/* 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.Collections;
  import java.util.List;
  import java.util.Map;
  import java.util.function.DoubleFunction;
  
  import org.hipparchus.CalculusFieldElement;
  import org.hipparchus.analysis.differentiation.Gradient;
  import org.hipparchus.util.FastMath;
  import org.orekit.time.AbsoluteDate;
  import org.orekit.time.TimeInterval;
  import org.orekit.utils.drivers.ParameterDriver;
  
  /**
   * Clock model for a clock with constant offset.
   *
   * @author Luc Maisonobe
   * @since 14.0
   */
  public class ConstantClockModel implements ClockModel {
  
      /** Constant offset. */
      private final ParameterDriver offset;
  
      /**
       * Simple constructor.
       *
       * @param offset constant offset
       */
      public ConstantClockModel(final double offset) {
          this.offset = new ParameterDriver("a0", 0.0, FastMath.scalb(1.0, -10),
                                            Double.NEGATIVE_INFINITY, Double.POSITIVE_INFINITY,
                                            TimeInterval.UNLIMITED);
          this.offset.setValue(offset);
      }
  
      /** {@inheritDoc} */
      @Override
      public AbsoluteDate getValidityStart() {
          return offset.getValidity().getStartDate();
      }
  
      /** {@inheritDoc} */
      @Override
      public AbsoluteDate getValidityEnd() {
          return offset.getValidity().getEndDate();
      }
  
      /** {@inheritDoc} */
      @Override
      public List<ParameterDriver> getParametersDrivers() {
          return Collections.singletonList(offset);
      }
  
      /** {@inheritDoc} */
      @Override
      public ClockOffset getOffset(final AbsoluteDate date) {
          return new ClockOffset(date, offset.getValue(), 0, 0);
      }
  
      /** {@inheritDoc} */
      @Override
      public <T extends CalculusFieldElement<T>> ConstantFieldClockModel<T> toField(final DoubleFunction<T> converter) {
          return new ConstantFieldClockModel<>(converter.apply(offset.getValue()));
      }
  
      /** {@inheritDoc} */
      @Override
      public ConstantFieldClockModel<Gradient> toGradient(final int freeParameters, final Map<String, Integer> indices) {
          return toField(v -> Gradient.constant(freeParameters, v));
      }
  
  }