Add code from express-unpkg repo

server/middleware/RegistryUtils.js

@@ -0,0 +1,104 @@
+require('isomorphic-fetch')
+const debug = require('debug')
+const gunzip = require('gunzip-maybe')
+const mkdirp = require('mkdirp')
+const tar = require('tar-fs')
+const RegistryCache = require('./RegistryCache')
+
+const log = debug('express-unpkg')
+
+const getPackageInfoFromRegistry = (registryURL, packageName) => {
+  let encodedPackageName
+  if (packageName.charAt(0) === '@') {
+    encodedPackageName = `@${encodeURIComponent(packageName.substring(1))}`
+  } else {
+    encodedPackageName = encodeURIComponent(packageName)
+  }
+
+  const url = `${registryURL}/${encodedPackageName}`
+
+  return fetch(url, {
+    headers: { 'Accept': 'application/json' }
+  }).then(response => (
+    response.status === 404 ? null : response.json()
+  ))
+}
+
+const OneMinute = 60 * 1000
+const PackageNotFound = 'PackageNotFound'
+
+const getPackageInfo = (registryURL, packageName, callback) => {
+  const cacheKey = registryURL + packageName
+
+  RegistryCache.get(cacheKey, (error, value) => {
+    if (error) {
+      callback(error)
+    } else if (value) {
+      callback(null, value === PackageNotFound ? null : value)
+    } else {
+      log('Registry cache miss for package %s', packageName)
+
+      getPackageInfoFromRegistry(registryURL, packageName).then(value => {
+        if (value == null) {
+          // Keep 404s in the cache for 5 minutes. This prevents us
+          // from making unnecessary requests to the registry for
+          // bad package names. In the worst case, a brand new
+          // package's info will be available within 5 minutes.
+          RegistryCache.set(cacheKey, PackageNotFound, OneMinute * 5)
+        } else {
+          RegistryCache.set(cacheKey, value, OneMinute)
+        }
+
+        callback(null, value)
+      }, error => {
+        // Do not cache errors.
+        RegistryCache.del(cacheKey)
+        callback(error)
+      })
+    }
+  })
+}
+
+const normalizeTarHeader = (header) => {
+  // Most packages have header names that look like "package/index.js"
+  // so we shorten that to just "index.js" here. A few packages use a
+  // prefix other than "package/". e.g. the firebase package uses the
+  // "firebase_npm/" prefix. So we just strip the first dir name.
+  header.name = header.name.replace(/^[^\/]+\//, '')
+  return header
+}
+
+const getPackage = (tarballURL, outputDir, callback) => {
+  mkdirp(outputDir, (error) => {
+    if (error) {
+      callback(error)
+    } else {
+      let callbackWasCalled = false
+
+      fetch(tarballURL).then(response => {
+        response.body
+          .pipe(gunzip())
+          .pipe(
+            tar.extract(outputDir, {
+              dmode: 0o666, // All dirs should be writable
+              fmode: 0o444, // All files should be readable
+              map: normalizeTarHeader
+            })
+          )
+          .on('finish', callback)
+          .on('error', (error) => {
+            if (callbackWasCalled) // LOL node streams
+              return
+
+            callbackWasCalled = true
+            callback(error)
+          })
+      })
+    }
+  })
+}
+
+module.exports = {
+  getPackageInfo,
+  getPackage
+}