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/**
 * @file precland.h
 *
 * Helper class to do precision landing with a landing target
 *
 * @author Nicolas de Palezieux (Sunflower Labs) <ndepal@gmail.com>
 */

#pragma once

#include <matrix/math.hpp>
#include <lib/ecl/geo/geo.h>
#include <px4_platform_common/module_params.h>
#include <uORB/Subscription.hpp>
#include <uORB/topics/landing_target_pose.h>

#include "navigator_mode.h"
#include "mission_block.h"

enum class PrecLandState {
	Start, // Starting state
	HorizontalApproach, // Positioning over landing target while maintaining altitude
	DescendAboveTarget, // Stay over landing target while descending
	FinalApproach, // Final landing approach, even without landing target
	Search, // Search for landing target
	Fallback, // Fallback landing method
	Done // Done landing
};

enum class PrecLandMode {
	Opportunistic = 1, // only do precision landing if landing target visible at the beginning
	Required = 2 // try to find landing target if not visible at the beginning
};

class PrecLand : public MissionBlock, public ModuleParams
{
public:
	PrecLand(Navigator *navigator);
	~PrecLand() override = default;

	void on_activation() override;
	void on_active() override;
	void on_inactivation() override;

	void set_mode(PrecLandMode mode) { _mode = mode; };

	PrecLandMode get_mode() { return _mode; };

	bool is_activated() { return _is_activated; };

private:

	void updateParams() override;

	// run the control loop for each state
	void run_state_start();
	void run_state_horizontal_approach();
	void run_state_descend_above_target();
	void run_state_final_approach();
	void run_state_search();
	void run_state_fallback();

	// attempt to switch to a different state. Returns true if state change was successful, false otherwise
	bool switch_to_state_start();
	bool switch_to_state_horizontal_approach();
	bool switch_to_state_descend_above_target();
	bool switch_to_state_final_approach();
	bool switch_to_state_search();
	bool switch_to_state_fallback();
	bool switch_to_state_done();

	// check if a given state could be changed into. Return true if possible to transition to state, false otherwise
	bool check_state_conditions(PrecLandState state);
	void slewrate(float &sp_x, float &sp_y);

	landing_target_pose_s _target_pose{}; /**< precision landing target position */

	uORB::Subscription _target_pose_sub{ORB_ID(landing_target_pose)};
	bool _target_pose_valid{false}; /**< whether we have received a landing target position message */
	bool _target_pose_updated{false}; /**< wether the landing target position message is updated */

	struct map_projection_reference_s _map_ref {}; /**< reference for local/global projections */

	uint64_t _state_start_time{0}; /**< time when we entered current state */
	uint64_t _last_slewrate_time{0}; /**< time when we last limited setpoint changes */
	uint64_t _target_acquired_time{0}; /**< time when we first saw the landing target during search */
	uint64_t _point_reached_time{0}; /**< time when we reached a setpoint */

	int _search_cnt{0}; /**< counter of how many times we had to search for the landing target */
	float _approach_alt{0.0f}; /**< altitude at which to stay during horizontal approach */

	matrix::Vector2f _sp_pev;
	matrix::Vector2f _sp_pev_prev;

	PrecLandState _state{PrecLandState::Start};

	PrecLandMode _mode{PrecLandMode::Opportunistic};

	bool _is_activated {false}; /**< indicates if precland is activated */

	DEFINE_PARAMETERS(
		(ParamFloat<px4::params::PLD_BTOUT>) _param_pld_btout,
		(ParamFloat<px4::params::PLD_HACC_RAD>) _param_pld_hacc_rad,
		(ParamFloat<px4::params::PLD_FAPPR_ALT>) _param_pld_fappr_alt,
		(ParamFloat<px4::params::PLD_SRCH_ALT>) _param_pld_srch_alt,
		(ParamFloat<px4::params::PLD_SRCH_TOUT>) _param_pld_srch_tout,
		(ParamInt<px4::params::PLD_MAX_SRCH>) _param_pld_max_srch
	)

	// non-navigator parameters
	param_t	_handle_param_acceleration_hor{PARAM_INVALID};
	param_t	_handle_param_xy_vel_cruise{PARAM_INVALID};
	float	_param_acceleration_hor{0.0f};
	float	_param_xy_vel_cruise{0.0f};

};