feat(search): build notmuch terms for the right-click actions

One place for the query grammar behind every search surface, with no widget
involved so it is tested without a painter or a web engine.

extend() parenthesises both sides. The query bar may hold a hand-written
disjunction, and 'a or b AND c' binds as 'a or (b AND c)', which widens a
search meant to narrow it and reports nothing.

1 files changed, 93 insertions, 0 deletions

diff --git a/src/searchterm.cpp b/src/searchterm.cpp
new file mode 100644
index 0000000..acc64c6
--- /dev/null
+++ b/src/searchterm.cpp
@@ -0,0 +1,93 @@
+/*
+ * qtmaildir - a Qt6 mail client for notmuch-indexed Maildirs
+ * Copyright (C) 2026 Danilo M. <danix@danix.xyz>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include "searchterm.h"
+
+#include <algorithm>
+
+namespace SearchTerm {
+
+QString quote(const QString &value)
+{
+    // simplified() collapses every run of whitespace, newlines and tabs
+    // included, and trims the ends. A selection spanning paragraphs arrives
+    // full of newlines, which would otherwise reach the query bar verbatim.
+    QString cleaned = value.simplified();
+    if (cleaned.isEmpty())
+        return {};
+
+    if (cleaned.size() > kMaxValueLength)
+        cleaned.truncate(kMaxValueLength);
+
+    // Backslashes first: escaping the quotes first would then escape the
+    // backslashes this step adds, doubling them.
+    cleaned.replace(QLatin1Char('\\'), QStringLiteral("\\\\"));
+    cleaned.replace(QLatin1Char('"'), QStringLiteral("\\\""));
+
+    return QLatin1Char('"') + cleaned + QLatin1Char('"');
+}
+
+QString field(const QString &name, const QString &value)
+{
+    const QString quoted = quote(value);
+    if (quoted.isEmpty())
+        return {};
+    return name + QLatin1Char(':') + quoted;
+}
+
+QString onDate(const QDate &day)
+{
+    if (!day.isValid())
+        return {};
+    const QString text = day.toString(QStringLiteral("yyyy-MM-dd"));
+    return QStringLiteral("date:%1..%1").arg(text);
+}
+
+QString tag(const QString &name)
+{
+    const QString trimmed = name.simplified();
+    if (trimmed.isEmpty())
+        return {};
+
+    // A tag is a token from a vocabulary the user chose, so it reads better
+    // unquoted in the bar they are about to edit. Quoted only when it holds
+    // something that would not survive.
+    const bool needsQuoting =
+        std::any_of(trimmed.cbegin(), trimmed.cend(), [](QChar ch) {
+            return !(ch.isLetterOrNumber() || ch == QLatin1Char('-')
+                     || ch == QLatin1Char('_') || ch == QLatin1Char('.')
+                     || ch == QLatin1Char('/'));
+        });
+
+    return QStringLiteral("tag:") + (needsQuoting ? quote(trimmed) : trimmed);
+}
+
+QString extend(const QString &existing, const QString &addition)
+{
+    const QString left = existing.trimmed();
+    const QString right = addition.trimmed();
+
+    if (right.isEmpty())
+        return left;
+    if (left.isEmpty())
+        return right;
+
+    return QStringLiteral("(%1) AND (%2)").arg(left, right);
+}
+
+}  // namespace SearchTerm