const findPage = require('../lib/find-page')
const getApplicableVersions = require('../lib/get-applicable-versions')
const { getVersionedPathWithLanguage } = require('../lib/path-utils')

// this middleware adds properties to the context object
module.exports = async (req, res, next) => {
  if (!req.context.page) return next()

  if (!(req.context.page.relativePath.endsWith('index.md') || req.context.page.layout === 'product-landing')) return next()

  req.context.gettingStartedLinks = await getLinkData(req.context.page.rawGettingStartedLinks, req.context)
  req.context.popularLinks = await getLinkData(req.context.page.rawPopularLinks, req.context)
  req.context.guideLinks = await getLinkData(req.context.page.rawGuideLinks, req.context)

  return next()
}

// rawLinks is an array of paths: [ '/foo' ]
// we need to convert it to an array of localized objects: [ { href: '/en/foo', title: 'Foo', intro: 'Description here' } ]
async function getLinkData (rawLinks, context) {
  if (!rawLinks) return

  const links = []

  for (const link of rawLinks) {
    const href = link.href
      ? getVersionedPathWithLanguage(link.href, context.currentVersion, context.currentLanguage)
      : getVersionedPathWithLanguage(link, context.currentVersion, context.currentLanguage)

    const linkedPage = findPage(href, context.pages, context.redirects, context.currentLanguage)
    if (!linkedPage) continue

    const applicableVersions = getApplicableVersions(linkedPage.versions, linkedPage.fullPath)

    // skip link if this is not the homepage and the link's versions do not include the current version
    if (context.currentVersion !== 'homepage' && !applicableVersions.includes(context.currentVersion)) continue

    const opts = { textOnly: true, encodeEntities: true }

    links.push({
      href,
      title: await linkedPage.renderTitle(context, opts),
      intro: await linkedPage.renderProp('intro', context, opts)
    })
  }

  return links
}