Fix user block list decryption timeout and state wiping

Refactored `js/userBlocks.js` to handle NIP-07 decryption timeouts gracefully.
Previously, if a background decryption timed out (common with busy extensions or queues), the user's block list was reset to an empty state, exposing them to blocked content until the next successful retry.
The fix ensures that if a timeout occurs, the existing (stale) block list is preserved while a retry is scheduled in the background.
Also increased the `BACKGROUND_DECRYPT_TIMEOUT_MS` from 2500ms to 5000ms to reduce false positives.

Added `tests/user-blocks-decryption.test.mjs` to verify the fix and audit the decryption flow.

Co-authored-by: PR0M3TH3AN <[email protected]>

js/userBlocks.js

@@ -80,7 +80,7 @@ const FAST_BLOCKLIST_RELAY_LIMIT = 3;
 const FAST_BLOCKLIST_TIMEOUT_MS = 2500;
 const BACKGROUND_BLOCKLIST_TIMEOUT_MS = 6000;
 const DECRYPT_TIMEOUT_MS = 15000;
-const BACKGROUND_DECRYPT_TIMEOUT_MS = 2500;
+const BACKGROUND_DECRYPT_TIMEOUT_MS = 5000;
 const DECRYPT_RETRY_DELAY_MS = 10000;
 const MAX_BLOCKLIST_ENTRIES = 5000;
 
@@ -1384,26 +1384,27 @@ class UserBlockListManager {
           if (decryptionError.code === "user-blocklist-decrypt-timeout") {
             const signerStatus =
               decryptionError.signerStatus || resolveSignerStatus();
-            // If decrypt times out, we can still load public mutes from standard event tags?
-            // For safety, we probably shouldn't partially load if we expect encryption.
-            // But preserving existing state is safer or applying empty.
-            // Current logic applies empty.
-            applySets(new Set(), new Set(), {
-              source,
-              reason: "decrypt-timeout",
-              signerStatus,
-              events: [newestStandard?.id, newestLegacy?.id].filter(Boolean),
-            });
-            this.loaded = true;
+
+            // If decrypt times out, restore the previous state to avoid wiping the user's blocks.
+            // We then schedule a background retry.
+            this.blockedPubkeys = previousState.blockedPubkeys;
+            this._privateBlocks = previousState.privateBlocks;
+            this._publicMutes = previousState.publicMutes;
+            this.blockEventId = previousState.blockEventId;
+            this.blockEventCreatedAt = previousState.blockEventCreatedAt;
+            this.loaded = true; // Mark as loaded so UI renders, even if stale
+
             emitStatus({
-              status: "applied-empty",
+              status: "stale",
               reason: "decrypt-timeout",
               signerStatus,
               source,
+              blockedPubkeys: Array.from(this.blockedPubkeys),
             });
             emitStatus({ status: "settled" });
+
             userLogger.warn(
-              "[UserBlockList] Decryption timed out; applying empty list and retrying in background.",
+              "[UserBlockList] Decryption timed out; keeping stale list and retrying in background.",
               {
                 signerStatus,
                 events: [newestStandard?.id, newestLegacy?.id].filter(Boolean),