/// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-

/*
  landing logic
 */

/*
  update navigation for landing. Called when on landing approach or
  final flare
 */
static bool verify_land()
{
    // we don't 'verify' landing in the sense that it never completes,
    // so we don't verify command completion. Instead we use this to
    // adjust final landing parameters

    float height = height_above_target();

    // calculate the sink rate.
    float sink_rate;
    Vector3f vel;
    if (ahrs.get_velocity_NED(vel)) {
        sink_rate = vel.z;
    } else if (gps.status() >= AP_GPS::GPS_OK_FIX_3D && gps.have_vertical_velocity()) {
        sink_rate = gps.velocity().z;
    } else {
        sink_rate = -barometer.get_climb_rate();        
    }

    // low pass the sink rate to take some of the noise out
    auto_state.land_sink_rate = 0.8f * auto_state.land_sink_rate + 0.2f*sink_rate;
    
    /* Set land_complete (which starts the flare) under 3 conditions:
       1) we are within LAND_FLARE_ALT meters of the landing altitude
       2) we are within LAND_FLARE_SEC of the landing point vertically
          by the calculated sink rate
       3) we have gone past the landing point (to prevent us keeping
          throttle on after landing if we've had positive baro drift)
    */
    if (height <= g.land_flare_alt ||
        height <= -auto_state.land_sink_rate * g.land_flare_sec ||
        location_passed_point(current_loc, prev_WP_loc, next_WP_loc)) {

        if (!auto_state.land_complete) {
            gcs_send_text_fmt(PSTR("Flare %.1fm sink=%.2f speed=%.1f"), 
                              height, auto_state.land_sink_rate, gps.ground_speed());
        }
        auto_state.land_complete = true;

        if (gps.ground_speed() < 3) {
            // reload any airspeed or groundspeed parameters that may have
            // been set for landing. We don't do this till ground
            // speed drops below 3.0 m/s as otherwise we will change
            // target speeds too early.
            g.airspeed_cruise_cm.load();
            g.min_gndspeed_cm.load();
            aparm.throttle_cruise.load();
        }
    }

    /*
      when landing we keep the L1 navigation waypoint 200m ahead. This
      prevents sudden turns if we overshoot the landing point
     */
    struct Location land_WP_loc = next_WP_loc;
	int32_t land_bearing_cd = get_bearing_cd(prev_WP_loc, next_WP_loc);
    location_update(land_WP_loc,
                    land_bearing_cd*0.01f, 
                    get_distance(prev_WP_loc, current_loc) + 200);
    nav_controller->update_waypoint(prev_WP_loc, land_WP_loc);

    /*
      we always return false as a landing mission item never
      completes - we stay on this waypoint unless the GCS commands us
      to change mission item or reset the mission
     */
    return false;
}