3 files changed, 126 insertions, 0 deletions
diff --git a/include/erebos/merge.h b/include/erebos/merge.h
new file mode 100644
index 0000000..bef8212
--- /dev/null
+++ b/include/erebos/merge.h
@@ -0,0 +1,20 @@
+#pragma once
+
+#include <erebos/storage.h>
+
+namespace erebos
+{
+
+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; }
+};
+
+}
diff --git a/include/erebos/set.h b/include/erebos/set.h
new file mode 100644
index 0000000..f625cb0
--- /dev/null
+++ b/include/erebos/set.h
@@ -0,0 +1,96 @@
+#pragma once
+
+#include <erebos/merge.h>
+#include <erebos/storage.h>
+
+namespace erebos
+{
+
+class SetViewBase;
+template<class T> class SetView;
+
+class SetBase
+{
+protected:
+	struct Priv;
+
+	SetBase();
+	SetBase(const vector<Ref> &);
+	SetBase(shared_ptr<const Priv>);
+	
+	shared_ptr<const Priv> add(Storage &, const vector<Ref> &) const;
+
+	vector<vector<Ref>> toList() const;
+
+public:
+	vector<Digest> digests() const;
+
+protected:
+	shared_ptr<const Priv> p;
+};
+
+template<class T>
+class Set : public SetBase
+{
+	Set(shared_ptr<const Priv> p): SetBase(p) {};
+public:
+	Set() = default;
+	Set(const vector<Ref> & refs): SetBase(move(refs)) {}
+	Set(const Set<T> &) = default;
+	Set(Set<T> &&) = default;
+	Set & operator=(const Set<T> &) = default;
+	Set & operator=(Set<T> &&) = default;
+
+	static Set<T> load(const vector<Ref> & refs) { return Set<T>(move(refs)); }
+
+	Set<T> add(Storage &, const T &) const;
+
+	template<class F>
+	SetView<T> view(F && cmp) const;
+};
+
+template<class T>
+class SetView
+{
+public:
+	template<class F>
+	SetView(F && cmp, const vector<vector<Ref>> & refs);
+
+	typename vector<T>::const_iterator begin() const { return items.begin(); }
+	typename vector<T>::const_iterator end() const { return items.end(); }
+
+private:
+	vector<T> items;
+};
+
+template<class T>
+Set<T> Set<T>::add(Storage & st, const T & x) const
+{
+	return Set<T>(SetBase::add(st, storedRefs(Mergeable<T>::components(x))));
+}
+
+template<class T>
+template<class F>
+SetView<T> Set<T>::view(F && cmp) const
+{
+	return SetView<T>(std::move(cmp), toList());
+}
+
+template<class T>
+template<class F>
+SetView<T>::SetView(F && cmp, const vector<vector<Ref>> & refs)
+{
+	items.reserve(refs.size());
+	for (const auto & crefs : refs) {
+		vector<Stored<typename Mergeable<T>::Component>> comps;
+		comps.reserve(crefs.size());
+		for (const auto & r : crefs)
+			comps.push_back(Stored<typename Mergeable<T>::Component>::load(r));
+
+		filterAncestors(comps);
+		items.push_back(Mergeable<T>::merge(comps));
+	}
+	std::sort(items.begin(), items.end(), cmp);
+}
+
+}
diff --git a/include/erebos/storage.h b/include/erebos/storage.h
index 15ee0bb..735b399 100644
--- a/include/erebos/storage.h
+++ b/include/erebos/storage.h
@@ -668,6 +668,16 @@ WatchedHead<T>::~WatchedHead()
 				T::headTypeId, Head<T>::id(), watcherId);
 }
 
+template<class T>
+vector<Ref> storedRefs(const vector<Stored<T>> & v)
+{
+	vector<Ref> res;
+	res.reserve(v.size());
+	for (const auto & x : v)
+		res.push_back(x.ref());
+	return res;
+}
+
 }
 
 namespace std