1 files changed, 73 insertions, 0 deletions
diff --git a/include/erebos/merge.h b/include/erebos/merge.h
new file mode 100644
index 0000000..9705e94
--- /dev/null
+++ b/include/erebos/merge.h
@@ -0,0 +1,73 @@
+#pragma once
+
+#include <erebos/storage.h>
+
+#include <optional>
+#include <vector>
+
+namespace erebos
+{
+
+using std::nullopt;
+using std::optional;
+using std::vector;
+
+template<class T> struct Mergeable
+{
+};
+
+template<> struct Mergeable<vector<Stored<Object>>>
+{
+	using Component = Object;
+
+	static vector<Stored<Object>> components(const vector<Stored<Object>> & x) { return x; }
+	static vector<Stored<Object>> merge(const vector<Stored<Object>> & x) { return x; }
+};
+
+vector<Stored<Object>> findPropertyObjects(const vector<Stored<Object>> & leaves, const string & prop);
+
+template<typename T>
+optional<Stored<typename Mergeable<T>::Component>> findPropertyComponent(const vector<Stored<typename Mergeable<T>::Component>> & components, const string & prop)
+{
+	vector<Stored<Object>> leaves;
+	leaves.reserve(components.size());
+
+	for (const auto & c : components)
+		leaves.push_back(Stored<Object>::load(c.ref()));
+
+	auto candidates = findPropertyObjects(leaves, prop);
+	if (!candidates.empty())
+		return Stored<typename Mergeable<T>::Component>::load(candidates[0].ref());
+	return nullopt;
+}
+
+template<typename T>
+optional<Stored<typename Mergeable<T>::Component>> findPropertyComponent(const T & x, const string & prop)
+{
+	return findPropertyComponent(x.components(), prop);
+}
+
+template<typename T>
+vector<Stored<typename Mergeable<T>::Component>> findPropertyComponents(const vector<Stored<typename Mergeable<T>::Component>> & components, const string & prop)
+{
+	vector<Stored<Object>> leaves;
+	leaves.reserve(components.size());
+
+	for (const auto & c : components)
+		leaves.push_back(Stored<Object>::load(c.ref()));
+
+	auto candidates = findPropertyObjects(leaves, prop);
+	vector<Stored<typename Mergeable<T>::Component>> result;
+	result.reserve(candidates.size());
+	for (const auto & obj : candidates)
+		result.push_back(Stored<typename Mergeable<T>::Component>::load(obj.ref()));
+	return result;
+}
+
+template<typename T>
+vector<Stored<typename Mergeable<T>::Component>> findPropertyComponents(const T & x, const string & prop)
+{
+	return findPropertyComponents(x.components(), prop);
+}
+
+}