Move some utils into middleware/utils

server/middleware/utils/getPackage.js

@@ -0,0 +1,88 @@
+require('isomorphic-fetch')
+const fs = require('fs')
+const path = require('path')
+const tmpdir = require('os-tmpdir')
+const gunzip = require('gunzip-maybe')
+const mkdirp = require('mkdirp')
+const tar = require('tar-fs')
+const createMutex = require('./createMutex')
+
+function createTempPath(name, version) {
+  const normalName = name.replace(/\//g, '-')
+  return path.join(tmpdir(), `unpkg-${normalName}-${version}`)
+}
+
+function stripNamePrefix(headers) {
+  // 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.
+  headers.name = headers.name.replace(/^[^\/]+\//, '')
+  return headers
+}
+
+function ignoreSymlinks(file, headers) {
+  return headers.type === 'link'
+}
+
+function extractResponse(response, outputDir) {
+  return new Promise(function (resolve, reject) {
+    const extract = tar.extract(outputDir, {
+      readable: true, // All dirs/files should be readable.
+      map: stripNamePrefix,
+      ignore: ignoreSymlinks
+    })
+
+    response.body
+      .pipe(gunzip())
+      .pipe(extract)
+      .on('finish', resolve)
+      .on('error', reject)
+  })
+}
+
+function fetchAndExtract(tarballURL, outputDir) {
+  console.log(`info: Fetching ${tarballURL} and extracting to ${outputDir}`)
+
+  return fetch(tarballURL).then(function (response) {
+    return extractResponse(response, outputDir)
+  })
+}
+
+const fetchMutex = createMutex(function (payload, callback) {
+  const { tarballURL, outputDir } = payload
+
+  fs.access(outputDir, function (error) {
+    if (error) {
+      if (error.code === 'ENOENT' || error.code === 'ENOTDIR') {
+        // ENOENT or ENOTDIR are to be expected when we haven't yet
+        // fetched a package for the first time. Carry on!
+        mkdirp(outputDir, function (error) {
+          if (error) {
+            callback(error)
+          } else {
+            fetchAndExtract(tarballURL, outputDir).then(function () {
+              callback()
+            }, callback)
+          }
+        })
+      } else {
+        callback(error)
+      }
+    } else {
+      // Best case: we already have this package cached on disk!
+      callback()
+    }
+  })
+})
+
+function getPackage(packageConfig, callback) {
+  const tarballURL = packageConfig.dist.tarball
+  const outputDir = createTempPath(packageConfig.name, packageConfig.version)
+
+  fetchMutex(tarballURL, { tarballURL, outputDir }, function (error) {
+    callback(error, outputDir)
+  })
+}
+
+module.exports = getPackage