Move middleware utils into server/utils

server/utils/getPackageInfo.js

@@ -0,0 +1,72 @@
+require("isomorphic-fetch");
+
+const config = require("../config");
+
+const createCache = require("./createCache");
+const createMutex = require("./createMutex");
+
+const packageInfoCache = createCache("packageInfo");
+
+function fetchPackageInfo(packageName) {
+  console.log(`info: Fetching package info for ${packageName}`);
+
+  let encodedPackageName;
+  if (packageName.charAt(0) === "@") {
+    encodedPackageName = `@${encodeURIComponent(packageName.substring(1))}`;
+  } else {
+    encodedPackageName = encodeURIComponent(packageName);
+  }
+
+  const url = `${config.registryURL}/${encodedPackageName}`;
+
+  return fetch(url, {
+    headers: {
+      Accept: "application/json"
+    }
+  }).then(res => {
+    return res.status === 404 ? null : res.json();
+  });
+}
+
+const PackageNotFound = "PackageNotFound";
+
+// This mutex prevents multiple concurrent requests to
+// the registry for the same package info.
+const fetchMutex = createMutex((packageName, callback) => {
+  fetchPackageInfo(packageName).then(
+    value => {
+      if (value == null) {
+        // Cache 404s 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.
+        packageInfoCache.set(packageName, PackageNotFound, 300, () => {
+          callback(null, value);
+        });
+      } else {
+        // Cache valid package info for 1 minute.
+        packageInfoCache.set(packageName, value, 60, () => {
+          callback(null, value);
+        });
+      }
+    },
+    error => {
+      // Do not cache errors.
+      packageInfoCache.del(packageName, () => {
+        callback(error);
+      });
+    }
+  );
+});
+
+function getPackageInfo(packageName, callback) {
+  packageInfoCache.get(packageName, (error, value) => {
+    if (error || value != null) {
+      callback(error, value === PackageNotFound ? null : value);
+    } else {
+      fetchMutex(packageName, packageName, callback);
+    }
+  });
+}
+
+module.exports = getPackageInfo;