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/**
 * @file rtl_direct.cpp
 *
 * Helper class to access RTL
 *
 * @author Julian Oes <julian@oes.ch>
 * @author Anton Babushkin <anton.babushkin@me.com>
 * @author Julian Kent <julian@auterion.com>
 */

#include <float.h>

#include "rtl_direct.h"
#include "navigator.h"
#include <px4_platform_common/events.h>

#include <lib/geo/geo.h>

using namespace math;

RtlDirect::RtlDirect(Navigator *navigator) :
	MissionBlock(navigator, vehicle_status_s::NAVIGATION_STATE_AUTO_RTL),
	ModuleParams(navigator)
{
	_destination.lat = static_cast<double>(NAN);
	_destination.lon = static_cast<double>(NAN);
	_land_approach.lat = static_cast<double>(NAN);
	_land_approach.lon = static_cast<double>(NAN);
	_land_approach.height_m = NAN;
}

void RtlDirect::on_inactivation()
{
	if (_navigator->get_precland()->is_activated()) {
		_navigator->get_precland()->on_inactivation();
	}

	_rtl_state = RTLState::IDLE;
}

void RtlDirect::on_activation()
{
	_global_pos_sub.update();
	_vehicle_status_sub.update();

	parameters_update();

	if (_vehicle_status_sub.get().vehicle_type == vehicle_status_s::VEHICLE_TYPE_ROVER) {
		_rtl_state = RTLState::LAND;

	} else {
		_rtl_state = getActivationLandState();
	}

	// reset cruising speed and throttle to default for RTL
	_navigator->reset_cruising_speed();
	_navigator->set_cruising_throttle();

	set_rtl_item();

	mavlink_log_info(_navigator->get_mavlink_log_pub(), "RTL: start return at %d m (%d m above destination)\t",
			 (int)ceilf(_rtl_alt), (int)ceilf(_rtl_alt - _destination.alt));
	events::send<int32_t, int32_t>(events::ID("vrtl_return_at"), events::Log::Info,
				       "RTL: start return at {1m_v} ({2m_v} above destination)",
				       (int32_t)ceilf(_rtl_alt), (int32_t)ceilf(_rtl_alt - _destination.alt));
}

void RtlDirect::on_active()
{
	_global_pos_sub.update();
	_vehicle_status_sub.update();

	parameters_update();

	if (_rtl_state != RTLState::IDLE && is_mission_item_reached_or_completed()) {
		_updateRtlState();
		set_rtl_item();
	}

	if (_rtl_state != RTLState::IDLE && _rtl_state != RTLState::LAND) {
		//check for terrain collision and update altitude if needed
		// note: it may trigger multiple times during a RTL, as every time the altitude set is reset
		updateAltToAvoidTerrainCollisionAndRepublishTriplet(_mission_item);
	}

	if (_rtl_state == RTLState::LAND && _mission_item.land_precision > 0) {
		// Need to update the position and type on the current setpoint triplet.
		_navigator->get_precland()->on_active();

	} else if (_navigator->get_precland()->is_activated()) {
		_navigator->get_precland()->on_inactivation();
	}
}

void RtlDirect::on_inactive()
{
	_global_pos_sub.update();
	_vehicle_status_sub.update();
}

void RtlDirect::setRtlPosition(PositionYawSetpoint rtl_position, loiter_point_s loiter_pos)
{
	_home_pos_sub.update();

	parameters_update();

	// Only allow to set a new approach if the mode is not activated yet.
	if (!isActive()) {
		_destination = rtl_position;
		_force_heading = false;

		// Input sanitation
		if (!PX4_ISFINITE(_destination.lat) || !PX4_ISFINITE(_destination.lon)) {
			// We don't have a valid rtl position, use the home position instead.
			_destination.lat = _home_pos_sub.get().lat;
			_destination.lon = _home_pos_sub.get().lon;
			_destination.alt = _home_pos_sub.get().alt;
			_destination.yaw = _home_pos_sub.get().yaw;
		}

		if (!PX4_ISFINITE(_destination.alt)) {
			// Not a valid rtl land altitude. Assume same altitude as home position.
			_destination.alt = _home_pos_sub.get().alt;
		}

		_land_approach = sanitizeLandApproach(loiter_pos);

		const float dist_to_destination{get_distance_to_next_waypoint(_land_approach.lat, _land_approach.lon, _destination.lat, _destination.lon)};

		if (dist_to_destination > _navigator->get_acceptance_radius()) {
			_force_heading = true;
		}
	}
}

void RtlDirect::_updateRtlState()
{
	// RTL_LAND_DELAY > 0 -> wait seconds, < 0 wait indefinitely
	const bool wait_at_rtl_descend_alt = fabsf(_param_rtl_land_delay.get()) > FLT_EPSILON;
	const bool is_multicopter = (_vehicle_status_sub.get().vehicle_type == vehicle_status_s::VEHICLE_TYPE_ROTARY_WING);

	RTLState new_state{RTLState::IDLE};

	switch (_rtl_state) {
	case RTLState::CLIMBING:
		new_state = RTLState::MOVE_TO_LOITER;
		break;

	case RTLState::MOVE_TO_LOITER:
		if (!is_multicopter || wait_at_rtl_descend_alt) {
			new_state = RTLState::LOITER_DOWN;

		} else {
			new_state = RTLState::LAND;
		}

		break;

	case RTLState::LOITER_DOWN:
		new_state = RTLState::LOITER_HOLD;
		break;

	case RTLState::LOITER_HOLD:
		if (_vehicle_status_sub.get().is_vtol
		    && _vehicle_status_sub.get().vehicle_type == vehicle_status_s::VEHICLE_TYPE_FIXED_WING) {
			new_state = RTLState::MOVE_TO_LAND;

		} else {
			new_state = RTLState::MOVE_TO_LAND_HOVER;
		}

		break;

	case RTLState::MOVE_TO_LAND:
		new_state = RTLState::TRANSITION_TO_MC;
		break;

	case RTLState::TRANSITION_TO_MC:
		new_state = RTLState::MOVE_TO_LAND_HOVER;
		break;

	case RTLState::MOVE_TO_LAND_HOVER:
		new_state = RTLState::LAND;
		break;

	case RTLState::LAND:
		new_state = RTLState::IDLE;
		break;

	case RTLState::IDLE: // Fallthrough
	default:
		new_state = RTLState::IDLE;
		break;
	}

	_rtl_state = new_state;
}


void RtlDirect::set_rtl_item()
{
	position_setpoint_triplet_s *pos_sp_triplet = _navigator->get_position_setpoint_triplet();

	const float destination_dist = get_distance_to_next_waypoint(_destination.lat, _destination.lon,
				       _global_pos_sub.get().lat, _global_pos_sub.get().lon);
	const float loiter_altitude = math::min(_land_approach.height_m, _rtl_alt);

	const bool is_close_to_destination = destination_dist < _param_rtl_min_dist.get();

	float altitude_acceptance_radius = static_cast<float>(NAN);

	switch (_rtl_state) {
	case RTLState::CLIMBING: {
			PositionYawSetpoint pos_yaw_sp {
				.lat = _global_pos_sub.get().lat,
				.lon = _global_pos_sub.get().lon,
				.alt = _rtl_alt,
				.yaw = _param_wv_en.get() ? NAN : _navigator->get_local_position()->heading,
			};
			setLoiterToAltMissionItem(_mission_item, pos_yaw_sp, _navigator->get_loiter_radius());

			break;
		}

	case RTLState::MOVE_TO_LOITER: {
			PositionYawSetpoint pos_yaw_sp {
				.lat = _land_approach.lat,
				.lon = _land_approach.lon,
				.alt = _rtl_alt,
			};

			// For FW flight:set to LOITER_TIME (with 0s loiter time), such that the loiter (orbit) status
			// can be displayed on groundstation and the WP is accepted once within loiter radius
			if (_vehicle_status_sub.get().vehicle_type == vehicle_status_s::VEHICLE_TYPE_FIXED_WING) {
				pos_yaw_sp.yaw = NAN;
				setLoiterHoldMissionItem(_mission_item, pos_yaw_sp, 0.f, _land_approach.loiter_radius_m);

			} else {
				// already set final yaw if close to destination and weather vane is disabled
				pos_yaw_sp.yaw = (is_close_to_destination && !_param_wv_en.get()) ? _destination.yaw : NAN;
				setMoveToPositionMissionItem(_mission_item, pos_yaw_sp);
			}

			break;
		}

	case RTLState::LOITER_DOWN: {
			PositionYawSetpoint pos_yaw_sp{
				.lat = _land_approach.lat,
				.lon = _land_approach.lon,
				.alt = loiter_altitude,
				.yaw = !_param_wv_en.get() ? _destination.yaw : NAN, // set final yaw if weather vane is disabled
			};

			setLoiterToAltMissionItem(_mission_item, pos_yaw_sp, _land_approach.loiter_radius_m);

			pos_sp_triplet->next.valid = true;
			pos_sp_triplet->next.lat = _destination.lat;
			pos_sp_triplet->next.lon = _destination.lon;
			pos_sp_triplet->next.type = position_setpoint_s::SETPOINT_TYPE_LAND;

			if (_force_heading) {
				_mission_item.force_heading = true;
			}

			// Disable previous setpoint to prevent drift.
			pos_sp_triplet->previous.valid = false;

			break;
		}

	case RTLState::LOITER_HOLD: {
			PositionYawSetpoint pos_yaw_sp {
				.lat = _land_approach.lat,
				.lon = _land_approach.lon,
				.alt = loiter_altitude,
				.yaw = !_param_wv_en.get() ? _destination.yaw : NAN, // set final yaw if weather vane is disabled
			};

			setLoiterHoldMissionItem(_mission_item, pos_yaw_sp, _param_rtl_land_delay.get(), _land_approach.loiter_radius_m);

			if (_param_rtl_land_delay.get() < -FLT_EPSILON) {
				mavlink_log_info(_navigator->get_mavlink_log_pub(), "RTL: completed, loitering\t");
				events::send(events::ID("rtl_completed_loiter"), events::Log::Info, "RTL: completed, loitering");

			} else {
				/* Set the altitude tracking to best effort but not strictly enforce it */
				altitude_acceptance_radius = FLT_MAX;

				if (_force_heading) {
					_mission_item.force_heading = true;
				}
			}

			break;
		}

	case RTLState::MOVE_TO_LAND: {

			PositionYawSetpoint pos_yaw_sp{_destination};
			pos_yaw_sp.alt = loiter_altitude;
			pos_yaw_sp.yaw = NAN;

			setMoveToPositionMissionItem(_mission_item, pos_yaw_sp);

			// Prepare for transition
			_mission_item.vtol_back_transition = true;
			_mission_item.force_heading = false;

			// set previous item location to loiter location such that vehicle tracks line between loiter
			// location and land location after exiting the loiter circle
			pos_sp_triplet->previous.lat = _land_approach.lat;
			pos_sp_triplet->previous.lon = _land_approach.lon;
			pos_sp_triplet->previous.alt = get_absolute_altitude_for_item(_mission_item);
			pos_sp_triplet->previous.valid = true;

			break;
		}

	case RTLState::TRANSITION_TO_MC: {
			set_vtol_transition_item(&_mission_item, vtol_vehicle_status_s::VEHICLE_VTOL_STATE_MC);

			break;
		}

	case RTLState::MOVE_TO_LAND_HOVER: {
			PositionYawSetpoint pos_yaw_sp{_destination};
			pos_yaw_sp.alt = loiter_altitude;
			pos_yaw_sp.yaw = !_param_wv_en.get() ? _destination.yaw : NAN; // set final yaw if weather vane is disabled

			altitude_acceptance_radius = FLT_MAX;
			setMoveToPositionMissionItem(_mission_item, pos_yaw_sp);
			_navigator->reset_position_setpoint(pos_sp_triplet->previous);

			break;
		}

	case RTLState::LAND: {
			PositionYawSetpoint pos_yaw_sp{_destination};
			pos_yaw_sp.yaw = !_param_wv_en.get() ? _destination.yaw : NAN; // set final yaw if weather vane is disabled
			setLandMissionItem(_mission_item, pos_yaw_sp);

			_mission_item.land_precision = _param_rtl_pld_md.get();

			if (_mission_item.land_precision > 0) {
				startPrecLand(_mission_item.land_precision);
			}

			mavlink_log_info(_navigator->get_mavlink_log_pub(), "RTL: land at destination\t");
			events::send(events::ID("rtl_land_at_destination"), events::Log::Info, "RTL: land at destination");
			break;
		}

	case RTLState::IDLE: {
			set_idle_item(&_mission_item);
			_navigator->mode_completed(getNavigatorStateId());
			break;
		}

	default:
		break;
	}

	reset_mission_item_reached();

	// Execute command if set. This is required for commands like VTOL transition.
	if (!MissionBlock::item_contains_position(_mission_item)) {
		issue_command(_mission_item);

	} else {
		// Convert mission item to current position setpoint and make it valid.
		if (mission_item_to_position_setpoint(_mission_item, &pos_sp_triplet->current)) {
			pos_sp_triplet->current.alt_acceptance_radius = altitude_acceptance_radius;
			_navigator->set_position_setpoint_triplet_updated();
		}
	}

	publish_rtl_direct_navigator_mission_item(); // for logging
}

RtlDirect::RTLState RtlDirect::getActivationLandState()
{
	_land_detected_sub.update();

	RTLState land_state;

	if (_land_detected_sub.get().landed) {
		// For safety reasons don't go into RTL if landed.
		land_state = RTLState::IDLE;

	} else if ((_global_pos_sub.get().alt < _rtl_alt) || _enforce_rtl_alt) {
		land_state = RTLState::CLIMBING;

	} else {
		land_state = RTLState::MOVE_TO_LOITER;
	}

	return land_state;
}

rtl_time_estimate_s RtlDirect::calc_rtl_time_estimate()
{
	_global_pos_sub.update();
	_rtl_time_estimator.update();
	_rtl_time_estimator.setVehicleType(_vehicle_status_sub.get().vehicle_type);
	_rtl_time_estimator.reset();

	RTLState start_state_for_estimate;

	if (isActive()) {
		start_state_for_estimate = _rtl_state;

	} else {
		start_state_for_estimate = getActivationLandState();
	}

	// Calculate RTL time estimate only when there is a valid destination
	// TODO: Also check if vehicle position is valid
	if (PX4_ISFINITE(_destination.lat) && PX4_ISFINITE(_destination.lon) && PX4_ISFINITE(_destination.alt)) {

		loiter_point_s land_approach = sanitizeLandApproach(_land_approach);

		const float loiter_altitude = min(land_approach.height_m, _rtl_alt);

		// Sum up time estimate for various segments of the landing procedure
		switch (start_state_for_estimate) {
		case RTLState::CLIMBING: {
				// Climb segment is only relevant if the drone is below return altitude
				if ((_global_pos_sub.get().alt < _rtl_alt) || _enforce_rtl_alt) {
					_rtl_time_estimator.addVertDistance(_rtl_alt - _global_pos_sub.get().alt);
				}
			}

		// FALLTHROUGH
		case RTLState::MOVE_TO_LOITER: {
				matrix::Vector2f direction{};
				get_vector_to_next_waypoint(_global_pos_sub.get().lat, _global_pos_sub.get().lon, land_approach.lat,
							    land_approach.lon, &direction(0), &direction(1));
				float move_to_land_dist{get_distance_to_next_waypoint(_global_pos_sub.get().lat, _global_pos_sub.get().lon, land_approach.lat, land_approach.lon)};

				if (_vehicle_status_sub.get().vehicle_type == vehicle_status_s::VEHICLE_TYPE_FIXED_WING) {
					move_to_land_dist = max(0.f, move_to_land_dist - land_approach.loiter_radius_m);
				}

				_rtl_time_estimator.addDistance(move_to_land_dist, direction, 0.f);
			}

		// FALLTHROUGH
		case RTLState::LOITER_DOWN: {
				// when descending, the target altitude is stored in the current mission item
				float initial_altitude = 0.f;

				if (start_state_for_estimate == RTLState::LOITER_DOWN) {
					// Take current vehicle altitude as the starting point for calculation
					initial_altitude = _global_pos_sub.get().alt;  // TODO: Check if this is in the right frame

				} else {
					// Take the return altitude as the starting point for the calculation
					initial_altitude = _rtl_alt; // CLIMB and RETURN
				}

				_rtl_time_estimator.addVertDistance(loiter_altitude - initial_altitude);
			}

		// FALLTHROUGH
		case RTLState::LOITER_HOLD:
			// Add land delay (the short pause for deploying landing gear)
			_rtl_time_estimator.addWait(_param_rtl_land_delay.get());

			if (_param_rtl_land_delay.get() < -FLT_EPSILON) { // Set to loiter infinitely and not land. Stop calculation here
				break;
			}


		// FALLTHROUGH
		case RTLState::MOVE_TO_LAND:
		case RTLState::TRANSITION_TO_MC:
		case RTLState::MOVE_TO_LAND_HOVER: {
				// Add cruise segment to home
				float move_to_land_dist{0.f};
				matrix::Vector2f direction{};

				if (start_state_for_estimate >= RTLState::MOVE_TO_LAND) {
					move_to_land_dist = get_distance_to_next_waypoint(
								    _global_pos_sub.get().lat, _global_pos_sub.get().lon, _destination.lat, _destination.lon);
					get_vector_to_next_waypoint(_global_pos_sub.get().lat, _global_pos_sub.get().lon, _destination.lat, _destination.lon,
								    &direction(0), &direction(1));

				} else {
					move_to_land_dist = get_distance_to_next_waypoint(
								    land_approach.lat, land_approach.lon, _destination.lat, _destination.lon);
					get_vector_to_next_waypoint(land_approach.lat, land_approach.lon, _destination.lat, _destination.lon, &direction(0),
								    &direction(1));
				}

				_rtl_time_estimator.addDistance(move_to_land_dist, direction, 0.f);
			}

		// FALLTHROUGH
		case RTLState::LAND: {
				float initial_altitude;

				// Add land segment (second landing phase) which comes after LOITER
				if (start_state_for_estimate == RTLState::LAND) {
					// If we are in this phase, use the current vehicle altitude  instead
					// of the altitude paramteter to get a continous time estimate
					initial_altitude = _global_pos_sub.get().alt;


				} else {
					// If this phase is not active yet, simply use the loiter altitude,
					// which is where the LAND phase will start
					initial_altitude = loiter_altitude;
				}

				if (_vehicle_status_sub.get().is_vtol) {
					_rtl_time_estimator.setVehicleType(vehicle_status_s::VEHICLE_TYPE_ROTARY_WING);
				}

				_rtl_time_estimator.addVertDistance(_destination.alt - initial_altitude);
			}

			break;

		case RTLState::IDLE:
			// Remaining time is 0
			break;
		}
	}

	return _rtl_time_estimator.getEstimate();
}

void RtlDirect::parameters_update()
{
	if (_parameter_update_sub.updated()) {
		parameter_update_s param_update;
		_parameter_update_sub.copy(&param_update);

		// If any parameter updated, call updateParams() to check if
		// this class attributes need updating (and do so).
		updateParams();
	}
}

loiter_point_s RtlDirect::sanitizeLandApproach(loiter_point_s land_approach) const
{
	loiter_point_s sanitized_land_approach{land_approach};

	if (!PX4_ISFINITE(land_approach.lat) || !PX4_ISFINITE(land_approach.lon)) {
		sanitized_land_approach.lat = _destination.lat;
		sanitized_land_approach.lon = _destination.lon;
	}

	if (!PX4_ISFINITE(land_approach.height_m)) {
		sanitized_land_approach.height_m = _destination.alt + _param_rtl_descend_alt.get();
	}

	if (!PX4_ISFINITE(land_approach.loiter_radius_m) || fabsf(land_approach.loiter_radius_m) <= FLT_EPSILON) {
		sanitized_land_approach.loiter_radius_m = _param_rtl_loiter_rad.get();
	}

	return sanitized_land_approach;
}

void RtlDirect::publish_rtl_direct_navigator_mission_item()
{
	navigator_mission_item_s navigator_mission_item{};

	navigator_mission_item.sequence_current = static_cast<uint16_t>(_rtl_state);
	navigator_mission_item.nav_cmd = _mission_item.nav_cmd;
	navigator_mission_item.latitude = _mission_item.lat;
	navigator_mission_item.longitude = _mission_item.lon;
	navigator_mission_item.altitude = _mission_item.altitude;

	navigator_mission_item.time_inside = get_time_inside(_mission_item);
	navigator_mission_item.acceptance_radius = _mission_item.acceptance_radius;
	navigator_mission_item.loiter_radius = _mission_item.loiter_radius;
	navigator_mission_item.yaw = _mission_item.yaw;

	navigator_mission_item.frame = _mission_item.frame;
	navigator_mission_item.frame = _mission_item.origin;

	navigator_mission_item.loiter_exit_xtrack = _mission_item.loiter_exit_xtrack;
	navigator_mission_item.force_heading = _mission_item.force_heading;
	navigator_mission_item.altitude_is_relative = _mission_item.altitude_is_relative;
	navigator_mission_item.autocontinue = _mission_item.autocontinue;
	navigator_mission_item.vtol_back_transition = _mission_item.vtol_back_transition;

	navigator_mission_item.timestamp = hrt_absolute_time();

	_navigator_mission_item_pub.publish(navigator_mission_item);
}