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tjp/core/future/FutureErase.hpp

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+// TJP COPYRIGHT HEADER
+
+#pragma once
+
+#include <tjp/core/future/Future.hpp>
+#include <tjp/core/ptr/Ptr.hpp>
+#include <tjp/core/ptr/strong_of.hpp>
+#include <tjp/core/ptr/strong_emplace.hpp>
+
+namespace tjp::core {
+namespace futures::v2 {
+
+struct FutureErase
+{
+	StrongPtr<Future<void>> future;
+	
+	FutureErase()
+	{}
+	
+	template<typename T>
+	FutureErase(Future<T> &&future_)
+	{
+		set(std::move(future_));
+	}
+	
+	~FutureErase()
+	{
+		clear();
+	}
+		
+	template<typename T>
+	void set(Future<T> &&future_)
+	{
+		strong_emplace(future);
+		
+		*future = future_.then([future_ = weak(future)](auto &&f){
+			if (auto future = strong(future_))
+				(*future) = {};
+		});
+		
+		if (future->is_set())
+			future = {};
+	}
+	
+	template<typename T>
+	void operator =(Future<T> &&future_)
+	{
+		return set(std::move(future_));
+	}
+	
+	void clear()
+	{
+		future.reset();
+	}
+	
+	bool has_value () const
+	{
+		return future && future->valid();
+	}
+	
+	bool empty() const
+	{
+		return !has_value();
+	}
+	
+	Future<void> get_future()
+	{
+		auto future_ = future;
+		return future_ ?
+			*future_ : future_of_value();
+	}
+} ;
+
+} // namespace
+
+using FutureErase = futures::v2::FutureErase;
+
+} // namespace
+