refactor: drive cache freshness from pushed key maps

app/javascript/dashboard/api/CacheEnabledApiClient.js

@@ -5,14 +5,15 @@ import ApiClient from './ApiClient';
 class CacheEnabledApiClient extends ApiClient {
   constructor(resource, options = {}) {
     super(resource, options);
+    // `cacheModel` is the Rails Model.name.underscore value — simultaneously
+    // the server cache-key name and the IDB object-store name.
+    this.cacheModelName = options.cacheModel;
+    // inbox/label endpoints wrap collections in { payload }; the rest return
+    // the bare array.
+    this.payloadEnvelope = options.payloadEnvelope || false;
     this.dataManager = new DataManager(this.accountIdFromRoute);
   }
 
-  // eslint-disable-next-line class-methods-use-this
-  get cacheModelName() {
-    throw new Error('cacheModelName is not defined');
-  }
-
   get(cache = false) {
     if (cache) {
       return this.getFromCache();
@@ -25,14 +26,14 @@ class CacheEnabledApiClient extends ApiClient {
     return axios.get(this.url);
   }
 
-  // eslint-disable-next-line class-methods-use-this
   extractDataFromResponse(response) {
-    return response.data.payload;
+    return this.payloadEnvelope ? response.data.payload : response.data;
   }
 
-  // eslint-disable-next-line class-methods-use-this
   marshallData(dataToParse) {
-    return { data: { payload: dataToParse } };
+    return this.payloadEnvelope
+      ? { data: { payload: dataToParse } }
+      : { data: dataToParse };
   }
 
   async getFromCache() {
@@ -43,24 +44,23 @@ class CacheEnabledApiClient extends ApiClient {
       return this.getFromNetwork();
     }
 
-    const { data } = await axios.get(
-      `/api/v1/accounts/${this.accountIdFromRoute}/cache_keys`
-    );
-    const cacheKeyFromApi = data.cache_keys[this.cacheModelName];
-    const isCacheValid = await this.validateCacheKey(cacheKeyFromApi);
+    // Trust the IDB cache. Freshness is maintained by the
+    // account.cache_invalidated event alone: RoomChannel pushes the cache-key
+    // map on every (re)subscribe — boot and reconnect included — and the
+    // server broadcasts it on every change. Skipping a per-call /cache_keys
+    // preflight eliminates N GET requests per cold settings-page load.
+    const localData = await this.dataManager.get({
+      modelName: this.cacheModelName,
+    });
 
-    let localData = [];
-    if (isCacheValid) {
-      localData = await this.dataManager.get({
-        modelName: this.cacheModelName,
-      });
+    if (localData.length > 0) {
+      return this.marshallData(localData);
     }
 
-    if (localData.length === 0) {
-      return this.refetchAndCommit(cacheKeyFromApi);
-    }
-
-    return this.marshallData(localData);
+    // Empty IDB (first load or wiped): fetch data without a cache key. The
+    // next pushed key map won't match the missing key and will refetch once,
+    // stamping the authoritative key — the client never pulls keys itself.
+    return this.refetchAndCommit(null);
   }
 
   async refetchAndCommit(newKey = null) {
@@ -69,7 +69,9 @@ class CacheEnabledApiClient extends ApiClient {
     try {
       await this.dataManager.initDb();
 
-      this.dataManager.replace({
+      // Await replace so data is persisted before the cache key is — otherwise
+      // a concurrent reader could see a fresh key paired with stale data.
+      await this.dataManager.replace({
         modelName: this.cacheModelName,
         data: this.extractDataFromResponse(response),
       });
@@ -89,8 +91,15 @@ class CacheEnabledApiClient extends ApiClient {
       await this.dataManager.initDb();
     }
 
-    const cachekey = await this.dataManager.getCacheKey(this.cacheModelName);
-    return cacheKeyFromApi === cachekey;
+    const cacheKey = await this.dataManager.getCacheKey(this.cacheModelName);
+    if (cacheKey === undefined) {
+      const localData = await this.dataManager.get({
+        modelName: this.cacheModelName,
+      });
+      return localData.length === 0;
+    }
+
+    return cacheKeyFromApi === cacheKey;
   }
 }