/*
    belle-sip - SIP (RFC3261) library.
    Copyright (C) 2019  Belledonne Communications SARL

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

#ifndef belle_sip_object_plusplus_h
#define belle_sip_object_plusplus_h

#include "belle-sip/object.h"
#include "belle-sip/types.h"
#include "belle-sip/utils.h"

#include <functional>
#include <list>
#include <memory>

namespace bellesip {

class ObjectCAccessors;

class BELLESIP_EXPORT Object {
	friend ObjectCAccessors;

public:
	Object();
	Object *ref();
	const Object *ref() const;
	void unref();
	// Overrides should keep	the size of toString() lower than BELLE_SIP_MAX_TO_STRING_SIZE
	virtual std::string toString() const;
	virtual Object *clone() const;
	belle_sip_cpp_object_t *getCObject();
	const belle_sip_cpp_object_t *getCObject() const;
	void *getCPtr() {
		return static_cast<void *>(getCObject());
	}
	const void *getCPtr() const {
		return static_cast<const void *>(getCObject());
	}
	static Object *getCppObject(void *);
	static const Object *getCppObject(const void *);
	int getRefCount() const {
		return mObject.ref;
	}

protected:
	virtual ~Object(); /*the destructor must be kept protected, never public, including for all classes inherting from
	                      this*/
	Object(const Object &other);
	Object(Object &&other);
	void constUnref() const;

private:
	void init();
	mutable belle_sip_cpp_object_t mObject{};
	belle_sip_error_code marshal(char *buff, size_t buff_size, size_t *offset);
};

/**
 * Template class to help define an Object usable in both C and C++
 * The template arguments are:
 * - _CType : the type used to represent this object in C
 * - _CppType : the type used in C++ to implement this object. _CppType is used to be set to the type
 *   of the class inheriting from HybridObject.
 * Example:
 * typedef struct _CExample CExample;
 * class Example : public HybridObject<CExample, Example>{
 * ...
 * }
 * The C object can be obtained with toC() method, directly casted in the expected type.
 * The C++ object can be obtained from C object with static method toCpp().
 *
 * VERY IMPORTANT USAGE RULES:
 * - make_shared\<\>() or shared_ptr\<\>(new ...) MUST NOT be used to instanciate an HybridObject, use create() instead.
 * - An HybridObject can be used on the stack like a regular object ONLY if used internally. If the instance is supposed
 *   to be returned and used by a client then it MUST be created with create().
 * - If create() or createCObject() are used on a derived class of the one inheriting this class then the derived type
 *   MUST be given explicitly, DerivedClass::create\<DerivedClass\>().
 *
 * A shared_ptr\<\> can be obtained at any time from an HybridObject using getSharedFromThis().
 * The static getSharedFromThis(_Ctype*) method can be used to directly obtain a shared_ptr from the C object.
 *
 * The clone() method must be overriden to return a new _CppType contructed with copy contructor,
 * or return nullptr if the object is defined to be not clonable.
 *
 * Rational for using this template:
 * - You have an existing library in C where all C objects are inheriting from belle_sip_object_t (for refcounting,
 *   data_set etc...).
 * - You want to use C++ in your library without making any disruption in the API.
 * IMPORTANT:
 * If you don't care about belle_sip_object_t inheritance in your C api,
 * or if you don't need any C api associated to this object at all, DON'T USE THIS.
 * An usage example is shown in tester/object_tester.cc .
 **/
template <typename _CType, typename _CppType>
class HybridObject : public Object {
public:
	// Create the C++ object returned as a shared_ptr. Reference counting is managed by shared_ptr automatically.
	template <typename _DerivedCppType = _CppType, typename... _Args>
	static inline std::shared_ptr<_DerivedCppType> create(_Args &&...__args) {
		return std::static_pointer_cast<_DerivedCppType>(
		    (new _DerivedCppType(std::forward<_Args>(__args)...))->toSharedPtr());
	}
	// Convenience creator to get the C object instead. Automatically acquires a ref. Consumers have the
	// responsibility to unref
	template <typename _DerivedCppType = _CppType, typename... _Args>
	static inline _CType *createCObject(_Args &&...__args) {
		return (new _DerivedCppType(std::forward<_Args>(__args)...))->toC();
	}
	// Obtain the C object from this.
	_CType *toC() {
		return static_cast<_CType *>(getCPtr());
	}
	// Obtain the C object this, when it is const.
	const _CType *toC() const {
		return static_cast<const _CType *>(getCPtr());
	}
	// Obtain the C++ object as a normal pointer.
	static _CppType *toCpp(_CType *ptr) {
		return static_cast<_CppType *>(getCppObject(ptr));
	}
	// Obtain the C++ object as a normal pointer, when the c++ object is const.
	static const _CppType *toCpp(const _CType *ptr) {
		return static_cast<const _CppType *>(getCppObject(ptr));
	}
	// Obtain a shared_ptr from the C++ object.
	std::shared_ptr<_CppType> getSharedFromThis() {
		return sharedFromThis(false);
	}
	// Obtain a shared_ptr from the C++ object in the const case.
	std::shared_ptr<const _CppType> getSharedFromThis() const {
		return sharedFromThis(false);
	}
	// Convenience method for easy CType -> shared_ptr<CppType> conversion
	static std::shared_ptr<_CppType> getSharedFromThis(_CType *ptr) {
		return toCpp(ptr)->getSharedFromThis();
	}
	// Convenience method for easy CType -> shared_ptr<CppType> conversion
	static std::shared_ptr<const _CppType> getSharedFromThis(const _CType *ptr) {
		return toCpp(const_cast<_CType *>(ptr))->getSharedFromThis();
	}
	// Obtain a shared_ptr that takes ownership of the object.
	// Use this method with caution as it will transfer the ownership of the object to the shared_ptr, unlike
	// getSharedFromThis() that gives you a new reference to the object. This method should be only useful to transfer
	// into a shared_ptr an object that was created as a normal pointer, for example by clone() or createCObject()
	// methods. There should be NO public const variant of this method.
	std::shared_ptr<_CppType> toSharedPtr() {
		return sharedFromThis(true);
	}

	// Convenience method for easy bctbx_list(_Ctype) -> std::list<_CppType> conversion
	// It does not take ownership of the hybrid object, but takes a ref.
	static std::list<std::shared_ptr<_CppType>> getCppListFromCList(const bctbx_list_t *cList) {
		std::list<std::shared_ptr<_CppType>> result;
		for (auto it = cList; it != nullptr; it = bctbx_list_next(it))
			result.push_back(toCpp(static_cast<_CType *>(bctbx_list_get_data(it)))->getSharedFromThis());
		return result;
	}
	// Convenience method for easy bctbx_list(_Ctype) -> std::list<_CppType> conversion
	// Applies 'func' to get _CppType from _CType. Used in case we do not want to call  `toCpp` on _Ctype
	static std::list<std::shared_ptr<_CppType>>
	getCppListFromCList(const bctbx_list_t *cList, const std::function<std::shared_ptr<_CppType>(_CType *)> &func) {
		std::list<std::shared_ptr<_CppType>> result;
		for (auto it = cList; it != nullptr; it = bctbx_list_next(it))
			result.push_back(func(static_cast<_CType *>(bctbx_list_get_data(it))));
		return result;
	}
	// Convenience method for easy std::list<shared_ptr<CppType>> -> bctbx_list(CType) conversion
	// The takeRef bool indicates whether a reference to the objects must be taken.
	static bctbx_list_t *getCListFromCppList(const std::list<std::shared_ptr<_CppType>> &cppList, bool takeRef = true) {
		return buildCList(cppList, takeRef);
	}
	// Convenience method for easy std::list<CppType*> -> bctbx_list(CType) conversion
	// The takeRef bool indicates whether a reference to the objects must be taken.
	static bctbx_list_t *getCListFromCppList(const std::list<_CppType *> &cppList, bool takeRef = true) {
		return buildCList(cppList, takeRef);
	}

	static const char *nullifyEmptyString(const std::string &cppString) {
		if (cppString.empty()) return nullptr;
		else return cppString.c_str();
	}
	typedef _CType CObjectType;
	typedef _CppType CppObjectType;

protected:
	virtual ~HybridObject() = default;
	HybridObject() = default;
	HybridObject(const HybridObject<_CType, _CppType> &other) : Object(other) {
	}
	HybridObject(HybridObject<_CType, _CppType> &&other) : Object(std::move(other)) {
		/* mSelf not stolen*/
	}

private:
	template <typename _ListType>
	static bctbx_list_t *buildCList(const _ListType &cppList, bool takeRef) {
		bctbx_list_t *begin = nullptr, *current = nullptr;
		for (auto cppPtr : cppList) {
			// Intentionnaly do not use bctbx_list_append() to construct the C list, because of its o(N) complexity,
			// as it is always returning the head of list.
			// Instead, remember the last added element for a constant time complexity.
			bctbx_list_t *newNode = bctbx_list_new(cppPtr->toC());
			if (takeRef) cppPtr->ref();
			if (!begin) {
				begin = newNode;
			} else {
				current->next = newNode;
				newNode->prev = current;
			}
			current = newNode;
		}
		return begin;
	}
	std::shared_ptr<_CppType> sharedFromThis(bool withTransfer) const {
		std::shared_ptr<_CppType> sp;
		if ((sp = mSelf.lock()) == nullptr) {
			sp = std::shared_ptr<_CppType>(static_cast<_CppType *>(const_cast<HybridObject<_CType, _CppType> *>(this)),
			                               std::mem_fn(&HybridObject<_CType, _CppType>::constUnref));
			mSelf = sp;
			if (!withTransfer) {
				sp->ref();
			}
		} else {
			if (withTransfer) {
				belle_sip_fatal("This HybridObject already has shared_ptr<> instances pointing to it.");
			}
		}
		return sp;
	}
	mutable std::weak_ptr<_CppType> mSelf;
};

template <typename _classT>
typename _classT::CObjectType *toC(_classT *obj) {
	if (obj) return obj->toC();
	return nullptr;
}

template <typename _classT>
const typename _classT::CObjectType *toC(const _classT *obj) {
	if (obj) return obj->toC();
	return nullptr;
}

template <typename _classT>
typename _classT::CObjectType *toC(const std::shared_ptr<_classT> &obj) {
	if (obj) return obj->toC();
	return nullptr;
}

template <typename _classT>
const typename _classT::CObjectType *toC(const std::shared_ptr<const _classT> &obj) {
	if (obj) return obj->toC();
	return nullptr;
}

template <typename _classT>
typename _classT::CppObjectType *toCpp(typename _classT::CObjectType *obj) {
	if (obj) return _classT::toCpp(obj);
	return nullptr;
}

template <typename _classT>
const typename _classT::CppObjectType *toCpp(const typename _classT::CObjectType *obj) {
	if (obj) return _classT::toCpp(obj);
	return nullptr;
}

template <typename _classT>
std::shared_ptr<typename _classT::CppObjectType> getSharedPtr(typename _classT::CObjectType *obj) {
	if (obj) return _classT::toCpp(obj)->getSharedFromThis();
	return nullptr;
}

template <typename _classT>
std::shared_ptr<const typename _classT::CppObjectType> getSharedPtr(const typename _classT::CObjectType *obj) {
	if (obj) return _classT::toCpp(obj)->getSharedFromThis();
	return nullptr;
}

} // namespace bellesip

extern "C" {
BELLE_SIP_DECLARE_VPTR(belle_sip_cpp_object_t);
}

#endif // belle_sip_object_plusplus_h
