Add hover cards in web UI (#30754)

Co-authored-by: Renaud Chaput <renchap@gmail.com>

app/javascript/mastodon/components/hover_card_controller.tsx

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+import { useEffect, useRef, useState, useCallback } from 'react';
+
+import { useLocation } from 'react-router-dom';
+
+import Overlay from 'react-overlays/Overlay';
+import type {
+  OffsetValue,
+  UsePopperOptions,
+} from 'react-overlays/esm/usePopper';
+
+import { useTimeout } from 'mastodon/../hooks/useTimeout';
+import { HoverCardAccount } from 'mastodon/components/hover_card_account';
+
+const offset = [-12, 4] as OffsetValue;
+const enterDelay = 650;
+const leaveDelay = 250;
+const popperConfig = { strategy: 'fixed' } as UsePopperOptions;
+
+const isHoverCardAnchor = (element: HTMLElement) =>
+  element.matches('[data-hover-card-account]');
+
+export const HoverCardController: React.FC = () => {
+  const [open, setOpen] = useState(false);
+  const [accountId, setAccountId] = useState<string | undefined>();
+  const [anchor, setAnchor] = useState<HTMLElement | null>(null);
+  const cardRef = useRef<HTMLDivElement>(null);
+  const [setLeaveTimeout, cancelLeaveTimeout] = useTimeout();
+  const [setEnterTimeout, cancelEnterTimeout] = useTimeout();
+  const location = useLocation();
+
+  const handleAnchorMouseEnter = useCallback(
+    (e: MouseEvent) => {
+      const { target } = e;
+
+      if (target instanceof HTMLElement && isHoverCardAnchor(target)) {
+        cancelLeaveTimeout();
+
+        setEnterTimeout(() => {
+          target.setAttribute('aria-describedby', 'hover-card');
+          setAnchor(target);
+          setOpen(true);
+          setAccountId(
+            target.getAttribute('data-hover-card-account') ?? undefined,
+          );
+        }, enterDelay);
+      }
+
+      if (target === cardRef.current?.parentNode) {
+        cancelLeaveTimeout();
+      }
+    },
+    [cancelLeaveTimeout, setEnterTimeout, setOpen, setAccountId, setAnchor],
+  );
+
+  const handleAnchorMouseLeave = useCallback(
+    (e: MouseEvent) => {
+      if (e.target === anchor || e.target === cardRef.current?.parentNode) {
+        cancelEnterTimeout();
+
+        setLeaveTimeout(() => {
+          anchor?.removeAttribute('aria-describedby');
+          setOpen(false);
+          setAnchor(null);
+        }, leaveDelay);
+      }
+    },
+    [cancelEnterTimeout, setLeaveTimeout, setOpen, setAnchor, anchor],
+  );
+
+  const handleClose = useCallback(() => {
+    cancelEnterTimeout();
+    cancelLeaveTimeout();
+    setOpen(false);
+    setAnchor(null);
+  }, [cancelEnterTimeout, cancelLeaveTimeout, setOpen, setAnchor]);
+
+  useEffect(() => {
+    handleClose();
+  }, [handleClose, location]);
+
+  useEffect(() => {
+    document.body.addEventListener('mouseenter', handleAnchorMouseEnter, {
+      passive: true,
+      capture: true,
+    });
+    document.body.addEventListener('mouseleave', handleAnchorMouseLeave, {
+      passive: true,
+      capture: true,
+    });
+
+    return () => {
+      document.body.removeEventListener('mouseenter', handleAnchorMouseEnter);
+      document.body.removeEventListener('mouseleave', handleAnchorMouseLeave);
+    };
+  }, [handleAnchorMouseEnter, handleAnchorMouseLeave]);
+
+  if (!accountId) return null;
+
+  return (
+    <Overlay
+      rootClose
+      onHide={handleClose}
+      show={open}
+      target={anchor}
+      placement='bottom-start'
+      flip
+      offset={offset}
+      popperConfig={popperConfig}
+    >
+      {({ props }) => (
+        <div {...props} className='hover-card-controller'>
+          <HoverCardAccount accountId={accountId} ref={cardRef} />
+        </div>
+      )}
+    </Overlay>
+  );
+};