Replace react-router-scroll-4 with inlined implementation (#36253)

app/javascript/mastodon/containers/scroll_container/scroll_context.tsx

@@ -0,0 +1,141 @@
+import React, { useEffect, useMemo, useRef, useState } from 'react';
+
+import { useLocation, useHistory } from 'react-router-dom';
+
+import type { LocationBase } from 'scroll-behavior';
+import ScrollBehavior from 'scroll-behavior';
+
+import type {
+  LocationState,
+  MastodonLocation,
+} from 'mastodon/components/router';
+import { usePrevious } from 'mastodon/hooks/usePrevious';
+
+import { defaultShouldUpdateScroll } from './default_should_update_scroll';
+import type { ShouldUpdateScrollFn } from './default_should_update_scroll';
+import { SessionStorage } from './state_storage';
+
+type ScrollBehaviorInstance = InstanceType<
+  typeof ScrollBehavior<LocationBase, MastodonLocation>
+>;
+
+export interface ScrollBehaviorContextType {
+  registerElement: (
+    key: string,
+    element: HTMLElement,
+    shouldUpdateScroll: (
+      prevLocationContext: MastodonLocation | null,
+      locationContext: MastodonLocation,
+    ) => boolean,
+  ) => void;
+  unregisterElement: (key: string) => void;
+  scrollBehavior?: ScrollBehaviorInstance;
+}
+
+export const ScrollBehaviorContext =
+  React.createContext<ScrollBehaviorContextType | null>(null);
+
+interface ScrollContextProps {
+  shouldUpdateScroll?: ShouldUpdateScrollFn;
+  children: React.ReactElement;
+}
+
+/**
+ * A top-level wrapper that provides the app with an instance of the
+ * ScrollBehavior object. scroll-behavior is a library for managing the
+ * scroll position of a single-page app in the same way the browser would
+ * normally do for a multi-page app. This means it'll scroll back to top
+ * when navigating to a new page, and will restore the scroll position
+ * when navigating e.g. using `history.back`.
+ * The library keeps a record of scroll positions in session storage.
+ *
+ * This component is a port of the unmaintained https://github.com/ytase/react-router-scroll/
+ */
+
+export const ScrollContext: React.FC<ScrollContextProps> = ({
+  children,
+  shouldUpdateScroll = defaultShouldUpdateScroll,
+}) => {
+  const location = useLocation<LocationState>();
+  const history = useHistory<LocationState>();
+
+  /**
+   * Keep the current location in a mutable ref so that ScrollBehavior's
+   * `getCurrentLocation` can access it without having to recreate the
+   * whole ScrollBehavior object
+   */
+  const currentLocationRef = useRef(location);
+  useEffect(() => {
+    currentLocationRef.current = location;
+  }, [location]);
+
+  /**
+   * Initialise ScrollBehavior object once – using state rather
+   * than a ref to simplify the types and ensure it's defined immediately.
+   */
+  const [scrollBehavior] = useState(
+    (): ScrollBehaviorInstance =>
+      new ScrollBehavior({
+        addNavigationListener: history.listen.bind(history),
+        stateStorage: new SessionStorage(),
+        getCurrentLocation: () =>
+          currentLocationRef.current as unknown as LocationBase,
+        shouldUpdateScroll: (
+          prevLocationContext: MastodonLocation | null,
+          locationContext: MastodonLocation,
+        ) =>
+          // Hack to allow accessing scrollBehavior._stateStorage
+          shouldUpdateScroll.call(
+            scrollBehavior,
+            prevLocationContext,
+            locationContext,
+          ),
+      }),
+  );
+
+  /**
+   * Handle scroll update when location changes
+   */
+  const prevLocation = usePrevious(location) ?? null;
+  useEffect(() => {
+    scrollBehavior.updateScroll(prevLocation, location);
+  }, [location, prevLocation, scrollBehavior]);
+
+  /**
+   * Stop Scrollbehavior on unmount
+   */
+  useEffect(() => {
+    return () => {
+      scrollBehavior.stop();
+    };
+  }, [scrollBehavior]);
+
+  /**
+   * Provide the app with a way to register separately scrollable
+   * elements to also be tracked by ScrollBehavior. (By default
+   * ScrollBehavior only handles scrolling on the main document body.)
+   */
+  const contextValue = useMemo<ScrollBehaviorContextType>(
+    () => ({
+      registerElement: (key, element, shouldUpdateScroll) => {
+        scrollBehavior.registerElement(
+          key,
+          element,
+          shouldUpdateScroll,
+          location,
+        );
+      },
+      unregisterElement: (key) => {
+        scrollBehavior.unregisterElement(key);
+      },
+      scrollBehavior,
+    }),
+    [location, scrollBehavior],
+  );
+
+  return (
+    <ScrollBehaviorContext.Provider value={contextValue}>
+      {React.Children.only(children)}
+    </ScrollBehaviorContext.Provider>
+  );
+};