/*
    Ousía
    Copyright (C) 2014, 2015  Benjamin Paaßen, Andreas Stöckel

    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 3 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/>.
*/

/**
 * @file Managed.hpp
 *
 * Describes the garbage collectable Managed class and Handle types pointing at
 * instances of this class.
 *
 * @author Andreas Stöckel (astoecke@techfak.uni-bielefeld.de)
 */

#ifndef _OUSIA_MANAGED_HPP_
#define _OUSIA_MANAGED_HPP_

#include "Manager.hpp"

namespace ousia {

template <class T>
class Handle;

template <class T>
class Rooted;

template <class T>
class Owned;

class Rtti;

// TODO: Implement clone, getReferenced and getReferencing

/**
 * The Managed class represents a garbage collected object. Instances of the
 * Managed class are managed (e.g. freed) by an instance of the Manager class.
 * Never free instances of this class yourself (even by playing an instance of
 * this class on the steck). Create any new instance of any managed object with
 * the makeRooted and makeOwned functions.
 *
 * Managed additionally offer the ability to attach arbitrary data to them (with
 * no overhead for objects which do not use this ability). RTTI type information
 * about the actual Managed object type can be retrieved using the type() and
 * isa() functions. The acquire() function allows to convinently convert an
 * Handle to another object to an Owned instance, owned by this Managed
 * instance.
 */
class Managed {
protected:
	/**
	 * mgr is the reference to the managed object manager which owns this
	 * managed object.
	 */
	Manager &mgr;

public:
	/**
	 * Constructor of the Managed class. Associates the new instance with the
	 * given Manager, which is now in charge for managing this instance. Never
	 * manually free instances of this class (even by using stack instances).
	 * Always use the Rooted and Owned smart pointer classes when refering to
	 * types derived from Managed.
	 *
	 * @param mgr is the Manager which should take ownership of this instance.
	 */
	Managed(Manager &mgr) : mgr(mgr) { mgr.manage(this); };

	/**
	 * Virtual destuctor which may be overwritten by child classes.
	 */
	virtual ~Managed() { mgr.unmanage(this); };

	/**
	 * Returns a reference ot the manager instance which owns this managed
	 * object.
	 *
	 * @return a reference at the underlying Manager object which manages this
	 * particular Managed instance.
	 */
	Manager &getManager() const { return mgr; }

	/**
	 * Returns the unique identifier (UID) of this object. Valid UIDs are
	 * positive non-zero values.
	 *
	 * @return the unique id of the object.
	 */
	ManagedUid getUid() const
	{
		/*
		 * Dear Bjarne Stroustroup, dear gods of C++, please excuse this
		 * const_cast, for I did try other means but was not able to apply them
		 * and in my despair turned to this folly, this ugliness, this heresy!
		 * I pledge my life to better programming and promise that this cast
		 * will do no harm to anyone.
		 */
		return mgr.getUid(const_cast<Managed *>(this));
	}

	/**
	 * Acquires a reference to the object wraped in the given handle -- creates
	 * a new Owned handle instance with this Managed instance as owner and the
	 * given object handle as the referenced object.
	 *
	 * @param h is a Handle pointing at the object that should be acquired.
	 * @return a Owned handle with this Managed instance as owner and the given
	 * object as reference.
	 */
	template <class T>
	Owned<T> acquire(const Handle<T> &h)
	{
		return Owned<T>{h, this};
	}

	/**
	 * Acquires a reference to the given pointer to a Managed object -- creates
	 * a new Owned handle instance with this Managed instance as owner and the
	 * given object as the referenced object.
	 *
	 * @param h is a Handle pointing at the object that should be acquired.
	 * @return a Owned handle with this Managed instance as owner and the given
	 * object pointer as reference.
	 */
	template <class T>
	Owned<T> acquire(T *t)
	{
		return Owned<T>{t, this};
	}

	/* Data store methods */

	/**
	 * Stores arbitrary data under the given key. Data will be overriden. This
	 * function can be used to attach data to the Managed object.
	 *
	 * @param key is an arbitrary string key that under which the data should
	 * be stored.
	 * @param h is the data that should be stored.
	 */
	void storeData(const std::string &key, Handle<Managed> h);

	/**
	 * Returns true if data was stored under the given key.
	 *
	 * @return true if data was stored under the given key, false otherwise.
	 */
	bool hasDataKey(const std::string &key);

	/**
	 * Returns data previously stored under the given key.
	 *
	 * @param key is the key specifying the slot from which the data should be
	 * read.
	 * @return previously stored data or nullptr if no data was stored for this
	 * key.
	 */
	Rooted<Managed> readData(const std::string &key);

	/**
	 * Returns a copy of all data that was attached to the node.
	 *
	 * @return a map between keys and stored data.
	 */
	std::map<std::string, Rooted<Managed>> readData();

	/**
	 * Deletes all data entries with the given key from the node.
	 *
	 * @param key is the key specifying the slot that should be deleted.
	 * @return true if the operation was successful, false otherwise.
	 */
	bool deleteData(const std::string &key);

	/* Event handling methods */

	/**
	 * Registers an event handler for an event of the given type.
	 *
	 * @param type is the event type that should be registered.
	 * @param handler is the callback function.
	 * @param owner is a managed object that owns the event handler. A reference
	 * from the the reference object to the owner is added. The argument may be
	 * nullptr in which case no reference is added. The owner is passed to the
	 * event handler as second parameter.
	 * @param data is some user defined data.
	 * @return a numeric event id, which is unique for the given reference
	 * object. The event id must be used when unregistering event handlers.
	 */
	EventId registerEvent(EventType type, EventHandler handler,
	                      Handle<Managed> owner, void *data = nullptr);

	/**
	 * Unregisters the event handler with the given signature.
	 *
	 * @param type is the event type that should be registered.
	 * @param handler is the callback function.
	 * @param owner is a managed object that owns the event handler. A reference
	 * from the the reference object to the owner is added. The argument may be
	 * nullptr in which case no reference is added. The owner is passed to the
	 * event handler as second parameter.
	 * @param data is some user defined data.
	 * @return a numeric event id, which is unique for the given reference
	 * object. The event id must be used when unregistering event handlers.
	 */
	bool unregisterEvent(EventType type, EventHandler handler,
	                     Handle<Managed> owner, void *data = nullptr);

	/**
	 * Unregisters the event with the given event id.
	 *
	 * @param id is the event that should be unregistered as returned by the
	 * registerEvent function.
	 * @return true if the operation was successful, false if either the
	 * reference object or the event id do not exist.
	 */
	bool unregisterEvent(EventId id);

	/**
	 * Triggers the event of the given type for the reference object.
	 *
	 * @param data is the event data that should be passed to the handlers.
	 */
	bool triggerEvent(Event &ev);

	/* RTTI methods */

	/**
	 * Returns the Rtti instance registered for instances of the type of
	 * this Managed instance.
	 *
	 * @return a reference to the registered Rtti for this particular
	 * Managed class.
	 */
	const Rtti *type() const;

	/**
	 * Returns true if this Managed instance is of the type described by the
	 * given Rtti instance.
	 *
	 * @param true if the Rtti registered for this particular Managed
	 * class is of the given type or one of the registered parent types is of
	 * the given type.
	 */
	bool isa(const Rtti *t) const;

	/**
	 * Returns true if this Managed instance may contain instances of the type
	 * described by the given Rtti instance.
	 *
	 * @param true if the Rtti registered for this particular Managed class
	 * may contain instance of the given type.
	 */
	bool composedOf(const Rtti *t) const;
};

/**
 * The Handle class is the base class for handles pointing at managed objects.
 * It implements methods for comparing handles to each other and to pointers
 * of the represented managed object type. Furthermore all other handle types
 * and pointers can be conveniently converted to a Handle instance. However,
 * the Handle class does not qualify the represented pointer for garbage
 * collection. Thus the Handle class should only be used as type for input
 * parameters in methods/functions and at no other ocasion. Use the Rooted or
 * the Owned class if the represented object should actually be garbage
 * collected.
 */
template <class T>
class Handle {
protected:
	friend class Rooted<T>;
	friend class Owned<T>;

	/**
	 * Reference to the represented managed object.
	 */
	T *ptr;

public:
	/**
	 * Constructor of the base Handle class.
	 *
	 * @param ptr is the pointer to the managed object the Handle should
	 * represent.
	 */
	Handle(T *ptr) : ptr(ptr) {}

	/**
	 * Copies the given Handle to this Handle instance.
	 *
	 * @param h is the Handle that should be asigned to this instance.
	 */
	Handle(const Handle<T> &h) : ptr(h.get()) {}

	/**
	 * Copies the given Handle for a managed object of a derived class to this
	 * Handle instance.
	 *
	 * @param h is the Handle that should be asigned to this instance.
	 */
	template <class T2>
	Handle(const Handle<T2> &h)
	    : ptr(h.get())
	{
	}

	/**
	 * Returns the underlying pointer.
	 */
	T *get() const { return ptr; }

	/**
	 * Provides access to the underlying managed object.
	 */
	T *operator->() { return ptr; }

	/**
	 * Provides access to the underlying managed object for immutable handles.
	 */
	const T *operator->() const { return ptr; }

	/**
	 * Provides access to the underlying managed object.
	 */
	T &operator*() { return *ptr; }

	/**
	 * Provides access to the underlying managed object for immutable handles.
	 */
	const T &operator*() const { return *ptr; }

	/**
	 * Comparison operator between base Owned and base Owned.
	 */
	template <class T2>
	bool operator==(const Handle<T2> &h) const
	{
		return ptr == h.get();
	}

	/**
	 * Comparison operator between base Owned and pointer.
	 */
	friend bool operator==(const Handle<T> &h, const Managed *o)
	{
		return h.get() == o;
	}

	/**
	 * Comparison operator between base Owned and pointer.
	 */
	friend bool operator==(const Managed *o, const Handle<T> &h)
	{
		return o == h.get();
	}

	/**
	 * Comparison operator between base Owned and base Owned.
	 */
	template <class T2>
	bool operator!=(const Handle<T2> &h) const
	{
		return ptr != h.get();
	}

	/**
	 * Comparison operator between base Owned and pointer.
	 */
	friend bool operator!=(const Handle<T> &h, const Managed *o)
	{
		return h.get() != o;
	}

	/**
	 * Comparison operator between base Owned and pointer.
	 */
	friend bool operator!=(const Managed *o, const Handle<T> &h)
	{
		return o != h.get();
	}

	/**
	 * Returns true if the handle is the null pointer.
	 */
	bool isNull() const { return ptr == nullptr; }

	/**
	 * Returns true if the handle is the null pointer.
	 */
	bool operator!() const { return isNull(); }

	/**
	 * Statically casts the handle to a handle of the given type.
	 */
	template <class T2>
	Handle<T2> cast() const
	{
		return Handle<T2>(static_cast<T2 *>(ptr));
	}
};

/**
 * A Rooted represents a directed, garbage collected pointer at a managed
 * object. The lifetime of the represented managed object is guaranteed to be at
 * least as long as the lifetime of the Rooted handle instance.
 */
template <class T>
class Rooted : public Handle<T> {
private:
	void addRef()
	{
		if (Handle<T>::ptr) {
			Handle<T>::ptr->getManager().addRef(Handle<T>::ptr, nullptr);
		}
	}

	void deleteRef()
	{
		if (Handle<T>::ptr) {
			Handle<T>::ptr->getManager().deleteRef(Handle<T>::ptr, nullptr);
		}
	}

public:
	/**
	 * Creates a Rooted handle pointing at the null pointer.
	 */
	Rooted() : Handle<T>(nullptr){};

	/**
	 * Copies the given Rooted to this Rooted instance. Both handles
	 * are indistinguishable after the operation.
	 *
	 * @param h is the Owned that should be asigned to this instance.
	 */
	Rooted(const Rooted<T> &h) : Handle<T>(h.ptr) { addRef(); }

	/**
	 * Move constructor. Moves the given rvalue Rooted to this instance.
	 *
	 * @param h is the Rooted to be moved to this instance.
	 */
	Rooted(Rooted<T> &&h) noexcept : Handle<T>(h.ptr) { h.ptr = nullptr; }

	/**
	 * Constructor of the Rooted class.
	 *
	 * @param ptr is the managed object the Rooted handle should represent.
	 */
	Rooted(T *ptr) : Handle<T>(ptr) { addRef(); }

	/**
	 * Constructor of the Rooted class.
	 *
	 * @param h is another Rooted whose managed object should be used.
	 */
	template <class T2>
	Rooted(const Handle<T2> &h)
	    : Handle<T>(h.get())
	{
		addRef();
	}

	/**
	 * Assignment operator. Assigns the given Owned to this Owned instance.
	 * Both handles are indistinguishable after the operation.
	 *
	 * @param h is the Owned that should be asigned to this instance.
	 */
	Rooted<T> &operator=(const Rooted<T> &h)
	{
		deleteRef();
		this->ptr = h.ptr;
		addRef();
		return *this;
	}

	/**
	 * Move assignment operator. Moves the given rvalue Owned into this
	 * instance.
	 *
	 * @param h is the Owned to be moved to this instance.
	 */
	Rooted<T> &operator=(Rooted<T> &&h) noexcept
	{
		deleteRef();
		this->ptr = h.ptr;
		h.ptr = nullptr;
		return *this;
	}

	/**
	 * Assignment operator. Assigns the given Owned to this Owned instance.
	 * Both handles are indistinguishable after the operation.
	 *
	 * @param h is the Owned that should be asigned to this instance.
	 */
	template <class T2>
	Rooted<T> &operator=(const Handle<T2> &h)
	{
		deleteRef();
		this->ptr = h.get();
		addRef();
		return *this;
	}

	/**
	 * Move assignment operator. Moves the given rvalue Owned into this
	 * instance.
	 *
	 * @param h is the Owned to be moved to this instance.
	 */
	Rooted<T> &operator=(Handle<T> &&h) noexcept
	{
		deleteRef();
		this->ptr = h.ptr;
		h.ptr = nullptr;
		return *this;
	}

	/**
	 * Destructor of the Rooted class, deletes all refrences the class is
	 * still holding.
	 */
	~Rooted() { deleteRef(); }
};

/**
 * The Owned class represents a directed, garbage collected pointer at a managed
 * instance. The lifetime of the represented managed object is guaranteed to be
 * at last as long as the lifetime of the Managed instance which owns this
 * reference.
 */
template <class T>
class Owned : public Handle<T> {
private:
	Managed *owner;

	void addRef()
	{
		if (Handle<T>::ptr) {
			if (owner) {
				owner->getManager().addRef(Handle<T>::ptr, owner);
			} else {
				Handle<T>::ptr->getManager().addRef(Handle<T>::ptr, owner);
			}
		}
	}

	void deleteRef()
	{
		if (Handle<T>::ptr) {
			if (owner) {
				owner->getManager().deleteRef(Handle<T>::ptr, owner);
			} else {
				Handle<T>::ptr->getManager().deleteRef(Handle<T>::ptr, owner);
			}
		}
	}

public:
	/**
	 * Creates an empty Owned.
	 */
	Owned() : Handle<T>(nullptr), owner(nullptr){};

	/**
	 * Copies the given Owned to this Owned instance. Both handles are
	 * indistinguishable after the operation. Note that especially the Owned
	 * owner is copied.
	 *
	 * @param h is the Owned that should be asigned to this instance.
	 */
	Owned(const Owned<T> &h) : Handle<T>(h.get()), owner(h.getOwner())
	{
		addRef();
	}

	/**
	 * Copies the given Owned of another derived type to this Owned instance.
	 * Both handles are indistinguishable after the operation (except for the
	 * type). Note that especially the Owned owner is copied.
	 *
	 * @param h is the Owned that should be asigned to this instance.
	 */
	template <class T2>
	Owned(const Owned<T2> &h)
	    : Handle<T>(h.get()), owner(h.getOwner())
	{
		addRef();
	}

	/**
	 * Move constructor. Moves the given rvalue Owned to this instance.
	 *
	 * @param h is the Owned to be moved to this instance.
	 */
	Owned(Owned<T> &&h) noexcept : Handle<T>(h.get()), owner(h.getOwner())
	{
		h.ptr = nullptr;
	}

	/**
	 * Assignment operator. Assigns the given Owned to this Owned instance.
	 * Both handles are indistinguishable after the operation. Note that
	 * especially the Owned owner is copied.
	 *
	 * @param h is the Owned that should be asigned to this instance.
	 */
	Owned<T> &operator=(const Owned<T> &h)
	{
		deleteRef();
		this->ptr = h.ptr;
		this->owner = h.getOwner();
		addRef();
		return *this;
	}

	/**
	 * Move assignment operator. Moves the given rvalue Owned into this
	 * instance.
	 *
	 * @param h is the Owned to be moved to this instance.
	 */
	Owned<T> &operator=(Owned<T> &&h) noexcept
	{
		deleteRef();
		this->ptr = h.ptr;
		this->owner = h.getOwner();
		h.ptr = nullptr;
		return *this;
	}

	/**
	 * Constructor of the Owned class.
	 *
	 * @param ptr is a pointer at the managed object the Owned handle should
	 * represent.
	 * @param owner is the managed object which owns this Owned handle instance.
	 * The managed object pointed to in the handle is guaranteed to live at
	 * least as long as the owner.
	 */
	Owned(T *ptr, Managed *owner) : Handle<T>(ptr), owner(owner) { addRef(); }

	/**
	 * Constructor of the Owned class.
	 *
	 * @param h is another Owned whose managed object should be used.
	 * @param owner is the managed object which owns this Owned handle instance.
	 * The managed object pointed to in the handle is guaranteed to live at
	 * least as long as the owner.
	 */
	template <class T2>
	Owned(const Handle<T2> &h, Managed *owner)
	    : Handle<T>(h.get()), owner(owner)
	{
		addRef();
	}

	/**
	 * Destructor of the Owned class, deletes all refrences the class is still
	 * holding.
	 */
	~Owned() { deleteRef(); }

	/**
	 * Returns the reference to the owner of the Owned.
	 *
	 * @return the Owned owner.
	 */
	Managed *getOwner() const { return owner; }
};
}

#endif /* _OUSIA_MANAGED_HPP_ */