feat(types): add MessageNode for message rows in the thread list

A message row has to be drawn without opening the message, so it needs sender,
subject and date. MessageRef carries none of them: it exists for rendering a
thread into the pane and holds only id, path, tags and matched.

depth defaults to 0, the thread's first message, which the root row stands for
rather than a child row. threadId is carried so a batch of nodes names the
thread it belongs to without the caller tracking it alongside.

2 files changed, 57 insertions, 0 deletions

diff --git a/src/types.h b/src/types.h
index 999d3f3..6b2ca4c 100644
--- a/src/types.h
+++ b/src/types.h
@@ -63,6 +63,37 @@ struct MessageRef
     bool matched = true;
 };
 
+/// One message as a row in the thread list.
+///
+/// Separate from MessageRef, which exists for RENDERING a thread and carries
+/// only what the message pane needs. A row has to be drawn without opening the
+/// message at all, so the display facts live here.
+struct MessageNode
+{
+    QString messageId;
+    QString threadId;  ///< The thread this message belongs to.
+    QString from;
+    QString subject;
+    QDateTime date;
+    QStringList tags;
+    QString filePath;
+
+    /// Reply depth within the thread. 0 is the thread's first message, which
+    /// occupies the ROOT row rather than a child row: the user's model is
+    /// "N replies", so a thread of 7 shows 1 root and 6 descendants.
+    int depth = 0;
+
+    bool isUnread() const { return tags.contains(QStringLiteral("unread")); }
+    bool isFlagged() const { return tags.contains(QStringLiteral("flagged")); }
+
+    /// notmuch applies "attachment" while indexing, so this needs no MIME
+    /// parsing, exactly as on ThreadSummary.
+    bool hasAttachment() const
+    {
+        return tags.contains(QStringLiteral("attachment"));
+    }
+};
+
 /// One tag mutation, kept so it can be inverted for undo.
 struct TagChange
 {
diff --git a/tests/test_threadlistmodel.cpp b/tests/test_threadlistmodel.cpp
index f84bbab..e2ca09f 100644
--- a/tests/test_threadlistmodel.cpp
+++ b/tests/test_threadlistmodel.cpp
@@ -27,6 +27,7 @@ class TestThreadListModel : public QObject
 {
     Q_OBJECT
 private slots:
+    void messageNodeHoldsDisplayFacts();
     void startsEmpty();
     void accountKeysComeFromTheAccountTags();
     void accountKeysCoverAThreadSpanningTwoAccounts();
@@ -116,6 +117,31 @@ void TestThreadListModel::accountKeysAreEmptyForAnUnknownThread()
     QVERIFY(model.accountKeysForThread(QStringLiteral("nope")).isEmpty());
 }
 
+void TestThreadListModel::messageNodeHoldsDisplayFacts()
+{
+    // A message ROW has to be drawn without opening the message, so the display
+    // facts live on the node itself. MessageRef, which exists for rendering a
+    // thread into the pane, carries none of them.
+    MessageNode node;
+    node.messageId = QStringLiteral("id@example.org");
+    node.from = QStringLiteral("A Sender <sender@example.org>");
+    node.subject = QStringLiteral("Re: a subject");
+    node.date = QDateTime::fromSecsSinceEpoch(1000);
+    node.depth = 2;
+    node.tags = QStringList{ QStringLiteral("unread") };
+
+    QCOMPARE(node.depth, 2);
+    QVERIFY(node.isUnread());
+    QCOMPARE(node.from, QStringLiteral("A Sender <sender@example.org>"));
+    QCOMPARE(node.subject, QStringLiteral("Re: a subject"));
+
+    // Depth 0 is the thread's first message, which the ROOT row stands for.
+    // Defaulting to 0 rather than 1 keeps "is this the root" a plain check.
+    const MessageNode fresh;
+    QCOMPARE(fresh.depth, 0);
+    QVERIFY(!fresh.isUnread());
+}
+
 void TestThreadListModel::startsEmpty()
 {
     ThreadListModel model;