/* Copyright 2022-2026 Thales Alenia Space
    * 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.time.clocks;
  
  import java.util.ArrayList;
  import java.util.List;
  import java.util.Map;
  
  import org.hipparchus.CalculusFieldElement;
  import org.hipparchus.analysis.differentiation.Gradient;
  import org.orekit.errors.OrekitException;
  import org.orekit.errors.OrekitMessages;
  import org.orekit.time.AbsoluteDate;
  import org.orekit.time.FieldAbsoluteDate;
  import org.orekit.utils.ParameterDriver;
  import org.orekit.utils.TimeSpanMap;
  
  /**
   * Offset clock model aggregating several other clock models.
   *
   * @author Luc Maisonobe
   * @since 12.1
   */
  public class AggregatedClockModel implements ClockModel {
  
      /** Underlying clock models. */
      private final TimeSpanMap<ClockModel> models;
  
      /** Simple constructor.
       * @param models underlying clock models
       */
      public AggregatedClockModel(final TimeSpanMap<ClockModel> models) {
          this.models = models;
      }
  
      /** Get the underlying models.
       * @return underlying models
       */
      public TimeSpanMap<ClockModel> getModels() {
          return models;
      }
  
      /** {@inheritDoc} */
      @Override
      public AbsoluteDate getValidityStart() {
          return models.getFirstNonNullSpan().getStart();
      }
  
      /** {@inheritDoc} */
      @Override
      public AbsoluteDate getValidityEnd() {
          return models.getLastNonNullSpan().getEnd();
      }
  
      /** {@inheritDoc} */
      @Override
      public List<ParameterDriver> getParametersDrivers() {
          final List<ParameterDriver> drivers = new ArrayList<>();
          models.forEach(model -> drivers.addAll(model.getParametersDrivers()));
          return drivers;
      }
  
      /** {@inheritDoc} */
      @Override
      public ClockOffset getOffset(final AbsoluteDate date) {
          return getModel(date).getOffset(date);
      }
  
      /** {@inheritDoc} */
      @Override
      public <T extends CalculusFieldElement<T>> FieldClockOffset<T> getFieldOffset(final FieldAbsoluteDate<T> date) {
          return getModel(date.toAbsoluteDate()).getFieldOffset(date);
      }
  
      /** {@inheritDoc} */
      @Override
      public FieldClockModel<Gradient> getFieldModel(final int freeParameters,
              final Map<String, Integer> indices, final AbsoluteDate date) {
          return getModel(date).getFieldModel(freeParameters, indices, date);
      }
  
      /**
       * Get the model valid at specified date.
       *
       * @param date date for which model is requested
      * @return clock model valid at date
      */
     private ClockModel getModel(final AbsoluteDate date) {
         final ClockModel clockModel = models.get(date);
         if (clockModel == null) {
             // this may happen if map is limited or not contiguous
             // typically for models retrieved from SP3Ephemeris
             throw new OrekitException(OrekitMessages.NO_DATA_GENERATED, date);
         }
         return clockModel;
     }
 
 }