/* SPDX-FileCopyrightText: 2020-2023 Blender Authors
 *
 * SPDX-License-Identifier: GPL-2.0-or-later */

/** \file
 * \ingroup GHOST
 */

#include <algorithm>
#include <cassert>
#include <chrono>
#include <cstdio>
#include <list>
#include <sstream>

#include "BLI_span.hh"

#include "GHOST_Context.hh"
#include "GHOST_IXrGraphicsBinding.hh"
#include "GHOST_XrAction.hh"
#include "GHOST_XrContext.hh"
#include "GHOST_XrControllerModel.hh"
#include "GHOST_XrException.hh"
#include "GHOST_XrSwapchain.hh"
#include "GHOST_Xr_intern.hh"

#include "GHOST_XrSession.hh"

struct OpenXRSessionData {
  XrSystemId system_id = XR_NULL_SYSTEM_ID;
  XrSession session = XR_NULL_HANDLE;
  XrSessionState session_state = XR_SESSION_STATE_UNKNOWN;

  /* Use stereo rendering by default. */
  XrViewConfigurationType view_type = XR_VIEW_CONFIGURATION_TYPE_PRIMARY_STEREO;
  bool foveation_supported = false;

  XrSpace reference_space;
  XrSpace view_space;
  XrSpace combined_eye_space;
  std::vector<XrView> views;
  std::vector<GHOST_XrSwapchain> swapchains;

  std::map<std::string, GHOST_XrActionSet> action_sets;
  /* Controller models identified by subaction path. */
  std::map<std::string, GHOST_XrControllerModel> controller_models;

  /* Meta Quest passthrough support. */
  bool passthrough_supported = false;
  XrCompositionLayerPassthroughFB passthrough_layer;
};

struct GHOST_XrDrawInfo {
  XrFrameState frame_state;

  /** Time at frame start to benchmark frame render durations. */
  std::chrono::high_resolution_clock::time_point frame_begin_time;
  /* Time previous frames took for rendering (in ms). */
  std::list<double> last_frame_times;

  /* Whether foveation is active for the frame. */
  bool foveation_active;
};

/* -------------------------------------------------------------------- */
/** \name Create, Initialize and Destruct
 * \{ */

GHOST_XrSession::GHOST_XrSession(GHOST_XrContext &xr_context)
    : context_(&xr_context), oxr_(std::make_unique<OpenXRSessionData>())
{
}

GHOST_XrSession::~GHOST_XrSession()
{
  unbindGraphicsContext();

  oxr_->swapchains.clear();
  oxr_->action_sets.clear();

  if (oxr_->reference_space != XR_NULL_HANDLE) {
    CHECK_XR_ASSERT(xrDestroySpace(oxr_->reference_space));
  }
  if (oxr_->view_space != XR_NULL_HANDLE) {
    CHECK_XR_ASSERT(xrDestroySpace(oxr_->view_space));
  }
  if (oxr_->combined_eye_space != XR_NULL_HANDLE) {
    CHECK_XR_ASSERT(xrDestroySpace(oxr_->combined_eye_space));
  }
  if (oxr_->session != XR_NULL_HANDLE) {
    CHECK_XR_ASSERT(xrDestroySession(oxr_->session));
  }

  oxr_->session = XR_NULL_HANDLE;
  oxr_->session_state = XR_SESSION_STATE_UNKNOWN;

  oxr_->passthrough_supported = false;
  oxr_->passthrough_layer.layerHandle = XR_NULL_HANDLE;

  context_->getCustomFuncs().session_exit_fn(context_->getCustomFuncs().session_exit_customdata);
}

/**
 * A system in OpenXR the combination of some sort of HMD plus controllers and whatever other
 * devices are managed through OpenXR. So this attempts to init the HMD and the other devices.
 */
void GHOST_XrSession::initSystem()
{
  assert(context_->getInstance() != XR_NULL_HANDLE);
  assert(oxr_->system_id == XR_NULL_SYSTEM_ID);

  XrSystemGetInfo system_info = {};
  system_info.type = XR_TYPE_SYSTEM_GET_INFO;
  system_info.formFactor = XR_FORM_FACTOR_HEAD_MOUNTED_DISPLAY;

  CHECK_XR(xrGetSystem(context_->getInstance(), &system_info, &oxr_->system_id),
           "Failed to get device information. Is a device plugged in?");
}

/** \} */ /* Create, Initialize and Destruct */

/* -------------------------------------------------------------------- */
/** \name State Management
 * \{ */

static void create_main_reference_space(OpenXRSessionData &oxr,
                                        const blender::Span<XrReferenceSpaceType> supported_spaces)
{
  XrReferenceSpaceCreateInfo create_info = {XR_TYPE_REFERENCE_SPACE_CREATE_INFO};
  create_info.poseInReferenceSpace.orientation.w = 1.0f;

  /* Use the most suitable space as the main reference space. By order of preference:
   * - Stage Reference Space
   * - Local Floor Reference Space
   * - Local Space
   * Defaulting to the next one if the prior one is not available.
   */

  /* Stage Reference Space. */
  if (supported_spaces.contains(XR_REFERENCE_SPACE_TYPE_STAGE)) {
    create_info.referenceSpaceType = XR_REFERENCE_SPACE_TYPE_STAGE;
    CHECK_XR(xrCreateReferenceSpace(oxr.session, &create_info, &oxr.reference_space),
             "Failed to create stage reference space.");

    /* Check if tracking bounds are valid. Tracking bounds may be invalid if the user did not
     * define a tracking space via the XR runtime. */
    XrExtent2Df extents;
    CHECK_XR(xrGetReferenceSpaceBoundsRect(oxr.session, XR_REFERENCE_SPACE_TYPE_STAGE, &extents),
             "Failed to get stage reference space bounds.");
    if (extents.width != 0.0f && extents.height != 0.0f) {
      /* Stage Reference Space is valid, return. */
      return;
    }

    /* Stage Reference Space is invalid, destroy it and try to create the next available space. */
    if (oxr.reference_space != XR_NULL_HANDLE) {
      CHECK_XR(xrDestroySpace(oxr.reference_space), "Failed to destroy stage reference space.");
    }

    CLOG_WARN(LOG_GHOST_XR,
              "Invalid stage reference space bounds, falling back to local floor reference "
              "space. To use the stage reference space, please define a tracking space via the "
              "XR runtime.");
  }

  /* Local Floor Reference Space. */
  if (supported_spaces.contains(XR_REFERENCE_SPACE_TYPE_LOCAL_FLOOR_EXT)) {
    CLOG_WARN(LOG_GHOST_XR,
              "Stage reference space unavailable, falling back to local floor reference space.");
    create_info.referenceSpaceType = XR_REFERENCE_SPACE_TYPE_LOCAL_FLOOR_EXT;
    CHECK_XR(xrCreateReferenceSpace(oxr.session, &create_info, &oxr.reference_space),
             "Failed to create local floor reference space.");
    return;
  }

  /* Local Reference Space. */
  CLOG_WARN(LOG_GHOST_XR,
            "Stage and local floor reference space unavailable, falling back to local "
            "reference space.");
  create_info.referenceSpaceType = XR_REFERENCE_SPACE_TYPE_LOCAL;
  CHECK_XR(xrCreateReferenceSpace(oxr.session, &create_info, &oxr.reference_space),
           "Failed to create local reference space.");
}

static void create_reference_spaces(OpenXRSessionData &oxr)
{
  XrReferenceSpaceCreateInfo create_info = {XR_TYPE_REFERENCE_SPACE_CREATE_INFO};
  create_info.poseInReferenceSpace.orientation.w = 1.0f;

  /* Enumerate supported reference spaces. */
  uint32_t space_count = 0;
  CHECK_XR(xrEnumerateReferenceSpaces(oxr.session, 0, &space_count, nullptr),
           "Failed to enumerate available reference space count.");

  std::vector<XrReferenceSpaceType> supported_spaces_vec(space_count);
  CHECK_XR(xrEnumerateReferenceSpaces(
               oxr.session, space_count, &space_count, supported_spaces_vec.data()),
           "Failed to enumerate available reference spaces.");

  const blender::Span supported_spaces(supported_spaces_vec);

  create_main_reference_space(oxr, supported_spaces);

  /* View reference space. */
  create_info.referenceSpaceType = XR_REFERENCE_SPACE_TYPE_VIEW;
  CHECK_XR(xrCreateReferenceSpace(oxr.session, &create_info, &oxr.view_space),
           "Failed to create view reference space.");

  /* Foveation reference spaces. */
  if (oxr.foveation_supported) {
    create_info.referenceSpaceType = XR_REFERENCE_SPACE_TYPE_COMBINED_EYE_VARJO;
    CHECK_XR(xrCreateReferenceSpace(oxr.session, &create_info, &oxr.combined_eye_space),
             "Failed to create combined eye reference space.");
  }
}

void GHOST_XrSession::start()
{
  assert(context_->getInstance() != XR_NULL_HANDLE);
  assert(oxr_->session == XR_NULL_HANDLE);
  if (context_->getCustomFuncs().gpu_ctx_bind_fn == nullptr) {
    throw GHOST_XrException(
        "Invalid API usage: No way to bind graphics context to the XR session. Call "
        "GHOST_XrGraphicsContextBindFuncs() with valid parameters before starting the "
        "session (through GHOST_XrSessionStart()).");
  }

  initSystem();

  bindGraphicsContext();
  if (gpu_ctx_ == nullptr) {
    throw GHOST_XrException(
        "Invalid API usage: No graphics context returned through the callback set with "
        "GHOST_XrGraphicsContextBindFuncs(). This is required for session starting (through "
        "GHOST_XrSessionStart()).");
  }

  std::string requirement_str;
  gpu_binding_ = GHOST_XrGraphicsBindingCreateFromType(context_->getGraphicsBindingType(),
                                                       *gpu_ctx_);
  if (!gpu_binding_->loadExtensionFunctions(context_->getInstance())) {
    throw GHOST_XrException(
        "Unable to load graphics bindings (could not load the needed extension functions from the "
        "XrInstance)");
  }
  if (!gpu_binding_->checkVersionRequirements(
          *gpu_ctx_, context_->getInstance(), oxr_->system_id, &requirement_str))
  {
    std::ostringstream strstream;
    strstream << "Available graphics context version does not meet the following requirements: "
              << requirement_str;
    throw GHOST_XrException(strstream.str().data());
  }
  gpu_binding_->initFromGhostContext(*gpu_ctx_, context_->getInstance(), oxr_->system_id);

  XrSessionCreateInfo create_info = {};
  create_info.type = XR_TYPE_SESSION_CREATE_INFO;
  create_info.systemId = oxr_->system_id;
  create_info.next = &gpu_binding_->oxr_binding;

  CHECK_XR(xrCreateSession(context_->getInstance(), &create_info, &oxr_->session),
           "Failed to create VR session. The OpenXR runtime may have additional requirements for "
           "the graphics driver that are not met. Other causes are possible too however.\nTip: "
           "The --debug-xr command line option for Blender might allow the runtime to output "
           "detailed error information to the command line.");

  prepareDrawing();
  create_reference_spaces(*oxr_);

  /* Create and bind actions here. */
  context_->getCustomFuncs().session_create_fn();
}

void GHOST_XrSession::requestEnd()
{
  xrRequestExitSession(oxr_->session);
}

void GHOST_XrSession::beginSession()
{
  XrSessionBeginInfo begin_info = {XR_TYPE_SESSION_BEGIN_INFO};
  begin_info.primaryViewConfigurationType = oxr_->view_type;
  CHECK_XR(xrBeginSession(oxr_->session, &begin_info), "Failed to cleanly begin the VR session.");
}

void GHOST_XrSession::endSession()
{
  assert(oxr_->session != XR_NULL_HANDLE);
  CHECK_XR(xrEndSession(oxr_->session), "Failed to cleanly end the VR session.");
}

GHOST_XrSession::LifeExpectancy GHOST_XrSession::handleStateChangeEvent(
    const XrEventDataSessionStateChanged &lifecycle)
{
  oxr_->session_state = lifecycle.state;

  /* Runtime may send events for apparently destroyed session. Our handle should be nullptr then.
   */
  assert(oxr_->session == XR_NULL_HANDLE || oxr_->session == lifecycle.session);

  switch (lifecycle.state) {
    case XR_SESSION_STATE_READY:
      beginSession();
      break;
    case XR_SESSION_STATE_STOPPING:
      endSession();
      break;
    case XR_SESSION_STATE_EXITING:
    case XR_SESSION_STATE_LOSS_PENDING:
      return SESSION_DESTROY;
    default:
      break;
  }

  return SESSION_KEEP_ALIVE;
}

/** \} */ /* State Management */

/* -------------------------------------------------------------------- */
/** \name Drawing
 * \{ */

void GHOST_XrSession::prepareDrawing()
{
  assert(context_->getInstance() != XR_NULL_HANDLE);

  std::vector<XrViewConfigurationView> view_configs;
  uint32_t view_count;

  /* Attempt to use quad view if supported. */
  if (context_->isExtensionEnabled(XR_VARJO_QUAD_VIEWS_EXTENSION_NAME)) {
    oxr_->view_type = XR_VIEW_CONFIGURATION_TYPE_PRIMARY_QUAD_VARJO;
  }

  oxr_->foveation_supported = context_->isExtensionEnabled(
      XR_VARJO_FOVEATED_RENDERING_EXTENSION_NAME);

  CHECK_XR(xrEnumerateViewConfigurationViews(
               context_->getInstance(), oxr_->system_id, oxr_->view_type, 0, &view_count, nullptr),
           "Failed to get count of view configurations.");
  view_configs.resize(view_count, {XR_TYPE_VIEW_CONFIGURATION_VIEW});
  CHECK_XR(xrEnumerateViewConfigurationViews(context_->getInstance(),
                                             oxr_->system_id,
                                             oxr_->view_type,
                                             view_configs.size(),
                                             &view_count,
                                             view_configs.data()),
           "Failed to get view configurations.");

  /* If foveated rendering is used, query the foveated views. */
  if (oxr_->foveation_supported) {
    std::vector<XrFoveatedViewConfigurationViewVARJO> request_foveated_config{
        view_count, {XR_TYPE_FOVEATED_VIEW_CONFIGURATION_VIEW_VARJO, nullptr, XR_TRUE}};

    auto foveated_views = std::vector<XrViewConfigurationView>(view_count,
                                                               {XR_TYPE_VIEW_CONFIGURATION_VIEW});

    for (uint32_t i = 0; i < view_count; i++) {
      foveated_views[i].next = &request_foveated_config[i];
    }
    CHECK_XR(xrEnumerateViewConfigurationViews(context_->getInstance(),
                                               oxr_->system_id,
                                               oxr_->view_type,
                                               view_configs.size(),
                                               &view_count,
                                               foveated_views.data()),
             "Failed to get foveated view configurations.");

    /* Ensure swapchains have correct size even when foveation is being used. */
    for (uint32_t i = 0; i < view_count; i++) {
      view_configs[i].recommendedImageRectWidth = std::max(
          view_configs[i].recommendedImageRectWidth, foveated_views[i].recommendedImageRectWidth);
      view_configs[i].recommendedImageRectHeight = std::max(
          view_configs[i].recommendedImageRectHeight,
          foveated_views[i].recommendedImageRectHeight);
    }
  }

  for (const XrViewConfigurationView &view_config : view_configs) {
    oxr_->swapchains.emplace_back(*gpu_binding_, oxr_->session, view_config);
  }

  oxr_->views.resize(view_count, {XR_TYPE_VIEW});

  draw_info_ = std::make_unique<GHOST_XrDrawInfo>();
}

void GHOST_XrSession::beginFrameDrawing()
{
  XrFrameWaitInfo wait_info = {XR_TYPE_FRAME_WAIT_INFO};
  XrFrameBeginInfo begin_info = {XR_TYPE_FRAME_BEGIN_INFO};
  XrFrameState frame_state = {XR_TYPE_FRAME_STATE};

  /* TODO Blocking call. Drawing should run on a separate thread to avoid interferences. */
  CHECK_XR(xrWaitFrame(oxr_->session, &wait_info, &frame_state),
           "Failed to synchronize frame rates between Blender and the device.");

  /* Check if we have foveation available for the current frame. */
  draw_info_->foveation_active = false;
  if (oxr_->foveation_supported) {
    XrSpaceLocation render_gaze_location{XR_TYPE_SPACE_LOCATION};
    CHECK_XR(xrLocateSpace(oxr_->combined_eye_space,
                           oxr_->view_space,
                           frame_state.predictedDisplayTime,
                           &render_gaze_location),
             "Failed to locate combined eye space.");

    draw_info_->foveation_active = (render_gaze_location.locationFlags &
                                    XR_SPACE_LOCATION_ORIENTATION_TRACKED_BIT) != 0;
  }

  CHECK_XR(xrBeginFrame(oxr_->session, &begin_info),
           "Failed to submit frame rendering start state.");

  draw_info_->frame_state = frame_state;

  if (context_->isDebugTimeMode()) {
    draw_info_->frame_begin_time = std::chrono::high_resolution_clock::now();
  }
}

static void print_debug_timings(GHOST_XrDrawInfo &draw_info)
{
  /** Render time of last 8 frames (in ms) to calculate an average. */
  std::chrono::duration<double, std::milli> duration = std::chrono::high_resolution_clock::now() -
                                                       draw_info.frame_begin_time;
  const double duration_ms = duration.count();
  const int avg_frame_count = 8;
  double avg_ms_tot = 0.0;

  if (draw_info.last_frame_times.size() >= avg_frame_count) {
    draw_info.last_frame_times.pop_front();
    assert(draw_info.last_frame_times.size() == avg_frame_count - 1);
  }
  draw_info.last_frame_times.push_back(duration_ms);
  for (double ms_iter : draw_info.last_frame_times) {
    avg_ms_tot += ms_iter;
  }

  CLOG_INFO(LOG_GHOST_XR,
            "VR frame render time: %.0fms - %.2f FPS (%.2f FPS 8 frames average)",
            duration_ms,
            1000.0 / duration_ms,
            1000.0 / (avg_ms_tot / draw_info.last_frame_times.size()));
}

void GHOST_XrSession::endFrameDrawing(std::vector<XrCompositionLayerBaseHeader *> &layers)
{
  XrFrameEndInfo end_info = {XR_TYPE_FRAME_END_INFO};

  end_info.displayTime = draw_info_->frame_state.predictedDisplayTime;
  end_info.environmentBlendMode = XR_ENVIRONMENT_BLEND_MODE_OPAQUE;
  end_info.layerCount = layers.size();
  end_info.layers = layers.data();

  CHECK_XR(xrEndFrame(oxr_->session, &end_info), "Failed to submit rendered frame.");

  if (context_->isDebugTimeMode()) {
    print_debug_timings(*draw_info_);
  }
}

void GHOST_XrSession::draw(void *draw_customdata)
{
  std::vector<XrCompositionLayerProjectionView>
      projection_layer_views; /* Keep alive until #xrEndFrame() call! */
  XrCompositionLayerProjection proj_layer;
  std::vector<XrCompositionLayerBaseHeader *> layers;

  beginFrameDrawing();

  if (context_->getCustomFuncs().passthrough_enabled_fn(draw_customdata)) {
    enablePassthrough();
    if (oxr_->passthrough_supported) {
      layers.push_back((XrCompositionLayerBaseHeader *)&oxr_->passthrough_layer);
    }
    else {
      context_->getCustomFuncs().disable_passthrough_fn(draw_customdata);
    }
  }

  if (draw_info_->frame_state.shouldRender) {
    proj_layer = drawLayer(projection_layer_views, draw_customdata);
    if (layers.size() > 0) {
      proj_layer.layerFlags = XR_COMPOSITION_LAYER_BLEND_TEXTURE_SOURCE_ALPHA_BIT;
    }
    layers.push_back(reinterpret_cast<XrCompositionLayerBaseHeader *>(&proj_layer));
  }

  endFrameDrawing(layers);
}

static void ghost_xr_draw_view_info_from_view(const XrView &view, GHOST_XrDrawViewInfo &r_info)
{
  /* Set and convert to Blender coordinate space. */
  copy_openxr_pose_to_ghost_pose(view.pose, r_info.eye_pose);

  r_info.fov.angle_left = view.fov.angleLeft;
  r_info.fov.angle_right = view.fov.angleRight;
  r_info.fov.angle_up = view.fov.angleUp;
  r_info.fov.angle_down = view.fov.angleDown;
}

void GHOST_XrSession::drawView(GHOST_XrSwapchain &swapchain,
                               XrSwapchainImageBaseHeader &swapchain_image,
                               XrCompositionLayerProjectionView &r_proj_layer_view,
                               const XrSpaceLocation &view_location,
                               const XrView &view,
                               uint32_t view_idx,
                               void *draw_customdata)
{
  r_proj_layer_view.type = XR_TYPE_COMPOSITION_LAYER_PROJECTION_VIEW;
  r_proj_layer_view.pose = view.pose;
  r_proj_layer_view.fov = view.fov;
  swapchain.updateCompositionLayerProjectViewSubImage(r_proj_layer_view.subImage);

  assert(view_idx < 256);
  GHOST_XrDrawViewInfo draw_view_info = {};
  draw_view_info.view_idx = char(view_idx);
  draw_view_info.swapchain_format = swapchain.getFormat();
  draw_view_info.gpu_swapchain_format = swapchain.getGPUFormat();
  draw_view_info.expects_srgb_buffer = swapchain.isBufferSRGB();
  draw_view_info.ofsx = r_proj_layer_view.subImage.imageRect.offset.x;
  draw_view_info.ofsy = r_proj_layer_view.subImage.imageRect.offset.y;
  draw_view_info.width = r_proj_layer_view.subImage.imageRect.extent.width;
  draw_view_info.height = r_proj_layer_view.subImage.imageRect.extent.height;
  copy_openxr_pose_to_ghost_pose(view_location.pose, draw_view_info.local_pose);
  ghost_xr_draw_view_info_from_view(view, draw_view_info);

  /* Draw! */
  context_->getCustomFuncs().draw_view_fn(&draw_view_info, draw_customdata);
  gpu_binding_->submitToSwapchainImage(swapchain_image, draw_view_info);
}

XrCompositionLayerProjection GHOST_XrSession::drawLayer(
    std::vector<XrCompositionLayerProjectionView> &r_proj_layer_views, void *draw_customdata)
{
  XrViewLocateInfo viewloc_info = {XR_TYPE_VIEW_LOCATE_INFO};
  XrViewLocateFoveatedRenderingVARJO foveated_info{
      XR_TYPE_VIEW_LOCATE_FOVEATED_RENDERING_VARJO, nullptr, true};
  XrViewState view_state = {XR_TYPE_VIEW_STATE};
  XrCompositionLayerProjection layer = {XR_TYPE_COMPOSITION_LAYER_PROJECTION};
  XrSpaceLocation view_location{XR_TYPE_SPACE_LOCATION};
  uint32_t view_count;

  viewloc_info.viewConfigurationType = oxr_->view_type;
  viewloc_info.displayTime = draw_info_->frame_state.predictedDisplayTime;
  viewloc_info.space = oxr_->reference_space;

  if (draw_info_->foveation_active) {
    viewloc_info.next = &foveated_info;
  }

  CHECK_XR(xrLocateViews(oxr_->session,
                         &viewloc_info,
                         &view_state,
                         oxr_->views.size(),
                         &view_count,
                         oxr_->views.data()),
           "Failed to query frame view and projection state.");

  assert(oxr_->swapchains.size() == view_count);

  CHECK_XR(xrLocateSpace(
               oxr_->view_space, oxr_->reference_space, viewloc_info.displayTime, &view_location),
           "Failed to query frame view space");

  r_proj_layer_views.resize(view_count);
  std::vector<XrSwapchainImageBaseHeader *> swapchain_images;
  swapchain_images.resize(view_count);

  for (uint32_t view_idx = 0; view_idx < view_count; view_idx++) {
    GHOST_XrSwapchain &swapchain = oxr_->swapchains[view_idx];
    swapchain_images[view_idx] = swapchain.acquireDrawableSwapchainImage();
  }

  gpu_binding_->submitToSwapchainBegin();
  for (uint32_t view_idx = 0; view_idx < view_count; view_idx++) {
    GHOST_XrSwapchain &swapchain = oxr_->swapchains[view_idx];
    XrSwapchainImageBaseHeader &swapchain_image = *swapchain_images[view_idx];
    drawView(swapchain,
             swapchain_image,
             r_proj_layer_views[view_idx],
             view_location,
             oxr_->views[view_idx],
             view_idx,
             draw_customdata);
  }
  gpu_binding_->submitToSwapchainEnd();

  for (uint32_t view_idx = 0; view_idx < view_count; view_idx++) {
    GHOST_XrSwapchain &swapchain = oxr_->swapchains[view_idx];
    swapchain.releaseImage();
    swapchain_images[view_idx] = nullptr;
  }

  layer.space = oxr_->reference_space;
  layer.viewCount = r_proj_layer_views.size();
  layer.views = r_proj_layer_views.data();

  return layer;
}

bool GHOST_XrSession::needsUpsideDownDrawing() const
{
  return gpu_binding_ && gpu_binding_->needsUpsideDownDrawing(*gpu_ctx_);
}

/** \} */ /* Drawing */

/* -------------------------------------------------------------------- */
/** \name State Queries
 * \{ */

bool GHOST_XrSession::isRunning() const
{
  if (oxr_->session == XR_NULL_HANDLE) {
    return false;
  }
  switch (oxr_->session_state) {
    case XR_SESSION_STATE_READY:
    case XR_SESSION_STATE_SYNCHRONIZED:
    case XR_SESSION_STATE_VISIBLE:
    case XR_SESSION_STATE_FOCUSED:
      return true;
    default:
      return false;
  }
}

/** \} */ /* State Queries */

/* -------------------------------------------------------------------- */
/** \name Graphics Context Injection
 *
 * Sessions need access to Ghost graphics context information. Additionally, this API allows
 * creating contexts on the fly (created on start, destructed on end). For this, callbacks to bind
 * (potentially create) and unbind (potentially destruct) a Ghost graphics context have to be set,
 * which will be called on session start and end respectively.
 *
 * \{ */

void GHOST_XrSession::bindGraphicsContext()
{
  const GHOST_XrCustomFuncs &custom_funcs = context_->getCustomFuncs();
  assert(custom_funcs.gpu_ctx_bind_fn);
  gpu_ctx_ = static_cast<GHOST_Context *>(custom_funcs.gpu_ctx_bind_fn());
}

void GHOST_XrSession::unbindGraphicsContext()
{
  const GHOST_XrCustomFuncs &custom_funcs = context_->getCustomFuncs();
  if (custom_funcs.gpu_ctx_unbind_fn) {
    custom_funcs.gpu_ctx_unbind_fn(gpu_ctx_);
  }
  gpu_ctx_ = nullptr;
}

/** \} */ /* Graphics Context Injection */

/* -------------------------------------------------------------------- */
/** \name Actions
 *
 * \{ */

static GHOST_XrActionSet *find_action_set(OpenXRSessionData *oxr, const char *action_set_name)
{
  std::map<std::string, GHOST_XrActionSet>::iterator it = oxr->action_sets.find(action_set_name);
  if (it == oxr->action_sets.end()) {
    return nullptr;
  }
  return &it->second;
}

bool GHOST_XrSession::createActionSet(const GHOST_XrActionSetInfo &info)
{
  std::map<std::string, GHOST_XrActionSet> &action_sets = oxr_->action_sets;
  if (action_sets.find(info.name) != action_sets.end()) {
    return false;
  }

  XrInstance instance = context_->getInstance();

  action_sets.emplace(
      std::piecewise_construct, std::make_tuple(info.name), std::make_tuple(instance, info));

  return true;
}

void GHOST_XrSession::destroyActionSet(const char *action_set_name)
{
  std::map<std::string, GHOST_XrActionSet> &action_sets = oxr_->action_sets;
  /* It's possible nothing is removed. */
  action_sets.erase(action_set_name);
}

bool GHOST_XrSession::createActions(const char *action_set_name,
                                    uint32_t count,
                                    const GHOST_XrActionInfo *infos)
{
  GHOST_XrActionSet *action_set = find_action_set(oxr_.get(), action_set_name);
  if (action_set == nullptr) {
    return false;
  }

  XrInstance instance = context_->getInstance();

  for (uint32_t i = 0; i < count; ++i) {
    if (!action_set->createAction(instance, infos[i])) {
      return false;
    }
  }

  return true;
}

void GHOST_XrSession::destroyActions(const char *action_set_name,
                                     uint32_t count,
                                     const char *const *action_names)
{
  GHOST_XrActionSet *action_set = find_action_set(oxr_.get(), action_set_name);
  if (action_set == nullptr) {
    return;
  }

  for (uint32_t i = 0; i < count; ++i) {
    action_set->destroyAction(action_names[i]);
  }
}

bool GHOST_XrSession::createActionBindings(const char *action_set_name,
                                           uint32_t count,
                                           const GHOST_XrActionProfileInfo *infos)
{
  GHOST_XrActionSet *action_set = find_action_set(oxr_.get(), action_set_name);
  if (action_set == nullptr) {
    return false;
  }

  XrInstance instance = context_->getInstance();
  XrSession session = oxr_->session;

  for (uint32_t profile_idx = 0; profile_idx < count; ++profile_idx) {
    const GHOST_XrActionProfileInfo &info = infos[profile_idx];

    GHOST_XrAction *action = action_set->findAction(info.action_name);
    if (action == nullptr) {
      continue;
    }

    action->createBinding(instance, session, info);
  }

  return true;
}

void GHOST_XrSession::destroyActionBindings(const char *action_set_name,
                                            uint32_t count,
                                            const char *const *action_names,
                                            const char *const *profile_paths)
{
  GHOST_XrActionSet *action_set = find_action_set(oxr_.get(), action_set_name);
  if (action_set == nullptr) {
    return;
  }

  for (uint32_t i = 0; i < count; ++i) {
    GHOST_XrAction *action = action_set->findAction(action_names[i]);
    if (action == nullptr) {
      continue;
    }

    action->destroyBinding(profile_paths[i]);
  }
}

bool GHOST_XrSession::attachActionSets()
{
  /* Suggest action bindings for all action sets. */
  std::map<XrPath, std::vector<XrActionSuggestedBinding>> profile_bindings;
  for (auto &[name, action_set] : oxr_->action_sets) {
    action_set.getBindings(profile_bindings);
  }

  if (profile_bindings.size() < 1) {
    return false;
  }

  XrInteractionProfileSuggestedBinding bindings_info{
      XR_TYPE_INTERACTION_PROFILE_SUGGESTED_BINDING};
  XrInstance instance = context_->getInstance();

  for (auto &[profile, bindings] : profile_bindings) {
    bindings_info.interactionProfile = profile;
    bindings_info.countSuggestedBindings = uint32_t(bindings.size());
    bindings_info.suggestedBindings = bindings.data();

    CHECK_XR(xrSuggestInteractionProfileBindings(instance, &bindings_info),
             "Failed to suggest interaction profile bindings.");
  }

  /* Attach action sets. */
  XrSessionActionSetsAttachInfo attach_info{XR_TYPE_SESSION_ACTION_SETS_ATTACH_INFO};
  attach_info.countActionSets = uint32_t(oxr_->action_sets.size());

  /* Create an aligned copy of the action sets to pass to xrAttachSessionActionSets(). */
  std::vector<XrActionSet> action_sets(attach_info.countActionSets);
  uint32_t i = 0;
  for (auto &[name, action_set] : oxr_->action_sets) {
    action_sets[i++] = action_set.getActionSet();
  }
  attach_info.actionSets = action_sets.data();

  CHECK_XR(xrAttachSessionActionSets(oxr_->session, &attach_info),
           "Failed to attach XR action sets.");

  return true;
}

bool GHOST_XrSession::syncActions(const char *action_set_name)
{
  std::map<std::string, GHOST_XrActionSet> &action_sets = oxr_->action_sets;

  XrActionsSyncInfo sync_info{XR_TYPE_ACTIONS_SYNC_INFO};
  sync_info.countActiveActionSets = (action_set_name != nullptr) ? 1 :
                                                                   uint32_t(action_sets.size());
  if (sync_info.countActiveActionSets < 1) {
    return false;
  }

  std::vector<XrActiveActionSet> active_action_sets(sync_info.countActiveActionSets);
  GHOST_XrActionSet *action_set = nullptr;

  if (action_set_name != nullptr) {
    action_set = find_action_set(oxr_.get(), action_set_name);
    if (action_set == nullptr) {
      return false;
    }

    XrActiveActionSet &active_action_set = active_action_sets[0];
    active_action_set.actionSet = action_set->getActionSet();
    active_action_set.subactionPath = XR_NULL_PATH;
  }
  else {
    uint32_t i = 0;
    for (auto &[name, action_set] : action_sets) {
      XrActiveActionSet &active_action_set = active_action_sets[i++];
      active_action_set.actionSet = action_set.getActionSet();
      active_action_set.subactionPath = XR_NULL_PATH;
    }
  }
  sync_info.activeActionSets = active_action_sets.data();

  CHECK_XR(xrSyncActions(oxr_->session, &sync_info), "Failed to synchronize XR actions.");

  /* Update action states (i.e. Blender custom data). */
  XrSession session = oxr_->session;
  XrSpace reference_space = oxr_->reference_space;
  const XrTime &predicted_display_time = draw_info_->frame_state.predictedDisplayTime;

  if (action_set != nullptr) {
    action_set->updateStates(session, reference_space, predicted_display_time);
  }
  else {
    for (auto &[name, action_set] : action_sets) {
      action_set.updateStates(session, reference_space, predicted_display_time);
    }
  }

  return true;
}

bool GHOST_XrSession::applyHapticAction(const char *action_set_name,
                                        const char *action_name,
                                        const char *subaction_path,
                                        const int64_t &duration,
                                        const float &frequency,
                                        const float &amplitude)
{
  GHOST_XrActionSet *action_set = find_action_set(oxr_.get(), action_set_name);
  if (action_set == nullptr) {
    return false;
  }

  GHOST_XrAction *action = action_set->findAction(action_name);
  if (action == nullptr) {
    return false;
  }

  action->applyHapticFeedback(
      oxr_->session, action_name, subaction_path, duration, frequency, amplitude);

  return true;
}

void GHOST_XrSession::stopHapticAction(const char *action_set_name,
                                       const char *action_name,
                                       const char *subaction_path)
{
  GHOST_XrActionSet *action_set = find_action_set(oxr_.get(), action_set_name);
  if (action_set == nullptr) {
    return;
  }

  GHOST_XrAction *action = action_set->findAction(action_name);
  if (action == nullptr) {
    return;
  }

  action->stopHapticFeedback(oxr_->session, action_name, subaction_path);
}

void *GHOST_XrSession::getActionSetCustomdata(const char *action_set_name)
{
  GHOST_XrActionSet *action_set = find_action_set(oxr_.get(), action_set_name);
  if (action_set == nullptr) {
    return nullptr;
  }

  return action_set->getCustomdata();
}

void *GHOST_XrSession::getActionCustomdata(const char *action_set_name, const char *action_name)
{
  GHOST_XrActionSet *action_set = find_action_set(oxr_.get(), action_set_name);
  if (action_set == nullptr) {
    return nullptr;
  }

  GHOST_XrAction *action = action_set->findAction(action_name);
  if (action == nullptr) {
    return nullptr;
  }

  return action->getCustomdata();
}

uint32_t GHOST_XrSession::getActionCount(const char *action_set_name)
{
  const GHOST_XrActionSet *action_set = find_action_set(oxr_.get(), action_set_name);
  if (action_set == nullptr) {
    return 0;
  }

  return action_set->getActionCount();
}

void GHOST_XrSession::getActionCustomdataArray(const char *action_set_name,
                                               void **r_customdata_array)
{
  GHOST_XrActionSet *action_set = find_action_set(oxr_.get(), action_set_name);
  if (action_set == nullptr) {
    return;
  }

  action_set->getActionCustomdataArray(r_customdata_array);
}

/** \} */ /* Actions */

/* -------------------------------------------------------------------- */
/** \name Controller Model
 *
 * \{ */

bool GHOST_XrSession::loadControllerModel(const char *subaction_path)
{
  if (!context_->isExtensionEnabled(XR_MSFT_CONTROLLER_MODEL_EXTENSION_NAME)) {
    return false;
  }

  XrSession session = oxr_->session;
  std::map<std::string, GHOST_XrControllerModel> &controller_models = oxr_->controller_models;
  std::map<std::string, GHOST_XrControllerModel>::iterator it = controller_models.find(
      subaction_path);

  if (it == controller_models.end()) {
    XrInstance instance = context_->getInstance();
    it = controller_models
             .emplace(std::piecewise_construct,
                      std::make_tuple(subaction_path),
                      std::make_tuple(instance, subaction_path))
             .first;
  }

  it->second.load(session);

  return true;
}

void GHOST_XrSession::unloadControllerModel(const char *subaction_path)
{
  std::map<std::string, GHOST_XrControllerModel> &controller_models = oxr_->controller_models;
  /* It's possible nothing is removed. */
  controller_models.erase(subaction_path);
}

bool GHOST_XrSession::updateControllerModelComponents(const char *subaction_path)
{
  XrSession session = oxr_->session;
  std::map<std::string, GHOST_XrControllerModel>::iterator it = oxr_->controller_models.find(
      subaction_path);
  if (it == oxr_->controller_models.end()) {
    return false;
  }

  it->second.updateComponents(session);

  return true;
}

bool GHOST_XrSession::getControllerModelData(const char *subaction_path,
                                             GHOST_XrControllerModelData &r_data)
{
  std::map<std::string, GHOST_XrControllerModel>::iterator it = oxr_->controller_models.find(
      subaction_path);
  if (it == oxr_->controller_models.end()) {
    return false;
  }

  it->second.getData(r_data);

  return true;
}

/** \} */ /* Controller Model */

/* -------------------------------------------------------------------- */
/** \name Meta Quest Passthrough
 *
 * \{ */

static PFN_xrCreatePassthroughFB g_xrCreatePassthroughFB = nullptr;
static PFN_xrCreatePassthroughLayerFB g_xrCreatePassthroughLayerFB = nullptr;
static PFN_xrPassthroughStartFB g_xrPassthroughStartFB = nullptr;
static PFN_xrPassthroughLayerResumeFB g_xrPassthroughLayerResumeFB = nullptr;

static void init_passthrough_extension_functions(XrInstance instance)
{
  if (g_xrCreatePassthroughFB == nullptr) {
    INIT_EXTENSION_FUNCTION(xrCreatePassthroughFB);
  }
  if (g_xrCreatePassthroughLayerFB == nullptr) {
    INIT_EXTENSION_FUNCTION(xrCreatePassthroughLayerFB);
  }
  if (g_xrPassthroughStartFB == nullptr) {
    INIT_EXTENSION_FUNCTION(xrPassthroughStartFB);
  }
  if (g_xrPassthroughLayerResumeFB == nullptr) {
    INIT_EXTENSION_FUNCTION(xrPassthroughLayerResumeFB);
  }
}

void GHOST_XrSession::enablePassthrough()
{
  oxr_->passthrough_supported = false;

  if (!context_->isExtensionEnabled(XR_FB_PASSTHROUGH_EXTENSION_NAME)) {
    return;
  }

  if (oxr_->passthrough_layer.layerHandle != XR_NULL_HANDLE) {
    oxr_->passthrough_supported = true;
    return; /* Already initialized. */
  }

  init_passthrough_extension_functions(context_->getInstance());

  XrPassthroughCreateInfoFB passthrough_create_info = {};
  passthrough_create_info.type = XR_TYPE_PASSTHROUGH_CREATE_INFO_FB;
  passthrough_create_info.next = nullptr;
  passthrough_create_info.flags |= XR_PASSTHROUGH_IS_RUNNING_AT_CREATION_BIT_FB;

  XrPassthroughFB passthrough_handle;
  CHECK_XR(g_xrCreatePassthroughFB(oxr_->session, &passthrough_create_info, &passthrough_handle),
           "Failed to create passthrough handle.");

  XrPassthroughLayerCreateInfoFB passthrough_layer_create_info = {};
  passthrough_layer_create_info.type = XR_TYPE_PASSTHROUGH_LAYER_CREATE_INFO_FB;
  passthrough_layer_create_info.next = nullptr;
  passthrough_layer_create_info.passthrough = passthrough_handle;
  passthrough_layer_create_info.flags |= XR_PASSTHROUGH_IS_RUNNING_AT_CREATION_BIT_FB;
  passthrough_layer_create_info.purpose = XR_PASSTHROUGH_LAYER_PURPOSE_RECONSTRUCTION_FB;

  XrPassthroughLayerFB passthrough_layer_handle;
  CHECK_XR(g_xrCreatePassthroughLayerFB(
               oxr_->session, &passthrough_layer_create_info, &passthrough_layer_handle),
           "Failed to create passthrough layer handle.");

  g_xrPassthroughStartFB(passthrough_handle);
  g_xrPassthroughLayerResumeFB(passthrough_layer_handle);

  oxr_->passthrough_layer.type = XR_TYPE_COMPOSITION_LAYER_PASSTHROUGH_FB;
  oxr_->passthrough_layer.next = nullptr;
  oxr_->passthrough_layer.flags = XR_COMPOSITION_LAYER_BLEND_TEXTURE_SOURCE_ALPHA_BIT;
  oxr_->passthrough_layer.space = XR_NULL_HANDLE;
  oxr_->passthrough_layer.layerHandle = passthrough_layer_handle;

  oxr_->passthrough_supported = true;
}

/** \} */ /* Meta Quest Passthrough */
