css/script/check-relative-links

#!/usr/bin/env node
const globby = require('globby')
const remark = require('remark-parse')
const stringify = require('remark-stringify')
const stringifyPosition = require('unist-util-stringify-position')
const unified = require('unified')
const {green, yellow, red} = require('colorette')
const {join} = require('path')
const {readFile} = require('fs-extra')
const {selectAll} = require('unist-util-select')

const processor = unified()
  .use(remark)
  .use(stringify)

const checks = {
  'relative (.)': ({href}) => href.startsWith('./'),
  'relative (..)': ({href}) => href.startsWith('../'),
  'trailing slash': ({href}) => stripFragment(href).endsWith('/')
}

const dir = join(__dirname, '../pages/css')
globby(join(dir, '**/*.md'))
  .then(docs => Promise.all(docs.map(getLinks)))
  .then(docs => {
    const links = docs
      .reduce((list, doc) => {
        const path = doc.path.substr(dir.length + 1)
        return list.concat(doc.links.map(link => Object.assign({path}, link)))
      }, [])
      // exclude anchor links
      .filter(({href}) => href.charAt(0) !== '#')
      // exclude fully-qualified URLs
      .filter(({href}) => !href.match(/^https?:/))

    for (const checkName of Object.keys(checks)) {
      const matches = links.filter(checks[checkName])
      if (matches.length) {
        console.warn(`${matches.length} link(s) with ${checkName}:`)
        for (const {path, text, href, position} of matches) {
          console.warn(`  ${path} @ ${yellow(position)}: ${green(href)} ('${text}')`)
        }
      }
    }
  })

function getLinks(path) {
  return readFile(path, 'utf8')
    .then(parseLinks)
    .then(links => ({path, links}))
}

function parseLinks(str) {
  const tree = processor.parse(str)
  const nodes = selectAll('link', tree)
  return nodes.map(node => ({
    href: node.url,
    text: processor.stringify({type: 'paragraph', children: node.children}).trim(),
    position: stringifyPosition(node)
  }))
}

function stripFragment(url) {
  return url.replace(/#.*$/, '')
}