@adobe/helix-pipeline/src/html/split-sections.js

(formerly known as Hypermedia Pipeline)

/*
 * Copyright 2018 Adobe. All rights reserved.
 * This file is licensed to you under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License. You may obtain a copy
 * of the License at http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under
 * the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR REPRESENTATIONS
 * OF ANY KIND, either express or implied. See the License for the specific language
 * governing permissions and limitations under the License.
 */

const { selectAll } = require('unist-util-select');
const { flat, obj, map } = require('ferrum');
const _ = require('lodash/fp');

// Compute the meta information for the section
function computeMeta(section) {
  return obj(flat(map(selectAll('yaml', section), ({ payload }) => payload)));
}

function split({ content }) {
  const { mdast } = content;

  // filter all children that are either yaml or break blocks
  const dividers = mdast.children.filter((node) => node.type === 'yaml' || node.type === 'thematicBreak')
  // then get their index in the list of children
    .map((node) => mdast.children.indexOf(node));

  // find pairwise permutations of spaces between blocks
  // include the very start and end of the document
  const starts = [0, ...dividers];
  const ends = [...dividers, mdast.children.length];

  content.mdast.children = _.zip(starts, ends)
  // but filter out empty section
    .filter(([start, end]) => start !== end)
  // then return all nodes that are in between
    .map(([start, end]) => {
    // skip 'thematicBreak' nodes
      const index = mdast.children[start].type === 'thematicBreak' ? start + 1 : start;
      const section = {
        type: 'section',
        children: mdast.children.slice(index, end),
      };
      section.meta = computeMeta(section);
      return section;
    });

  // unwrap sole section directly on the root
  if (content.mdast.children.length === 1 && content.mdast.children[0].type === 'section') {
    content.mdast.children = content.mdast.children[0].children;
  }
}

module.exports = split;