1 files changed, 61 insertions, 0 deletions
diff --git a/desktop-widgets/command_private.h b/desktop-widgets/command_private.h
new file mode 100644
index 000000000..06e4516c1
--- /dev/null
+++ b/desktop-widgets/command_private.h
@@ -0,0 +1,61 @@
+// SPDX-License-Identifier: GPL-2.0
+// Private definitions for the command-objects
+
+#ifndef COMMAND_PRIVATE_H
+#define COMMAND_PRIVATE_H
+
+#include <vector>
+#include <utility>
+#include <QVector>
+
+struct dive;
+struct dive_trip;
+
+namespace Command {
+
+// Generally, signals are sent in batches per trip. To avoid writing the same loop
+// again and again, this template takes a vector of trip / dive pairs, sorts it
+// by trip and then calls a function-object with trip and a QVector of dives in that trip.
+// Input parameters:
+//	- dives: a vector of trip,dive pairs, which will be sorted and processed in batches by trip.
+//	- action: a function object, taking a trip-pointer and a QVector of dives, which will be called for each batch.
+template<typename Function>
+void processByTrip(std::vector<std::pair<dive_trip *, dive *>> &dives, Function action)
+{
+	// Use std::tie for lexicographical sorting of trip, then start-time
+	std::sort(dives.begin(), dives.end(),
+		  [](const std::pair<dive_trip *, dive *> &e1, const std::pair<dive_trip *, dive *> &e2)
+		  { return std::tie(e1.first, e1.second->when) < std::tie(e2.first, e2.second->when); });
+
+	// Then, process the dives in batches by trip
+	size_t i, j; // Begin and end of batch
+	for (i = 0; i < dives.size(); i = j) {
+		dive_trip *trip = dives[i].first;
+		for (j = i + 1; j < dives.size() && dives[j].first == trip; ++j)
+			; // pass
+		// Copy dives into a QVector. Some sort of "range_view" would be ideal, but Qt doesn't work this way.
+		QVector<dive *> divesInTrip(j - i);
+		for (size_t k = i; k < j; ++k)
+			divesInTrip[k - i] = dives[k].second;
+
+		// Finally, emit the signal
+		action(trip, divesInTrip);
+	}
+}
+
+// The processByTrip() function above takes a vector if (trip, dive) pairs.
+// This overload takes a vector of dives.
+template<typename Vector, typename Function>
+void processByTrip(Vector &divesIn, Function action)
+{
+	std::vector<std::pair<dive_trip *, dive *>> dives;
+	dives.reserve(divesIn.size());
+	for (dive *d: divesIn)
+		dives.push_back({ d->divetrip, d });
+	processByTrip(dives, action);
+
+}
+
+} // namespace Command
+
+#endif // COMMAND_PRIVATE_H