fix: enhance fetch fallback mechanism with retry logic and exponential back-off

dist/js/app.js

@@ -462,12 +462,17 @@ const Utils = (() => {
     const errors = [];
 
     for (const url of urls) {
-      try {
-        const response = await fetchWithTimeout(url, options);
-        return await response.json();
-      } catch (error) {
-        errors.push({ url, error: error.message });
-        continue;
+      for (let attempt = 0; attempt <= CONFIG.API.RETRY_ATTEMPTS; attempt++) {
+        try {
+          const response = await fetchWithTimeout(url, options);
+          return await response.json();
+        } catch (error) {
+          errors.push({ url, attempt, error: error.message });
+          if (attempt < CONFIG.API.RETRY_ATTEMPTS) {
+            // Exponential back-off: 200ms, 400ms, …
+            await new Promise(r => setTimeout(r, 200 * 2 ** attempt));
+          }
+        }
       }
     }
 
@@ -1013,9 +1018,21 @@ class StateManager {
   }
 
   update(updates) {
+    const changed = [];
+
     Object.entries(updates).forEach(([key, value]) => {
-      this.set(key, value);
+      const oldValue = this.#state[key];
+      this.#state[key] = value;
+      if (this.#listeners.has(key)) {
+        changed.push({ key, value, oldValue });
+      }
     });
+
+    // Notify after all values are in place
+    changed.forEach(({ key, value, oldValue }) => {
+      this.#listeners.get(key)?.forEach(cb => cb(value, oldValue));
+    });
+
     return this;
   }
 
@@ -1853,24 +1870,6 @@ class ComparisonManager {
     this.#lifecycle.destroy();
   }
 
-  #handleCompare() {
-    const service1 = this.#elements.select1.value;
-    const service2 = this.#elements.select2.value;
-
-    console.log('Comparing services:', { service1, service2 });
-
-    if (!service1 || !service2) {
-      this.#showEmptyState();
-      return;
-    }
-
-    if (service1 === service2) {
-      this.#showSameProviderWarning();
-      return;
-    }
-
-    this.#renderComparison(service1, service2);
-  }
 
   #renderComparison(service1, service2) {
     const hosts = Object.keys(this.#data);
@@ -2294,8 +2293,8 @@ class App {
 
       // Fetch data
       const dataPromises = [
-        Utils.fetchWithFallback(CONFIG.API.FILE_HOSTS),
-        Utils.fetchWithFallback(CONFIG.API.ADULT_HOSTS)
+        DataService.fetchHosts('file-hosts'),
+        DataService.fetchHosts('adult-hosts')
       ];
 
       const results = await Promise.allSettled(dataPromises);