import { Value, Block, Range, Selection } from 'slate';
import { List } from 'immutable';

import Options from '../options';
import isList from './isList';
import getCurrentItem from './getCurrentItem';

/**
 * Return the list of items at the given range. The returned items are
 * the highest list item blocks that cover the range.
 *
 * Returns an empty list if no list of items can cover the range
 */
const getItemsAtRange = (opts: Options) => (
  value: Value,
  range?: Range | Selection
): List<Block> => {
  range = range || value.selection;

  if (!range.start.key) {
    return List();
  }

  const { document } = value;

  const startBlock = document.getClosestBlock(range.start.key);
  const endBlock = document.getClosestBlock(range.end.key);

  if (startBlock === endBlock) {
    const item = getCurrentItem(opts)(value, startBlock);
    return item ? List([item]) : List();
  }

  const ancestor = document.getCommonAncestor(
    startBlock.key,
    endBlock.key
  ) as Block;

  if (isList(opts)(ancestor)) {
    const startPath = ancestor.getPath(startBlock.key);
    const endPath = ancestor.getPath(endBlock.key);

    return ancestor.nodes.slice(startPath[0], endPath[0] + 1) as List<Block>;
  } else if (ancestor.type === opts.typeItem) {
    // The ancestor is the highest list item that covers the range
    return List([ancestor]);
  }
  // No list of items can cover the range
  return List();
};

export default getItemsAtRange;