/* Copyright 2002-2025 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,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
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  package org.orekit.estimation.leastsquares;
  
  import java.util.List;
  
  import org.orekit.estimation.measurements.EstimatedMeasurement;
  import org.orekit.estimation.measurements.ObservableSatellite;
  import org.orekit.estimation.measurements.ObservedMeasurement;
  import org.orekit.propagation.SpacecraftState;
  import org.orekit.propagation.sampling.MultiSatStepHandler;
  import org.orekit.propagation.sampling.OrekitStepInterpolator;
  import org.orekit.time.AbsoluteDate;
  
  /** {@link org.orekit.propagation.sampling.OrekitStepHandler Step handler} picking up
   * {@link ObservedMeasurement measurements}.
   * @author Luc Maisonobe
   * @since 8.0
   */
  class MeasurementHandler implements MultiSatStepHandler {
  
      /** Least squares model. */
      private final AbstractBatchLSModel model;
  
      /** Underlying measurements. */
      private final List<PreCompensation> precompensated;
  
      /** Number of the next measurement. */
      private int number;
  
      /** Index of the next measurement component in the model. */
      private int index;
  
      /** Simple constructor.
       * @param model least squares model
       * @param precompensated underlying measurements
       */
      MeasurementHandler(final AbstractBatchLSModel model, final List<PreCompensation> precompensated) {
          this.model          = model;
          this.precompensated = precompensated;
      }
  
      /** {@inheritDoc} */
      @Override
      public void init(final List<SpacecraftState> initialStates, final AbsoluteDate target) {
          number = 0;
          index  = 0;
      }
  
      /** {@inheritDoc} */
      @Override
      public void handleStep(final List<OrekitStepInterpolator> interpolators) {
  
          while (number < precompensated.size()) {
  
              // Consider the next measurement to handle
              final PreCompensation next = precompensated.get(number);
  
              // Current state date for interpolator 0
              final AbsoluteDate currentDate = interpolators.get(0).getCurrentState().getDate();
              if (model.isForwardPropagation()  && next.getDate().compareTo(currentDate) > 0 ||
                  !model.isForwardPropagation() && next.getDate().compareTo(currentDate) < 0) {
                  return;
              }
  
              // get the observed measurement
              final ObservedMeasurement<?> observed = next.getMeasurement();
  
              // estimate the theoretical measurement
              final SpacecraftState[] states = new SpacecraftState[observed.getSatellites().size()];
              for (int i = 0; i < states.length; ++i) {
                  final ObservableSatellite satellite = observed.getSatellites().get(i);
                  states[i] = interpolators.get(satellite.getPropagatorIndex()).getInterpolatedState(next.getDate());
              }
              final EstimatedMeasurement<?> estimated = observed.estimate(model.getIterationsCount(),
                                                                          model.getEvaluationsCount(),
                                                                          states);
  
              // fetch the evaluated measurement to the estimator
              model.fetchEvaluatedMeasurement(index, estimated);
  
              // prepare handling of next measurement
              ++number;
              index += observed.getDimension();
  
         }
 
     }
 
 }