Cache responses

package.json

@@ -24,6 +24,7 @@
   },
   "homepage": "https://github.com/lukechilds/onionoo-node-client#readme",
   "dependencies": {
+    "node-cache": "^3.2.1",
     "request": "^2.74.0"
   }
 }

src/index.js

@@ -1,4 +1,7 @@
-const request = require('request');
+const request   = require('request');
+const NodeCache = require('node-cache');
+
+const cache = new NodeCache();
 
 const baseUrl   = 'https://onionoo.torproject.org/';
 const endpoints = [
@@ -10,14 +13,33 @@ const endpoints = [
   'uptime'
 ];
 
+function checkResponseCache(response) {
+  const cacheControl = response.headers['cache-control'];
+  const maxAgeRegex = /max-age=(\d+)/;
+  const maxAge = cacheControl && cacheControl.match(maxAgeRegex);
+  return maxAge && maxAge[1];
+}
+
 module.exports = endpoints.reduce((onionoo, endpoint) => {
   onionoo[endpoint] = args => new Promise((resolve, reject) => {
-    request({
+    const requestOptions = {
       uri:  `${baseUrl}${endpoint}`,
       qs:   args,
       json: true
-    }, (error, response, body) => {
+    };
+    const cacheKey = JSON.stringify(requestOptions);
+
+    const cachedResult = cache.get(cacheKey);
+    if(cachedResult) {
+      resolve(cachedResult);
+    }
+
+    request(requestOptions, (error, response, body) => {
       if (!error && response.statusCode == 200) {
+        const ttl = checkResponseCache(response);
+        if(ttl) {
+          cache.set(cacheKey, body, ttl);
+        }
         resolve(body);
       } else {
         reject(error || {