Merge: searching from the message pane (item 85)

Five surfaces in the message pane offer a search built from what they show:
the header's subject and date, its sender and recipients on a single-message
thread, a tag chip, a body selection, and every header per message in the
details dialog. Each offers Search for this, which replaces the query, and
Add to search, which narrows it.

The details dialog became labelled rows along the way, which the user wanted
independently of this feature.

Hand tested through every surface, including the case the parenthesising
exists for: adding a sender to 'tag:inbox or tag:flagged' narrows it rather
than widening it.

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