/* 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
   * limitations under the License.
   */
  package org.orekit.frames;
  
  import org.hipparchus.CalculusFieldElement;
  import org.hipparchus.geometry.euclidean.threed.FieldRotation;
  import org.hipparchus.geometry.euclidean.threed.Rotation;
  import org.hipparchus.geometry.euclidean.threed.RotationConvention;
  import org.hipparchus.geometry.euclidean.threed.RotationOrder;
  import org.orekit.time.AbsoluteDate;
  import org.orekit.time.FieldAbsoluteDate;
  import org.orekit.time.TimeScalarFunction;
  import org.orekit.time.TimeScales;
  import org.orekit.time.TimeVectorFunction;
  import org.orekit.utils.IERSConventions;
  
  /** Provider for True of Date (ToD) frame.
   * <p>This frame handles nutation effects according to selected IERS conventions.</p>
   * <p>Transform is computed with reference to the {@link MODProvider Mean of Date} frame.</p>
   * @author Pascal Parraud
   */
  class TODProvider implements EOPBasedTransformProvider {
  
      /** Conventions. */
      private final IERSConventions conventions;
  
      /** EOP history. */
      private final EOPHistory eopHistory;
  
      /** Function computing the mean obliquity. */
      private final TimeScalarFunction obliquityFunction;
  
      /** Function computing the nutation angles. */
      private final TimeVectorFunction nutationFunction;
  
  
      /**
       * Simple constructor.
       *  @param conventions IERS conventions to apply
       * @param eopHistory  EOP history, or {@code null} if no correction should be
       *                    applied.
       * @param timeScales         TAI time scale.
       */
      TODProvider(final IERSConventions conventions,
                  final EOPHistory eopHistory,
                  final TimeScales timeScales) {
          this.conventions       = conventions;
          this.eopHistory        = eopHistory;
          this.obliquityFunction = conventions.getMeanObliquityFunction(timeScales);
          this.nutationFunction  =
                  conventions.getNutationFunction(timeScales);
      }
  
      /**
       * Private constructor.
       *
       * @param conventions       IERS conventions to use.
       * @param eopHistory        or {@code null} if no correction should be applied.
       * @param obliquityFunction to use.
       * @param nutationFunction  to use.
       */
      private TODProvider(final IERSConventions conventions,
                          final EOPHistory eopHistory,
                          final TimeScalarFunction obliquityFunction,
                          final TimeVectorFunction nutationFunction) {
          this.conventions = conventions;
          this.eopHistory = eopHistory;
          this.obliquityFunction = obliquityFunction;
          this.nutationFunction = nutationFunction;
      }
  
      /** {@inheritDoc} */
      @Override
      public EOPHistory getEOPHistory() {
          return eopHistory;
      }
  
      /** {@inheritDoc} */
      @Override
      public TODProvider getNonInterpolatingProvider() {
          return new TODProvider(conventions, eopHistory.getEOPHistoryWithoutCachedTidalCorrection(),
                  obliquityFunction, nutationFunction);
      }
  
      /** {@inheritDoc} */
     @Override
     public Transform getTransform(final AbsoluteDate date) {
 
         // compute nutation angles
         final double[] angles = nutationFunction.value(date);
 
         // compute the mean obliquity of the ecliptic
         final double moe = obliquityFunction.value(date);
 
         double dpsi = angles[0];
         double deps = angles[1];
         if (eopHistory != null) {
             // apply the corrections for the nutation parameters
             final double[] correction = eopHistory.getEquinoxNutationCorrection(date);
             dpsi += correction[0];
             deps += correction[1];
         }
 
         // compute the true obliquity of the ecliptic
         final double toe = moe + deps;
 
         // complete nutation
         final Rotation nutation = new Rotation(RotationOrder.XZX, RotationConvention.FRAME_TRANSFORM,
                                                moe, -dpsi, -toe);
 
         // set up the transform from parent MOD
         return new Transform(date, nutation);
 
     }
 
     /** Replace the instance with a data transfer object for serialization.
     /** {@inheritDoc} */
     @Override
     public <T extends CalculusFieldElement<T>> FieldTransform<T> getTransform(final FieldAbsoluteDate<T> date) {
 
         // compute nutation angles
         final T[] angles = nutationFunction.value(date);
 
         // compute the mean obliquity of the ecliptic
         final T moe = obliquityFunction.value(date);
 
         T dpsi = angles[0];
         T deps = angles[1];
         if (eopHistory != null) {
             // apply the corrections for the nutation parameters
             final T[] correction = eopHistory.getEquinoxNutationCorrection(date);
             dpsi = dpsi.add(correction[0]);
             deps = deps.add(correction[1]);
         }
 
         // compute the true obliquity of the ecliptic
         final T toe = moe.add(deps);
 
         // complete nutation
         final FieldRotation<T> nutation = new FieldRotation<>(RotationOrder.XZX, RotationConvention.FRAME_TRANSFORM,
                                                               moe, dpsi.negate(), toe.negate());
 
         // set up the transform from parent MOD
         return new FieldTransform<>(date, nutation);
 
     }
 
 }