feat(search): offer the header's fields for searching

The menu lists what is searchable rather than hit-testing which line of a
rich-text label was clicked, which breaks as soon as the label wraps. The
values are collected by the pass that renders the header, so nothing parses
the markup back into structure.

From, To and Cc appear only for a single-message thread, sharing the condition
with the header's own display: a thread's recipient differs message to
message, and the menu must not offer what the header is not stating.

The test fixture's Date: header named the wrong weekday, which Qt::RFC2822Date
rejects outright, so no date offer would have been produced from it.

1 files changed, 72 insertions, 0 deletions

diff --git a/src/messageview.cpp b/src/messageview.cpp
index d2be380..8a1976d 100644
--- a/src/messageview.cpp
+++ b/src/messageview.cpp
@@ -30,6 +30,7 @@
 #include <QHBoxLayout>
 #include <QLabel>
 #include <QLocale>
+#include <QMenu>
 #include <QMouseEvent>
 #include <QPushButton>
 #include <QStandardPaths>
@@ -50,6 +51,7 @@
 #include "cidschemehandler.h"
 #include "htmlbuilder.h"
 #include "requestinterceptor.h"
+#include "searchterm.h"
 #include "tagstrip.h"
 #include "threadcidmap.h"
 #include "version.h"
@@ -163,6 +165,12 @@ MessageView::MessageView(QWidget *parent)
     m_headerLabel->setWordWrap(true);
     m_headerLabel->setTextInteractionFlags(Qt::TextSelectableByMouse);
 
+    // Item 85: the header's values are searchable. CustomContextMenu rather
+    // than an action list, since the entries depend on what is displayed.
+    m_headerLabel->setContextMenuPolicy(Qt::CustomContextMenu);
+    connect(m_headerLabel, &QWidget::customContextMenuRequested,
+            this, &MessageView::showHeaderContextMenu);
+
     // To the right of the header, per the user's decision: the summary answers
     // "who is this from", this answers "what actually happened to it". A button
     // and not only a shortcut, since "everything needs a memorized key" is the
@@ -428,6 +436,11 @@ QString MessageView::headerMark(Marks::Mark mark) const
 
 void MessageView::updateHeader()
 {
+    // A stale offer list must not survive either exit: the early return below
+    // leaves nothing on screen to search, and the normal path rebuilds it from
+    // scratch a few lines down.
+    m_headerOffers.clear();
+
     if (m_items.isEmpty()) {
         m_headerLabel->clear();
         m_detailsButton->hide();
@@ -440,6 +453,30 @@ void MessageView::updateHeader()
     // Re: prefixes that add nothing.
     const QString subject = m_items.first().message.subject;
 
+    // Collected by the pass that renders the label, from the same values, so
+    // nothing has to parse the rendered markup back into structure.
+    auto elided = [](const QString &value) {
+        constexpr int kMaxLabel = 40;
+        return value.size() > kMaxLabel
+                   ? value.left(kMaxLabel) + QStringLiteral("...")
+                   : value;
+    };
+
+    auto offer = [this](const QString &label, const QString &query) {
+        if (query.isEmpty())
+            return;
+        m_headerOffers.append({ label, query });
+    };
+
+    offer(tr("subject \"%1\"").arg(elided(subject)),
+          SearchTerm::field(QStringLiteral("subject"), subject));
+
+    const QDateTime sent = MimeParser::parseDate(m_items.first().message.date);
+    if (sent.isValid()) {
+        offer(tr("mail from %1").arg(sent.date().toString(Qt::ISODate)),
+              SearchTerm::onDate(sent.date()));
+    }
+
     // Item 70's marks, beside the subject and OUTSIDE the message area. The
     // user asked for these two only: whether the thread is flagged and whether
     // it carries an attachment, which are the two states worth knowing before
@@ -489,6 +526,16 @@ void MessageView::updateHeader()
         row(tr("From:"), message.from);
         row(tr("To:"), message.to);
         row(tr("Cc:"), message.cc);
+
+        // Only here, sharing the condition with the header's own display: for
+        // a real thread these differ message to message, and the details
+        // dialog is where they are unambiguous.
+        offer(tr("sender %1").arg(elided(message.from)),
+              SearchTerm::field(QStringLiteral("from"), message.from));
+        offer(tr("recipient %1").arg(elided(message.to)),
+              SearchTerm::field(QStringLiteral("to"), message.to));
+        offer(tr("copied to %1").arg(elided(message.cc)),
+              SearchTerm::field(QStringLiteral("cc"), message.cc));
     } else {
         text += QStringLiteral("<br><small>%1</small>")
                     .arg(tr("%n message(s) in thread", "", m_items.size()));
@@ -497,6 +544,31 @@ void MessageView::updateHeader()
     m_headerLabel->setText(text);
 }
 
+void MessageView::addSearchEntries(QMenu *menu, const QList<SearchOffer> &offers)
+{
+    for (const SearchOffer &entry : offers) {
+        auto *sub = menu->addMenu(tr("Search for %1").arg(entry.label));
+
+        auto *replace = sub->addAction(tr("Search for this"));
+        connect(replace, &QAction::triggered, this,
+                [this, entry]() { emit searchRequested(entry.query, false); });
+
+        auto *narrow = sub->addAction(tr("Add to search"));
+        connect(narrow, &QAction::triggered, this,
+                [this, entry]() { emit searchRequested(entry.query, true); });
+    }
+}
+
+void MessageView::showHeaderContextMenu(const QPoint &pos)
+{
+    if (m_headerOffers.isEmpty())
+        return;
+
+    QMenu menu(this);
+    addSearchEntries(&menu, m_headerOffers);
+    menu.exec(m_headerLabel->mapToGlobal(pos));
+}
+
 void MessageView::showDetailsDialog()
 {
     if (m_items.isEmpty())