docs/lib/page.js

const assert = require('assert')
const fs = require('fs').promises
const path = require('path')
const cheerio = require('cheerio')
const patterns = require('./patterns')
const getMapTopicContent = require('./get-map-topic-content')
const rewriteAssetPathsToS3 = require('./rewrite-asset-paths-to-s3')
const rewriteLocalLinks = require('./rewrite-local-links')
const getApplicableVersions = require('./get-applicable-versions')
const encodeBracketedParentheticals = require('./encode-bracketed-parentheticals')
const generateRedirectsForPermalinks = require('./redirects/permalinks')
const getEnglishHeadings = require('./get-english-headings')
const useEnglishHeadings = require('./use-english-headings')
const getTocItems = require('./get-toc-items')
const pathUtils = require('./path-utils')
const Permalink = require('./permalink')
const languages = require('./languages')
const renderContent = require('./render-content')
const { renderReact } = require('./react/engine')
const frontmatter = require('./frontmatter')
const products = require('./all-products')
const slash = require('slash')
const statsd = require('./statsd')

class Page {
  static async init (opts) {
    assert(opts.relativePath, 'relativePath is required')
    assert(opts.basePath, 'basePath is required')

    const relativePath = slash(opts.relativePath)
    const fullPath = slash(path.join(opts.basePath, relativePath))

    // Per https://nodejs.org/api/fs.html#fs_fs_exists_path_callback
    // its better to read and handle errors than to check access/stats first
    try {
      const raw = await fs.readFile(fullPath, 'utf8')
      return new Page({ ...opts, relativePath, fullPath, raw })
    } catch (err) {
      if (err.code === 'ENOENT') return false
      console.error(err)
    }
  }

  constructor (opts) {
    assert(opts.languageCode, 'languageCode is required')

    Object.assign(this, { ...opts })

    // TODO remove this when crowdin-support issue 66 has been resolved
    if (this.languageCode !== 'en' && this.raw.includes(': verdadero')) {
      this.raw = this.raw.replace(': verdadero', ': true')
    }

    // parse fronmatter and save any errors for validation in the test suite
    const { content, data, errors: frontmatterErrors } = frontmatter(this.raw, { filepath: this.fullPath })
    this.frontmatterErrors = frontmatterErrors

    if (this.frontmatterErrors.length) {
      throw new Error(JSON.stringify(this.frontmatterErrors, null, 2))
    }

    // preserve the frontmatter-free markdown content,
    this.markdown = content

    // prevent `[foo] (bar)` strings with a space between from being interpreted as markdown links
    this.markdown = encodeBracketedParentheticals(this.markdown)

    Object.assign(this, data)

    // Store raw data so we can cache parsed versions
    this.rawIntro = this.intro
    this.rawTitle = this.title
    this.rawShortTitle = this.shortTitle
    this.rawProduct = this.product
    this.rawPermissions = this.permissions

    // a page should only be available in versions that its parent product is available in
    const versionsParentProductIsNotAvailableIn = getApplicableVersions(this.versions, this.fullPath)
      // only the homepage will not have this.parentProduct
      .filter(availableVersion => this.parentProduct && !this.parentProduct.versions.includes(availableVersion))

    if (versionsParentProductIsNotAvailableIn.length) {
      throw new Error(`\`versions\` frontmatter in ${this.fullPath} contains ${versionsParentProductIsNotAvailableIn}, which ${this.parentProduct.id} product is not available in!`)
    }

    // derive array of Permalink objects
    this.permalinks = Permalink.derive(this.languageCode, this.relativePath, this.title, this.versions)

    // create backwards-compatible old paths for page permalinks and frontmatter redirects
    this.redirects = generateRedirectsForPermalinks(this.permalinks, this.redirect_from)

    // get an array of linked items in product and category TOCs
    this.tocItems = getTocItems(this)

    // if this is an article and it doesn't have showMiniToc = false, set mini TOC to true
    if (!this.relativePath.endsWith('index.md') && !this.mapTopic) {
      this.showMiniToc = this.showMiniToc === false
        ? this.showMiniToc
        : true
    }

    // Instrument the `_render` method, so externally we call #render
    // but it's wrapped in a timer that reports to Datadog
    this.render = statsd.asyncTimer(this._render.bind(this), 'page.render')

    return this
  }

  // Infer the parent product ID from the page's relative file path
  get parentProductId () {
    // Each page's top-level content directory matches its product ID
    const id = this.relativePath.split('/')[0]

    // ignore top-level content/index.md
    if (id === 'index.md') return null

    // make sure the ID is valid
    if (process.env.NODE_ENV !== 'test') {
      assert(
        Object.keys(products).includes(id),
        `page ${this.fullPath} has an invalid product ID: ${id}`
      )
    }

    return id
  }

  get parentProduct () {
    return products[this.parentProductId]
  }

  async renderTitle (context, opts = {}) {
    return this.shortTitle
      ? this.renderProp('shortTitle', context, opts)
      : this.renderProp('title', context, opts)
  }

  async _render (context) {
    this.intro = await renderContent(this.rawIntro, context)

    // rewrite local links in the intro to include current language code and GHE version if needed
    const introHtml = cheerio.load(this.intro)
    rewriteLocalLinks(introHtml, context.currentVersion, context.currentLanguage)
    this.intro = introHtml('body').html()

    this.introPlainText = await renderContent(this.rawIntro, context, { textOnly: true })
    this.title = await renderContent(this.rawTitle, context, { textOnly: true, encodeEntities: true })
    this.shortTitle = await renderContent(this.shortTitle, context, { textOnly: true, encodeEntities: true })

    let markdown = this.mapTopic
      ? getMapTopicContent(this, context.pages, context.redirects)
      : this.markdown

    // If the article is interactive parse the React!
    if (this.interactive) {
      // Search for the react code comments to find the react components
      const reactComponents = markdown.match(/<!--react-->(.*?)<!--end-react-->/gs)

      // Render each of the react components in the markdown
      await Promise.all(reactComponents.map(async (reactComponent) => {
        let componentStr = reactComponent

        // Remove the React comment indicators
        componentStr = componentStr.replace('<!--react-->\n', '').replace('<!--react-->', '')
        componentStr = componentStr.replace('\n<!--end-react-->', '').replace('<!--end-react-->', '')

        // Get the rendered component
        const renderedComponent = await renderReact(componentStr)

        // Replace the react component with the rendered markdown
        markdown = markdown.replace(reactComponent, renderedComponent)
      }))
    }

    const html = await renderContent(markdown, context)

    // product frontmatter may contain liquid
    if (this.product) {
      this.product = await renderContent(this.rawProduct, context)
    }

    // permissions frontmatter may contain liquid
    if (this.permissions) {
      this.permissions = await renderContent(this.rawPermissions, context)
    }

    const $ = cheerio.load(html)

    // set a flag so layout knows whether to render a mac/windows/linux switcher element
    this.includesPlatformSpecificContent = $('[class^="platform-"], .mac, .windows, .linux, .all').length > 0

    // rewrite asset paths to s3 if it's a dotcom article on any GHE version
    // or if it's an enterprise article on any GHE version EXCEPT latest version
    rewriteAssetPathsToS3($, context.currentVersion, this.relativePath)

    // use English IDs/anchors for translated headings, so links don't break (see #8572)
    if (this.languageCode !== 'en') {
      const englishHeadings = getEnglishHeadings(this, context.pages)
      if (englishHeadings) useEnglishHeadings($, englishHeadings)
    }

    // rewrite local links to include current language code and GHE version if needed
    rewriteLocalLinks($, context.currentVersion, context.currentLanguage)

    // wrap ordered list images in a container div
    $('ol > li img').each((i, el) => {
      $(el).wrap('<div class="procedural-image-wrapper" />')
    })

    const cleanedHTML = $('body').html()

    return cleanedHTML
  }

  // Allow other modules (like custom liquid tags) to make one-off requests
  // for a page's rendered properties like `title` and `intro`
  async renderProp (propName, context, opts = { unwrap: false }) {
    let prop
    if (propName === 'title') {
      prop = this.rawTitle
    } else if (propName === 'shortTitle') {
      prop = this.rawShortTitle || this.rawTitle // fall back to title
    } else if (propName === 'intro') {
      prop = this.rawIntro
    } else {
      prop = this[propName]
    }

    const html = await renderContent(prop, context, opts)

    if (!opts.unwrap) return html

    // The unwrap option removes surrounding tags from a string, preserving any inner HTML
    const $ = cheerio.load(html, { xmlMode: true })
    return $.root().contents().html()
  }

  // infer current page's corresponding homepage
  // /en/articles/foo                          -> /en
  // /en/enterprise/2.14/user/articles/foo     -> /en/enterprise/2.14/user
  static getHomepage (requestPath) {
    return requestPath.replace(/\/articles.*/, '')
  }

  // given a page path, return an array of objects containing hrefs
  // for that page in all languages
  static getLanguageVariants (href) {
    const suffix = pathUtils.getPathWithoutLanguage(href)
    return Object.values(languages).map(({ name, code, hreflang }) => { // eslint-disable-line
      return {
        name,
        code,
        hreflang,
        href: `/${code}${suffix}`.replace(patterns.trailingSlash, '$1')
      }
    })
  }
}

module.exports = Page