Basic thread filtering

The reply pagination logic is a bit weird rn though.

src/timeline/TimelineFilter.cpp

@@ -0,0 +1,75 @@
+#include "TimelineFilter.h"
+
+#include "Logging.h"
+
+TimelineFilter::TimelineFilter(QObject *parent)
+  : QSortFilterProxyModel(parent)
+{
+    setDynamicSortFilter(true);
+}
+
+void
+TimelineFilter::setThreadId(const QString &t)
+{
+    nhlog::ui()->debug("Filtering by thread '{}'", t.toStdString());
+    if (this->threadId != t) {
+        this->threadId = t;
+        invalidateFilter();
+    }
+    emit threadIdChanged();
+}
+
+void
+TimelineFilter::setSource(TimelineModel *s)
+{
+    if (auto orig = this->source(); orig != s) {
+        if (orig)
+            disconnect(orig,
+                       &TimelineModel::currentIndexChanged,
+                       this,
+                       &TimelineFilter::currentIndexChanged);
+        this->setSourceModel(s);
+        connect(s, &TimelineModel::currentIndexChanged, this, &TimelineFilter::currentIndexChanged);
+        emit sourceChanged();
+        invalidateFilter();
+    }
+}
+
+TimelineModel *
+TimelineFilter::source() const
+{
+    return qobject_cast<TimelineModel *>(sourceModel());
+}
+
+void
+TimelineFilter::setCurrentIndex(int idx)
+{
+    // TODO: maybe send read receipt in thread timeline? Or not at all?
+    if (auto s = source()) {
+        s->setCurrentIndex(this->mapToSource(index(idx, 0)).row());
+    }
+}
+
+int
+TimelineFilter::currentIndex() const
+{
+    if (auto s = source())
+        return this->mapFromSource(s->index(s->currentIndex())).row();
+    else
+        return -1;
+}
+
+bool
+TimelineFilter::filterAcceptsRow(int source_row, const QModelIndex &) const
+{
+    if (threadId.isEmpty())
+        return true;
+
+    if (auto s = sourceModel()) {
+        auto idx = s->index(source_row, 0);
+        return s->data(idx, TimelineModel::EventId) == threadId ||
+               s->data(idx, TimelineModel::ThreadId) == threadId;
+    } else {
+        return true;
+    }
+}