Implement stale entry cleanup in FreebitOperationsService to prevent memory leaks

- Added a method to periodically clean up stale operation timestamps, ensuring efficient memory usage.
- Introduced rate limiting for cleanup operations to minimize performance overhead.
- Enhanced the getOperationWindow method to invoke cleanup, maintaining optimal state of operation timestamps.
- Included validation to ensure at least one feature is specified during updates, improving error handling.

apps/bff/src/integrations/freebit/services/freebit-operations.service.ts

@@ -55,7 +55,51 @@ export class FreebitOperationsService {
     }
   >();
 
+  // Rate limit cleanup to avoid running on every operation
+  private lastCleanupTime = 0;
+  private readonly cleanupIntervalMs = 5 * 60 * 1000; // Run cleanup at most every 5 minutes
+  private readonly staleThresholdMs = 35 * 60 * 1000; // Remove entries older than 35 minutes (beyond 30-min window)
+
+  /**
+   * Cleanup stale entries from operationTimestamps to prevent memory leak.
+   * Entries are considered stale when all their timestamps are older than staleThresholdMs.
+   */
+  private cleanupStaleEntries(): void {
+    const now = Date.now();
+
+    // Rate limit cleanup to avoid performance overhead
+    if (now - this.lastCleanupTime < this.cleanupIntervalMs) {
+      return;
+    }
+    this.lastCleanupTime = now;
+
+    const staleThreshold = now - this.staleThresholdMs;
+    const accountsToRemove: string[] = [];
+
+    for (const [account, entry] of this.operationTimestamps) {
+      const timestamps = [entry.voice, entry.network, entry.plan, entry.cancellation].filter(
+        (t): t is number => typeof t === "number"
+      );
+
+      // If all timestamps are stale (or entry is empty), mark for removal
+      if (timestamps.length === 0 || timestamps.every(t => t < staleThreshold)) {
+        accountsToRemove.push(account);
+      }
+    }
+
+    for (const account of accountsToRemove) {
+      this.operationTimestamps.delete(account);
+    }
+
+    if (accountsToRemove.length > 0) {
+      this.logger.debug(`Cleaned up ${accountsToRemove.length} stale operation timestamp entries`);
+    }
+  }
+
   private getOperationWindow(account: string) {
+    // Run cleanup periodically to prevent memory leak
+    this.cleanupStaleEntries();
+
     if (!this.operationTimestamps.has(account)) {
       this.operationTimestamps.set(account, {});
     }
@@ -457,6 +501,14 @@ export class FreebitOperationsService {
         );
       }
 
+      // Validate that at least one feature is specified
+      if (!hasVoiceFeatures && !hasNetworkTypeChange) {
+        throw new BadRequestException(
+          "No features specified for update. Please provide at least one of: " +
+            "voiceMailEnabled, callWaitingEnabled, internationalRoamingEnabled, or networkType."
+        );
+      }
+
       if (hasVoiceFeatures) {
         // Only voice features (PA05-06)
         await this.updateVoiceFeatures(account, voiceFeatures);