/* Copyright 2002-2024 Luc Maisonobe
    * 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,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.orekit.estimation.measurements.generation;
  
  import java.util.Map;
  import java.util.function.ToDoubleFunction;
  
  import org.hipparchus.random.CorrelatedRandomVectorGenerator;
  import org.orekit.estimation.measurements.EstimationModifier;
  import org.orekit.estimation.measurements.ObservableSatellite;
  import org.orekit.estimation.measurements.gnss.OneWayGNSSRange;
  import org.orekit.propagation.SpacecraftState;
  import org.orekit.propagation.sampling.OrekitStepInterpolator;
  import org.orekit.time.AbsoluteDate;
  import org.orekit.utils.ParameterDriver;
  
  
  /** Builder for {@link OneWayGNSSRange} measurements.
   * @author Luc Maisonobe
   * @since 12.0
   */
  public class OneWayGNSSRangeBuilder extends AbstractMeasurementBuilder<OneWayGNSSRange> {
  
      /** Satellite which receives the signal and performs the measurement. */
      private final ObservableSatellite local;
  
      /** Satellite which simply emits the signal. */
      private final ObservableSatellite remote;
  
      /** Clock model of the remote satellite that provides clock offset. */
      private ToDoubleFunction<AbsoluteDate> remoteClockModel;
  
      /** Simple constructor.
       * @param noiseSource noise source, may be null for generating perfect measurements
       * @param local satellite which receives the signal and performs the measurement
       * @param remote satellite which simply emits the signal
       * @param remoteClockModel clock model of the remote satellite that provides clock offset
       * @param sigma theoretical standard deviation
       * @param baseWeight base weight
       */
      public OneWayGNSSRangeBuilder(final CorrelatedRandomVectorGenerator noiseSource,
                                    final ObservableSatellite local, final ObservableSatellite remote,
                                    final ToDoubleFunction<AbsoluteDate> remoteClockModel,
                                    final double sigma, final double baseWeight) {
          super(noiseSource, sigma, baseWeight, local, remote);
          this.local            = local;
          this.remote           = remote;
          this.remoteClockModel = remoteClockModel;
      }
  
      /** {@inheritDoc} */
      @Override
      public OneWayGNSSRange build(final AbsoluteDate date, final Map<ObservableSatellite, OrekitStepInterpolator> interpolators) {
  
          final double sigma               = getTheoreticalStandardDeviation()[0];
          final double baseWeight          = getBaseWeight()[0];
          final SpacecraftState[] relevant = new SpacecraftState[] {
              interpolators.get(local).getInterpolatedState(date),
              interpolators.get(remote).getInterpolatedState(date)
          };
          final double offset              = remoteClockModel.applyAsDouble(date);
  
          // create a dummy measurement
          final OneWayGNSSRange dummy = new OneWayGNSSRange(interpolators.get(remote), offset, date,
                                                            Double.NaN, sigma, baseWeight, local);
          for (final EstimationModifier<OneWayGNSSRange> 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
          double range = dummy.estimateWithoutDerivatives(relevant).getEstimatedValue()[0];
  
          // add the noise
          final double[] noise = getNoise();
          if (noise != null) {
              range += noise[0];
         }
 
         // generate measurement
         final OneWayGNSSRange measurement = new OneWayGNSSRange(interpolators.get(remote), offset, date,
                                                                 range, sigma, baseWeight, local);
         for (final EstimationModifier<OneWayGNSSRange> modifier : getModifiers()) {
             measurement.addModifier(modifier);
         }
         return measurement;
 
     }
 
 }