/* Contributed in the public domain.
    * Licensed to CS Systèmes d'Information (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.files.ccsds;
  
  import org.orekit.errors.OrekitException;
  import org.orekit.errors.OrekitMessages;
  import org.orekit.time.AbsoluteDate;
  import org.orekit.time.DateTimeComponents;
  import org.orekit.time.TimeScale;
  import org.orekit.time.TimeScalesFactory;
  import org.orekit.utils.Constants;
  import org.orekit.utils.IERSConventions;
  
  /**
   * The set of time scales defined in Annex A of the ODM CCSDS standard 502.0-B-2.
   *
   * @author Evan Ward
   */
  public enum CcsdsTimeScale {
  
      /** Greenwich Mean Sidereal Time. */
      GMST {
          @Override
          public TimeScale getTimeScale(final IERSConventions conventions) {
              return TimeScalesFactory.getGMST(conventions, false);
          }
      },
      /** Global Positioning System. */
      GPS {
          @Override
          public TimeScale getTimeScale(final IERSConventions conventions) {
              return TimeScalesFactory.getGPS();
          }
      },
      /** Mission Elapsed Time. */
      MET {
          @Override
          public AbsoluteDate parseDate(final String date,
                                        final IERSConventions conventions,
                                        final AbsoluteDate missionReferenceDate) {
              final DateTimeComponents clock = DateTimeComponents.parseDateTime(date);
              final double offset = clock.getDate().getYear() * Constants.JULIAN_YEAR +
                      clock.getDate().getDayOfYear() * Constants.JULIAN_DAY +
                      clock.getTime().getSecondsInUTCDay();
              return missionReferenceDate.shiftedBy(offset);
          }
  
          @Override
          public TimeScale getTimeScale(final IERSConventions conventions) {
              throw new OrekitException(
                      OrekitMessages.CCSDS_NO_CORRESPONDING_TIME_SCALE,
                      "MET");
          }
      },
      /** Mission Relative Time. */
      MRT {
          @Override
          public AbsoluteDate parseDate(final String date,
                                        final IERSConventions conventions,
                                        final AbsoluteDate missionReferenceDate) {
              final DateTimeComponents clock = DateTimeComponents.parseDateTime(date);
              final double offset = clock.getDate().getYear() * Constants.JULIAN_YEAR +
                      clock.getDate().getDayOfYear() * Constants.JULIAN_DAY +
                      clock.getTime().getSecondsInUTCDay();
              return missionReferenceDate.shiftedBy(offset);
          }
  
          @Override
          public TimeScale getTimeScale(final IERSConventions conventions) {
              throw new OrekitException(
                      OrekitMessages.CCSDS_NO_CORRESPONDING_TIME_SCALE,
                      "MRT");
          }
      },
      /** Spacecraft Clock. Not currently Implemented. */
      SCLK {
          @Override
          public AbsoluteDate parseDate(final String date,
                                        final IERSConventions conventions,
                                        final AbsoluteDate missionReferenceDate) {
              throw new OrekitException(
                      OrekitMessages.CCSDS_TIME_SYSTEM_NOT_IMPLEMENTED,
                      this.name());
          }
  
         @Override
         public TimeScale getTimeScale(final IERSConventions conventions) {
             throw new OrekitException(
                     OrekitMessages.CCSDS_NO_CORRESPONDING_TIME_SCALE,
                     this.name());
         }
     },
     /** International Atomic Time. */
     TAI {
         @Override
         public TimeScale getTimeScale(final IERSConventions conventions) {
             return TimeScalesFactory.getTAI();
         }
     },
     /** Barycentric Coordinate Time. */
     TCB {
         @Override
         public TimeScale getTimeScale(final IERSConventions conventions) {
             return TimeScalesFactory.getTCB();
         }
     },
     /** Barycentric Dynamical Time. */
     TDB {
         @Override
         public TimeScale getTimeScale(final IERSConventions conventions) {
             return TimeScalesFactory.getTDB();
         }
     },
     /** Geocentric Coordinate Time. */
     TCG {
         @Override
         public TimeScale getTimeScale(final IERSConventions conventions) {
             return TimeScalesFactory.getTCG();
         }
     },
     /** Terrestrial Time. */
     TT {
         @Override
         public TimeScale getTimeScale(final IERSConventions conventions) {
             return TimeScalesFactory.getTT();
         }
     },
     /** Universal Time. */
     UT1 {
         @Override
         public TimeScale getTimeScale(final IERSConventions conventions) {
             return TimeScalesFactory.getUT1(conventions, false);
         }
     },
     /** Universal Coordinated Time. */
     UTC {
         @Override
         public TimeScale getTimeScale(final IERSConventions conventions) {
             return TimeScalesFactory.getUTC();
         }
     };
 
     /**
      * Parse a date in this time scale.
      *
      * @param date                 a CCSDS date string.
      * @param conventions          IERS conventions for {@link #UT1} and {@link #GMST}.
      * @param missionReferenceDate epoch for {@link #MET} and {@link #MRT}.
      * @return parsed {@code date}.
      */
     public AbsoluteDate parseDate(final String date,
                                   final IERSConventions conventions,
                                   final AbsoluteDate missionReferenceDate) {
         return new AbsoluteDate(date, this.getTimeScale(conventions));
     }
 
     /**
      * Get the corresponding {@link TimeScale}.
      *
      * @param conventions IERS Conventions for the {@link #GMST} and {@link #UT1} scales.
      * @return the time scale.
      */
     public abstract TimeScale getTimeScale(IERSConventions conventions);
 
     /**
      * Check if {@code timeScale} is one of the values supported by this enum.
      *
      * @param timeScale specifier.
      * @return {@code true} if {@link #valueOf(String)} will not throw an exception with
      * the same string.
      */
     public static boolean contains(final String timeScale) {
         for (final CcsdsTimeScale scale : values()) {
             if (scale.name().equals(timeScale)) {
                 return true;
             }
         }
         return false;
     }
 
 }