import type { Root as MdastRoot } from 'mdast';
import { CONTINUE, visit } from 'unist-util-visit';

export function remarkProperlyFormatEmphasis() {
  return function (root: MdastRoot) {
    return properlyFormatEmphasis(root);
  };
}

const spaceNode = {
  type: 'text' as const,
  value: ' ',
};

function properlyFormatEmphasis(root: MdastRoot) {
  visit(root, ['emphasis', 'strong'], function (node, index, parent) {
    if (node.type !== 'emphasis' && node.type !== 'strong') return CONTINUE;
    if (
      node.children.length !== 1 ||
      !node.children[0] ||
      node.children[0].type !== 'text' ||
      !parent ||
      typeof index !== 'number'
    )
      return CONTINUE;

    const child = node.children[0];
    if (child.value.startsWith(' ') || child.value.endsWith(' ')) {
      if (index !== 0 && child.value.startsWith(' ')) parent.children.splice(index, 0, spaceNode);
      if (parent.children.length > index + 1 && child.value.endsWith(' '))
        parent.children.splice(index + 1, 0, spaceNode);

      child.value = child.value.trim();
      node.children[0] = child;
    }
  });
}