const LRU = require('lru-cache')
const mime = require('mime')
const request = require('request')
const streamifier = require('streamifier')
const url = require('url')
const cache = LRU(50)

const staticPages = [
  '',
  '/help',
  '/help/markdown',
  '/about',
  '/about/careers',
  '/about/contact',
  '/about/team',
  '/subscribe',
  '/styleguide',
  '/terms',
  '/terms/privacy',
  '/newapp'
]

const transformPathname = pathname => {
  // remove trailing slash
  pathname = pathname.replace(/\/$/, '')

  // a path without an extension should be served by index.html in
  // the folder of the same name.
  if (!pathname.match(/\.\w{2,4}$/)) {
    pathname += '/index.html'
  }

  // add the deploy-specific (cache-busting) path prefix
  if (!pathname.startsWith('/assets')) {
    pathname = `/assets/${process.env.BUNDLE_VERSION}${pathname}`
  }

  return pathname
}

const handlePage = (req, res) => {
  if (process.env.DISABLE_PROXY) {
    return res.status(503).send('Service Unavailable')
  }

  var u = url.parse(req.url)
  u.pathname = transformPathname(u.pathname)
  var newUrl = process.env.ASSET_HOST.replace(/\/$/, '') + url.format(u)

  // use path without query params as cache key
  const cacheKey = u.pathname
  const cachedValue = (cacheKey ? cache.get(cacheKey) : null)

  if (cachedValue) {
    console.log(` ☺ ${newUrl}`)
    var mimeType = mime.lookup(u.pathname)

    res.set('Content-Type', mimeType)
    streamifier.createReadStream(cachedValue).pipe(res)
  } else {
    console.log(` ↑ ${newUrl}`)
    var chunks = []

    request.get(newUrl)
    .on('response', upstreamRes => {
      upstreamRes.on('data', d => chunks.push(d))
      upstreamRes.on('end', () => cacheKey && cache.set(cacheKey, Buffer.concat(chunks)))
    })
    .on('error', err => res.serverError(err.message))
    .pipe(res)
  }
}

export const handleStaticPages = server => {
  staticPages.forEach(page => {
    if (page === '') page = '/'
    server.get(page, handlePage)
  })
}

@@ -1100,13 +1100,13 @@
 env.
-ASSET
+PROXY
 _HOS

change env var for proxy host