1 + PRELOAD_IMAGES_COUNT)
+    );
+
+    const imagesToPreload = useSelector((state) => getImagesByNamedImageIds(state, namedImageIdsToPreload));
+
+    useEffect(() => {
+        imagesToPreload.forEach(image => {
+            if (preloaded.current[image.id]) {
+                return;
+            }
+
+            preloaded.current[image.id] = preloadImageEntity(image);
+        });
+    }, [currentNamedImageIndex]);
+
+    useEffect(() => () => {
+        Object.values(preloaded.current).forEach(preload => preload?.());
+    }, []);
+};
 
 export function VisualChecksPage(): ReactNode {
     const dispatch = useDispatch();
@@ -41,6 +72,8 @@ export function VisualChecksPage(): ReactNode {
     const onPreviousImageHandler = (): void => void dispatch(visualChecksPageSetCurrentNamedImage(visibleNamedImageIds[currentNamedImageIndex - 1]));
     const onNextImageHandler = (): void => void dispatch(visualChecksPageSetCurrentNamedImage(visibleNamedImageIds[currentNamedImageIndex + 1]));
 
+    usePreloadImages(currentNamedImageIndex, visibleNamedImageIds);
+
     const diffMode = useSelector(state => state.view.diffMode);
     const onChangeHandler = (diffModeId: DiffModeId): void => {
         dispatch(setDiffMode({diffModeId}));

lib/static/new-ui/features/visual-checks/selectors.ts

@@ -111,6 +111,25 @@ export const getCurrentImage = (state: State): ImageEntity | null => {
     return getImages(state)[currentImageId];
 };
 
+export const getImagesByNamedImageIds = (state: State, names: string[]): ImageEntity[] => {
+    const results: ImageEntity[] = [];
+
+    const images = getImages(state);
+    const namedImages = getNamedImages(state);
+
+    for (const name of names) {
+        const namedImage = namedImages[name];
+
+        if (!namedImage) {
+            continue;
+        }
+
+        results.push(...namedImage.imageIds.map(id => images[id]));
+    }
+
+    return results;
+};
+
 export const getVisibleNamedImageIds = createSelector([getNamedImages], (namedImages): string[] => {
     return Object.values(namedImages).map(namedImage => namedImage.id);
 });

test/unit/lib/static/new-ui/features/visual-checks/components/VisualChecksPage.jsx

@@ -0,0 +1,68 @@
+import React from 'react';
+import {addBrowserToTree, addImageToTree, addResultToTree, addSuiteToTree, mkBrowserEntity, mkEmptyTree, mkImageEntityFail, mkRealStore, mkResultEntity, mkSuiteEntityLeaf, renderWithStore} from '../../../../utils';
+import proxyquire from 'proxyquire';
+
+describe('<VisualChecksPage />', () => {
+    const sandbox = sinon.sandbox.create();
+
+    const prepareTestStore = () => {
+        const tree = mkEmptyTree();
+
+        const suite = mkSuiteEntityLeaf(`test-1`);
+        addSuiteToTree({tree, suite});
+
+        const browser = mkBrowserEntity(`bro-1`, {parentId: suite.id});
+        addBrowserToTree({tree, browser});
+
+        const result = mkResultEntity(`res-1`, {parentId: browser.id});
+        addResultToTree({tree, result});
+
+        for (const i of Array.from({length: 10}).map((_, i) => i + 1)) {
+            const image = mkImageEntityFail(`img-${i}`, {parentId: result.id});
+            addImageToTree({tree, image});
+        }
+
+        const store = mkRealStore({
+            initialState: {
+                app: {
+                    isInitialized: true
+                },
+                tree
+            }
+        });
+
+        return store;
+    };
+
+    let store;
+    let component;
+    let preloadImageEntityStub;
+
+    beforeEach(() => {
+        preloadImageEntityStub = sandbox.stub();
+
+        store = prepareTestStore();
+
+        const VisualChecksPage = proxyquire('lib/static/new-ui/features/visual-checks/components/VisualChecksPage', {
+            '../../../../../modules/utils/imageEntity': {preloadImageEntity: preloadImageEntityStub}
+        }).VisualChecksPage;
+
+        component = renderWithStore(<VisualChecksPage />, store);
+    });
+
+    afterEach(() => {
+        sandbox.restore();
+    });
+
+    it('should preload current and 3 adjacent images on mount', async () => {
+        const state = store.getState();
+        const orderedImages = Object.values(state.tree.images.byId);
+
+        for (let i = 0; i < 3; i++) {
+            assert.calledWith(
+                preloadImageEntityStub,
+                orderedImages[i]
+            );
+        }
+    });
+});