text: /*
   * Copyright (C) 2018 Open Source Robotics Foundation
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   *
   */
  #ifndef IGNITION_GAZEBO_SYSTEMS_DIFFDRIVE_HH_
  #define IGNITION_GAZEBO_SYSTEMS_DIFFDRIVE_HH_
  
  #include <memory>
  
  #include <ignition/gazebo/System.hh>
  
  namespace ignition
  {
  namespace gazebo
  {
  // Inline bracket to help doxygen filtering.
  inline namespace IGNITION_GAZEBO_VERSION_NAMESPACE {
  namespace systems
  {
    // Forward declaration
    class DiffDrivePrivate;
  
    /// \brief Differential drive controller which can be attached to a model
    /// with any number of left and right wheels.
    ///
    /// # System Parameters
    ///
    /// `<left_joint>`: Name of a joint that controls a left wheel. This
    /// element can appear multiple times, and must appear at least once.
    ///
    /// `<right_joint>`: Name of a joint that controls a right wheel. This
    /// element can appear multiple times, and must appear at least once.
    ///
    /// `<wheel_separation>`: Distance between wheels, in meters. This element
    /// is optional, although it is recommended to be included with an
    /// appropriate value. The default value is 1.0m.
    ///
    /// `<wheel_radius>`: Wheel radius in meters. This element is optional,
    /// although it is recommended to be included with an appropriate value. The
    /// default value is 0.2m.
    ///
    /// `<odom_publish_frequency>`: Odometry publication frequency. This
    /// element is optional, and the default value is 50Hz.
    ///
    /// `<topic>`: Custom topic that this system will subscribe to in order to
    /// receive command velocity messages. This element if optional, and the
    /// default value is `/model/{name_of_model}/cmd_vel`.
    ///
    /// `<odom_topic>`: Custom topic on which this system will publish odometry
    /// messages. This element if optional, and the default value is
    /// `/model/{name_of_model}/odometry`.
    ///
    /// `<tf_topic>`: Custom topic on which this system will publish the
    /// transform from `frame_id` to `child_frame_id`. This element if optional,
    ///  and the default value is `/model/{name_of_model}/tf`.
    ///
    /// `<frame_id>`: Custom `frame_id` field that this system will use as the
    /// origin of the odometry transform in both the `<tf_topic>`
    /// `ignition.msgs.Pose_V` message and the `<odom_topic>`
    /// `ignition.msgs.Odometry` message. This element if optional, and the
    /// default value is `{name_of_model}/odom`.
    ///
    /// `<child_frame_id>`: Custom `child_frame_id` that this system will use as
    /// the target of the odometry trasnform in both the `<tf_topic>`
    /// `ignition.msgs.Pose_V` message and the `<odom_topic>`
    /// `ignition.msgs.Odometry` message. This element if optional,
    ///  and the default value is `{name_of_model}/{name_of_link}`.
    class IGNITION_GAZEBO_VISIBLE DiffDrive
        : public System,
          public ISystemConfigure,
          public ISystemPreUpdate,
          public ISystemPostUpdate
    {
      /// \brief Constructor
      public: DiffDrive();
  
      /// \brief Destructor
      public: ~DiffDrive() override = default;
  
      // Documentation inherited
      public: void Configure(const Entity &_entity,
                             const std::shared_ptr<const sdf::Element> &_sdf,
                             EntityComponentManager &_ecm,
                             EventManager &_eventMgr) override;
  
      // Documentation inherited
      public: void PreUpdate(
                  const ignition::gazebo::UpdateInfo &_info,
                  ignition::gazebo::EntityComponentManager &_ecm) override;
  
      // Documentation inherited
      public: void PostUpdate(
                  const UpdateInfo &_info,
                  const EntityComponentManager &_ecm) override;
  
      /// \brief Private data pointer
      private: std::unique_ptr<DiffDrivePrivate> dataPtr;
    };
    }
  }
  }
  }
  
  #endif
  