service-worker: cleaner handling of config.js (ref. #30)

service-worker.js

@@ -140,6 +140,29 @@ let cacheConfigJSON = async (configURL, cresponse) => {
     }
 }
 
+
+/**
+ * get config JSON and verify it's valid
+ * 
+ * cresponse - the Response object to work with
+ */
+let getConfigJSON = async (cresponse) => {
+    if (cresponse == undefined) {
+        self.log('service-worker', 'config.json response is undefined')
+        return false;
+    }
+    if (cresponse.status != 200) {
+        self.log('service-worker', `config.json response status is not 200: ${cdata.status} ${cdata.statusText})`)
+        return false;
+    }
+    var cdata = await cresponse.clone().json()
+    if (verifyConfigData(cdata)) {
+        return cdata;
+    }
+    return false;
+}
+
+
 // flag signifying the SW has been initialized already
 var initDone = false
 
@@ -159,40 +182,45 @@ let initServiceWorker = async () => {
         // self.registration.scope contains the scope this service worker is registered for
         // so it makes sense to pull config from `config.json` file directly under that location
         try {
+            
             // config.json URL
             var configURL = self.registration.scope + "config.json"
-            // we need to know if the config was already cached
-            var wasCached = true
-            // get the config file, cached or otherwise
+            
+            // get the config data from cache
             var cresponse = await caches.match(configURL)
-            if (cresponse != undefined) {
-                self.log('service-worker', `config file retrieved from cache.`)
+            var cdata = await getConfigJSON(cresponse)
+            
+            // did it work?
+            if (cdata != false) {
+                // we need to know if the config was already cached
+                self.log('service-worker', `valid config file retrieved from cache.`)
+                var wasCached = true
+                
+            // cache failed to deliver
             } else {
-                self.log('service-worker', `config file not found in cache, fetching.`)
-                wasCached = false
-                cresponse = await fetch(configURL)
-            }
-            // check for sanity
-            // TODO: check also after cache retrieval?
-            if (cresponse.status != 200) {
-                self.log('service-worker', `failed to fetch config (${cdata.status} ${cdata.statusText}).`)
-            } else {
-                // process the data
-                cdata = await cresponse.clone().json()
-                // verify the config
-                if (verifyConfigData(cdata)) {
-                    // merge the config
-                    self.LibResilientConfig = {...self.LibResilientConfig, ...cdata}
-                    self.log('service-worker', 'config loaded.')
-                    // cache the valid config.json
-                    if (!wasCached) {
-                        // was not retrieved from cache? cache, then!
-                        cacheConfigJSON(configURL, cresponse)
-                    }
+                
+                // try fetching directly from the main domain
+                var cresponse = await fetch(configURL)
+                cdata = await getConfigJSON(cresponse)
+                
+                // did that work?
+                if (cdata != false) {
+                    self.log('service-worker', `config file not found in cache, fetching.`)
+                    var wasCached = false
+                    // cache it, asynchronously
+                    cacheConfigJSON(configURL, cresponse)
+                
                 } else {
+                    // we ain't got nothing useful -- justs set cdata to an empty object
+                    cdata = {}
                     self.log('service-worker', 'ignoring invalid config, using defaults.')
                 }
             }
+            
+            // merge configs
+            self.LibResilientConfig = {...self.LibResilientConfig, ...cdata}
+            self.log('service-worker', 'config loaded.')
+            
         } catch (e) {
             self.log('service-worker', 'config loading failed, using defaults; error:', e)
         }