/****************************************************************************
 *
 *   Copyright (c) 2013-2018 PX4 Development Team. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name PX4 nor the names of its contributors may be
 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 ****************************************************************************/
/**
 * @file rtl.cpp
 *
 * Helper class to access RTL
 *
 * @author Julian Oes <julian@oes.ch>
 * @author Anton Babushkin <anton.babushkin@me.com>
 */

#include "rtl.h"
#include "navigator.h"


static constexpr float DELAY_SIGMA = 0.01f;

RTL::RTL(Navigator *navigator) :
	MissionBlock(navigator),
	ModuleParams(navigator)
{
}

void
RTL::on_inactive()
{
	// Reset RTL state.
	_rtl_state = RTL_STATE_NONE;
}

int
RTL::rtl_type() const
{
	return _param_rtl_type.get();
}

void
RTL::on_activation()
{
	if (_navigator->get_land_detected()->landed) {
		// For safety reasons don't go into RTL if landed.
		_rtl_state = RTL_STATE_LANDED;

	} else if ((rtl_type() == RTL_LAND) && _navigator->on_mission_landing()) {
		// RTL straight to RETURN state, but mission will takeover for landing.

	} else if ((_navigator->get_global_position()->alt < _navigator->get_home_position()->alt + _param_rtl_return_alt.get())
		   || _rtl_alt_min) {

		// If lower than return altitude, climb up first.
		// If rtl_alt_min is true then forcing altitude change even if above.
		_rtl_state = RTL_STATE_CLIMB;

	} else {
		// Otherwise go straight to return
		_rtl_state = RTL_STATE_RETURN;
	}

	set_rtl_item();
}

void
RTL::on_active()
{
	if (_rtl_state != RTL_STATE_LANDED && is_mission_item_reached()) {
		advance_rtl();
		set_rtl_item();
	}
}

void
RTL::set_return_alt_min(bool min)
{
	_rtl_alt_min = min;
}

void
RTL::set_rtl_item()
{
	// RTL_TYPE: mission landing.
	// Landing using planned mission landing, fly to DO_LAND_START instead of returning HOME.
	// Do nothing, let navigator takeover with mission landing.
	if (rtl_type() == RTL_LAND) {
		if (_rtl_state > RTL_STATE_CLIMB) {
			if (_navigator->start_mission_landing()) {
				mavlink_and_console_log_info(_navigator->get_mavlink_log_pub(), "RTL: using mission landing");
				return;

			} else {
				// Otherwise use regular RTL.
				mavlink_log_critical(_navigator->get_mavlink_log_pub(), "RTL: unable to use mission landing");
			}
		}
	}

	_navigator->set_can_loiter_at_sp(false);

	const home_position_s &home = *_navigator->get_home_position();
	const vehicle_global_position_s &gpos = *_navigator->get_global_position();

	position_setpoint_triplet_s *pos_sp_triplet = _navigator->get_position_setpoint_triplet();

	// Check if we are pretty close to home already.
	const float home_dist = get_distance_to_next_waypoint(home.lat, home.lon, gpos.lat, gpos.lon);

	// Compute the return altitude.
	float return_alt = math::max(home.alt + _param_rtl_return_alt.get(), gpos.alt);

	// We are close to home, limit climb to min.
	if (home_dist < _param_rtl_min_dist.get()) {
		return_alt = home.alt + _param_rtl_descend_alt.get();
	}

	// Compute the loiter altitude.
	const float loiter_altitude = math::min(home.alt + _param_rtl_descend_alt.get(), gpos.alt);

	switch (_rtl_state) {
	case RTL_STATE_CLIMB: {

			_mission_item.nav_cmd = NAV_CMD_WAYPOINT;
			_mission_item.lat = gpos.lat;
			_mission_item.lon = gpos.lon;
			_mission_item.altitude = return_alt;
			_mission_item.altitude_is_relative = false;
			_mission_item.yaw = _navigator->get_local_position()->yaw;
			_mission_item.acceptance_radius = _navigator->get_acceptance_radius();
			_mission_item.time_inside = 0.0f;
			_mission_item.autocontinue = true;
			_mission_item.origin = ORIGIN_ONBOARD;

			mavlink_and_console_log_info(_navigator->get_mavlink_log_pub(), "RTL: climb to %d m (%d m above home)",
						     (int)ceilf(return_alt), (int)ceilf(return_alt - _navigator->get_home_position()->alt));
			break;
		}

	case RTL_STATE_RETURN: {

			// Don't change altitude.
			_mission_item.nav_cmd = NAV_CMD_WAYPOINT;
			_mission_item.lat = home.lat;
			_mission_item.lon = home.lon;
			_mission_item.altitude = return_alt;
			_mission_item.altitude_is_relative = false;

			// Use home yaw if close to home.
			// Check if we are pretty close to home already.
			if (home_dist < _param_rtl_min_dist.get()) {
				_mission_item.yaw = home.yaw;

			} else {
				// Use current heading to home.
				_mission_item.yaw = get_bearing_to_next_waypoint(gpos.lat, gpos.lon, home.lat, home.lon);
			}

			_mission_item.acceptance_radius = _navigator->get_acceptance_radius();
			_mission_item.time_inside = 0.0f;
			_mission_item.autocontinue = true;
			_mission_item.origin = ORIGIN_ONBOARD;

			mavlink_and_console_log_info(_navigator->get_mavlink_log_pub(), "RTL: return at %d m (%d m above home)",
						     (int)ceilf(_mission_item.altitude), (int)ceilf(_mission_item.altitude - home.alt));

			break;
		}

	case RTL_STATE_TRANSITION_TO_MC: {
			set_vtol_transition_item(&_mission_item, vtol_vehicle_status_s::VEHICLE_VTOL_STATE_MC);
			break;
		}

	case RTL_STATE_DESCEND: {
			_mission_item.nav_cmd = NAV_CMD_WAYPOINT;
			_mission_item.lat = home.lat;
			_mission_item.lon = home.lon;
			_mission_item.altitude = loiter_altitude;
			_mission_item.altitude_is_relative = false;

			// Except for vtol which might be still off here and should point towards this location.
			const float d_current = get_distance_to_next_waypoint(gpos.lat, gpos.lon, _mission_item.lat, _mission_item.lon);

			if (_navigator->get_vstatus()->is_vtol && (d_current > _navigator->get_acceptance_radius())) {
				_mission_item.yaw = get_bearing_to_next_waypoint(gpos.lat, gpos.lon, _mission_item.lat, _mission_item.lon);

			} else {
				_mission_item.yaw = home.yaw;
			}

			_mission_item.acceptance_radius = _navigator->get_acceptance_radius();
			_mission_item.time_inside = 0.0f;
			_mission_item.autocontinue = true;
			_mission_item.origin = ORIGIN_ONBOARD;

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

			mavlink_and_console_log_info(_navigator->get_mavlink_log_pub(), "RTL: descend to %d m (%d m above home)",
						     (int)ceilf(_mission_item.altitude), (int)ceilf(_mission_item.altitude - home.alt));
			break;
		}

	case RTL_STATE_LOITER: {
			const bool autoland = (_param_rtl_land_delay.get() > FLT_EPSILON);

			// Don't change altitude.
			_mission_item.lat = home.lat;
			_mission_item.lon = home.lon;
			_mission_item.altitude = loiter_altitude;
			_mission_item.altitude_is_relative = false;
			_mission_item.yaw = home.yaw;
			_mission_item.loiter_radius = _navigator->get_loiter_radius();
			_mission_item.acceptance_radius = _navigator->get_acceptance_radius();
			_mission_item.time_inside = math::max(_param_rtl_land_delay.get(), 0.0f);
			_mission_item.autocontinue = autoland;
			_mission_item.origin = ORIGIN_ONBOARD;

			_navigator->set_can_loiter_at_sp(true);

			if (autoland && (get_time_inside(_mission_item) > FLT_EPSILON)) {
				_mission_item.nav_cmd = NAV_CMD_LOITER_TIME_LIMIT;
				mavlink_and_console_log_info(_navigator->get_mavlink_log_pub(), "RTL: loiter %.1fs",
							     (double)get_time_inside(_mission_item));

			} else {
				_mission_item.nav_cmd = NAV_CMD_LOITER_UNLIMITED;
				mavlink_and_console_log_info(_navigator->get_mavlink_log_pub(), "RTL: completed, loitering");
			}

			break;
		}

	case RTL_STATE_LAND: {
			// Land at home position.
			_mission_item.nav_cmd = NAV_CMD_LAND;
			_mission_item.lat = home.lat;
			_mission_item.lon = home.lon;
			_mission_item.yaw = home.yaw;
			_mission_item.altitude = home.alt;
			_mission_item.altitude_is_relative = false;
			_mission_item.acceptance_radius = _navigator->get_acceptance_radius();
			_mission_item.time_inside = 0.0f;
			_mission_item.autocontinue = true;
			_mission_item.origin = ORIGIN_ONBOARD;

			mavlink_and_console_log_info(_navigator->get_mavlink_log_pub(), "RTL: land at home");
			break;
		}

	case RTL_STATE_LANDED: {
			set_idle_item(&_mission_item);
			set_return_alt_min(false);
			break;
		}

	default:
		break;
	}

	reset_mission_item_reached();

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

	// Convert mission item to current position setpoint and make it valid.
	mission_apply_limitation(_mission_item);

	if (mission_item_to_position_setpoint(_mission_item, &pos_sp_triplet->current)) {
		_navigator->set_position_setpoint_triplet_updated();
	}
}

void
RTL::advance_rtl()
{
	switch (_rtl_state) {
	case RTL_STATE_CLIMB:
		_rtl_state = RTL_STATE_RETURN;
		break;

	case RTL_STATE_RETURN:
		_rtl_state = RTL_STATE_DESCEND;

		if (_navigator->get_vstatus()->is_vtol && !_navigator->get_vstatus()->is_rotary_wing) {
			_rtl_state = RTL_STATE_TRANSITION_TO_MC;
		}

		break;

	case RTL_STATE_TRANSITION_TO_MC:
		_rtl_state = RTL_STATE_RETURN;
		break;

	case RTL_STATE_DESCEND:

		// Only go to land if autoland is enabled.
		if (_param_rtl_land_delay.get() < -DELAY_SIGMA || _param_rtl_land_delay.get() > DELAY_SIGMA) {
			_rtl_state = RTL_STATE_LOITER;

		} else {
			_rtl_state = RTL_STATE_LAND;
		}

		break;

	case RTL_STATE_LOITER:
		_rtl_state = RTL_STATE_LAND;
		break;

	case RTL_STATE_LAND:
		_rtl_state = RTL_STATE_LANDED;
		break;

	default:
		break;
	}
}