/* 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.gnss;
  
  import java.util.HashMap;
  import java.util.Map;
  import java.util.function.Function;
  
  import org.orekit.errors.OrekitIllegalArgumentException;
  import org.orekit.errors.OrekitMessages;
  import org.orekit.time.TimeScale;
  import org.orekit.time.TimeScales;
  
  /** Enumerate for the time systems used in navigation files.
   *
   * @author Thomas Neidhart
   * @author Evan Ward
   * @author Thomas Paulet
   * @since 11.0
   */
  public enum TimeSystem {
  
      /** Global Positioning System. */
      GPS("GPS", "GP", "G", TimeScales::getGPS),
  
      /** GLONASS. */
      GLONASS("GLO", "GL", "R", TimeScales::getGLONASS),
  
      /** GALILEO. */
      GALILEO("GAL", "GA", "E", TimeScales::getGST),
  
      /** International Atomic Time. */
      TAI("TAI", null, null, TimeScales::getTAI),
  
      /** Coordinated Universal Time. */
      UTC("UTC", "UT", null, TimeScales::getUTC),
  
      /** Quasi-Zenith System. */
      QZSS("QZS", "QZ", "J", TimeScales::getQZSS),
  
      /** Beidou. */
      BEIDOU("BDT", "BD", "C", TimeScales::getBDT),
  
      /** NavIC. */
      NAVIC("IRN", "IR", "I", TimeScales::getNavIC),
  
      /** SBAS.
       * @since 12.0
       */
      SBAS(null, "SB", "S", TimeScales::getUTC),
  
      /** GMT (should only be used in RUN BY / DATE entries).
       * @since 12.0
       */
      GMT("GMT", null, null, TimeScales::getUTC),
  
      /** Unknown (should only be used in RUN BY / DATE entries). */
      UNKNOWN("LCL", null, null, TimeScales::getGPS);
  
      /** Parsing key map. */
      private static final Map<String, TimeSystem> KEYS_MAP = new HashMap<>();
  
      /** Parsing two letters code map.
       * @since 12.0
       */
      private static final Map<String, TimeSystem> TLC_MAP = new HashMap<>();
  
      /** Parsing one letters code map.
       * @since 12.0
       */
      private static final Map<String, TimeSystem> OLC_MAP = new HashMap<>();
  
      static {
          for (final TimeSystem timeSystem : values()) {
              if (timeSystem.key != null) {
                  KEYS_MAP.put(timeSystem.key, timeSystem);
              }
              if (timeSystem.twoLettersCode != null) {
                  TLC_MAP.put(timeSystem.twoLettersCode, timeSystem);
              }
              if (timeSystem.oneLetterCode != null) {
                  OLC_MAP.put(timeSystem.oneLetterCode, timeSystem);
              }
          }
      }
 
     /** Key for the system. */
     private final String key;
 
     /** Two-letters code.
      * @since 12.0
      */
     private final String twoLettersCode;
 
     /** One-letter code.
      * @since 12.0
      */
     private final String oneLetterCode;
 
     /** Time scale provider.
      * @since 12.0
      */
     private final Function<TimeScales, TimeScale> timeScaleProvider;
 
     /** Simple constructor.
      * @param key key letter (may be null)
      * @param twoLettersCode two letters code (may be null)
      * @param oneLetterCode one letter code (may be null)
      * @param timeScaleProvider time scale provider
      */
     TimeSystem(final String key, final String twoLettersCode, final String oneLetterCode,
                final Function<TimeScales, TimeScale> timeScaleProvider) {
         this.key               = key;
         this.twoLettersCode    = twoLettersCode;
         this.oneLetterCode     = oneLetterCode;
         this.timeScaleProvider = timeScaleProvider;
     }
 
     /** Get the 3 letters key of the time system.
      * @return 3 letters key
      * @since 12.0
      */
     public String getKey() {
         return key;
     }
 
     /** Get the two letters code.
      * @return two letters code (may be null for non-GNSS time systems)
      * @since 12.2
      */
     public String getTwoLettersCode() {
         return twoLettersCode;
     }
 
     /** Get the one letter code.
      * @return one letter code (may be null for non-GNSS time systems)
      * @since 12.2
      */
     public String getOneLetterCode() {
         return oneLetterCode;
     }
 
     /** Parse a string to get the time system.
      * <p>
      * The string must be the time system.
      * </p>
      * @param s string to parse
      * @return the time system
      * @exception OrekitIllegalArgumentException if the string does not correspond to a time system key
      */
     public static TimeSystem parseTimeSystem(final String s)
         throws OrekitIllegalArgumentException {
         final TimeSystem timeSystem = KEYS_MAP.get(s);
         if (timeSystem == null) {
             throw new OrekitIllegalArgumentException(OrekitMessages.UNKNOWN_TIME_SYSTEM, s);
         }
         return timeSystem;
     }
 
     /** Parse a string to get the time system.
      * <p>
      * The string must be the two letters code of the time system.
      * </p>
      * @param code string to parse
      * @return the time system
      * @exception OrekitIllegalArgumentException if the string does not correspond to a time system key
      */
     public static TimeSystem parseTwoLettersCode(final String code)
         throws OrekitIllegalArgumentException {
         final TimeSystem timeSystem = TLC_MAP.get(code);
         if (timeSystem == null) {
             throw new OrekitIllegalArgumentException(OrekitMessages.UNKNOWN_TIME_SYSTEM, code);
         }
         return timeSystem;
     }
 
     /** Parse a string to get the time system.
      * <p>
      * The string must be the one letters code of the time system.
      * The one letter code is the RINEX GNSS system flag.
      * </p>
      * @param code string to parse
      * @return the time system
      * @exception OrekitIllegalArgumentException if the string does not correspond to a time system key
      */
     public static TimeSystem parseOneLetterCode(final String code)
         throws OrekitIllegalArgumentException {
         final TimeSystem timeSystem = OLC_MAP.get(code);
         if (timeSystem == null) {
             throw new OrekitIllegalArgumentException(OrekitMessages.UNKNOWN_TIME_SYSTEM, code);
         }
         return timeSystem;
     }
 
     /** Get the time scale corresponding to time system.
      * @param timeScales the set of time scales to use
      * @return the time scale corresponding to time system in the set of time scales
      */
     public TimeScale getTimeScale(final TimeScales timeScales) {
         return timeScaleProvider.apply(timeScales);
     }
 
 }