/*************************************************************************/
/*  openxr_api.h                                                         */
/*************************************************************************/
/*                       This file is part of:                           */
/*                           GODOT ENGINE                                */
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/* Copyright (c) 2007-2022 Juan Linietsky, Ariel Manzur.                 */
/* Copyright (c) 2014-2022 Godot Engine contributors (cf. AUTHORS.md).   */
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#ifndef OPENXR_DRIVER_H
#define OPENXR_DRIVER_H

#include "core/error/error_macros.h"
#include "core/math/camera_matrix.h"
#include "core/math/transform_3d.h"
#include "core/math/vector2.h"
#include "core/os/memory.h"
#include "core/string/ustring.h"
#include "core/templates/map.h"
#include "core/templates/rid_owner.h"
#include "core/templates/vector.h"
#include "servers/xr/xr_pose.h"

#include "thirdparty/openxr/src/common/xr_linear.h"
#include <openxr/openxr.h>

#include "action_map/openxr_action.h"

#include "extensions/openxr_composition_layer_provider.h"
#include "extensions/openxr_extension_wrapper.h"

// Note, OpenXR code that we wrote for our plugin makes use of C++20 notation for initialising structs which ensures zeroing out unspecified members.
// Godot is currently restricted to C++17 which doesn't allow this notation. Make sure critical fields are set.

// forward declarations, we don't want to include these fully
class OpenXRVulkanExtension;
class OpenXRInterface;

class OpenXRAPI {
private:
	// our singleton
	static OpenXRAPI *singleton;

	// linked XR interface
	OpenXRInterface *xr_interface = nullptr;

	// layers
	uint32_t num_layer_properties = 0;
	XrApiLayerProperties *layer_properties = nullptr;

	// extensions
	uint32_t num_supported_extensions = 0;
	XrExtensionProperties *supported_extensions = nullptr;
	Vector<OpenXRExtensionWrapper *> registered_extension_wrappers;
	Vector<const char *> enabled_extensions;

	// composition layer providers
	Vector<OpenXRCompositionLayerProvider *> composition_layer_providers;

	// view configuration
	uint32_t num_view_configuration_types = 0;
	XrViewConfigurationType *supported_view_configuration_types = nullptr;

	// reference spaces
	uint32_t num_reference_spaces = 0;
	XrReferenceSpaceType *supported_reference_spaces = nullptr;

	// swapchains (note these are platform dependent)
	uint32_t num_swapchain_formats = 0;
	int64_t *supported_swapchain_formats = nullptr;

	// configuration
	XrFormFactor form_factor = XR_FORM_FACTOR_HEAD_MOUNTED_DISPLAY;
	XrViewConfigurationType view_configuration = XR_VIEW_CONFIGURATION_TYPE_PRIMARY_STEREO;
	XrReferenceSpaceType reference_space = XR_REFERENCE_SPACE_TYPE_STAGE;
	XrEnvironmentBlendMode environment_blend_mode = XR_ENVIRONMENT_BLEND_MODE_OPAQUE;

	// state
	XrInstance instance = XR_NULL_HANDLE;
	XrSystemId system_id;
	String system_name;
	uint32_t vendor_id;
	XrSystemTrackingProperties tracking_properties;
	XrSession session = XR_NULL_HANDLE;
	XrSessionState session_state = XR_SESSION_STATE_UNKNOWN;
	bool running = false;
	XrFrameState frame_state = { XR_TYPE_FRAME_STATE, NULL, 0, 0, false };

	OpenXRGraphicsExtensionWrapper *graphics_extension = nullptr;
	XrSystemGraphicsProperties graphics_properties;
	void *swapchain_graphics_data = nullptr;
	uint32_t image_index = 0;
	bool image_acquired = false;

	uint32_t view_count = 0;
	XrViewConfigurationView *view_configuration_views = nullptr;
	XrView *views = nullptr;
	XrCompositionLayerProjectionView *projection_views = nullptr;
	XrSwapchain swapchain = XR_NULL_HANDLE;

	XrSpace play_space = XR_NULL_HANDLE;
	XrSpace view_space = XR_NULL_HANDLE;
	bool view_pose_valid = false;
	XRPose::TrackingConfidence head_pose_confidence = XRPose::XR_TRACKING_CONFIDENCE_NONE;

	bool load_layer_properties();
	bool load_supported_extensions();
	bool is_extension_supported(const char *p_extension) const;

	// instance
	bool create_instance();
	bool get_system_info();
	bool load_supported_view_configuration_types();
	bool is_view_configuration_supported(XrViewConfigurationType p_configuration_type) const;
	bool load_supported_view_configuration_views(XrViewConfigurationType p_configuration_type);
	void destroy_instance();

	// session
	bool create_session();
	bool load_supported_reference_spaces();
	bool is_reference_space_supported(XrReferenceSpaceType p_reference_space);
	bool setup_spaces();
	bool load_supported_swapchain_formats();
	bool is_swapchain_format_supported(int64_t p_swapchain_format);
	bool create_main_swapchain();
	void destroy_session();

	// swapchains
	bool create_swapchain(int64_t p_swapchain_format, uint32_t p_width, uint32_t p_height, uint32_t p_sample_count, uint32_t p_array_size, XrSwapchain &r_swapchain, void **r_swapchain_graphics_data);
	bool acquire_image(XrSwapchain p_swapchain, uint32_t &r_image_index);
	bool release_image(XrSwapchain p_swapchain);

	// action map
	struct Tracker { // Trackers represent tracked physical objects such as controllers, pucks, etc.
		String name; // Name for this tracker (i.e. "/user/hand/left")
		XrPath toplevel_path; // OpenXR XrPath for this tracker
		RID active_profile_rid; // RID of the active profile for this tracker
	};
	RID_Owner<Tracker, true> tracker_owner;
	RID get_tracker_rid(XrPath p_path);

	struct ActionSet { // Action sets define a set of actions that can be enabled together
		String name; // Name for this action set (i.e. "godot_action_set")
		bool is_attached; // If true our action set has been attached to the session and can no longer be modified
		XrActionSet handle; // OpenXR handle for this action set
	};
	RID_Owner<ActionSet, true> action_set_owner;

	struct ActionTracker { // Links and action to a tracker
		RID tracker_rid; // RID of the tracker
		XrSpace space; // Optional space for pose actions
		bool was_location_valid; // If true the last position we obtained was valid
	};

	struct Action { // Actions define the inputs and outputs in OpenXR
		RID action_set_rid; // RID of the action set this action belongs to
		String name; // Name for this action (i.e. "aim_pose")
		XrActionType action_type; // Type of action (bool, float, etc.)
		Vector<ActionTracker> trackers; // The trackers this action can be used with
		XrAction handle; // OpenXR handle for this action
	};
	RID_Owner<Action, true> action_owner;
	RID get_action_rid(XrAction p_action);

	struct InteractionProfile { // Interaction profiles define suggested bindings between the physical inputs on controller types and our actions
		String name; // Name of the interaction profile (i.e. "/interaction_profiles/valve/index_controller")
		XrPath path; // OpenXR path for this profile
		Vector<XrActionSuggestedBinding> bindings; // OpenXR action bindings
	};
	RID_Owner<InteractionProfile, true> interaction_profile_owner;
	RID get_interaction_profile_rid(XrPath p_path);
	XrPath get_interaction_profile_path(RID p_interaction_profile);

	// state changes
	bool poll_events();
	bool on_state_idle();
	bool on_state_ready();
	bool on_state_synchronized();
	bool on_state_visible();
	bool on_state_focused();
	bool on_state_stopping();
	bool on_state_loss_pending();
	bool on_state_exiting();

	// convencience
	void copy_string_to_char_buffer(const String p_string, char *p_buffer, int p_buffer_len);

protected:
	friend class OpenXRVulkanExtension;

	XrInstance get_instance() const { return instance; };
	XrSystemId get_system_id() const { return system_id; };
	XrSession get_session() const { return session; };

	// helper method to convert an XrPosef to a Transform3D
	Transform3D transform_from_pose(const XrPosef &p_pose);

	// helper method to get a valid Transform3D from an openxr space location
	XRPose::TrackingConfidence transform_from_location(const XrSpaceLocation &p_location, Transform3D &r_transform);
	XRPose::TrackingConfidence transform_from_location(const XrHandJointLocationEXT &p_location, Transform3D &r_transform);
	void parse_velocities(const XrSpaceVelocity &p_velocity, Vector3 &r_linear_velocity, Vector3 r_angular_velocity);

public:
	static void setup_global_defs();
	static bool openxr_is_enabled();
	static OpenXRAPI *get_singleton();

	String get_error_string(XrResult result);
	String get_swapchain_format_name(int64_t p_swapchain_format) const;

	void set_xr_interface(OpenXRInterface *p_xr_interface);
	void register_extension_wrapper(OpenXRExtensionWrapper *p_extension_wrapper);

	bool is_initialized();
	bool is_running();
	bool initialise(const String &p_rendering_driver);
	bool initialise_session();
	void finish();

	XrTime get_next_frame_time() { return frame_state.predictedDisplayTime + frame_state.predictedDisplayPeriod; };
	bool can_render() { return instance != XR_NULL_HANDLE && session != XR_NULL_HANDLE && running && view_pose_valid && frame_state.shouldRender; };

	Size2 get_recommended_target_size();
	XRPose::TrackingConfidence get_head_center(Transform3D &r_transform, Vector3 &r_linear_velocity, Vector3 &r_angular_velocity);
	bool get_view_transform(uint32_t p_view, Transform3D &r_transform);
	bool get_view_projection(uint32_t p_view, double p_z_near, double p_z_far, CameraMatrix &p_camera_matrix);
	bool process();

	void pre_render();
	bool pre_draw_viewport(RID p_render_target);
	void post_draw_viewport(RID p_render_target);
	void end_frame();

	// action map
	String get_default_action_map_resource_name();

	RID tracker_create(const String p_name);
	String tracker_get_name(RID p_tracker);
	void tracker_check_profile(RID p_tracker, XrSession p_session = XR_NULL_HANDLE);
	void tracker_free(RID p_tracker);

	RID action_set_create(const String p_name, const String p_localized_name, const int p_priority);
	String action_set_get_name(RID p_action_set);
	bool action_set_attach(RID p_action_set);
	void action_set_free(RID p_action_set);

	RID action_create(RID p_action_set, const String p_name, const String p_localized_name, OpenXRAction::ActionType p_action_type, const Vector<RID> &p_trackers);
	String action_get_name(RID p_action);
	void action_free(RID p_action);

	RID interaction_profile_create(const String p_name);
	String interaction_profile_get_name(RID p_interaction_profile);
	void interaction_profile_clear_bindings(RID p_interaction_profile);
	bool interaction_profile_add_binding(RID p_interaction_profile, RID p_action, const String p_path);
	bool interaction_profile_suggest_bindings(RID p_interaction_profile);
	void interaction_profile_free(RID p_interaction_profile);

	bool sync_action_sets(const Vector<RID> p_active_sets);
	bool get_action_bool(RID p_action, RID p_tracker);
	float get_action_float(RID p_action, RID p_tracker);
	Vector2 get_action_vector2(RID p_action, RID p_tracker);
	XRPose::TrackingConfidence get_action_pose(RID p_action, RID p_tracker, Transform3D &r_transform, Vector3 &r_linear_velocity, Vector3 &r_angular_velocity);
	bool trigger_haptic_pulse(RID p_action, RID p_tracker, float p_frequency, float p_amplitude, XrDuration p_duration_ns);

	OpenXRAPI();
	~OpenXRAPI();
};

#endif // !OPENXR_DRIVER_H