import { EditorState, Modifier, SelectionState } from 'draft-js';
import { findWithRegex } from '@draft-js-plugins/utils';
import emojiToolkit from 'emoji-toolkit';

const unicodeRegex = new RegExp(emojiToolkit.regAscii, 'g');

/*
 * Attaches Immutable DraftJS Entities to the Emoji text.
 *
 * This is necessary as emojis consist of 2 characters (unicode). By making them
 * immutable the whole Emoji is removed when hitting backspace.
 */
export default function attachImmutableEntitiesToEmojis(
  editorState: EditorState
): EditorState {
  const contentState = editorState.getCurrentContent();
  const blocks = contentState.getBlockMap();
  let newContentState = contentState;

  blocks.forEach((block) => {
    if (block) {
      const plainText = block.getText();

      const addEntityToEmoji = (start: number, end: number): void => {
        const existingEntityKey = block.getEntityAt(start);
        if (existingEntityKey) {
          // avoid manipulation in case the emoji already has an entity
          const entity = newContentState.getEntity(existingEntityKey);
          if (entity && entity.getType() === 'emoji') {
            return;
          }
        }

        const selection: SelectionState = SelectionState.createEmpty(
          block.getKey()
        )
          .set('anchorOffset', start)
          .set('focusOffset', end) as SelectionState;

        const emojiText = plainText.substring(start, end);
        const contentStateWithEntity = newContentState.createEntity(
          'emoji',
          'IMMUTABLE',
          { emojiUnicode: emojiText }
        );
        const entityKey = contentStateWithEntity.getLastCreatedEntityKey();

        newContentState = Modifier.replaceText(
          newContentState,
          selection,
          emojiText,
          undefined,
          entityKey
        );
      };
      findWithRegex(unicodeRegex, block, addEntityToEmoji);
    }
  });

  if (!newContentState.equals(contentState)) {
    return EditorState.push(editorState, newContentState, 'change-block-data');
  }

  return editorState;
}