/*=========================================================================

  Program:   Visualization Toolkit
  Module:    vtkOpenXRManager.h

  Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen
  All rights reserved.
  See Copyright.txt or http://www.kitware.com/Copyright.htm for details.

     This software is distributed WITHOUT ANY WARRANTY; without even
     the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
     PURPOSE.  See the above copyright notice for more information.

=========================================================================*/
/**
 * @class   vtkOpenXRManager
 * @brief   Singleton class that holds a collection of utility functions
 *          and member variables to communicate with the OpenXR runtime
 *
 * vtkOpenXRManager is not a vtkObject, the singleton unique instance gets
 * allocated on the stack the first time vtkOpenXRManager::GetInstance() is
 * called.
 */

#ifndef vtkOpenXRManager_h
#define vtkOpenXRManager_h

#include "vtkRenderingOpenXRModule.h" // needed for exports

#include "vtkOpenXR.h"
#include "vtkSystemIncludes.h"

#include <array>
#include <memory>
#include <string>
#include <vector>

class vtkOpenGLRenderWindow;

class VTKRENDERINGOPENXR_EXPORT vtkOpenXRManager
{
public:
  //@{
  /**
   * Return the singleton instance.
   */
  static vtkOpenXRManager& GetInstance()
  {
    static vtkOpenXRManager UniqueInstance;
    return UniqueInstance;
  }
  //@}

  //@{
  /**
   * Utility function to check the XrResult, print the result message
   * and raise an error if the result failed.
   */
  bool XrCheckError(const XrResult&, const std::string& message);
  //@}

  //@{
  /**
   * Utility function to check the XrResult, print the result message
   * and raise a warning if the result failed.
   */
  bool XrCheckWarn(const XrResult&, const std::string& message);
  //@}

  //@{
  /**
   * Utility functions to print information about OpenXR manager internal structures.
   */
  void PrintInstanceProperties();
  void PrintSystemProperties(XrSystemProperties* system_properties);
  void PrintSupportedViewConfigs();
  void PrintViewConfigViewInfo(const std::vector<XrViewConfigurationView>&);
  bool PrintReferenceSpaces();
  //@}

  //@{
  /**
   * Initialize the OpenXR SDK to render images in a virtual reality device.
   * The helper window must be a vtkWin32OpenGLRenderWindow if the platform is Win32,
   * else a vtkXOpenGLRenderWindow if the platform is X.
   */
  bool Initialize(vtkOpenGLRenderWindow*);
  //@}

  //@{
  /**
   * End the OpenXR session and destroy it and the OpenXR instance.
   */
  void Finalize();
  //@}

  //@{
  /**
   * Return as a tuple the OpenXR recommended texture size to be sent to the device.
   */
  std::tuple<uint32_t, uint32_t> GetRecommendedImageRectSize();
  //@}

  /**
   * Return the number of OpenXR views (typically one per physical display / eye)
   */
  uint32_t GetViewCount()
  {
    return static_cast<uint32_t>(this->RenderResources->ConfigViews.size());
  }

  //@{
  /**
   * Return the OpenXR properties as a string, with format
   * "RuntimeName MAJOR.MINOR.PATCH"
   */
  std::string GetOpenXRPropertiesAsString();
  //@}

  //@{
  /**
   * Returns a pointer to the view pose that contains the view orientation
   * and position for the specified eye, or nullptr if eye exceeds or equals
   * the number of configured views.  This class retains responsibility for
   * the memory pointed to by the return value.
   */
  const XrPosef* GetViewPose(uint32_t eye)
  {
    if (eye >= this->GetViewCount())
    {
      return nullptr;
    }
    return &(this->RenderResources->Views[eye].pose);
  }
  //@}

  //@{
  /**
   * Returns a pointer to the projection field of view for the specified eye,
   * or nullptr if eye exceeds or equals the number of configured views.  This
   * class retains responsibility for the memory pointed to by the return value.
   */
  const XrFovf* GetProjectionFov(uint32_t eye)
  {
    if (eye >= this->GetViewCount())
    {
      return nullptr;
    }
    return &(this->RenderResources->Views[eye].fov);
  }
  //@}

  //@{
  /**
   * Return true if the runtime supports the depth extension.
   */
  bool IsDepthExtensionSupported() { return this->OptionalExtensions.DepthExtensionSupported; }
  //@}

  //@{
  /**
   * Return true if the current frame should be rendered.
   * This value is updated each time we call WaitAndBeginFrame and
   * EndFrame.
   */
  bool GetShouldRenderCurrentFrame() { return this->ShouldRenderCurrentFrame; }
  //@}

  //@{
  /**
   * Start the OpenXR session.
   * If successful, SessionRunning becomes true.
   */
  bool BeginSession();
  //@}

  //@{
  /**
   * Return the OpenXR Session.
   */
  const XrSession& GetSession() { return this->Session; }
  //@}

  //@{
  /**
   * Return the instance used to communicate with the runtime
   */
  const XrInstance& GetXrRuntimeInstance() { return this->Instance; }
  //@}

  //@{
  /**
   * Return true if the OpenXR session is currently running, ie.
   * the call to BeginSession was successful.
   */
  bool IsSessionRunning() { return this->SessionRunning; }
  //@}

  //@{
  /**
   * This function is used to start a frame. If the frame should be rendered,
   * then we locate the views to update the view pose and projection for each
   * eye / display
   */
  bool WaitAndBeginFrame();
  //@}

  //@{
  /**
   * Prepare the rendering resources for the specified eye and store in \p colorTextureId and
   * in \p depthTextureId (if the depth extension is supported) the OpenGL texture in which
   * we need to draw pixels.
   * Return true if no error occurred.
   */
  bool PrepareRendering(uint32_t eye, GLuint& colorTextureId, GLuint& depthTextureId);
  //@}

  //@{
  /**
   * When the rendering in a swapchain image is done, it must be released with
   * this function.
   */
  void ReleaseSwapchainImage(uint32_t eye);
  //@}

  //@{
  /**
   * Submit the composition layers for the predicted display time of the current frame.
   * It must be called at the end of each frame.
   */
  bool EndFrame();
  //@}

  //@{
  /**
   * Store in eventData the result of xrPollEvent.
   */
  bool PollEvent(XrEventDataBuffer& eventData);
  //@}

  //@{
  /**
   * Get the XrPath from the well-formed string \p path.
   */
  XrPath GetXrPath(const std::string& path);
  //@}

  const std::array<XrPath, 2>& GetSubactionPaths() { return this->SubactionPaths; }

  //@{
  /**
   * Creates an action set and add it to the vector of action sets.
   */
  bool CreateActionSet(const std::string& actionSetName, const std::string& localizedActionSetName);
  //@}

  //@{
  /**
   * Selects the current active action set from the
   * ActionSets vector using its index.
   */
  bool SelectActiveActionSet(unsigned int index);
  //@}

  //@{
  /**
   * Attach all action sets in the ActionSets vector to the session.
   */
  bool AttachSessionActionSets();
  //@}

  //@{
  /**
   * Iterate over and destroy all action sets that have been created.
   */
  //@}
  void DestroyActionSets();

  struct Action_t;

  //@{
  /**
   * Creates one action with name \p name and localizedName \p localizedName
   * and store the action handle inside \p actionT using the selected
   * active action set.
   */
  bool CreateOneAction(
    Action_t& actionT, const std::string& name, const std::string& localizedName);
  //@}

  //@{
  /**
   * Suggest actions stored in \p actionSuggestedBindings for the interaction profile \p profile
   */
  bool SuggestActions(
    const std::string& profile, std::vector<XrActionSuggestedBinding>& actionSuggestedBindings);
  //@}

  //@{
  /**
   * Update the action states using the active action set. This function should be called
   * before UpdateActionData
   */
  bool SyncActions();
  //@}

  //@{
  /**
   * Update the action data and store it in action_t.States for one hand.
   * For pose actions :
   *  - we locate its space in the ReferenceSpace space
   *    using the PredictedDisplayTime
   *  - we can store its pose velocity if StorePoseVelocities is true.
   */
  bool UpdateActionData(Action_t& action_t, const int hand);
  //@}

  /**
   * Apply haptic vibration
   * \p action to emit vibration on \p hand to emit on \p amplitude 0.0 to 1.0.
   * \p duration nanoseconds, default 25ms \p frequency (hz)
   */
  bool ApplyVibration(const Action_t& actionT, const int hand, const float amplitude = 0.5f,
    const float duration = 25000000.0f, const float frequency = XR_FREQUENCY_UNSPECIFIED);

  enum ControllerIndex
  {
    Inactive = -1,
    Left = 0,
    Right = 1,
    Head = 2,
    Generic = 3,
    NumberOfControllers = 4
  };

  struct Action_t
  {
    XrAction Action;
    XrActionType ActionType;

    union {
      XrActionStateFloat _float;
      XrActionStateBoolean _boolean;
      XrActionStatePose _pose;
      XrActionStateVector2f _vec2f;
    } States[ControllerIndex::NumberOfControllers];

    XrSpace PoseSpaces[ControllerIndex::NumberOfControllers];
    XrSpaceLocation PoseLocations[ControllerIndex::NumberOfControllers];
    XrSpaceVelocity PoseVelocities[ControllerIndex::NumberOfControllers];
  };

protected:
  vtkOpenXRManager() = default;
  ~vtkOpenXRManager() = default;

  //@{
  /**
   * OpenXR Instance creation.
   * This is where we select the extensions using
   * SelectExtensions
   */
  bool CreateInstance();
  std::vector<const char*> SelectExtensions();
  //@}

  //@{
  /**
   * Print the optional extensions which were found and enabled.
   */
  void PrintOptionalExtensions();
  //@}

  //@{
  /**
   * OpenXR System creation
   */
  bool CreateSystem();
  //@}

  //@{
  /**
   * OpenXR requires checking graphics requirements before creating a session.
   * This uses a function pointer loaded with the selected graphics API extension.
   */
  bool CheckGraphicsRequirements();
  //@}

  //@{
  /**
   * Create the graphics binding and store it in GraphicsBindings ptr.
   * It points to a XrGraphicsBindingXXX structure, depending on the
   * desired rendering backend.
   * \pre \p helperWindow must be initialized
   */
  bool CreateGraphicsBinding(vtkOpenGLRenderWindow* helperWindow);
  //@}

  //@{
  /**
   * Create the session and pass the GraphicsBinding to the next pointer
   * of the XrSessionCreateInfo
   * \pre CreateGraphicsBinding must be called
   */
  bool CreateSession();
  //@}

  //@{
  /**
   * Swapchaines creation : there is one swapchain per view / display.
   * This function calls CreateConfigViews
   */
  bool CreateSwapchains();
  //@}

  //@{
  /**
   * There is one configuration view per view, and it contains the recommended
   * texture resolution in pixels and the recommended swapchain samples
   */
  bool CreateConfigViews();
  //@}

  //@{
  /**
   * During the creation of the swapchains, we need to
   * check the runtime available pixels formats, and we pick
   * the first one from the list of our supported color and
   * depth formats returned by GetSupportedColorFormats and
   * GetSupportedDepthFormats
   */
  std::tuple<int64_t, int64_t> SelectSwapchainPixelFormats();
  const std::vector<int64_t>& GetSupportedColorFormats();
  const std::vector<int64_t>& GetSupportedDepthFormats();
  //@}

  struct SwapchainOpenGL_t;

  //@{
  /**
   * Create an XrSwapchain handle used to present rendered image
   * to the user with the given parameters for the XrSwapchainCreateInfo structure
   */
  SwapchainOpenGL_t CreateSwapchainOpenGL(int64_t format, uint32_t width, uint32_t height,
    uint32_t sampleCount, XrSwapchainCreateFlags createFlags, XrSwapchainUsageFlags usageFlags);
  //@}

  //@{
  /**
   *  Creates the reference space of type ReferenceSpaceType that will be used to locate views
   */
  bool CreateReferenceSpace();
  //@}

  bool LoadControllerModels();

  //@{
  /**
   * For pose actions, we must create an action space to locate it
   */
  bool CreateOneActionSpace(const XrAction& action, const XrPath& subactionPath,
    const XrPosef& poseInActionSpace, XrSpace& space);
  //@}

  //@{
  /**
   * Creates one subaction path for each hand.
   */
  bool CreateSubactionPaths();
  //@}

  //@{
  /**
   * When preparing the rendering for an eye, we must ask the runtime
   * for a texture to draw in it.
   */
  uint32_t WaitAndAcquireSwapchainImage(const XrSwapchain& swapchainHandle);
  //@}

  // Currently VTK only supports HeadMountedDisplay (HMD)
  constexpr static XrFormFactor FormFactor = XR_FORM_FACTOR_HEAD_MOUNTED_DISPLAY;

  // Pick the view type to be stereo rather than mono or anything else
  constexpr static XrViewConfigurationType ViewType = XR_VIEW_CONFIGURATION_TYPE_PRIMARY_STEREO;

  // PRIMARY_STEREO view configuration always has 2 views
  constexpr static uint32_t StereoViewCount = 2;

  // Three available types: VIEW, LOCAL and STAGE.  We use LOCAL space which
  // establishes a world-locked origin, rather than VIEW space, which tracks the
  // view origin.
  constexpr static XrReferenceSpaceType ReferenceSpaceType = XR_REFERENCE_SPACE_TYPE_STAGE;

  // Communication with the runtime happens through this instance
  XrInstance Instance;

  // A system is defined by an id and is used to create a session
  XrSystemId SystemId;

  XrSession Session;
  XrSessionState SessionState;
  XrSpace ReferenceSpace;

  // At the end of a frame, we must select en environment blend mode
  // to tell the runtime how we want to blend the image with the user's
  // view of the physical world. For example, in VR, we will generally
  // choose XR_ENVIRONMENT_BLEND_MODE_OPAQUE while AR will generally
  // choose XR_ENVIRONMENT_BLEND_MODE_ADDITIVE or XR_ENVIRONMENT_BLEND_MODE_ALPHA_BLEND
  XrEnvironmentBlendMode EnvironmentBlendMode;

  // See vtkXrExtensions.h
  xr::ExtensionDispatchTable Extensions;

  // Non optional extension
  bool HasOpenGLExtension = false;

  //@{
  /**
   * Structure to hold optional extensions
   * loaded with SelectExtensions
   */
  struct
  {
    bool DepthExtensionSupported{ false };
    bool ControllerModelExtensionSupported{ false };
    bool UnboundedRefSpaceSupported{ false };
    bool SpatialAnchorSupported{ false };
    bool HandTrackingSupported{ false };
  } OptionalExtensions;
  //@}

  std::shared_ptr<void> GraphicsBinding;

  /**
   * Swapchain structure for OpenGL backend.
   */
  struct SwapchainOpenGL_t
  {
    XrSwapchain Swapchain;
    int64_t Format{ GL_NONE };
    uint32_t Width{ 0 };
    uint32_t Height{ 0 };
    std::vector<XrSwapchainImageOpenGLKHR> Images;
  };

  //@{
  /**
   * This struct stores all needed information to render the images
   * and send it to the user
   * We can't make a vector of struct because OpenXR SDK needs
   * an array of XrXXX for xrEnumerate functions
   */
  struct RenderResources_t
  {
    XrViewState ViewState{ XR_TYPE_VIEW_STATE };
    // Each physical Display/Eye is described by a view
    std::vector<XrView> Views;
    // One configuration view per view : this store
    std::vector<XrViewConfigurationView> ConfigViews;

    std::vector<SwapchainOpenGL_t> ColorSwapchains;
    std::vector<SwapchainOpenGL_t> DepthSwapchains;

    std::vector<XrCompositionLayerProjectionView> ProjectionLayerViews;
    std::vector<XrCompositionLayerDepthInfoKHR> DepthInfoViews;
  };
  std::unique_ptr<RenderResources_t> RenderResources{};
  //@}

  // There is one subaction path for each hand.
  std::array<XrPath, 2> SubactionPaths;

  std::vector<XrActionSet> ActionSets;
  XrActionSet* ActiveActionSet = nullptr;

  /**
   * Store the frame predicted display time in WaitAndBeginFrame
   * To get the action data at this time and to submit it in EndFrame
   */
  XrTime PredictedDisplayTime;

  bool SessionRunning = false;
  // After each WaitAndBeginFrame, the OpenXR runtime may inform us that
  // the current frame should not be rendered. Store it to avoid a render
  bool ShouldRenderCurrentFrame = false;
  // If true, the function UpdateActionData will store
  // pose velocities for pose actions
  bool StorePoseVelocities = false;

private:
  vtkOpenXRManager(const vtkOpenXRManager&) = delete;
  void operator=(const vtkOpenXRManager&) = delete;
};

#endif
// VTK-HeaderTest-Exclude: vtkOpenXRManager.h