2 files changed, 31 insertions, 0 deletions
diff --git a/src/notmuchworker.cpp b/src/notmuchworker.cpp
index 2588f4e..d41b54b 100644
--- a/src/notmuchworker.cpp
+++ b/src/notmuchworker.cpp
@@ -41,6 +41,7 @@
 #include "maildirname.h"
 #include "mimeparser.h"
 #include "nmraii.h"
+#include "searchterm.h"
 
 namespace {
 
@@ -1082,6 +1083,27 @@ void NotmuchWorker::applyTagsToThreads(const QStringList &threadIds,
     applyTags(TagChange{ messageIds, add, remove, description });
 }
 
+void NotmuchWorker::applyTagsToQuery(const QString &query,
+                                     const QStringList &add,
+                                     const QStringList &remove,
+                                     const QString &description)
+{
+    if (!openReadOnly())
+        return;
+
+    QStringList messageIds;
+    if (!collectMessageIds(m_db, SearchTerm::changes(query, add, remove),
+                           &messageIds)) {
+        emit errorOccurred(QStringLiteral("Cannot resolve the rule's query"));
+        return;
+    }
+
+    // Empty is not an error: the rule has nothing left to do. applyTags()
+    // returns at once on an empty list, and stays silent, as it must
+    // (CLAUDE.md, item 176).
+    applyTags(TagChange{ messageIds, add, remove, description });
+}
+
 void NotmuchWorker::applyTags(const TagChange &change)
 {
     if (change.messageIds.isEmpty())
diff --git a/src/notmuchworker.h b/src/notmuchworker.h
index ad5f616..fa223e6 100644
--- a/src/notmuchworker.h
+++ b/src/notmuchworker.h
@@ -232,6 +232,15 @@ public slots:
                             const QStringList &remove,
                             const QString &description);
 
+    /// Applies `+add -remove` to every message the change would move within
+    /// `query` (item 212, a rule applied to existing mail). The query is
+    /// narrowed with SearchTerm::changes() so already-correct messages are
+    /// never written, then the ids go through applyTags(), which reports the
+    /// effective set for undo. Emits nothing when nothing would change.
+    void applyTagsToQuery(const QString &query, const QStringList &add,
+                          const QStringList &remove,
+                          const QString &description);
+
     /// Resolves whole threads to the message ids and file paths they contain.
     ///
     /// Delete thread MOVES every message, and a move needs message ids, which