class PlanningComponent final
    : public cyber::Component<prediction::PredictionObstacles,
             canbus::Chassis, localization::LocalizationEstimate>

bool PlanningComponent::Init() {
  if (FLAGS_open_space_planner_switchable) {
    planning_base_ = std::make_unique<OpenSpacePlanning>();
  } else {
    if (FLAGS_use_navigation_mode) {
      planning_base_ = std::make_unique<NaviPlanning>();
    } else {
      planning_base_ = std::make_unique<StdPlanning>();
    }
  }

/**
* @brief main logic of the planning module,
* runs periodically triggered by timer.
*/
void RunOnce(const LocalView& local_view,
             ADCTrajectory* const trajectory_pb) override;

// /modules/planning/common/planning_gflags.cc

DEFINE_string(planning_config_file,
              "/apollo/modules/planning/conf/planning_config.pb.txt",
              "planning config file");

// modules/planning/conf/planning_config.pb.txt

standard_planning_config {
  planner_type: PUBLIC_ROAD
  planner_type: OPEN_SPACE
  planner_public_road_config {
     scenario_type: LANE_FOLLOW
     scenario_type: SIDE_PASS
     scenario_type: STOP_SIGN_UNPROTECTED
  }
}

std::unique_ptr<Planner> StdPlannerDispatcher::DispatchPlanner() {
  PlanningConfig planning_config;
  apollo::common::util::GetProtoFromFile(FLAGS_planning_config_file,
                                         &planning_config);
  if (FLAGS_open_space_planner_switchable) {
    return planner_factory_.CreateObject(
        planning_config.standard_planning_config().planner_type(1));
  }
  return planner_factory_.CreateObject(
      planning_config.standard_planning_config().planner_type(0));
}

// /modules/planning/common/planning_gflags.cc

DEFINE_bool(open_space_planner_switchable, false,
            "true for std planning being able to switch to open space planner "
            "when close enough to target parking spot");

struct LocalView {
  std::shared_ptr<prediction::PredictionObstacles> prediction_obstacles;
  std::shared_ptr<canbus::Chassis> chassis;
  std::shared_ptr<localization::LocalizationEstimate> localization_estimate;
  std::shared_ptr<perception::TrafficLightDetection> traffic_light;
  std::shared_ptr<routing::RoutingResponse> routing;
  bool is_new_routing = false;
  std::shared_ptr<relative_map::MapMsg> relative_map;
};

Status PublicRoadPlanner::Plan(const TrajectoryPoint& planning_start_point,
                               Frame* frame) {
  DCHECK_NOTNULL(frame);
  scenario_manager_.Update(planning_start_point, *frame); ①
  scenario_ = scenario_manager_.mutable_scenario(); ②
  auto result = scenario_->Process(planning_start_point, frame); ③

  ...
  if (result == scenario::Scenario::STATUS_DONE) {
    scenario_manager_.Update(planning_start_point, *frame); ④
  } else if (result == scenario::Scenario::STATUS_UNKNOWN) {
    return Status(common::PLANNING_ERROR, "scenario returned unknown");
  }
  return Status::OK();
}

// proto/planning_config.proto
message ScenarioConfig {
  
  message StageConfig {
    optional StageType stage_type = 1;
    optional bool enabled = 2 [default = true];
    repeated TaskConfig.TaskType task_type = 3;
    repeated TaskConfig task_config = 4;
  }

  optional ScenarioType scenario_type = 1;
  oneof scenario_config {
    ScenarioLaneFollowConfig lane_follow_config = 2;
    ScenarioSidePassConfig side_pass_config = 3;
    ScenarioStopSignUnprotectedConfig stop_sign_unprotected_config = 4;
    ScenarioTrafficLightProtectedConfig traffic_light_protected_config = 5;
    ScenarioTrafficLightUnprotectedRightTurnConfig traffic_light_unprotected_right_turn_config = 6;
  }

  repeated StageType stage_type = 7;
  repeated StageConfig stage_config = 8;
}

enum ScenarioType {
    LANE_FOLLOW = 0;  // default scenario
    CHANGE_LANE = 1;
    SIDE_PASS = 2;  // go around an object when it blocks the road
    APPROACH = 3;   // approach to an intersection
    STOP_SIGN_PROTECTED = 4;
    STOP_SIGN_UNPROTECTED = 5;
    TRAFFIC_LIGHT_PROTECTED = 6;
    TRAFFIC_LIGHT_UNPROTECTED_LEFT_TURN = 7;
    TRAFFIC_LIGHT_UNPROTECTED_RIGHT_TURN = 8;
}
  
enum StageType {
    NO_STAGE = 0;
    
    LANE_FOLLOW_DEFAULT_STAGE = 1;
    
    STOP_SIGN_UNPROTECTED_PRE_STOP = 100;
    STOP_SIGN_UNPROTECTED_STOP = 101;
    STOP_SIGN_UNPROTECTED_CREEP = 102 ;
    STOP_SIGN_UNPROTECTED_INTERSECTION_CRUISE = 103;
    
    SIDE_PASS_APPROACH_OBSTACLE = 200;
    SIDE_PASS_GENERATE_PATH= 201;
    SIDE_PASS_STOP_ON_WAITPOINT = 202;
    SIDE_PASS_DETECT_SAFETY = 203;
    SIDE_PASS_PASS_OBSTACLE = 204;
    SIDE_PASS_BACKUP = 205;
    
    TRAFFIC_LIGHT_PROTECTED_STOP = 300;
    TRAFFIC_LIGHT_PROTECTED_INTERSECTION_CRUISE = 301;
    
    TRAFFIC_LIGHT_UNPROTECTED_RIGHT_TURN_STOP = 310;
    TRAFFIC_LIGHT_UNPROTECTED_RIGHT_TURN_CREEP = 311 ;
    TRAFFIC_LIGHT_UNPROTECTED_RIGHT_TURN_INTERSECTION_CRUISE = 312;
};

void ScenarioManager::RegisterScenarios() {
  CHECK(Scenario::LoadConfig(FLAGS_scenario_lane_follow_config_file,
                             &config_map_[ScenarioConfig::LANE_FOLLOW]));
  CHECK(Scenario::LoadConfig(FLAGS_scenario_side_pass_config_file,
                             &config_map_[ScenarioConfig::SIDE_PASS]));
  CHECK(Scenario::LoadConfig(
      FLAGS_scenario_stop_sign_unprotected_config_file,
      &config_map_[ScenarioConfig::STOP_SIGN_UNPROTECTED]));
  CHECK(Scenario::LoadConfig(
      FLAGS_scenario_traffic_light_protected_config_file,
      &config_map_[ScenarioConfig::TRAFFIC_LIGHT_PROTECTED]));
  CHECK(Scenario::LoadConfig(
      FLAGS_scenario_traffic_light_unprotected_right_turn_config_file,
      &config_map_[ScenarioConfig::TRAFFIC_LIGHT_UNPROTECTED_RIGHT_TURN]));
}

void ScenarioManager::Update(const common::TrajectoryPoint& ego_point,
                             const Frame& frame) {

Status StdPlanning::InitFrame(const uint32_t sequence_num,
                              const TrajectoryPoint& planning_start_point,
                              const double start_time,
                              const VehicleState& vehicle_state,
                              ADCTrajectory* output_trajectory) {
  frame_.reset(new Frame(sequence_num, local_view_, planning_start_point,
                         start_time, vehicle_state,
                         reference_line_provider_.get(), output_trajectory));
  ...

  std::list<ReferenceLine> reference_lines;
  std::list<hdmap::RouteSegments> segments;
  if (!reference_line_provider_->GetReferenceLines(&reference_lines,
                                                   &segments)) {

bool Frame::CreateReferenceLineInfo(
    const std::list<ReferenceLine> &reference_lines,
    const std::list<hdmap::RouteSegments> &segments) {
  reference_line_info_.clear();
  auto ref_line_iter = reference_lines.begin();
  auto segments_iter = segments.begin();
  while (ref_line_iter != reference_lines.end()) {
    if (segments_iter->StopForDestination()) {
      is_near_destination_ = true;
    }
    reference_line_info_.emplace_back(vehicle_state_, planning_start_point_,
                                      *ref_line_iter, *segments_iter);
    ++ref_line_iter;
    ++segments_iter;
  }
  ...

bool Stage::ExecuteTaskOnReferenceLine(
    const common::TrajectoryPoint& planning_start_point, Frame* frame) {
  for (auto& reference_line_info : *frame->mutable_reference_line_info()) {
    ...
    
    if (reference_line_info.speed_data().empty()) {
      *reference_line_info.mutable_speed_data() =
          SpeedProfileGenerator::GenerateFallbackSpeedProfile();
      reference_line_info.AddCost(kSpeedOptimizationFallbackCost);
      reference_line_info.set_trajectory_type(ADCTrajectory::SPEED_FALLBACK);
    } else {
      reference_line_info.set_trajectory_type(ADCTrajectory::NORMAL);
    }
    DiscretizedTrajectory trajectory;
    if (!reference_line_info.CombinePathAndSpeedProfile(
            planning_start_point.relative_time(),
            planning_start_point.path_point().s(), &trajectory)) {
      AERROR << "Fail to aggregate planning trajectory.";
      return false;
    }
    reference_line_info.SetTrajectory(trajectory);
    reference_line_info.SetDrivable(true);
    return true;
  }
  return true;
}

Status TrafficDecider::Execute(Frame *frame,
                               ReferenceLineInfo *reference_line_info) {
  for (const auto &rule_config : rule_configs_.config()) {
    if (!rule_config.enabled()) { ①
      continue;
    }
    auto rule = s_rule_factory.CreateObject(rule_config.rule_id(), rule_config); ②
    if (!rule) {
      continue;
    }
    rule->ApplyRule(frame, reference_line_info); ③
  }

  BuildPlanningTarget(reference_line_info); ④
  return Status::OK();
}

Status Task::Execute(Frame* frame, ReferenceLineInfo* reference_line_info) {
  frame_ = frame;
  reference_line_info_ = reference_line_info;
  return Status::OK();
}

Stage::Stage(const ScenarioConfig::StageConfig& config) : config_(config) {
  name_ = ScenarioConfig::StageType_Name(config_.stage_type());
  next_stage_ = config_.stage_type();
  std::unordered_map<TaskConfig::TaskType, const TaskConfig*, std::hash<int>>
      config_map;
  for (const auto& task_config : config_.task_config()) {
    config_map[task_config.task_type()] = &task_config;
  }
  for (int i = 0; i < config_.task_type_size(); ++i) {
    auto task_type = config_.task_type(i);
    CHECK(config_map.find(task_type) != config_map.end())
        << "Task: " << TaskConfig::TaskType_Name(task_type)
        << " used but not configured";
    auto ptr = TaskFactory::CreateTask(*config_map[task_type]);
    task_list_.push_back(ptr.get());
    tasks_[task_type] = std::move(ptr);
  }
}

bool Stage::ExecuteTaskOnReferenceLine(
    const common::TrajectoryPoint& planning_start_point, Frame* frame) {
  for (auto& reference_line_info : *frame->mutable_reference_line_info()) {
    ...

    auto ret = common::Status::OK();
    for (auto* task : task_list_) {
      ret = task->Execute(frame, &reference_line_info);
      if (!ret.ok()) {
        AERROR << "Failed to run tasks[" << task->Name()
               << "], Error message: " << ret.error_message();
        break;
      }
    }

    ...
  }
  return true;
}