alphabetical-list-items.js

const rule = require('unified-lint-rule');
const visit = require('unist-util-visit');
const toString = require('mdast-util-to-string');

function normalize(text) {
  const removeAtBeginning = /^([-._(《"'])*/;
  const removeInside = /[,:]/;
  const replaceWithSpace = /-/;
  return text.toLowerCase()
    .trim()
    .replace(removeAtBeginning, '')
    .replace(removeInside, '')
    .replace(replaceWithSpace, ' ');
}


function alphaCheck(tree, file, language = 'en-US') {
  visit(tree, 'list', (node) => {
    const items = node.children;
    let lastLine = -1;
    let lastText = '';

    items.forEach((item) => {
      if (item.children.length) {
        const text = normalize(toString(item.children[0].children[0]));
        const line = item.position.start.line;
        const comp = new Intl.Collator(language).compare(lastText, text);
        if (comp > 0) {
          file.message(`Alphabetical ordering: swap l.${item.children[0].children[0].position.start.line} and l.${lastLine}`, node);
        }
        lastLine = line;
        lastText = text;
      }
    });
  });
}

module.exports = rule('remark-lint:alphabetize-lists', alphaCheck);