/*************************************************************************/
/*  xr_interface.h                                                       */
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#ifndef XR_INTERFACE_H
#define XR_INTERFACE_H

#include "core/math/camera_matrix.h"
#include "core/os/thread_safe.h"
#include "servers/xr_server.h"

// forward declaration
struct BlitToScreen;

/**
	@author Bastiaan Olij <mux213@gmail.com>

	The XR interface is a template class on top of which we build interface to different AR, VR and tracking SDKs.
	The idea is that we subclass this class, implement the logic, and then instantiate a singleton of each interface
	when Godot starts. These instances do not initialize themselves but register themselves with the AR/VR server.

	If the user wants to enable AR/VR the choose the interface they want to use and initialize it.

	Note that we may make this into a fully instantiable class for GDNative support.
*/

class XRInterface : public RefCounted {
	GDCLASS(XRInterface, RefCounted);

public:
	enum Capabilities { /* purely meta data, provides some info about what this interface supports */
		XR_NONE = 0, /* no capabilities */
		XR_MONO = 1, /* can be used with mono output */
		XR_STEREO = 2, /* can be used with stereo output */
		XR_AR = 4, /* offers a camera feed for AR */
		XR_EXTERNAL = 8 /* renders to external device */
	};

	enum Eyes {
		EYE_MONO, /* my son says we should call this EYE_CYCLOPS */
		EYE_LEFT,
		EYE_RIGHT
	};

	enum TrackingStatus { /* tracking status currently based on AR but we can start doing more with this for VR as well */
		XR_NORMAL_TRACKING,
		XR_EXCESSIVE_MOTION,
		XR_INSUFFICIENT_FEATURES,
		XR_UNKNOWN_TRACKING,
		XR_NOT_TRACKING
	};

private:
protected:
	_THREAD_SAFE_CLASS_

	static void _bind_methods();

public:
	/** general interface information **/
	virtual StringName get_name() const = 0;
	virtual uint32_t get_capabilities() const = 0;

	bool is_primary();
	void set_primary(bool p_is_primary);

	virtual bool is_initialized() const = 0; /* returns true if we've initialized this interface */
	virtual bool initialize() = 0; /* initialize this interface, if this has an HMD it becomes the primary interface */
	virtual void uninitialize() = 0; /* deinitialize this interface */

	virtual TrackingStatus get_tracking_status() const; /* get the status of our current tracking */

	/** specific to VR **/
	// nothing yet

	/** specific to AR **/
	virtual bool get_anchor_detection_is_enabled() const;
	virtual void set_anchor_detection_is_enabled(bool p_enable);
	virtual int get_camera_feed_id();

	/** rendering and internal **/

	virtual Size2 get_render_target_size() = 0; /* returns the recommended render target size per eye for this device */
	virtual uint32_t get_view_count() = 0; /* returns the view count we need (1 is monoscopic, 2 is stereoscopic but can be more) */
	virtual Transform3D get_camera_transform() = 0; /* returns the position of our camera for updating our camera node. For monoscopic this is equal to the views transform, for stereoscopic this should be an average */
	virtual Transform3D get_transform_for_view(uint32_t p_view, const Transform3D &p_cam_transform) = 0; /* get each views transform */
	virtual CameraMatrix get_projection_for_view(uint32_t p_view, double p_aspect, double p_z_near, double p_z_far) = 0; /* get each view projection matrix */

	// note, external color/depth/vrs texture support will be added here soon.

	virtual Vector<BlitToScreen> commit_views(RID p_render_target, const Rect2 &p_screen_rect) = 0; /* commit rendered views to the XR interface */

	virtual void process() = 0;
	virtual void notification(int p_what);

	XRInterface();
	~XRInterface();
};

VARIANT_ENUM_CAST(XRInterface::Capabilities);
VARIANT_ENUM_CAST(XRInterface::Eyes);
VARIANT_ENUM_CAST(XRInterface::TrackingStatus);

#endif // !XR_INTERFACE_H