// Copyright 2018 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "gpu/command_buffer/service/multi_draw_manager.h"

#include <algorithm>

#include "base/check.h"
#include "base/compiler_specific.h"
#include "base/notreached.h"
#include "base/numerics/checked_math.h"

namespace gpu {
namespace gles2 {

MultiDrawManager::ResultData::ResultData() = default;
MultiDrawManager::ResultData::~ResultData() = default;

MultiDrawManager::ResultData::ResultData(ResultData&& rhs)
    : draw_function(rhs.draw_function),
      drawcount(rhs.drawcount),
      mode(rhs.mode),
      type(rhs.type),
      firsts(std::move(rhs.firsts)),
      counts(std::move(rhs.counts)),
      offsets(std::move(rhs.offsets)),
      indices(std::move(rhs.indices)),
      instance_counts(std::move(rhs.instance_counts)),
      basevertices(std::move(rhs.basevertices)),
      baseinstances(std::move(rhs.baseinstances)) {}

MultiDrawManager::ResultData& MultiDrawManager::ResultData::operator=(
    ResultData&& rhs) {
  if (&rhs == this) {
    return *this;
  }
  draw_function = rhs.draw_function;
  drawcount = rhs.drawcount;
  mode = rhs.mode;
  type = rhs.type;
  std::swap(firsts, rhs.firsts);
  std::swap(counts, rhs.counts);
  std::swap(offsets, rhs.offsets);
  std::swap(indices, rhs.indices);
  std::swap(instance_counts, rhs.instance_counts);
  std::swap(basevertices, rhs.basevertices);
  std::swap(baseinstances, rhs.baseinstances);
  return *this;
}

MultiDrawManager::MultiDrawManager(IndexStorageType index_type)
    : draw_state_(DrawState::End),
      current_draw_offset_(0),
      index_type_(index_type),
      result_() {}

bool MultiDrawManager::Begin(GLsizei drawcount) {
  if (draw_state_ != DrawState::End) {
    return false;
  }
  result_.drawcount = drawcount;
  current_draw_offset_ = 0;
  draw_state_ = DrawState::Begin;
  return true;
}

bool MultiDrawManager::End(ResultData* result) {
  DCHECK(result);
  if (draw_state_ != DrawState::Draw ||
      current_draw_offset_ != result_.drawcount) {
    return false;
  }
  draw_state_ = DrawState::End;
  *result = std::move(result_);
  return true;
}

bool MultiDrawManager::MultiDrawArrays(GLenum mode,
                                       const GLint* firsts,
                                       const GLsizei* counts,
                                       GLsizei drawcount) {
  if (!EnsureDrawArraysFunction(DrawFunction::DrawArrays, mode, drawcount)) {
    return false;
  }
  CopyArraysHelper(drawcount, firsts, counts, nullptr, nullptr, nullptr,
                   nullptr);
  return true;
}

bool MultiDrawManager::MultiDrawArraysInstanced(GLenum mode,
                                                const GLint* firsts,
                                                const GLsizei* counts,
                                                const GLsizei* instance_counts,
                                                GLsizei drawcount) {
  if (!EnsureDrawArraysFunction(DrawFunction::DrawArraysInstanced, mode,
                                drawcount)) {
    return false;
  }
  CopyArraysHelper(drawcount, firsts, counts, nullptr, instance_counts, nullptr,
                   nullptr);
  return true;
}

bool MultiDrawManager::MultiDrawArraysInstancedBaseInstance(
    GLenum mode,
    const GLint* firsts,
    const GLsizei* counts,
    const GLsizei* instance_counts,
    const GLuint* baseinstances,
    GLsizei drawcount) {
  if (!EnsureDrawArraysFunction(DrawFunction::DrawArraysInstancedBaseInstance,
                                mode, drawcount)) {
    return false;
  }
  CopyArraysHelper(drawcount, firsts, counts, nullptr, instance_counts, nullptr,
                   baseinstances);
  return true;
}

bool MultiDrawManager::MultiDrawElements(GLenum mode,
                                         const GLsizei* counts,
                                         GLenum type,
                                         const GLsizei* offsets,
                                         GLsizei drawcount) {
  if (!EnsureDrawElementsFunction(DrawFunction::DrawElements, mode, type,
                                  drawcount)) {
    return false;
  }
  CopyArraysHelper(drawcount, nullptr, counts, offsets, nullptr, nullptr,
                   nullptr);
  return true;
}

bool MultiDrawManager::MultiDrawElementsInstanced(
    GLenum mode,
    const GLsizei* counts,
    GLenum type,
    const GLsizei* offsets,
    const GLsizei* instance_counts,
    GLsizei drawcount) {
  if (!EnsureDrawElementsFunction(DrawFunction::DrawElementsInstanced, mode,
                                  type, drawcount)) {
    return false;
  }
  CopyArraysHelper(drawcount, nullptr, counts, offsets, instance_counts,
                   nullptr, nullptr);
  return true;
}

bool MultiDrawManager::MultiDrawElementsInstancedBaseVertexBaseInstance(
    GLenum mode,
    const GLsizei* counts,
    GLenum type,
    const GLsizei* offsets,
    const GLsizei* instance_counts,
    const GLint* basevertices,
    const GLuint* baseinstances,
    GLsizei drawcount) {
  if (!EnsureDrawElementsFunction(
          DrawFunction::DrawElementsInstancedBaseVertexBaseInstance, mode, type,
          drawcount)) {
    return false;
  }
  CopyArraysHelper(drawcount, nullptr, counts, offsets, instance_counts,
                   basevertices, baseinstances);
  return true;
}

void MultiDrawManager::ResizeArrays() {
  switch (result_.draw_function) {
    case DrawFunction::DrawArraysInstancedBaseInstance:
      result_.baseinstances.resize(result_.drawcount);
      [[fallthrough]];
    case DrawFunction::DrawArraysInstanced:
      result_.instance_counts.resize(result_.drawcount);
      [[fallthrough]];
    case DrawFunction::DrawArrays:
      result_.firsts.resize(result_.drawcount);
      result_.counts.resize(result_.drawcount);
      break;
    case DrawFunction::DrawElementsInstancedBaseVertexBaseInstance:
      result_.basevertices.resize(result_.drawcount);
      result_.baseinstances.resize(result_.drawcount);
      [[fallthrough]];
    case DrawFunction::DrawElementsInstanced:
      result_.instance_counts.resize(result_.drawcount);
      [[fallthrough]];
    case DrawFunction::DrawElements:
      result_.counts.resize(result_.drawcount);
      switch (index_type_) {
        case IndexStorageType::Offset:
          result_.offsets.resize(result_.drawcount);
          break;
        case IndexStorageType::Pointer:
          result_.indices.resize(result_.drawcount);
          break;
      }
      break;
    default:
      NOTREACHED();
  }
}

bool MultiDrawManager::ValidateDrawcount(GLsizei drawcount) const {
  if (drawcount < 0) {
    return false;
  }
  GLsizei new_offset;
  if (!base::CheckAdd(current_draw_offset_, drawcount)
           .AssignIfValid(&new_offset)) {
    return false;
  }
  if (new_offset > result_.drawcount) {
    return false;
  }
  return true;
}

bool MultiDrawManager::EnsureDrawArraysFunction(DrawFunction draw_function,
                                                GLenum mode,
                                                GLsizei drawcount) {
  if (!ValidateDrawcount(drawcount)) {
    return false;
  }
  bool invalid_draw_state = draw_state_ == DrawState::End;
  bool first_call = draw_state_ == DrawState::Begin;
  bool enums_match = result_.mode == mode;

  if (invalid_draw_state || (!first_call && !enums_match)) {
    return false;
  }
  if (first_call) {
    draw_state_ = DrawState::Draw;
    result_.draw_function = draw_function;
    result_.mode = mode;
    ResizeArrays();
  }
  return true;
}

bool MultiDrawManager::EnsureDrawElementsFunction(DrawFunction draw_function,
                                                  GLenum mode,
                                                  GLenum type,
                                                  GLsizei drawcount) {
  if (!ValidateDrawcount(drawcount)) {
    return false;
  }
  bool invalid_draw_state = draw_state_ == DrawState::End;
  bool first_call = draw_state_ == DrawState::Begin;
  bool enums_match = result_.mode == mode && result_.type == type;

  if (invalid_draw_state || (!first_call && !enums_match)) {
    return false;
  }
  if (first_call) {
    draw_state_ = DrawState::Draw;
    result_.draw_function = draw_function;
    result_.mode = mode;
    result_.type = type;
    ResizeArrays();
  }
  return true;
}

void MultiDrawManager::CopyArraysHelper(GLsizei drawcount,
                                        const GLint* firsts,
                                        const GLsizei* counts,
                                        const GLsizei* offsets,
                                        const GLsizei* instance_counts,
                                        const GLint* basevertices,
                                        const GLuint* baseinstances) {
  if (firsts) {
    std::copy(firsts, UNSAFE_TODO(firsts + drawcount),
              &result_.firsts[current_draw_offset_]);
  }

  if (counts) {
    std::copy(counts, UNSAFE_TODO(counts + drawcount),
              &result_.counts[current_draw_offset_]);
  }

  if (instance_counts) {
    std::copy(instance_counts, UNSAFE_TODO(instance_counts + drawcount),
              &result_.instance_counts[current_draw_offset_]);
  }

  if (basevertices) {
    std::copy(basevertices, UNSAFE_TODO(basevertices + drawcount),
              &result_.basevertices[current_draw_offset_]);
  }

  if (baseinstances) {
    std::copy(baseinstances, UNSAFE_TODO(baseinstances + drawcount),
              &result_.baseinstances[current_draw_offset_]);
  }

  if (offsets) {
    switch (index_type_) {
      case IndexStorageType::Offset:
        std::copy(offsets, UNSAFE_TODO(offsets + drawcount),
                  &result_.offsets[current_draw_offset_]);
        break;
      case IndexStorageType::Pointer:
        std::transform(
            offsets, UNSAFE_TODO(offsets + drawcount),
            &result_.indices[current_draw_offset_], [](uint32_t offset) {
              return reinterpret_cast<void*>(static_cast<intptr_t>(offset));
            });
        break;
    }
  }

  current_draw_offset_ += drawcount;
}

}  // namespace gles2
}  // namespace gpu