feat(ui): add a Maildir overview under Help

Nothing in the UI reported database-level facts: every query gave a
thread count for that query, and nothing said how much mail there is
overall. A dialog under Help now shows messages, threads and tags from
notmuch, plus the account list from config, since notmuch does not model
accounts at all.

A separate worker call rather than a reuse of requestCounts, which counts
threads to match the row count of a query. This counts messages, which is
what a user means by "how much mail is in here". The test pins 4 messages
in 3 threads against the fixture and fails if they are ever made equal,
so routing both through one count cannot pass unnoticed.

Every field starts at -1 and renders as "unknown" when notmuch could not
answer it. Printing 0 would say the Maildir is empty, and telling someone
their mail is gone is the worst way to report an index that failed to
open.

The dialog opens showing "Counting..." rather than blocking, since
counting every message is not free on a large database. That makes two
lifetimes matter: the reply can arrive after the dialog is closed, so the
label is a QPointer, and the dialog can be closed and reopened while a
count runs, so a generation counter drops the older answer. The test
drains DeferredDelete before firing the late reply, because close()
deletes through deleteLater and without that the dangling case is never
actually reached.

1 files changed, 93 insertions, 0 deletions

diff --git a/src/mainwindow.cpp b/src/mainwindow.cpp
index 3f8a53d..0ce94a8 100644
--- a/src/mainwindow.cpp
+++ b/src/mainwindow.cpp
@@ -288,6 +288,7 @@ MainWindow::MainWindow(const Config &config, QWidget *parent)
     qRegisterMetaType<ThreadSummary>();
     qRegisterMetaType<MessageRef>();
     qRegisterMetaType<TagChange>();
+    qRegisterMetaType<DatabaseStats>();
     qRegisterMetaType<QVector<ThreadSummary>>();
     qRegisterMetaType<QVector<MessageRef>>();
 
@@ -885,6 +886,13 @@ void MainWindow::buildMenus()
     auto *shortcuts = helpMenu->addAction(tr("&Keyboard shortcuts"));
     connect(shortcuts, &QAction::triggered,
             this, &MainWindow::showShortcutReference);
+    // A dialog the user asks for, per item 34: counting every message is not
+    // free on a large database, so this must not be anything that refreshes on
+    // its own.
+    auto *maildirInfo = helpMenu->addAction(tr("&Maildir overview"));
+    maildirInfo->setObjectName(QStringLiteral("maildirOverview"));
+    connect(maildirInfo, &QAction::triggered,
+            this, &MainWindow::showMaildirOverview);
     auto *about = helpMenu->addAction(tr("&About"));
     connect(about, &QAction::triggered, this, &MainWindow::showAbout);
 
@@ -1031,6 +1039,89 @@ void MainWindow::showShortcutReference()
     dialog.exec();
 }
 
+void MainWindow::showMaildirOverview()
+{
+    auto *dialog = new QDialog(this);
+    dialog->setWindowTitle(tr("Maildir overview"));
+    dialog->setObjectName(QStringLiteral("maildirOverviewDialog"));
+    // Deleted on close, which is what makes m_overviewCounts a QPointer: the
+    // worker's reply can arrive after the user has dismissed it.
+    dialog->setAttribute(Qt::WA_DeleteOnClose);
+
+    auto *counts = new QLabel(dialog);
+    counts->setObjectName(QStringLiteral("maildirCounts"));
+    counts->setTextFormat(Qt::RichText);
+    // Shown as pending rather than as zero. The dialog opens before the answer
+    // arrives, and a zero would read as "no mail", which is a claim rather than
+    // an absence of one.
+    counts->setText(tr("<b>Counting...</b>"));
+    m_overviewCounts = counts;
+
+    // From config, never from notmuch, which does not model accounts at all.
+    // That is the whole reason per-account subdirectories are configured.
+    QString accountText;
+    const QList<Account> accounts = m_config.accounts();
+    accountText += tr("<b>%n account(s)</b>", "", int(accounts.size()));
+    if (!accounts.isEmpty()) {
+        accountText += QStringLiteral("<ul>");
+        for (const Account &account : accounts) {
+            // Account names are user-written config, and this label is rich
+            // text, so they are escaped like any other untrusted value.
+            const QString label = account.label.isEmpty() ? account.key
+                                                          : account.label;
+            accountText += QStringLiteral("<li>%1</li>")
+                               .arg(label.toHtmlEscaped());
+        }
+        accountText += QStringLiteral("</ul>");
+    }
+
+    auto *accountLabel = new QLabel(accountText, dialog);
+    accountLabel->setObjectName(QStringLiteral("maildirAccounts"));
+    accountLabel->setTextFormat(Qt::RichText);
+
+    auto *buttons = new QDialogButtonBox(QDialogButtonBox::Close, dialog);
+    connect(buttons, &QDialogButtonBox::rejected, dialog, &QDialog::reject);
+
+    auto *layout = new QVBoxLayout(dialog);
+    layout->addWidget(counts);
+    layout->addWidget(accountLabel);
+    layout->addStretch();
+    layout->addWidget(buttons);
+
+    // Asked for when the dialog opens and never on a timer: counting every
+    // message in a large database is not free, which is the constraint that
+    // made this a dialog rather than a status-bar field.
+    QMetaObject::invokeMethod(m_worker, "requestDatabaseStats",
+                              Qt::QueuedConnection,
+                              Q_ARG(quint64, ++m_statsGeneration));
+
+    dialog->show();
+}
+
+void MainWindow::onDatabaseStatsReady(const DatabaseStats &stats,
+                                      quint64 generation)
+{
+    // Closed and reopened while the count ran: this answer belongs to the old
+    // dialog. The QPointer covers "closed", this covers "closed and reopened".
+    if (generation != m_statsGeneration)
+        return;
+
+    if (!m_overviewCounts)
+        return;
+
+    // A field notmuch could not answer stays unknown. Printing 0 would say the
+    // database is empty, which is the opposite of "we could not tell".
+    const auto number = [](int value) {
+        return value < 0 ? tr("unknown") : QLocale().toString(value);
+    };
+
+    m_overviewCounts->setText(
+        tr("<b>%1</b> messages in <b>%2</b> threads<br>"
+           "<b>%3</b> tags")
+            .arg(number(stats.messages), number(stats.threads),
+                 number(stats.tags)));
+}
+
 void MainWindow::showAbout()
 {
     QDialog dialog(this);
@@ -1098,6 +1189,8 @@ void MainWindow::wireWorker()
             this, &MainWindow::onAllTagsReady);
     connect(m_worker, &NotmuchWorker::countsReady,
             this, &MainWindow::onCountsReady);
+    connect(m_worker, &NotmuchWorker::databaseStatsReady,
+            this, &MainWindow::onDatabaseStatsReady);
 
     // A confirmed write clears the pending revert: without this, a later
     // unrelated error would roll back a change that actually succeeded.