/* Copyright 2002-2021 CS GROUP
    * Licensed to CS GROUP (CS) under one or more
    * contributor license agreements.  See the NOTICE file distributed with
    * this work for additional information regarding copyright ownership.
    * CS licenses this file to You under the Apache License, Version 2.0
    * (the "License"); you may not use this file except in compliance with
    * the License.  You may obtain a copy of the License at
    *
    *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
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   * See the License for the specific language governing permissions and
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  package org.orekit.estimation.measurements.generation;
  
  import org.hipparchus.random.CorrelatedRandomVectorGenerator;
  import org.orekit.estimation.measurements.AngularAzEl;
  import org.orekit.estimation.measurements.EstimationModifier;
  import org.orekit.estimation.measurements.GroundStation;
  import org.orekit.estimation.measurements.ObservableSatellite;
  import org.orekit.propagation.SpacecraftState;
  import org.orekit.time.AbsoluteDate;
  import org.orekit.utils.ParameterDriver;
  
  
  /** Builder for {@link AngularAzEl} measurements.
   * @author Luc Maisonobe
   * @since 9.3
   */
  public class AngularAzElBuilder extends AbstractMeasurementBuilder<AngularAzEl> {
  
      /** Ground station from which measurement is performed. */
      private final GroundStation station;
  
      /** Simple constructor.
       * @param noiseSource noise source, may be null for generating perfect measurements
       * @param station ground station from which measurement is performed
       * @param sigma theoretical standard deviation
       * @param baseWeight base weight
       * @param satellite satellite related to this builder
       */
      public AngularAzElBuilder(final CorrelatedRandomVectorGenerator noiseSource,
                                final GroundStation station,
                                final double[] sigma, final double[] baseWeight,
                                final ObservableSatellite satellite) {
          super(noiseSource, sigma, baseWeight, satellite);
          this.station = station;
      }
  
      /** {@inheritDoc} */
      @Override
      public AngularAzEl build(final SpacecraftState[] states) {
  
          final ObservableSatellite satellite = getSatellites()[0];
          final double[] sigma                = getTheoreticalStandardDeviation();
          final double[] baseWeight           = getBaseWeight();
          final SpacecraftState[] relevant    = new SpacecraftState[] { states[satellite.getPropagatorIndex()] };
  
          // create a dummy measurement
          final AngularAzEl dummy = new AngularAzEl(station, relevant[0].getDate(),
                                                    new double[] {
                                                        0.0, 0.0
                                                    }, sigma, baseWeight, satellite);
          for (final EstimationModifier<AngularAzEl> modifier : getModifiers()) {
              dummy.addModifier(modifier);
          }
  
          // set a reference date for parameters missing one
          for (final ParameterDriver driver : dummy.getParametersDrivers()) {
              if (driver.getReferenceDate() == null) {
                  final AbsoluteDate start = getStart();
                  final AbsoluteDate end   = getEnd();
                  driver.setReferenceDate(start.durationFrom(end) <= 0 ? start : end);
              }
          }
  
          // estimate the perfect value of the measurement
          final double[] angular = dummy.estimate(0, 0, relevant).getEstimatedValue();
  
          // add the noise
          final double[] noise = getNoise();
          if (noise != null) {
              angular[0] += noise[0];
              angular[1] += noise[1];
          }
  
          // generate measurement
          final AngularAzEl measurement = new AngularAzEl(station, relevant[0].getDate(), angular,
                                                          sigma, baseWeight, satellite);
          for (final EstimationModifier<AngularAzEl> modifier : getModifiers()) {
              measurement.addModifier(modifier);
          }
          return measurement;
  
      }
  
 }