// Copyright 2017 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "garnet/lib/ui/gfx/engine/engine.h"

#include <fbl/string.h>
#include <fs/pseudo-dir.h>
#include <set>

#include <lib/async/cpp/task.h>
#include <lib/async/default.h>
#include <trace/event.h>
#include <zx/time.h>

#include "garnet/lib/ui/gfx/engine/engine_renderer.h"
#include "garnet/lib/ui/gfx/engine/frame_scheduler.h"
#include "garnet/lib/ui/gfx/engine/frame_timings.h"
#include "garnet/lib/ui/gfx/engine/hardware_layer_assignment.h"
#include "garnet/lib/ui/gfx/engine/session.h"
#include "garnet/lib/ui/gfx/engine/session_handler.h"
#include "garnet/lib/ui/gfx/resources/compositor/compositor.h"
#include "garnet/lib/ui/gfx/resources/dump_visitor.h"
#include "garnet/lib/ui/gfx/resources/nodes/traversal.h"
#include "garnet/lib/ui/gfx/swapchain/display_swapchain.h"
#include "garnet/lib/ui/gfx/swapchain/vulkan_display_swapchain.h"
#include "garnet/lib/ui/scenic/session.h"
#include "lib/escher/impl/vulkan_utils.h"
#include "lib/escher/renderer/batch_gpu_uploader.h"

namespace scenic_impl {
namespace gfx {

// Determine a plausible memory type index for importing memory from VMOs.
static uint32_t GetImportedMemoryTypeIndex(vk::PhysicalDevice physical_device,
                                           vk::Device device) {
  // Is there a better way to get the memory type bits than creating and
  // immediately destroying a buffer?
  // TODO(SCN-79): Use sysmem for this when it's available.
  constexpr vk::DeviceSize kUnimportantBufferSize = 30000;
  vk::BufferCreateInfo buffer_create_info;
  buffer_create_info.size = kUnimportantBufferSize;
  buffer_create_info.usage = vk::BufferUsageFlagBits::eTransferSrc |
                             vk::BufferUsageFlagBits::eTransferDst |
                             vk::BufferUsageFlagBits::eStorageTexelBuffer |
                             vk::BufferUsageFlagBits::eStorageBuffer |
                             vk::BufferUsageFlagBits::eIndexBuffer |
                             vk::BufferUsageFlagBits::eVertexBuffer;
  buffer_create_info.sharingMode = vk::SharingMode::eExclusive;
  auto vk_buffer =
      escher::ESCHER_CHECKED_VK_RESULT(device.createBuffer(buffer_create_info));

  vk::MemoryRequirements reqs = device.getBufferMemoryRequirements(vk_buffer);
  device.destroyBuffer(vk_buffer);

  // TODO(SCN-998): Decide how to determine if we're on an UMA platform
  // or not.
  return escher::impl::GetMemoryTypeIndex(
      physical_device, reqs.memoryTypeBits,
      vk::MemoryPropertyFlagBits::eDeviceLocal |
          vk::MemoryPropertyFlagBits::eHostVisible);
}

CommandContext::CommandContext(escher::BatchGpuUploaderPtr uploader)
    : batch_gpu_uploader_(std::move(uploader)) {}

void CommandContext::Flush() {
  if (batch_gpu_uploader_) {
    // Submit regardless of whether or not there are updates to release the
    // underlying CommandBuffer so the pool and sequencer don't stall out.
    // TODO(ES-115) to remove this restriction.
    batch_gpu_uploader_->Submit(escher::SemaphorePtr());
  }
}

Engine::Engine(DisplayManager* display_manager,
               escher::EscherWeakPtr weak_escher)
    : display_manager_(display_manager),
      escher_(std::move(weak_escher)),
      engine_renderer_(std::make_unique<EngineRenderer>(escher_)),
      image_factory_(std::make_unique<escher::SimpleImageFactory>(
          escher()->resource_recycler(), escher()->gpu_allocator())),
      rounded_rect_factory_(
          std::make_unique<escher::RoundedRectFactory>(escher_)),
      release_fence_signaller_(std::make_unique<escher::ReleaseFenceSignaller>(
          escher()->command_buffer_sequencer())),
      session_manager_(std::make_unique<SessionManager>()),
      imported_memory_type_index_(GetImportedMemoryTypeIndex(
          escher()->vk_physical_device(), escher()->vk_device())),
      has_vulkan_(escher_ && escher_->vk_device()),
      weak_factory_(this) {
  FXL_DCHECK(display_manager_);
  FXL_DCHECK(escher_);

  InitializeFrameScheduler();
}

Engine::Engine(
    DisplayManager* display_manager,
    std::unique_ptr<escher::ReleaseFenceSignaller> release_fence_signaller,
    std::unique_ptr<SessionManager> session_manager,
    escher::EscherWeakPtr weak_escher)
    : display_manager_(display_manager),
      escher_(std::move(weak_escher)),
      release_fence_signaller_(std::move(release_fence_signaller)),
      session_manager_(std::move(session_manager)),
      imported_memory_type_index_(
          escher_ ? GetImportedMemoryTypeIndex(escher_->vk_physical_device(),
                                               escher_->vk_device())
                  : 0),
      has_vulkan_(escher_ && escher_->vk_device()),
      weak_factory_(this) {
  FXL_DCHECK(display_manager_);

  InitializeFrameScheduler();
}

Engine::~Engine() = default;

void Engine::InitializeFrameScheduler() {
  // TODO(SCN-1092): make |frame_scheduler_| non-nullable.  For testing, this
  // might entail plugging in a dummy Display.  Relates to SCN-452.
  if (display_manager_->default_display()) {
    frame_scheduler_ =
        std::make_unique<FrameScheduler>(display_manager_->default_display());
    frame_scheduler_->set_delegate(this);
  }
}

void Engine::ScheduleUpdate(uint64_t presentation_time) {
  // TODO(SCN-1092): make |frame_scheduler_| non-nullable.  This is feasible now
  // that we can use TestLoopFixture::RunLoopFor() to cause the scheduler to
  // render.
  if (frame_scheduler_) {
    frame_scheduler_->RequestFrame(presentation_time);
  } else {
    // Apply update immediately.  This is done for tests.
    FXL_LOG(WARNING)
        << "No FrameScheduler available; applying update immediately";
    RenderFrame(FrameTimingsPtr(), presentation_time, 0, false);
  }
}

std::unique_ptr<Swapchain> Engine::CreateDisplaySwapchain(Display* display) {
  FXL_DCHECK(!display->is_claimed());
#if SCENIC_VULKAN_SWAPCHAIN
  return std::make_unique<VulkanDisplaySwapchain>(display, event_timestamper(),
                                                  escher());
#else
  return std::make_unique<DisplaySwapchain>(display_manager_, display,
                                            event_timestamper(), escher());
#endif
}

void Engine::InitializeCommandContext(uint64_t frame_number_for_tracing) {
  FXL_DCHECK(!command_context_) << "CommandContext already exists.";
  command_context_ = std::make_unique<CommandContext>(
      has_vulkan()
          ? escher::BatchGpuUploader::New(escher_, frame_number_for_tracing)
          : escher::BatchGpuUploaderPtr());
}

void Engine::FlushAndInvalidateCommandContext() {
  FXL_DCHECK(command_context_) << "CommandContext does not exist.";
  command_context_->Flush();
  command_context_ = nullptr;
}

bool Engine::UpdateSessions(uint64_t presentation_time,
                            uint64_t presentation_interval,
                            uint64_t frame_number_for_tracing) {
  InitializeCommandContext(frame_number_for_tracing);
  bool any_updates_were_applied =
      session_manager_->ApplyScheduledSessionUpdates(presentation_time,
                                                     presentation_interval);
  FlushAndInvalidateCommandContext();
  return any_updates_were_applied;
}

// Helper for RenderFrame().  Generate a mapping between a Compositor's Layer
// resources and the hardware layers they should be displayed on.
// TODO(SCN-1088): there should be a separate mechanism that is responsible
// for inspecting the compositor's resource tree and optimizing the assignment
// of rendered content to hardware display layers.
std::optional<HardwareLayerAssignment> GetHardwareLayerAssignment(
    const Compositor& compositor) {
  // TODO(SCN-1098): this is a placeholder; currently only a single hardware
  // layer is supported, and we don't know its ID (it is hidden within the
  // DisplayManager implementation), so we just say 0.
  std::vector<Layer*> layers = compositor.GetDrawableLayers();
  if (layers.empty() || !compositor.swapchain()) {
    return {};
  }
  return {
      {.items = {{
           .hardware_layer_id = 0,
           .layers = std::move(layers),
       }},
       .swapchain = compositor.swapchain()},
  };
}

bool Engine::RenderFrame(const FrameTimingsPtr& timings,
                         uint64_t presentation_time,
                         uint64_t presentation_interval, bool force_render) {
  TRACE_DURATION("gfx", "RenderFrame", "frame_number", timings->frame_number(),
                 "time", presentation_time, "interval", presentation_interval);

  // TODO(SCN-1092): make |timings| non-nullable, and unconditionally use
  // timings->frame_number() below.  When this is done, uncomment the following
  // line:
  // FXL_DCHECK(timings);

  // TODO(SCN-1108): consider applying updates as each fence is signalled.
  if (!UpdateSessions(presentation_time, presentation_interval,
                      timings ? timings->frame_number() : 0) &&
      !force_render) {
    return false;
  }
  UpdateAndDeliverMetrics(presentation_time);

  // Some updates were applied; we interpret this to mean that the scene may
  // have changed, and therefore needs to be rendered.
  // TODO(SCN-1091): this is a very conservative approach that may result in
  // excessive rendering.

  // TODO(SCN-1089): the FrameTimings are passed to the Compositor's swapchain
  // to notify when the frame is finished rendering, presented, dropped, etc.
  // This doesn't make any sense if there are multiple compositors.
  FXL_DCHECK(compositors_.size() <= 1);

  std::vector<HardwareLayerAssignment> hlas;
  for (auto& compositor : compositors_) {
    if (auto hla = GetHardwareLayerAssignment(*compositor)) {
      hlas.push_back(std::move(hla.value()));

      // Verbose logging of the entire Compositor resource tree.
      if (FXL_VLOG_IS_ON(3)) {
        std::ostringstream output;
        DumpVisitor visitor(output);
        compositor->Accept(&visitor);
        FXL_VLOG(3) << "Compositor dump\n" << output.str();
      }
    } else {
      // Nothing to be drawn; either the Compositor has no layers to draw or
      // it has no valid Swapchain.  The latter will be true if Escher/Vulkan
      // is unavailable for whatever reason.
    }
  }
  if (hlas.empty()) {
    // No compositor has any renderable content.
    return false;
  }

  escher::FramePtr frame =
      escher()->NewFrame("Scenic Compositor", timings->frame_number());

  bool success = true;
  for (size_t i = 0; i < hlas.size(); ++i) {
    const bool is_last_hla = (i == hlas.size() - 1);
    HardwareLayerAssignment& hla = hlas[i];

    success &= hla.swapchain->DrawAndPresentFrame(
        timings, hla,
        [is_last_hla, &frame, engine_renderer{engine_renderer_.get()}](
            zx_time_t target_presentation_time,
            const escher::ImagePtr& output_image,
            const HardwareLayerAssignment::Item hla_item,
            const escher::SemaphorePtr& acquire_semaphore,
            const escher::SemaphorePtr& frame_done_semaphore) {
          output_image->SetWaitSemaphore(acquire_semaphore);
          engine_renderer->RenderLayers(frame, target_presentation_time,
                                        output_image, hla_item.layers);
          if (!is_last_hla) {
            frame->SubmitPartialFrame(frame_done_semaphore);
          } else {
            frame->EndFrame(frame_done_semaphore, nullptr);
          }
        });
  }
  if (!success) {
    // TODO(SCN-1089): what is the proper behavior when some swapchains
    // are displayed and others aren't?  This isn't currently an issue because
    // there is only one Compositor; see above.
    FXL_DCHECK(hlas.size() == 1);
    return false;
  }

  CleanupEscher();
  return true;
}

void Engine::AddCompositor(Compositor* compositor) {
  FXL_DCHECK(compositor);
  FXL_DCHECK(compositor->session()->engine() == this);

  bool success = compositors_.insert(compositor).second;
  FXL_DCHECK(success);
}

void Engine::RemoveCompositor(Compositor* compositor) {
  FXL_DCHECK(compositor);
  FXL_DCHECK(compositor->session()->engine() == this);

  size_t count = compositors_.erase(compositor);
  FXL_DCHECK(count == 1);
}

Compositor* Engine::GetFirstCompositor() const {
  FXL_DCHECK(!compositors_.empty());
  return compositors_.empty() ? nullptr : *compositors_.begin();
}

Compositor* Engine::GetCompositor(scenic_impl::GlobalId compositor_id) const {
  for (Compositor* compositor : compositors_) {
    if (compositor->global_id() == compositor_id) {
      return compositor;
    }
  }
  return nullptr;
}

void Engine::UpdateAndDeliverMetrics(uint64_t presentation_time) {
  TRACE_DURATION("gfx", "UpdateAndDeliverMetrics", "time", presentation_time);

  // Gather all of the scene which might need to be updated.
  std::set<Scene*> scenes;
  for (auto compositor : compositors_) {
    compositor->CollectScenes(&scenes);
  }
  if (scenes.empty())
    return;

  // TODO(MZ-216): Traversing the whole graph just to compute this is pretty
  // inefficient.  We should optimize this.
  ::fuchsia::ui::gfx::Metrics metrics;
  metrics.scale_x = 1.f;
  metrics.scale_y = 1.f;
  metrics.scale_z = 1.f;
  std::vector<Node*> updated_nodes;
  for (auto scene : scenes) {
    UpdateMetrics(scene, metrics, &updated_nodes);
  }

  // TODO(MZ-216): Deliver events to sessions in batches.
  // We probably want delivery to happen somewhere else which can also
  // handle delivery of other kinds of events.  We should probably also
  // have some kind of backpointer from a session to its handler.
  for (auto node : updated_nodes) {
    if (node->session()) {
      auto event = ::fuchsia::ui::gfx::Event();
      event.set_metrics(::fuchsia::ui::gfx::MetricsEvent());
      event.metrics().node_id = node->id();
      event.metrics().metrics = node->reported_metrics();
      node->session()->EnqueueEvent(std::move(event));
    }
  }
}

// TODO(mikejurka): move this to appropriate util file
bool MetricsEquals(const ::fuchsia::ui::gfx::Metrics& a,
                   const ::fuchsia::ui::gfx::Metrics& b) {
  return a.scale_x == b.scale_x && a.scale_y == b.scale_y &&
         a.scale_z == b.scale_z;
}

void Engine::UpdateMetrics(Node* node,
                           const ::fuchsia::ui::gfx::Metrics& parent_metrics,
                           std::vector<Node*>* updated_nodes) {
  ::fuchsia::ui::gfx::Metrics local_metrics;
  local_metrics.scale_x = parent_metrics.scale_x * node->scale().x;
  local_metrics.scale_y = parent_metrics.scale_y * node->scale().y;
  local_metrics.scale_z = parent_metrics.scale_z * node->scale().z;

  if ((node->event_mask() & ::fuchsia::ui::gfx::kMetricsEventMask) &&
      !MetricsEquals(node->reported_metrics(), local_metrics)) {
    node->set_reported_metrics(local_metrics);
    updated_nodes->push_back(node);
  }

  ForEachDirectDescendantFrontToBack(
      *node, [this, &local_metrics, updated_nodes](Node* node) {
        UpdateMetrics(node, local_metrics, updated_nodes);
      });
}

void Engine::CleanupEscher() {
  // Either there is already a cleanup scheduled (meaning that this was already
  // called recently), or there is no Escher because we're running tests.
  if (!escher_ || escher_cleanup_scheduled_) {
    return;
  }
  // Only trace when there is the possibility of doing work.
  TRACE_DURATION("gfx", "Engine::CleanupEscher");

  if (!escher_->Cleanup()) {
    // Wait long enough to give GPU work a chance to finish.
    const zx::duration kCleanupDelay = zx::msec(1);
    escher_cleanup_scheduled_ = true;
    async::PostDelayedTask(
        async_get_default_dispatcher(),
        [weak = weak_factory_.GetWeakPtr()] {
          if (weak) {
            // Recursively reschedule if cleanup is
            // incomplete.
            weak->escher_cleanup_scheduled_ = false;
            weak->CleanupEscher();
          }
        },
        kCleanupDelay);
  }
}

std::string Engine::DumpScenes() const {
  std::ostringstream output;
  DumpVisitor visitor(output);

  bool first = true;
  for (auto compositor : compositors_) {
    if (first)
      first = false;
    else
      output << std::endl << "===" << std::endl << std::endl;

    compositor->Accept(&visitor);
  }
  return output.str();
}

}  // namespace gfx
}  // namespace scenic_impl