2 files changed, 52 insertions, 0 deletions

diff --git a/src/notmuchworker.cpp b/src/notmuchworker.cpp
index 2672f6a..2588f4e 100644
--- a/src/notmuchworker.cpp
+++ b/src/notmuchworker.cpp
@@ -764,6 +764,30 @@ void NotmuchWorker::loadThreadTree(const QString &threadId,
 
 QString NotmuchWorker::threadIdForTesting(const QString &query)
 {
+    return firstThreadIdMatching(query);
+}
+
+void NotmuchWorker::resolveThreadForMessage(const QString &messageId)
+{
+    if (messageId.isEmpty()) {
+        emit threadForMessageResolved(messageId, QString());
+        return;
+    }
+    // This id came off another program's command line, and notmuch reads
+    // unquoted query syntax AS syntax. Quoted here rather than through
+    // SearchTerm::quote(): that escapes an embedded quote with a backslash,
+    // which notmuch's (Xapian's) parser does not honour inside a phrase, so
+    // the quote closes the phrase and the rest is parsed as query. notmuch
+    // escapes a quote by DOUBLING it.
+    QString escaped = messageId;
+    escaped.replace(QLatin1Char('"'), QStringLiteral("\"\""));
+    emit threadForMessageResolved(
+        messageId,
+        firstThreadIdMatching(QStringLiteral("id:\"%1\"").arg(escaped)));
+}
+
+QString NotmuchWorker::firstThreadIdMatching(const QString &query)
+{
     if (!openReadOnly())
         return QString();
 
diff --git a/src/notmuchworker.h b/src/notmuchworker.h
index b4e9707..3183729 100644
--- a/src/notmuchworker.h
+++ b/src/notmuchworker.h
@@ -138,6 +138,13 @@ public:
     /// be reached across the thread boundary by accident.
     QString threadIdForTesting(const QString &query);
 
+private:
+    /// The first thread id matching \p query, or empty. Shared by
+    /// threadIdForTesting() and resolveThreadForMessage().
+    QString firstThreadIdMatching(const QString &query);
+
+public:
+
 public slots:
 
     /// Loads ONE message, for a message row selected in the list.
@@ -147,6 +154,21 @@ public slots:
     /// reporting.
     void loadMessage(const QString &messageId, quint64 generation);
 
+    /// Answers which thread a Message-ID belongs to (item 200).
+    ///
+    /// For `--message`, which knows an id and needs the conversation: opening
+    /// a message means opening its thread with that message selected, never an
+    /// `id:` query showing one card out of a conversation (item 91).
+    ///
+    /// Answers with an EMPTY thread id when the message is unknown rather than
+    /// staying silent, since the window reports the miss and a slot that never
+    /// replies would leave it waiting forever.
+    ///
+    /// **The id is quoted before it reaches notmuch.** Unlike every other id in
+    /// this class, this one came from argv rather than from notmuch itself, and
+    /// notmuch parses garbage happily while matching nothing.
+    void resolveThreadForMessage(const QString &messageId);
+
     /// Applies tag changes. Opens the database read-write, applies, and closes
     /// immediately: notmuch's write lock is exclusive process-wide, so holding
     /// it would block the user's cron `notmuch new`.
@@ -346,6 +368,12 @@ signals:
                           quint64 generation);
     void messageLoaded(const QVector<MessageRef> &messages, quint64 generation);
 
+    /// The answer to resolveThreadForMessage(). The message id is echoed back
+    /// so a caller can tell which request this answers; the thread id is empty
+    /// when nothing matched.
+    void threadForMessageResolved(const QString &messageId,
+                                  const QString &threadId);
+
     /// The dashboard's digest. `generation` is the dashboard's own counter,
     /// echoed back so a stale answer can be discarded.
     void threadDigestLoaded(const ThreadDigest &digest, quint64 generation);