From 258d08723fd3cf5afa2010a0051390b5d0b452ba Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Daniel=20D=E2=80=99Aquino?= <daniel@daquino.me>
Date: Fri, 26 Sep 2025 12:04:51 -0700
Subject: [PATCH] Check if Ndb is closed before running subscribe and query
 operations
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This should prevent background crashes caused by race conditions between
usages of Ndb and the Ndb/app lifecycle operations.

Signed-off-by: Daniel D’Aquino <daniel@daquino.me>
---
 nostrdb/Ndb.swift | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/nostrdb/Ndb.swift b/nostrdb/Ndb.swift
index 134d4f0d..0dabf95d 100644
--- a/nostrdb/Ndb.swift
+++ b/nostrdb/Ndb.swift
@@ -623,6 +623,7 @@ class Ndb {
     /// - Returns: Array of note keys matching the filters
     /// - Throws: NdbStreamError if the query fails
     func query<Y>(with txn: NdbTxn<Y>, filters: [NdbFilter], maxResults: Int) throws(NdbStreamError) -> [NoteKey] {
+        guard !self.is_closed else { throw .ndbClosed }
         let filtersPointer = UnsafeMutablePointer<ndb_filter>.allocate(capacity: filters.count)
         defer { filtersPointer.deallocate() }
         
@@ -636,6 +637,7 @@ class Ndb {
         let results = UnsafeMutablePointer<ndb_query_result>.allocate(capacity: maxResults)
         defer { results.deallocate() }
         
+        guard !self.is_closed else { throw .ndbClosed }
         guard ndb_query(&txn.txn, filtersPointer, Int32(filters.count), results, Int32(maxResults), count) == 1 else {
             throw NdbStreamError.initialQueryFailed
         }
@@ -707,6 +709,7 @@ class Ndb {
     }
     
     func subscribe(filters: [NdbFilter], maxSimultaneousResults: Int = 1000) throws(NdbStreamError) -> AsyncStream<StreamItem> {
+        guard !self.is_closed else { throw .ndbClosed }
         // Fetch initial results
         guard let txn = NdbTxn(ndb: self) else { throw .cannotOpenTransaction }
         
@@ -914,6 +917,7 @@ extension Ndb {
         case initialQueryFailed
         case timeout
         case cancelled
+        case ndbClosed
     }
     
     /// An error that may happen when looking something up