plugin_mux.h

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#ifndef NAV_2D_UTILS_PLUGIN_MUX_H
#define NAV_2D_UTILS_PLUGIN_MUX_H
 
#include <ros/ros.h>
#include <pluginlib/class_loader.h>
#include <std_msgs/String.h>
#include <nav_2d_msgs/SwitchPlugin.h>
#include <map>
#include <string>
#include <vector>
 
namespace nav_2d_utils
{
template<class T>
class PluginMux
{
public:
  PluginMux(const std::string& plugin_package, const std::string& plugin_class,
            const std::string& parameter_name, const std::string& default_value,
            const std::string& ros_name = "current_plugin", const std::string& switch_service_name = "switch_plugin");
 
  void addPlugin(const std::string& plugin_name, const std::string& plugin_class_name);
 
  bool usePlugin(const std::string& name)
  {
    // If plugin with given name doesn't exist, return false
    if (plugins_.count(name) == 0) return false;
 
    if (switch_callback_)
    {
      switch_callback_(current_plugin_, name);
    }
 
    // Switch Mux
    current_plugin_ = name;
 
    // Update ROS info
    std_msgs::String str_msg;
    str_msg.data = current_plugin_;
    current_plugin_pub_.publish(str_msg);
    private_nh_.setParam(ros_name_, current_plugin_);
 
    return true;
  }
 
  std::string getCurrentPluginName() const
  {
    return current_plugin_;
  }
 
  bool hasPlugin(const std::string& name) const
  {
    return plugins_.find(name) != plugins_.end();
  }
 
  T& getPlugin(const std::string& name)
  {
    if (!hasPlugin(name))
      throw std::invalid_argument("Plugin not found");
    return *plugins_[name];
  }
 
  T& getCurrentPlugin()
  {
    return getPlugin(current_plugin_);
  }
 
  std::vector<std::string> getPluginNames() const
  {
    std::vector<std::string> names;
    for (auto& kv : plugins_)
    {
      names.push_back(kv.first);
    }
    return names;
  }
 
  using SwitchCallback = std::function<void(const std::string&, const std::string&)>;
 
  void setSwitchCallback(SwitchCallback switch_callback) { switch_callback_ = switch_callback; }
 
protected:
  bool switchPluginService(nav_2d_msgs::SwitchPlugin::Request &req, nav_2d_msgs::SwitchPlugin::Response &resp)
  {
    std::string name = req.new_plugin;
    if (usePlugin(name))
    {
      resp.success = true;
      resp.message = "Loaded plugin namespace " + name + ".";
    }
    else
    {
      resp.success = false;
      resp.message = "Namespace " + name + " not configured!";
    }
    return true;
  }
 
  // Plugin Management
  pluginlib::ClassLoader<T> plugin_loader_;
  std::map<std::string, boost::shared_ptr<T>> plugins_;
  std::string current_plugin_;
 
  // ROS Interface
  ros::ServiceServer switch_plugin_srv_;
  ros::Publisher current_plugin_pub_;
  ros::NodeHandle private_nh_;
  std::string ros_name_;
 
  // Switch Callback
  SwitchCallback switch_callback_;
};
 
// *********************************************************************************************************************
// ****************** Implementation of Templated Methods **************************************************************
// *********************************************************************************************************************
template<class T>
PluginMux<T>::PluginMux(const std::string& plugin_package, const std::string& plugin_class,
                        const std::string& parameter_name, const std::string& default_value,
                        const std::string& ros_name, const std::string& switch_service_name)
  : plugin_loader_(plugin_package, plugin_class), private_nh_("~"), ros_name_(ros_name), switch_callback_(nullptr)
{
  // Create the latched publisher
  current_plugin_pub_ = private_nh_.advertise<std_msgs::String>(ros_name_, 1, true);
 
  // Load Plugins
  std::string plugin_class_name;
  std::vector<std::string> plugin_namespaces;
  private_nh_.getParam(parameter_name, plugin_namespaces);
  if (plugin_namespaces.size() == 0)
  {
    // If no namespaces are listed, use the name of the default class as the singular namespace.
    std::string plugin_name = plugin_loader_.getName(default_value);
    plugin_namespaces.push_back(plugin_name);
  }
 
  for (const std::string& the_namespace : plugin_namespaces)
  {
    // Load the class name from namespace/plugin_class, or use default value
    private_nh_.param(std::string(the_namespace + "/plugin_class"), plugin_class_name, default_value);
    addPlugin(the_namespace, plugin_class_name);
  }
 
  // By default, use the first one as current
  usePlugin(plugin_namespaces[0]);
 
  // Now that the plugins are created, advertise the service if there are multiple
  if (plugin_namespaces.size() > 1)
  {
    switch_plugin_srv_ = private_nh_.advertiseService(switch_service_name, &PluginMux::switchPluginService, this);
  }
}
 
template<class T>
void PluginMux<T>::addPlugin(const std::string& plugin_name, const std::string& plugin_class_name)
{
  try
  {
    plugins_[plugin_name] = plugin_loader_.createInstance(plugin_class_name);
  }
  catch (const pluginlib::PluginlibException& ex)
  {
    ROS_FATAL_NAMED("PluginMux",
                    "Failed to load the plugin: %s. Exception: %s", plugin_name.c_str(), ex.what());
    exit(EXIT_FAILURE);
  }
}
 
}  // namespace nav_2d_utils
 
#endif  // NAV_2D_UTILS_PLUGIN_MUX_H