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#ifndef ROSCPP_CALLBACK_QUEUE_H
#define ROSCPP_CALLBACK_QUEUE_H

#include "ros/callback_queue_interface.h"
#include "ros/time.h"

#include <boost/shared_ptr.hpp>
#include <boost/thread/mutex.hpp>
#include <boost/thread/shared_mutex.hpp>
#include <boost/thread/condition_variable.hpp>
#include <boost/thread/tss.hpp>

#include <list>
#include <deque>

namespace ros
{

/**
 * \brief This is the default implementation of the ros::CallbackQueueInterface
 */
class CallbackQueue : public CallbackQueueInterface
{
public:
  CallbackQueue(bool enabled = true);
  virtual ~CallbackQueue();

  virtual void addCallback(const CallbackInterfacePtr& callback, uint64_t removal_id = 0);
  virtual void removeByID(uint64_t removal_id);

  enum CallOneResult
  {
    Called,
    TryAgain,
    Disabled,
    Empty,
  };

  /**
   * \brief Pop a single callback off the front of the queue and invoke it.  If the callback was not ready to be called,
   * pushes it back onto the queue.
   */
  CallOneResult callOne()
  {
    return callOne(ros::WallDuration());
  }

  /**
   * \brief Pop a single callback off the front of the queue and invoke it.  If the callback was not ready to be called,
   * pushes it back onto the queue.  This version includes a timeout which lets you specify the amount of time to wait for
   * a callback to be available before returning.
   *
   * \param timeout The amount of time to wait for a callback to be available.  If there is already a callback available,
   * this parameter does nothing.
   */
  CallOneResult callOne(ros::WallDuration timeout);

  /**
   * \brief Invoke all callbacks currently in the queue.  If a callback was not ready to be called, pushes it back onto the queue.
   */
  void callAvailable()
  {
    callAvailable(ros::WallDuration());
  }
  /**
   * \brief Invoke all callbacks currently in the queue.  If a callback was not ready to be called, pushes it back onto the queue.  This version
   * includes a timeout which lets you specify the amount of time to wait for a callback to be available before returning.
   *
   * \param timeout The amount of time to wait for at least one callback to be available.  If there is already at least one callback available,
   * this parameter does nothing.
   */
  void callAvailable(ros::WallDuration timeout);

  /**
   * \brief returns whether or not the queue is empty
   */
  bool empty() { return isEmpty(); }
  /**
   * \brief returns whether or not the queue is empty
   */
  bool isEmpty();
  /**
   * \brief Removes all callbacks from the queue.  Does \b not wait for calls currently in progress to finish.
   */
  void clear();

  /**
   * \brief Enable the queue (queue is enabled by default)
   */
  void enable();
  /**
   * \brief Disable the queue, meaning any calls to addCallback() will have no effect
   */
  void disable();
  /**
   * \brief Returns whether or not this queue is enabled
   */
  bool isEnabled();

protected:
  void setupTLS();

  struct TLS;
  CallOneResult callOneCB(TLS* tls);

  struct IDInfo
  {
    uint64_t id;
    boost::shared_mutex calling_rw_mutex;
  };
  typedef boost::shared_ptr<IDInfo> IDInfoPtr;
  typedef std::map<uint64_t, IDInfoPtr> M_IDInfo;

  IDInfoPtr getIDInfo(uint64_t id);

  struct CallbackInfo
  {
    CallbackInfo()
    : removal_id(0)
    , marked_for_removal(false)
    {}
    CallbackInterfacePtr callback;
    uint64_t removal_id;
    bool marked_for_removal;
  };
  typedef std::list<CallbackInfo> L_CallbackInfo;
  typedef std::deque<CallbackInfo> D_CallbackInfo;
  D_CallbackInfo callbacks_;
  size_t calling_;
  boost::mutex mutex_;
  boost::condition_variable condition_;

  boost::mutex id_info_mutex_;
  M_IDInfo id_info_;

  struct TLS
  {
    TLS()
    : calling_in_this_thread(0xffffffffffffffffULL)
    , cb_it(callbacks.end())
    {}
    uint64_t calling_in_this_thread;
    D_CallbackInfo callbacks;
    D_CallbackInfo::iterator cb_it;
  };
  boost::thread_specific_ptr<TLS> tls_;

  bool enabled_;
};
typedef boost::shared_ptr<CallbackQueue> CallbackQueuePtr;

}

#endif
