deduplicate server code for caching rendered API endpoints

server.js

@@ -201,13 +201,46 @@ app.use("/customize.dist", Express.static(__dirname + '/customize.dist'));
 app.use(/^\/[^\/]*$/, Express.static('customize'));
 app.use(/^\/[^\/]*$/, Express.static('customize.dist'));
 
-var serveConfig = (function () {
-    // if dev mode: never cache
-    var cacheString = function () {
+// if dev mode: never cache
+var cacheString = function () {
     return (Env.FRESH_KEY? '-' + Env.FRESH_KEY: '') + (Env.DEV_MODE? '-' + (+new Date()): '');
+};
+
+var makeRouteCache = function (template, cacheName) {
+    var cleanUp = {};
+    var cache = Env[cacheName] = Env[cacheName] || {};
+
+    return function (req, res) {
+        var host = req.headers.host.replace(/\:[0-9]+/, '');
+        res.setHeader('Content-Type', 'text/javascript');
+        // don't cache anything if you're in dev mode
+        if (Env.DEV_MODE) {
+            return void res.send(template(host));
+        }
+        // generate a lookup key for the cache
+        var cacheKey = host + ':' + cacheString();
+
+        // FIXME mutable
+        // we must be able to clear the cache when updating any mutable key
+        // if there's nothing cached for that key...
+        if (!cache[cacheKey]) {
+            // generate the response and cache it in memory
+            cache[cacheKey] = template(host);
+            // and create a function to conditionally evict cache entries
+            // which have not been accessed in the last 20 seconds
+            cleanUp[cacheKey] = Util.throttle(function () {
+                delete cleanUp[cacheKey];
+                delete cache[cacheKey];
+            }, 20000);
+        }
+
+        // successive calls to this function
+        cleanUp[cacheKey]();
+        return void res.send(cache[cacheKey]);
     };
+};
 
-    var template = function (host) {
+var serveConfig = makeRouteCache(function (host) {
     return [
         'define(function(){',
         'var obj = ' + JSON.stringify({
@@ -238,52 +271,15 @@ var serveConfig = (function () {
         'return obj',
         '});'
     ].join(';\n')
-    };
-
-    var cleanUp = {};
-
-    return function (req, res) {
-        var host = req.headers.host.replace(/\:[0-9]+/, '');
-        res.setHeader('Content-Type', 'text/javascript');
-        // don't cache anything if you're in dev mode
-        if (Env.DEV_MODE) {
-            return void res.send(template(host));
-        }
-        // generate a lookup key for the cache
-        var cacheKey = host + ':' + cacheString();
+}, 'configCache');
 
-        // FIXME mutable
-        // we must be able to clear the cache when updating any mutable key
-        // if there's nothing cached for that key...
-        if (!Env.configCache[cacheKey]) {
-            // generate the response and cache it in memory
-            Env.configCache[cacheKey] = template(host);
-            // and create a function to conditionally evict cache entries
-            // which have not been accessed in the last 20 seconds
-            cleanUp[cacheKey] = Util.throttle(function () {
-                delete cleanUp[cacheKey];
-                delete Env.configCache[cacheKey];
-            }, 20000);
-        }
-
-        // successive calls to this function
-        cleanUp[cacheKey]();
-        return void res.send(Env.configCache[cacheKey]);
-    };
-}());
-
-var serveBroadcast = (function () { // XXX deduplicate
-    var cacheString = function () {
-        return (Env.FRESH_KEY? '-' + Env.FRESH_KEY: '') + (Env.DEV_MODE? '-' + (+new Date()): '');
-    };
-
-    var template = function (host) {
+var serveBroadcast = makeRouteCache(function (host) {
     var maintenance = Env.maintenance;
     if (maintenance && maintenance.end && maintenance.end < (+new Date())) {
         maintenance = undefined;
     }
     return [
-            'define(function(){', // XXX maybe this could just be JSON
+        'define(function(){',
         'return ' + JSON.stringify({
             lastBroadcastHash: Env.lastBroadcastHash,
             surveyURL: Env.surveyURL,
@@ -291,37 +287,7 @@ var serveBroadcast = (function () { // XXX deduplicate
         }, null, '\t'),
         '});'
     ].join(';\n')
-    };
-
-    var cleanUp = {};
-
-    return function (req, res) {
-        var host = req.headers.host.replace(/\:[0-9]+/, '');
-        res.setHeader('Content-Type', 'text/javascript');
-        // don't cache anything if you're in dev mode
-        if (Env.DEV_MODE) {
-            return void res.send(template(host));
-        }
-        // generate a lookup key for the cache
-        var cacheKey = host + ':' + cacheString();
-
-        // XXX do we need a cache for /api/broadcast?
-        if (!Env.broadcastCache[cacheKey]) {
-            // generate the response and cache it in memory
-            Env.broadcastCache[cacheKey] = template(host);
-            // and create a function to conditionally evict cache entries
-            // which have not been accessed in the last 20 seconds
-            cleanUp[cacheKey] = Util.throttle(function () {
-                delete cleanUp[cacheKey];
-                delete Env.broadcastCache[cacheKey];
-            }, 20000);
-        }
-
-        // successive calls to this function
-        cleanUp[cacheKey]();
-        return void res.send(Env.broadcastCache[cacheKey]);
-    };
-}());
+}, 'broadcastCache');
 
 app.get('/api/config', serveConfig);
 app.get('/api/broadcast', serveBroadcast);