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/*  callable.h                                                           */
/*************************************************************************/
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#ifndef CALLABLE_H
#define CALLABLE_H

#include "core/object/object_id.h"
#include "core/string/string_name.h"
#include "core/templates/list.h"

class Object;
class Variant;
class CallableCustom;

// This is an abstraction of things that can be called.
// It is used for signals and other cases where efficient calling of functions
// is required. It is designed for the standard case (object and method)
// but can be optimized or customized.

// Enforce 16 bytes with `alignas` to avoid arch-specific alignment issues on x86 vs armv7.

class Callable {
	alignas(8) StringName method;
	union {
		uint64_t object = 0;
		CallableCustom *custom;
	};

public:
	struct CallError {
		enum Error {
			CALL_OK,
			CALL_ERROR_INVALID_METHOD,
			CALL_ERROR_INVALID_ARGUMENT, // expected is variant type
			CALL_ERROR_TOO_MANY_ARGUMENTS, // expected is number of arguments
			CALL_ERROR_TOO_FEW_ARGUMENTS, // expected is number of arguments
			CALL_ERROR_INSTANCE_IS_NULL,
			CALL_ERROR_METHOD_NOT_CONST,
		};
		Error error = Error::CALL_OK;
		int argument = 0;
		int expected = 0;
	};

	void callp(const Variant **p_arguments, int p_argcount, Variant &r_return_value, CallError &r_call_error) const;
	void call_deferredp(const Variant **p_arguments, int p_argcount) const;
	Variant callv(const Array &p_arguments) const;

	Error rpcp(int p_id, const Variant **p_arguments, int p_argcount, CallError &r_call_error) const;

	_FORCE_INLINE_ bool is_null() const {
		return method == StringName() && object == 0;
	}
	_FORCE_INLINE_ bool is_custom() const {
		return method == StringName() && custom != nullptr;
	}
	_FORCE_INLINE_ bool is_standard() const {
		return method != StringName();
	}
	bool is_valid() const;

	template <typename... VarArgs>
	Callable bind(VarArgs... p_args);

	Callable bindp(const Variant **p_arguments, int p_argcount) const;
	Callable unbind(int p_argcount) const;

	Object *get_object() const;
	ObjectID get_object_id() const;
	StringName get_method() const;
	CallableCustom *get_custom() const;

	uint32_t hash() const;

	const Callable *get_base_comparator() const; //used for bind/unbind to do less precise comparisons (ignoring binds) in signal connect/disconnect

	bool operator==(const Callable &p_callable) const;
	bool operator!=(const Callable &p_callable) const;
	bool operator<(const Callable &p_callable) const;

	void operator=(const Callable &p_callable);

	operator String() const;

	Callable(const Object *p_object, const StringName &p_method);
	Callable(ObjectID p_object, const StringName &p_method);
	Callable(CallableCustom *p_custom);
	Callable(const Callable &p_callable);
	Callable() {}
	~Callable();
};

class CallableCustom {
	friend class Callable;
	SafeRefCount ref_count;
	bool referenced = false;

public:
	typedef bool (*CompareEqualFunc)(const CallableCustom *p_a, const CallableCustom *p_b);
	typedef bool (*CompareLessFunc)(const CallableCustom *p_a, const CallableCustom *p_b);

	//for every type that inherits, these must always be the same for this type
	virtual uint32_t hash() const = 0;
	virtual String get_as_text() const = 0;
	virtual CompareEqualFunc get_compare_equal_func() const = 0;
	virtual CompareLessFunc get_compare_less_func() const = 0;
	virtual StringName get_method() const;
	virtual ObjectID get_object() const = 0; //must always be able to provide an object
	virtual void call(const Variant **p_arguments, int p_argcount, Variant &r_return_value, Callable::CallError &r_call_error) const = 0;
	virtual Error rpc(int p_peer_id, const Variant **p_arguments, int p_argcount, Callable::CallError &r_call_error) const;
	virtual const Callable *get_base_comparator() const;

	CallableCustom();
	virtual ~CallableCustom() {}
};

// This is just a proxy object to object signals, its only
// allocated on demand by/for scripting languages so it can
// be put inside a Variant, but it is not
// used by the engine itself.

// Enforce 16 bytes with `alignas` to avoid arch-specific alignment issues on x86 vs armv7.
class Signal {
	alignas(8) StringName name;
	ObjectID object;

public:
	_FORCE_INLINE_ bool is_null() const {
		return object.is_null() && name == StringName();
	}
	Object *get_object() const;
	ObjectID get_object_id() const;
	StringName get_name() const;

	bool operator==(const Signal &p_signal) const;
	bool operator!=(const Signal &p_signal) const;
	bool operator<(const Signal &p_signal) const;

	operator String() const;

	Error emit(const Variant **p_arguments, int p_argcount) const;
	Error connect(const Callable &p_callable, uint32_t p_flags = 0);
	void disconnect(const Callable &p_callable);
	bool is_connected(const Callable &p_callable) const;

	Array get_connections() const;
	Signal(const Object *p_object, const StringName &p_name);
	Signal(ObjectID p_object, const StringName &p_name);
	Signal() {}
};

struct CallableComparator {
	const Callable &func;

	bool operator()(const Variant &p_l, const Variant &p_r) const;
};

#endif // CALLABLE_H