// This demonstrates a problem with boost::serialization and boost::enable_shared_from_this.
// (boost version 1.53)
// See boost TRAC ticket #9567
//
// Given the following class structure:
//    Base is a simple class
//    Derived inherits from Base
//    Derived also inherits from boost::enable_shared_from_this<Derived>
//    Base and Derived implement boost::serialization
//
// When deserializing an instance of Derived into a vector of boost::shared_ptr<Derived>:
//    Base and Derived members are reconstructed correctly.
//	  Derived::shared_from_this() works as expected.
//
// But when deserializing an instance of Derived into a vector of boost::shared_ptr<Base>:
//    Base and Derived members are still reconstructed correctly.
//	  Derived::shared_from_this() throws a bad_weak_ptr exception.
//    This is because enable_shared_from_this::weak_ptr is NOT reconstructed - It is zero.
#define BOOST_TEST_MAIN
#include <boost/test/unit_test.hpp>
#include <boost/test/output_test_stream.hpp>
#include <vector>
#include <boost/shared_ptr.hpp>
#include <boost/enable_shared_from_this.hpp>
#include <boost/serialization/shared_ptr.hpp>
#include <boost/archive/xml_oarchive.hpp>
#include <boost/archive/xml_iarchive.hpp>
#include <boost/serialization/vector.hpp>
#include <boost/serialization/export.hpp>

class Base {
public:
	Base() {}
	virtual ~Base() {}		// "virtual" forces RTTI, to enable serialization of Derived from Base pointer
	int m_base;

	template<class Archive>
	void serialize(Archive & ar, const unsigned int version)
	{
		ar & BOOST_SERIALIZATION_NVP(m_base);
	}
};

class Derived : public Base, public boost::enable_shared_from_this<Derived> {
public:
	Derived() {}
	~Derived() {}
	boost::shared_ptr<Derived> SharedPtr() { return shared_from_this(); }
	int m_derived;

	template<class Archive>
	void serialize(Archive & ar, const unsigned int version)
	{
		ar & BOOST_SERIALIZATION_BASE_OBJECT_NVP(Base);
		ar & BOOST_SERIALIZATION_NVP(m_derived);
	}
};
// The following is required to enable serialization from Base pointer
BOOST_CLASS_EXPORT(Derived)

BOOST_AUTO_TEST_SUITE(test_shared_from_this)

// This test passes
BOOST_AUTO_TEST_CASE(deserialize_pointer_Derived)
{
	std::stringstream ss;

	{
		// Create a vector of shared_ptr<Derived> containing an instance of shared_ptr<Derived> 
		std::vector<boost::shared_ptr<Derived>> vec_d;
		boost::shared_ptr<Derived> d(new Derived());
		d->m_base = 1;
		d->m_derived = 2;
		vec_d.push_back(d);
		d.reset();

		// Get a raw pointer to Derived
		Derived* raw_d = vec_d[0].get();

		// Verify base and derived members
		BOOST_CHECK(raw_d->m_base==1);
		BOOST_CHECK(raw_d->m_derived==2);

		// verify shared_from_this
		d = raw_d->SharedPtr();	
		BOOST_CHECK(d == vec_d[0]);

		// Serialize the vector
		boost::archive::xml_oarchive oa(ss);
		oa & BOOST_SERIALIZATION_NVP(vec_d);
	}
	{
		// Deserialize it back into a vector of shared_ptr<Derived>
		std::vector<boost::shared_ptr<Derived>> vec_d;
		ss.seekg(0);
		boost::archive::xml_iarchive ia(ss);
		ia & BOOST_SERIALIZATION_NVP(vec_d);

		// Get a raw pointer to Derived
		Derived* raw_d = vec_d[0].get();

		// Verify base and derived members
		BOOST_CHECK(raw_d->m_base==1);
		BOOST_CHECK(raw_d->m_derived==2);

		// verify shared_from_this
		boost::shared_ptr<Derived> d = raw_d->SharedPtr();	
		BOOST_CHECK(d == vec_d[0]);
	}	
}

// This test fails
BOOST_AUTO_TEST_CASE(deserialize_vector_Base)
{
	std::stringstream ss;

	{
		// Create a vector of shared_ptr<Base> containing an instance of shared_ptr<Derived> 
		std::vector<boost::shared_ptr<Base>> vec_b;
		boost::shared_ptr<Base> b(new Derived());
		Derived* raw_d1 = static_cast<Derived*>(b.get());
		raw_d1->m_base = 1;
		raw_d1->m_derived = 2;
		vec_b.push_back(b);
		
		// Get a raw pointer to Derived via shared_ptr<Base>
		Derived* raw_d = static_cast<Derived*>(vec_b[0].get());

		// Verify base and derived members
		BOOST_CHECK(raw_d->m_base==1);
		BOOST_CHECK(raw_d->m_derived==2);

		// verify shared_from_this
		boost::shared_ptr<Derived> d = raw_d->SharedPtr();
		BOOST_CHECK(d == vec_b[0]);
		// Serialize the vector
		boost::archive::xml_oarchive oa(ss);
		oa & BOOST_SERIALIZATION_NVP(vec_b);
	}
	{
		// Deserialize it back into a vector of shared_ptr<Base>
		std::vector<boost::shared_ptr<Base>> vec_b;
		ss.seekg(0);
		boost::archive::xml_iarchive ia(ss);
		ia & BOOST_SERIALIZATION_NVP(vec_b);

		// Get a raw pointer to Derived via shared_ptr<Base>
		Derived* raw_d = static_cast<Derived*>(vec_b[0].get());
		// Verify base and derived members
		BOOST_CHECK(raw_d->m_base==1);
		BOOST_CHECK(raw_d->m_derived==2);

		// verify shared_from_this
		// FAIL: The following line throws bad_weak_ptr exception 
		boost::shared_ptr<Derived> d = raw_d->SharedPtr();
		BOOST_CHECK(d == vec_b[0]);
	}	
}

// This test demonstrates a workaround by reconstructing the weak_ptr after deserialization
BOOST_AUTO_TEST_CASE(deserialize_vector_Base_workaround)
{
	std::stringstream ss;

	{
		// Create a vector of shared_ptr<Base> containing an instance of shared_ptr<Derived> 
		std::vector<boost::shared_ptr<Base>> vec_b;
		boost::shared_ptr<Base> b(new Derived());
		Derived* raw_d1 = static_cast<Derived*>(b.get());
		raw_d1->m_base = 1;
		raw_d1->m_derived = 2;
		vec_b.push_back(b);
		
		// Get a raw pointer to Derived via shared_ptr<Base>
		Derived* raw_d = static_cast<Derived*>(vec_b[0].get());

		// Verify base and derived members
		BOOST_CHECK(raw_d->m_base==1);
		BOOST_CHECK(raw_d->m_derived==2);

		// verify shared_from_this
		boost::shared_ptr<Derived> d = raw_d->SharedPtr();
		BOOST_CHECK(d == vec_b[0]);
		// Serialize the vector
		boost::archive::xml_oarchive oa(ss);
		oa & BOOST_SERIALIZATION_NVP(vec_b);
	}
	{
		// Deserialize it back into a vector of shared_ptr<Base>
		std::vector<boost::shared_ptr<Base>> vec_b;
		ss.seekg(0);
		boost::archive::xml_iarchive ia(ss);
		ia & BOOST_SERIALIZATION_NVP(vec_b);

		// Get a raw pointer to Derived via shared_ptr<Base>
		Derived* raw_d = static_cast<Derived*>(vec_b[0].get());
		// Verify base and derived members
		BOOST_CHECK(raw_d->m_base==1);
		BOOST_CHECK(raw_d->m_derived==2);

		// WORKAROUND: reconstruct enable_shared_from_this weak_ptr
		raw_d->_internal_accept_owner(&vec_b[0], raw_d);

		// verify shared_from_this
		boost::shared_ptr<Derived> d = raw_d->SharedPtr();
		BOOST_CHECK(d == vec_b[0]);
	}	
}
BOOST_AUTO_TEST_SUITE_END()