// Copyright 2023 Dolphin Emulator Project
// SPDX-License-Identifier: GPL-2.0-or-later

#include "VideoCommon/Widescreen.h"

#include "Common/ChunkFile.h"
#include "Core/Config/SYSCONFSettings.h"
#include "Core/ConfigManager.h"

#include "VideoCommon/VertexManagerBase.h"

std::unique_ptr<WidescreenManager> g_widescreen;

WidescreenManager::WidescreenManager()
{
  Update();

  m_config_changed = ConfigChangedEvent::Register(
      [this](u32 bits) {
        if (bits & (CONFIG_CHANGE_BIT_ASPECT_RATIO))
          Update();
      },
      "Widescreen");

  // VertexManager doesn't maintain statistics in Wii mode.
  if (!SConfig::GetInstance().bWii)
  {
    m_update_widescreen =
        AfterFrameEvent::Register([this] { UpdateWidescreenHeuristic(); }, "WideScreen Heuristic");
  }
}

void WidescreenManager::Update()
{
  if (SConfig::GetInstance().bWii)
    m_is_game_widescreen = Config::Get(Config::SYSCONF_WIDESCREEN);

  // suggested_aspect_mode overrides SYSCONF_WIDESCREEN
  if (g_ActiveConfig.suggested_aspect_mode == AspectMode::Analog)
    m_is_game_widescreen = false;
  else if (g_ActiveConfig.suggested_aspect_mode == AspectMode::AnalogWide)
    m_is_game_widescreen = true;

  // If widescreen hack is disabled override game's AR if UI is set to 4:3 or 16:9.
  if (!g_ActiveConfig.bWidescreenHack)
  {
    const auto aspect_mode = g_ActiveConfig.aspect_mode;
    if (aspect_mode == AspectMode::Analog)
      m_is_game_widescreen = false;
    else if (aspect_mode == AspectMode::AnalogWide)
      m_is_game_widescreen = true;
  }
}

// Heuristic to detect if a GameCube game is in 16:9 anamorphic widescreen mode.
void WidescreenManager::UpdateWidescreenHeuristic()
{
  const auto flush_statistics = g_vertex_manager->ResetFlushAspectRatioCount();

  // If suggested_aspect_mode (GameINI) is configured don't use heuristic.
  if (g_ActiveConfig.suggested_aspect_mode != AspectMode::Auto)
    return;

  Update();

  // If widescreen hack isn't active and aspect_mode (UI) is 4:3 or 16:9 don't use heuristic.
  if (!g_ActiveConfig.bWidescreenHack && (g_ActiveConfig.aspect_mode == AspectMode::Analog ||
                                          g_ActiveConfig.aspect_mode == AspectMode::AnalogWide))
    return;

  // Modify the threshold based on which aspect ratio we're already using:
  // If the game's in 4:3, it probably won't switch to anamorphic, and vice-versa.
  static constexpr u32 TRANSITION_THRESHOLD = 3;

  const auto looks_normal = [](auto& counts) {
    return counts.normal_vertex_count > counts.anamorphic_vertex_count * TRANSITION_THRESHOLD;
  };
  const auto looks_anamorphic = [](auto& counts) {
    return counts.anamorphic_vertex_count > counts.normal_vertex_count * TRANSITION_THRESHOLD;
  };

  const auto& persp = flush_statistics.perspective;
  const auto& ortho = flush_statistics.orthographic;

  const auto ortho_looks_anamorphic = looks_anamorphic(ortho);

  if (looks_anamorphic(persp) || ortho_looks_anamorphic)
  {
    // If either perspective or orthographic projections look anamorphic, it's a safe bet.
    m_is_game_widescreen = true;
  }
  else if (looks_normal(persp) || (m_was_orthographically_anamorphic && looks_normal(ortho)))
  {
    // Many widescreen games (or AR/GeckoCodes) use anamorphic perspective projections
    // with NON-anamorphic orthographic projections.
    // This can cause incorrect changes to 4:3 when perspective projections are temporarily not
    // shown. e.g. Animal Crossing's inventory menu.
    // Unless we were in a situation which was orthographically anamorphic
    // we won't consider orthographic data for changes from 16:9 to 4:3.
    m_is_game_widescreen = false;
  }

  m_was_orthographically_anamorphic = ortho_looks_anamorphic;
}

void WidescreenManager::DoState(PointerWrap& p)
{
  p.Do(m_is_game_widescreen);

  if (p.IsReadMode())
  {
    m_was_orthographically_anamorphic = false;
  }
}