// Copyright 2022 Dolphin Emulator Project
// SPDX-License-Identifier: GPL-2.0-or-later

#include "VideoBackends/Metal/MTLBoundingBox.h"

#include "VideoBackends/Metal/MTLObjectCache.h"
#include "VideoBackends/Metal/MTLStateTracker.h"

static constexpr size_t BUFFER_SIZE = sizeof(BBoxType) * NUM_BBOX_VALUES;

Metal::BoundingBox::~BoundingBox()
{
  if (g_state_tracker)
    g_state_tracker->SetBBoxBuffer(nullptr, nullptr, nullptr);
}

bool Metal::BoundingBox::Initialize()
{
  const MTLResourceOptions gpu_options =
      MTLResourceStorageModeShared | MTLResourceHazardTrackingModeUntracked;
  const id<MTLDevice> dev = g_device;
  m_upload_fence = MRCTransfer([dev newFence]);
  [m_upload_fence setLabel:@"BBox Upload Fence"];
  m_download_fence = MRCTransfer([dev newFence]);
  [m_download_fence setLabel:@"BBox Download Fence"];
  m_gpu_buffer = MRCTransfer([dev newBufferWithLength:BUFFER_SIZE options:gpu_options]);
  [m_gpu_buffer setLabel:@"BBox Buffer"];
  m_cpu_buffer_ptr = static_cast<BBoxType*>([m_gpu_buffer contents]);
  g_state_tracker->SetBBoxBuffer(m_gpu_buffer, m_upload_fence, m_download_fence);
  return true;
}

std::vector<BBoxType> Metal::BoundingBox::Read(u32 index, u32 length)
{
  @autoreleasepool
  {
    g_state_tracker->EndRenderPass();
    g_state_tracker->FlushEncoders();
    g_state_tracker->NotifyOfCPUGPUSync();
    g_state_tracker->WaitForFlushedEncoders();
    return std::vector<BBoxType>(m_cpu_buffer_ptr + index, m_cpu_buffer_ptr + index + length);
  }
}

void Metal::BoundingBox::Write(u32 index, std::span<const BBoxType> values)
{
  const u32 size = values.size() * sizeof(BBoxType);
  if (!g_state_tracker->HasUnflushedData() && !g_state_tracker->GPUBusy())
  {
    // We can just write directly to the buffer!
    memcpy(m_cpu_buffer_ptr + index, values.data(), size);
  }
  else
  {
    @autoreleasepool
    {
      StateTracker::Map map = g_state_tracker->AllocateForTextureUpload(size);
      memcpy(map.cpu_buffer, values.data(), size);
      g_state_tracker->EndRenderPass();
      id<MTLBlitCommandEncoder> upload = [g_state_tracker->GetRenderCmdBuf() blitCommandEncoder];
      [upload setLabel:@"BBox Upload"];
      [upload waitForFence:m_download_fence];
      [upload copyFromBuffer:map.gpu_buffer
                sourceOffset:map.gpu_offset
                    toBuffer:m_gpu_buffer
           destinationOffset:index * sizeof(BBoxType)
                        size:size];
      [upload updateFence:m_upload_fence];
      [upload endEncoding];
    }
  }
}