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  /**
   * @file FlightTask.hpp
   *
   * Abstract base class for different advanced flight tasks like orbit, follow me, ...
   *
   * @author Matthias Grob <maetugr@gmail.com>
   */
  
  #pragma once
  
  #include <px4_module_params.h>
  #include <drivers/drv_hrt.h>
  #include <matrix/matrix/math.hpp>
  #include <uORB/Subscription.hpp>
  #include <uORB/topics/vehicle_local_position.h>
  #include <uORB/topics/vehicle_local_position_setpoint.h>
  #include <uORB/topics/vehicle_command.h>
  #include <uORB/topics/vehicle_constraints.h>
  #include <uORB/topics/vehicle_attitude.h>
  #include "../SubscriptionArray.hpp"
  
  class FlightTask : public ModuleParams
  {
  public:
  	FlightTask() :
  		ModuleParams(nullptr)
  	{
  		_resetSetpoints();
  		_constraints = empty_constraints;
  	}
  
  	virtual ~FlightTask() = default;
  
  	/**
  	 * Initialize the uORB subscriptions using an array
  	 * @return true on success, false on error
  	 */
  	virtual bool initializeSubscriptions(SubscriptionArray &subscription_array);
  
  	/**
  	 * Call once on the event where you switch to the task
  	 * @return true on success, false on error
  	 */
  	virtual bool activate();
  
  	/**
  	 * To be called to adopt parameters from an arrived vehicle command
  	 * @return true if accepted, false if declined
  	 */
  	virtual bool applyCommandParameters(const vehicle_command_s &command) { return true; };
  
  	/**
  	 * Call before activate() or update()
  	 * to initialize time and input data
  	 * @return true on success, false on error
  	 */
  	virtual bool updateInitialize();
  
  	/**
  	 * To be called regularly in the control loop cycle to execute the task
  	 * @return true on success, false on error
  	 */
  	virtual bool update() = 0;
  
  	/**
  	 * Get the output data
  	 */
  	const vehicle_local_position_setpoint_s getPositionSetpoint();
  
  	/**
  	 * Get vehicle constraints.
  	 * The constraints can vary with task.
  	 * @return constraints
  	 */
  	const vehicle_constraints_s getConstraints() {return _constraints;};
  
  	/**
  	 * Empty setpoint.
  	 * All setpoints are set to NAN.
  	 */
  	static const vehicle_local_position_setpoint_s empty_setpoint;
  
  	/**
  	 * Empty constraints.
  	 * All constraints are set to NAN.
  	 */
  	static const vehicle_constraints_s empty_constraints;
  
  	/**
  	 * Call this whenever a parameter update notification is received (parameter_update uORB message)
  	 */
  	void handleParameterUpdate()
  	{
  		updateParams();
  	}
  
  protected:
  
  	uORB::Subscription<vehicle_local_position_s> *_sub_vehicle_local_position{nullptr};
  	uORB::Subscription<vehicle_attitude_s> *_sub_attitude{nullptr};
  	uint8_t _heading_reset_counter{0}; /**< estimator heading reset */
  
  	/**
  	 * Reset all setpoints to NAN
  	 */
  	void _resetSetpoints();
  
  	/*
  	 * Check and update local position
  	 */
  	bool _evaluateVehicleLocalPosition();
  
  	/**
  	 * Set constraints to default values
  	 */
  	virtual void  _setDefaultConstraints();
  
  	/* Time abstraction */
  	static constexpr uint64_t _timeout = 500000; /**< maximal time in us before a loop or data times out */
  	float _time = 0; /**< passed time in seconds since the task was activated */
  	float _deltatime = 0; /**< passed time in seconds since the task was last updated */
  	hrt_abstime _time_stamp_activate = 0; /**< time stamp when task was activated */
  	hrt_abstime _time_stamp_current = 0; /**< time stamp at the beginning of the current task update */
  	hrt_abstime _time_stamp_last = 0; /**< time stamp when task was last updated */
  
  	/* Current vehicle state */
  	matrix::Vector3f _position; /**< current vehicle position */
  	matrix::Vector3f _velocity; /**< current vehicle velocity */
  	float _yaw = 0.f; /**< current vehicle yaw heading */
  	float _dist_to_bottom = 0.0f; /**< current height above ground level */
  
  	/**
  	 * Setpoints which the position controller has to execute.
  	 * Setpoints that are set to NAN are not controlled. Not all setpoints can be set at the same time.
  	 * If more than one type of setpoint is set, then order of control is a as follow: position, velocity,
  	 * acceleration, thrust. The exception is _position_setpoint together with _velocity_setpoint, where the
  	 * _velocity_setpoint is used as feedforward.
  	 * _acceleration_setpoint is currently not supported.
  	 */
  	matrix::Vector3f _position_setpoint;
  	matrix::Vector3f _velocity_setpoint;
  	matrix::Vector3f _acceleration_setpoint;
  	matrix::Vector3f _thrust_setpoint;
  	float _yaw_setpoint;
  	float _yawspeed_setpoint;
  
  	/**
  	 * Vehicle constraints.
  	 * The constraints can vary with tasks.
  	 */
  	vehicle_constraints_s _constraints;
  
  	DEFINE_PARAMETERS_CUSTOM_PARENT(ModuleParams,
  					(ParamFloat<px4::params::MPC_XY_VEL_MAX>) MPC_XY_VEL_MAX,
  					(ParamFloat<px4::params::MPC_Z_VEL_MAX_DN>) MPC_Z_VEL_MAX_DN,
  					(ParamFloat<px4::params::MPC_Z_VEL_MAX_UP>) MPC_Z_VEL_MAX_UP,
  					(ParamFloat<px4::params::MPC_TILTMAX_AIR>) MPC_TILTMAX_AIR
  				       )
  };
  