#ifndef INTERPOLATOR_H
#define INTERPOLATOR_H

/*************************************************************************/
/*  interpolator.h                                                       */
/*************************************************************************/
/*                         This file is part of:                         */
/*                          PANDEMONIUM ENGINE                           */
/*             https://github.com/Relintai/pandemonium_engine            */
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/*************************************************************************/

/**
	@author AndreaCatania
*/

#include "core/containers/vector.h"
#include "core/object/class_db.h"

class Interpolator : public Object {
	GDCLASS(Interpolator, Object);

public:
	enum Fallback {
		FALLBACK_INTERPOLATE,
		FALLBACK_DEFAULT,
		FALLBACK_OLD_OR_NEAREST,
		FALLBACK_NEW_OR_NEAREST,
		FALLBACK_CUSTOM_INTERPOLATOR
	};

private:
	struct VariableInfo {
		// TODO Do we need a name?
		Variant default_value;
		Fallback fallback;
		ObjectID custom_interpolator_object;
		StringName custom_interpolator_function;
	};

	LocalVector<VariableInfo> variables;

	/// Epoch ids, sorted from youngest to oldest.
	LocalVector<uint32_t> epochs;
	/// Epoch data.
	LocalVector<Vector<Variant>> buffer;

	bool init_phase = true;
	uint32_t write_position = UINT32_MAX;
	uint32_t last_pop_epoch = 0;

	static void _bind_methods();

public:
	Interpolator() = default;

	void clear();
	void reset();

	int register_variable(const Variant &p_default, Fallback p_fallback);
	void set_variable_default(int p_var_id, const Variant &p_default);
	void set_variable_custom_interpolator(int p_var_id, Object *p_object, const StringName &p_function_name);
	void terminate_init();

	/// Returns the epochs stored.
	uint32_t known_epochs_count() const;
	void begin_write(uint32_t p_epoch);
	void epoch_insert(int p_var_id, const Variant &p_value);
	void end_write();

	Vector<Variant> pop_epoch(uint32_t p_epoch, real_t p_fraction);
	uint32_t get_last_pop_epoch() const; // TODO do I need this? Remove if not.
	uint32_t get_youngest_epoch() const;
	uint32_t get_oldest_epoch() const;

	/// Returns the epochs count between the two last received time window.
	uint32_t epochs_between_last_time_window() const;

	static Variant interpolate(const Variant &p_v1, const Variant &p_v2, real_t p_delta);
};

VARIANT_ENUM_CAST(Interpolator::Fallback);
#endif