chameleon/viewer/frontend/src/components/lexical/ImageComponent.tsx

/**
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 *
 * This source code is licensed under the Chameleon License found in the
 * LICENSE file in the root directory of this source tree.
 *
 */

import type {
  GridSelection,
  LexicalEditor,
  NodeKey,
  NodeSelection,
  RangeSelection,
} from "lexical";

import "./ImageNode.css";

import { useLexicalComposerContext } from "@lexical/react/LexicalComposerContext";
import { useLexicalNodeSelection } from "@lexical/react/useLexicalNodeSelection";
import { mergeRegister } from "@lexical/utils";
import {
  $getNodeByKey,
  $getSelection,
  $isNodeSelection,
  $setSelection,
  CLICK_COMMAND,
  COMMAND_PRIORITY_LOW,
  DRAGSTART_COMMAND,
  KEY_BACKSPACE_COMMAND,
  KEY_DELETE_COMMAND,
  KEY_ENTER_COMMAND,
  KEY_ESCAPE_COMMAND,
  SELECTION_CHANGE_COMMAND,
} from "lexical";
import * as React from "react";
import { Suspense, useCallback, useEffect, useRef, useState } from "react";

import { $isImageNode } from "./ImageNode";

const imageCache = new Set();

function useSuspenseImage(src: string) {
  if (!imageCache.has(src)) {
    throw new Promise((resolve) => {
      const img = new Image();
      img.src = src;
      img.onload = () => {
        imageCache.add(src);
        resolve(null);
      };
    });
  }
}

function LazyImage({
  altText,
  className,
  imageRef,
  src,
  width,
  height,
  maxWidth,
}: {
  altText: string;
  className: string | null;
  height: "inherit" | number;
  imageRef: { current: null | HTMLImageElement };
  maxWidth: number;
  src: string;
  width: "inherit" | number;
}): JSX.Element {
  useSuspenseImage(src);
  return (
    <img
      className={className || undefined}
      src={src}
      alt={altText}
      ref={imageRef}
      style={{
        height,
        maxWidth,
        width,
      }}
      draggable="false"
    />
  );
}

export default function ImageComponent({
  src,
  altText,
  nodeKey,
  width,
  height,
  maxWidth,
  showCaption,
  caption,
}: {
  altText: string;
  caption: LexicalEditor;
  height: "inherit" | number;
  maxWidth: number;
  nodeKey: NodeKey;
  showCaption: boolean;
  src: string;
  width: "inherit" | number;
}): JSX.Element {
  const imageRef = useRef<null | HTMLImageElement>(null);
  const buttonRef = useRef<HTMLButtonElement | null>(null);
  const [isSelected, setSelected, clearSelection] =
    useLexicalNodeSelection(nodeKey);
  const [editor] = useLexicalComposerContext();
  const [selection, setSelection] = useState<
    RangeSelection | NodeSelection | GridSelection | null
  >(null);
  const activeEditorRef = useRef<LexicalEditor | null>(null);

  const onDelete = useCallback(
    (payload: KeyboardEvent) => {
      if (isSelected && $isNodeSelection($getSelection())) {
        const event: KeyboardEvent = payload;
        event.preventDefault();
        const node = $getNodeByKey(nodeKey);
        if ($isImageNode(node)) {
          node.remove();
        }
      }
      return false;
    },
    [isSelected, nodeKey],
  );

  const onEnter = useCallback(
    (event: KeyboardEvent) => {
      const latestSelection = $getSelection();
      const buttonElem = buttonRef.current;
      if (
        isSelected &&
        $isNodeSelection(latestSelection) &&
        latestSelection.getNodes().length === 1
      ) {
        if (showCaption) {
          // Move focus into nested editor
          $setSelection(null);
          event.preventDefault();
          caption.focus();
          return true;
        } else if (
          buttonElem !== null &&
          buttonElem !== document.activeElement
        ) {
          event.preventDefault();
          buttonElem.focus();
          return true;
        }
      }
      return false;
    },
    [caption, isSelected, showCaption],
  );

  const onEscape = useCallback(
    (event: KeyboardEvent) => {
      if (
        activeEditorRef.current === caption ||
        buttonRef.current === event.target
      ) {
        $setSelection(null);
        editor.update(() => {
          setSelected(true);
          const parentRootElement = editor.getRootElement();
          if (parentRootElement !== null) {
            parentRootElement.focus();
          }
        });
        return true;
      }
      return false;
    },
    [caption, editor, setSelected],
  );

  useEffect(() => {
    let isMounted = true;
    const unregister = mergeRegister(
      editor.registerUpdateListener(({ editorState }) => {
        if (isMounted) {
          setSelection(editorState.read(() => $getSelection()));
        }
      }),
      editor.registerCommand(
        SELECTION_CHANGE_COMMAND,
        (_, activeEditor) => {
          activeEditorRef.current = activeEditor;
          return false;
        },
        COMMAND_PRIORITY_LOW,
      ),
      editor.registerCommand<MouseEvent>(
        CLICK_COMMAND,
        (payload) => {
          const event = payload;

          if (event.target === imageRef.current) {
            if (event.shiftKey) {
              setSelected(!isSelected);
            } else {
              clearSelection();
              setSelected(true);
            }
            return true;
          }

          return false;
        },
        COMMAND_PRIORITY_LOW,
      ),
      editor.registerCommand(
        DRAGSTART_COMMAND,
        (event) => {
          if (event.target === imageRef.current) {
            // TODO This is just a temporary workaround for FF to behave like other browsers.
            // Ideally, this handles drag & drop too (and all browsers).
            event.preventDefault();
            return true;
          }
          return false;
        },
        COMMAND_PRIORITY_LOW,
      ),
      editor.registerCommand(
        KEY_DELETE_COMMAND,
        onDelete,
        COMMAND_PRIORITY_LOW,
      ),
      editor.registerCommand(
        KEY_BACKSPACE_COMMAND,
        onDelete,
        COMMAND_PRIORITY_LOW,
      ),
      editor.registerCommand(KEY_ENTER_COMMAND, onEnter, COMMAND_PRIORITY_LOW),
      editor.registerCommand(
        KEY_ESCAPE_COMMAND,
        onEscape,
        COMMAND_PRIORITY_LOW,
      ),
    );
    return () => {
      isMounted = false;
      unregister();
    };
  }, [
    clearSelection,
    editor,
    isSelected,
    nodeKey,
    onDelete,
    onEnter,
    onEscape,
    setSelected,
  ]);

  const draggable = isSelected && $isNodeSelection(selection);
  const isFocused = isSelected;
  return (
    <Suspense fallback={null}>
      <>
        <div draggable={draggable}>
          <LazyImage
            className={
              isFocused
                ? `focused ${$isNodeSelection(selection) ? "draggable" : ""}`
                : null
            }
            src={src}
            altText={altText}
            imageRef={imageRef}
            width={width}
            height={height}
            maxWidth={maxWidth}
          />
        </div>
      </>
    </Suspense>
  );
}