docbrown/app/javascript/article-form/components/EditorBody.jsx

import { h } from 'preact';
import PropTypes from 'prop-types';
import Textarea from 'preact-textarea-autosize';
import { useEffect, useRef } from 'preact/hooks';
import { Toolbar } from './Toolbar';
import {
  handleImageDrop,
  handleImageFailure,
  onDragOver,
  onDragExit,
} from './dragAndDropHelpers';
import { useDragAndDrop } from '@utilities/dragAndDrop';

function handleImageSuccess(textAreaRef) {
  return function (response) {
    // Function is within the component to be able to access
    // textarea ref.
    const editableBodyElement = textAreaRef.current.base;
    const { links, image } = response;
    const altText = image[0].name.replace(/\.[^.]+$/, '');
    const markdownImageLink = `![${altText}](${links[0]})\n`;
    const { selectionStart, selectionEnd, value } = editableBodyElement;
    const before = value.substring(0, selectionStart);
    const after = value.substring(selectionEnd, value.length);

    editableBodyElement.value = `${before + markdownImageLink} ${after}`;
    editableBodyElement.selectionStart =
      selectionStart + markdownImageLink.length;
    editableBodyElement.selectionEnd = editableBodyElement.selectionStart;

    // Dispatching a new event so that linkstate, https://github.com/developit/linkstate,
    // the function used to create the onChange prop gets called correctly.
    editableBodyElement.dispatchEvent(new Event('input'));
  };
}

export const EditorBody = ({
  onChange,
  defaultValue,
  switchHelpContext,
  version,
}) => {
  const textAreaRef = useRef(null);
  const { setElement } = useDragAndDrop({
    onDrop: handleImageDrop(
      handleImageSuccess(textAreaRef),
      handleImageFailure,
    ),
    onDragOver,
    onDragExit,
  });

  useEffect(() => {
    if (textAreaRef.current) {
      setElement(textAreaRef.current.base);
    }
  });

  return (
    <div
      data-testid="article-form__body"
      className="crayons-article-form__body text-padding"
    >
      <Toolbar version={version} />

      <Textarea
        className="crayons-textfield crayons-textfield--ghost crayons-article-form__body__field"
        id="article_body_markdown"
        aria-label="Post Content"
        placeholder="Write your post content here..."
        value={defaultValue}
        onInput={onChange}
        onFocus={(_event) => {
          switchHelpContext(_event);
        }}
        name="body_markdown"
        ref={textAreaRef}
      />
    </div>
  );
};

EditorBody.propTypes = {
  onChange: PropTypes.func.isRequired,
  defaultValue: PropTypes.string.isRequired,
  switchHelpContext: PropTypes.func.isRequired,
  version: PropTypes.string.isRequired,
};

EditorBody.displayName = 'EditorBody';