/* 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.files.ccsds.ndm.odm.ocm;
  
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.List;
  import java.util.Map;
  import java.util.function.Function;
  import java.util.regex.Pattern;
  
  import org.orekit.bodies.OneAxisEllipsoid;
  import org.orekit.data.DataContext;
  import org.orekit.data.DataSource;
  import org.orekit.errors.OrekitException;
  import org.orekit.errors.OrekitIllegalArgumentException;
  import org.orekit.errors.OrekitMessages;
  import org.orekit.files.ccsds.ndm.ParsedUnitsBehavior;
  import org.orekit.files.ccsds.ndm.odm.OdmHeader;
  import org.orekit.files.ccsds.ndm.odm.OdmMetadataKey;
  import org.orekit.files.ccsds.ndm.odm.OdmParser;
  import org.orekit.files.ccsds.ndm.odm.UserDefined;
  import org.orekit.files.ccsds.section.HeaderProcessingState;
  import org.orekit.files.ccsds.section.KvnStructureProcessingState;
  import org.orekit.files.ccsds.section.MetadataKey;
  import org.orekit.files.ccsds.section.Segment;
  import org.orekit.files.ccsds.section.XmlStructureProcessingState;
  import org.orekit.files.ccsds.utils.ContextBinding;
  import org.orekit.files.ccsds.utils.FileFormat;
  import org.orekit.files.ccsds.utils.lexical.ParseToken;
  import org.orekit.files.ccsds.utils.lexical.TokenType;
  import org.orekit.files.ccsds.utils.lexical.UserDefinedXmlTokenBuilder;
  import org.orekit.files.ccsds.utils.lexical.XmlTokenBuilder;
  import org.orekit.files.ccsds.utils.parsing.ProcessingState;
  import org.orekit.files.general.EphemerisFileParser;
  import org.orekit.time.AbsoluteDate;
  import org.orekit.utils.IERSConventions;
  import org.orekit.utils.units.Unit;
  
  /** A parser for the CCSDS OCM (Orbit Comprehensive Message).
   * <p>
   * Note than starting with Orekit 11.0, CCSDS message parsers are
   * mutable objects that gather the data being parsed, until the
   * message is complete and the {@link #parseMessage(org.orekit.data.DataSource)
   * parseMessage} method has returned. This implies that parsers
   * should <em>not</em> be used in a multi-thread context. The recommended
   * way to use parsers is to either dedicate one parser for each message
   * and drop it afterwards, or to use a single-thread loop.
   * </p>
   * @author Luc Maisonobe
   * @since 11.0
   */
  public class OcmParser extends OdmParser<Ocm, OcmParser> implements EphemerisFileParser<Ocm> {
  
      /** Pattern for splitting strings at blanks. */
      private static final Pattern SPLIT_AT_BLANKS = Pattern.compile("\\s+");
  
      /** File header. */
      private OdmHeader header;
  
      /** Metadata for current observation block. */
      private OcmMetadata metadata;
  
      /** Central body equatorial radius.
       * @since 12.0
       */
      private final double equatorialRadius;
  
      /** Central body flattening.
       * @since 12.0
       */
      private final double flattening;
  
      /** Context binding valid for current metadata. */
      private ContextBinding context;
  
      /** Trajectory state histories logical blocks. */
      private List<TrajectoryStateHistory> trajectoryBlocks;
  
      /** Current trajectory state metadata. */
      private TrajectoryStateHistoryMetadata currentTrajectoryStateHistoryMetadata;
  
      /** Current trajectory state time history being read. */
      private List<TrajectoryState> currentTrajectoryStateHistory;
  
     /** Physical properties logical block. */
     private OrbitPhysicalProperties physicBlock;
 
     /** Covariance logical blocks. */
     private List<OrbitCovarianceHistory> covarianceBlocks;
 
     /** Current covariance metadata. */
     private OrbitCovarianceHistoryMetadata currentCovarianceHistoryMetadata;
 
     /** Current covariance history being read. */
     private List<OrbitCovariance> currentCovarianceHistory;
 
     /** Maneuver logical blocks. */
     private List<OrbitManeuverHistory> maneuverBlocks;
 
     /** Current maneuver metadata. */
     private OrbitManeuverHistoryMetadata currentManeuverHistoryMetadata;
 
     /** Current maneuver history being read. */
     private List<OrbitManeuver> currentManeuverHistory;
 
     /** Perturbations logical block. */
     private Perturbations perturbationsBlock;
 
     /** Orbit determination logical block. */
     private OrbitDetermination orbitDeterminationBlock;
 
     /** User defined parameters logical block. */
     private UserDefined userDefinedBlock;
 
     /** Processor for global message structure. */
     private ProcessingState structureProcessor;
 
     /**
      * Complete constructor.
      * <p>
      * Calling this constructor directly is not recommended. Users should rather use
      * {@link org.orekit.files.ccsds.ndm.ParserBuilder#buildOcmParser()
      * parserBuilder.buildOcmParser()}.
      * </p>
      * @param conventions IERS Conventions
      * @param equatorialRadius central body equatorial radius
      * @param flattening central body flattening
      * @param simpleEOP if true, tidal effects are ignored when interpolating EOP
      * @param dataContext used to retrieve frames, time scales, etc.
      * @param mu gravitational coefficient
      * @param parsedUnitsBehavior behavior to adopt for handling parsed units
      * @param filters filters to apply to parse tokens
      * @since 12.0
      */
     public OcmParser(final IERSConventions conventions,
                      final double equatorialRadius, final double flattening,
                      final boolean simpleEOP, final DataContext dataContext,
                      final double mu, final ParsedUnitsBehavior parsedUnitsBehavior,
                      final Function<ParseToken, List<ParseToken>>[] filters) {
         super(Ocm.ROOT, Ocm.FORMAT_VERSION_KEY, conventions, simpleEOP, dataContext, null,
               mu, parsedUnitsBehavior, filters);
         this.equatorialRadius = equatorialRadius;
         this.flattening       = flattening;
     }
 
     /** {@inheritDoc} */
     @Override
     public Map<String, XmlTokenBuilder> getSpecialXmlElementsBuilders() {
 
         final Map<String, XmlTokenBuilder> builders = super.getSpecialXmlElementsBuilders();
 
         // special handling of user-defined parameters
         builders.put(UserDefined.USER_DEFINED_XML_TAG, new UserDefinedXmlTokenBuilder());
 
         return builders;
 
     }
 
     /** {@inheritDoc} */
     @Override
     public Ocm parse(final DataSource source) {
         return parseMessage(source);
     }
 
     /** {@inheritDoc} */
     @Override
     public OdmHeader getHeader() {
         return header;
     }
 
     /** {@inheritDoc} */
     @Override
     public void reset(final FileFormat fileFormat) {
         header                  = new OdmHeader();
         metadata                = null;
         context                 = null;
         trajectoryBlocks        = null;
         physicBlock             = null;
         covarianceBlocks        = null;
         maneuverBlocks          = null;
         perturbationsBlock      = null;
         orbitDeterminationBlock = null;
         userDefinedBlock        = null;
         if (fileFormat == FileFormat.XML) {
             structureProcessor = new XmlStructureProcessingState(Ocm.ROOT, this);
             reset(fileFormat, structureProcessor);
         } else {
             structureProcessor = new KvnStructureProcessingState(this);
             reset(fileFormat, new HeaderProcessingState(this));
         }
     }
 
     /** {@inheritDoc} */
     @Override
     public boolean prepareHeader() {
         anticipateNext(new HeaderProcessingState(this));
         return true;
     }
 
     /** {@inheritDoc} */
     @Override
     public boolean inHeader() {
         anticipateNext(structureProcessor);
         return true;
     }
 
     /** {@inheritDoc} */
     @Override
     public boolean finalizeHeader() {
         header.validate(header.getFormatVersion());
         return true;
     }
 
     /** {@inheritDoc} */
     @Override
     public boolean prepareMetadata() {
         if (metadata != null) {
             return false;
         }
         metadata  = new OcmMetadata(getDataContext());
         context   = new ContextBinding(this::getConventions, this::isSimpleEOP, this::getDataContext,
                                        this::getParsedUnitsBehavior, metadata::getEpochT0, metadata::getTimeSystem,
                                        metadata::getSclkOffsetAtEpoch, metadata::getSclkSecPerSISec);
         anticipateNext(this::processMetadataToken);
         return true;
     }
 
     /** {@inheritDoc} */
     @Override
     public boolean inMetadata() {
         anticipateNext(structureProcessor);
         return true;
     }
 
     /** {@inheritDoc} */
     @Override
     public boolean finalizeMetadata() {
         metadata.validate(header.getFormatVersion());
         anticipateNext(this::processDataSubStructureToken);
         return true;
     }
 
     /** {@inheritDoc} */
     @Override
     public boolean prepareData() {
         anticipateNext(this::processDataSubStructureToken);
         return true;
     }
 
     /** {@inheritDoc} */
     @Override
     public boolean inData() {
         return true;
     }
 
     /** {@inheritDoc} */
     @Override
     public boolean finalizeData() {
         final List<TrajectoryStateHistory> old = trajectoryBlocks;
         if (old != null) {
             final OneAxisEllipsoid body =
                             currentTrajectoryStateHistoryMetadata.getTrajType() == OrbitElementsType.GEODETIC ?
                             new OneAxisEllipsoid(equatorialRadius, flattening,
                                                  currentTrajectoryStateHistoryMetadata.getTrajReferenceFrame().asFrame()) :
                             null;
             trajectoryBlocks = new ArrayList<>(old.size());
             for (final TrajectoryStateHistory osh : old) {
                 trajectoryBlocks.add(new TrajectoryStateHistory(osh.getMetadata(), osh.getTrajectoryStates(),
                                                                 body, getSelectedMu()));
             }
         }
         return true;
     }
 
     /** Manage trajectory state history section.
      * @param starting if true, parser is entering the section
      * otherwise it is leaving the section
      * @return always return true
      */
     boolean manageTrajectoryStateSection(final boolean starting) {
         if (starting) {
             if (trajectoryBlocks == null) {
                 // this is the first trajectory block, we need to allocate the container
                 trajectoryBlocks = new ArrayList<>();
             }
             currentTrajectoryStateHistoryMetadata = new TrajectoryStateHistoryMetadata(metadata.getEpochT0(),
                                                                                        getDataContext());
             currentTrajectoryStateHistory         = new ArrayList<>();
             anticipateNext(this::processTrajectoryStateToken);
         } else {
             final OneAxisEllipsoid body =
                             currentTrajectoryStateHistoryMetadata.getTrajType() == OrbitElementsType.GEODETIC ?
                             new OneAxisEllipsoid(equatorialRadius, flattening,
                                                  currentTrajectoryStateHistoryMetadata.getTrajReferenceFrame().asFrame()) :
                             null;
             anticipateNext(structureProcessor);
             if (currentTrajectoryStateHistoryMetadata.getCenter().getBody() != null) {
                 setMuCreated(currentTrajectoryStateHistoryMetadata.getCenter().getBody().getGM());
             }
             // we temporarily set gravitational parameter to NaN,
             // as we may get a proper one in the perturbations section
             trajectoryBlocks.add(new TrajectoryStateHistory(currentTrajectoryStateHistoryMetadata,
                                                             currentTrajectoryStateHistory,
                                                             body, Double.NaN));
         }
         return true;
     }
 
     /** Manage physical properties section.
      * @param starting if true, parser is entering the section
      * otherwise it is leaving the section
      * @return always return true
      */
     boolean managePhysicalPropertiesSection(final boolean starting) {
         if (starting) {
             if (physicBlock == null) {
                 // this is the first (and unique) physical properties block, we need to allocate the container
                 physicBlock = new OrbitPhysicalProperties(metadata.getEpochT0());
             }
             anticipateNext(this::processPhysicalPropertyToken);
         } else {
             anticipateNext(structureProcessor);
         }
         return true;
     }
 
     /** Manage covariance history section.
      * @param starting if true, parser is entering the section
      * otherwise it is leaving the section
      * @return always return true
      */
     boolean manageCovarianceHistorySection(final boolean starting) {
         if (starting) {
             if (covarianceBlocks == null) {
                 // this is the first covariance block, we need to allocate the container
                 covarianceBlocks = new ArrayList<>();
             }
             currentCovarianceHistoryMetadata = new OrbitCovarianceHistoryMetadata(metadata.getEpochT0());
             currentCovarianceHistory         = new ArrayList<>();
             anticipateNext(this::processCovarianceToken);
         } else {
             anticipateNext(structureProcessor);
             covarianceBlocks.add(new OrbitCovarianceHistory(currentCovarianceHistoryMetadata,
                                                             currentCovarianceHistory));
             currentCovarianceHistoryMetadata = null;
             currentCovarianceHistory         = null;
         }
         return true;
     }
 
     /** Manage maneuvers section.
      * @param starting if true, parser is entering the section
      * otherwise it is leaving the section
      * @return always return true
      */
     boolean manageManeuversSection(final boolean starting) {
         if (starting) {
             if (maneuverBlocks == null) {
                 // this is the first maneuver block, we need to allocate the container
                 maneuverBlocks = new ArrayList<>();
             }
             currentManeuverHistoryMetadata = new OrbitManeuverHistoryMetadata(metadata.getEpochT0());
             currentManeuverHistory         = new ArrayList<>();
             anticipateNext(this::processManeuverToken);
         } else {
             anticipateNext(structureProcessor);
             maneuverBlocks.add(new OrbitManeuverHistory(currentManeuverHistoryMetadata,
                                                         currentManeuverHistory));
             currentManeuverHistoryMetadata = null;
             currentManeuverHistory         = null;
         }
         return true;
     }
 
     /** Manage perturbation parameters section.
      * @param starting if true, parser is entering the section
      * otherwise it is leaving the section
      * @return always return true
      */
     boolean managePerturbationParametersSection(final boolean starting) {
         if (starting) {
             if (perturbationsBlock == null) {
                 // this is the first (and unique) perturbations parameters block, we need to allocate the container
                 perturbationsBlock = new Perturbations(context.getDataContext().getCelestialBodies());
             }
             anticipateNext(this::processPerturbationToken);
         } else {
             anticipateNext(structureProcessor);
         }
         return true;
     }
 
     /** Manage orbit determination section.
      * @param starting if true, parser is entering the section
      * otherwise it is leaving the section
      * @return always return true
      */
     boolean manageOrbitDeterminationSection(final boolean starting) {
         if (starting) {
             if (orbitDeterminationBlock == null) {
                 // this is the first (and unique) orbit determination block, we need to allocate the container
                 orbitDeterminationBlock = new OrbitDetermination();
             }
             anticipateNext(this::processOrbitDeterminationToken);
         } else {
             anticipateNext(structureProcessor);
         }
         return true;
     }
 
     /** Manage user-defined parameters section.
      * @param starting if true, parser is entering the section
      * otherwise it is leaving the section
      * @return always return true
      */
     boolean manageUserDefinedParametersSection(final boolean starting) {
         if (starting) {
             if (userDefinedBlock == null) {
                 // this is the first (and unique) user-defined parameters block, we need to allocate the container
                 userDefinedBlock = new UserDefined();
             }
             anticipateNext(this::processUserDefinedToken);
         } else {
             anticipateNext(structureProcessor);
         }
         return true;
     }
 
     /** {@inheritDoc} */
     @Override
     public Ocm build() {
 
         // OCM KVN file lack a DATA_STOP keyword, hence we can't call finalizeData()
         // automatically before the end of the file
         finalizeData();
         if (userDefinedBlock != null && userDefinedBlock.getParameters().isEmpty()) {
             userDefinedBlock = null;
         }
 
         // the mu is needed only if there are trajectories
         final double mu;
         if (trajectoryBlocks == null) {
             mu = Double.NaN;
         } else {
             if (perturbationsBlock != null) {
                 // this may be Double.NaN, but it will be handled correctly
                 setMuParsed(perturbationsBlock.getGm());
             }
             mu = getSelectedMu();
         }
 
         final OcmData data = new OcmData(trajectoryBlocks, physicBlock, covarianceBlocks,
                                          maneuverBlocks, perturbationsBlock,
                                          orbitDeterminationBlock, userDefinedBlock);
         data.validate(header.getFormatVersion());
 
         return new Ocm(header, Collections.singletonList(new Segment<>(metadata, data)),
                            getConventions(), getDataContext(), mu);
 
     }
 
     /** Process one metadata token.
      * @param token token to process
      * @return true if token was processed, false otherwise
      */
     private boolean processMetadataToken(final ParseToken token) {
         inMetadata();
         try {
             return token.getName() != null &&
                    MetadataKey.valueOf(token.getName()).process(token, context, metadata);
         } catch (IllegalArgumentException iaeM) {
             try {
                 return OdmMetadataKey.valueOf(token.getName()).process(token, context, metadata);
             } catch (IllegalArgumentException iaeD) {
                 try {
                     return OcmMetadataKey.valueOf(token.getName()).process(token, context, metadata);
                 } catch (IllegalArgumentException iaeC) {
                     // token has not been recognized
                     return false;
                 }
             }
         }
     }
 
     /** Process one data substructure token.
      * @param token token to process
      * @return true if token was processed, false otherwise
      */
     private boolean processDataSubStructureToken(final ParseToken token) {
         try {
             return token.getName() != null &&
                    OcmDataSubStructureKey.valueOf(token.getName()).process(token, this);
         } catch (IllegalArgumentException iae) {
             // token has not been recognized
             return false;
         }
     }
 
     /** Process one trajectory state history data token.
      * @param token token to process
      * @return true if token was processed, false otherwise
      */
     private boolean processTrajectoryStateToken(final ParseToken token) {
         if (token.getName() != null && !token.getName().equals(Ocm.TRAJ_LINE)) {
             // we are in the section metadata part
             try {
                 return TrajectoryStateHistoryMetadataKey.valueOf(token.getName()).
                        process(token, context, currentTrajectoryStateHistoryMetadata);
             } catch (IllegalArgumentException iae) {
                 // token has not been recognized
                 return false;
             }
         } else {
             // we are in the section data part
             if (currentTrajectoryStateHistory.isEmpty()) {
                 // we are starting the real data section, we can now check metadata is complete
                 currentTrajectoryStateHistoryMetadata.validate(header.getFormatVersion());
                 anticipateNext(this::processDataSubStructureToken);
             }
             if (token.getType() == TokenType.START || token.getType() == TokenType.STOP) {
                 return true;
             }
             try {
                 final String[] fields = SPLIT_AT_BLANKS.split(token.getRawContent().trim());
                 // as TRAJ_UNITS is optional and indeed MUST match type, get them directly from type
                 final List<Unit> units = currentTrajectoryStateHistoryMetadata.getTrajType().getUnits();
                 if (fields.length != units.size() + 1) {
                     throw new OrekitException(OrekitMessages.UNABLE_TO_PARSE_LINE_IN_FILE,
                                               token.getLineNumber(), token.getFileName(), token.getContentAsNormalizedString());
                 }
                 final AbsoluteDate epoch = context.getTimeSystem().getConverter(context).parse(fields[0]);
                 return currentTrajectoryStateHistory.add(new TrajectoryState(currentTrajectoryStateHistoryMetadata.getTrajType(),
                                                                              epoch, fields, 1, units));
             } catch (NumberFormatException | OrekitIllegalArgumentException e) {
                 throw new OrekitException(e, OrekitMessages.UNABLE_TO_PARSE_LINE_IN_FILE,
                                           token.getLineNumber(), token.getFileName(), token.getContentAsNormalizedString());
             }
         }
     }
 
     /** Process one physical property data token.
      * @param token token to process
      * @return true if token was processed, false otherwise
      */
     private boolean processPhysicalPropertyToken(final ParseToken token) {
         if (physicBlock == null) {
             physicBlock = new OrbitPhysicalProperties(metadata.getEpochT0());
         }
         anticipateNext(this::processDataSubStructureToken);
         try {
             return token.getName() != null &&
                    OrbitPhysicalPropertiesKey.valueOf(token.getName()).process(token, context, physicBlock);
         } catch (IllegalArgumentException iae) {
             // token has not been recognized
             return false;
         }
     }
 
     /** Process one covariance history history data token.
      * @param token token to process
      * @return true if token was processed, false otherwise
      */
     private boolean processCovarianceToken(final ParseToken token) {
         if (token.getName() != null && !token.getName().equals(Ocm.COV_LINE)) {
             // we are in the section metadata part
             try {
                 return OrbitCovarianceHistoryMetadataKey.valueOf(token.getName()).
                        process(token, context, currentCovarianceHistoryMetadata);
             } catch (IllegalArgumentException iae) {
                 // token has not been recognized
                 return false;
             }
         } else {
             // we are in the section data part
             if (currentCovarianceHistory.isEmpty()) {
                 // we are starting the real data section, we can now check metadata is complete
                 currentCovarianceHistoryMetadata.validate(header.getFormatVersion());
                 anticipateNext(this::processDataSubStructureToken);
             }
             if (token.getType() == TokenType.START || token.getType() == TokenType.STOP) {
                 return true;
             }
             try {
                 final String[] fields = SPLIT_AT_BLANKS.split(token.getRawContent().trim());
                 final int n = currentCovarianceHistoryMetadata.getCovType().getUnits().size();
                 if (fields.length - 1 != currentCovarianceHistoryMetadata.getCovOrdering().nbElements(n)) {
                     throw new OrekitException(OrekitMessages.UNABLE_TO_PARSE_LINE_IN_FILE,
                                               token.getLineNumber(), token.getFileName(), token.getContentAsNormalizedString());
                 }
                 currentCovarianceHistory.add(new OrbitCovariance(currentCovarianceHistoryMetadata.getCovType(),
                                                             currentCovarianceHistoryMetadata.getCovOrdering(),
                                                             context.getTimeSystem().getConverter(context).parse(fields[0]),
                                                             fields, 1));
                 return true;
             } catch (NumberFormatException nfe) {
                 throw new OrekitException(nfe, OrekitMessages.UNABLE_TO_PARSE_LINE_IN_FILE,
                                           token.getLineNumber(), token.getFileName(), token.getContentAsNormalizedString());
             }
         }
     }
 
     /** Process one maneuver data token.
      * @param token token to process
      * @return true if token was processed, false otherwise
      */
     private boolean processManeuverToken(final ParseToken token) {
         if (token.getName() != null && !token.getName().equals(Ocm.MAN_LINE)) {
             // we are in the section metadata part
             try {
                 return OrbitManeuverHistoryMetadataKey.valueOf(token.getName()).
                        process(token, context, currentManeuverHistoryMetadata);
             } catch (IllegalArgumentException iae) {
                 // token has not been recognized
                 return false;
             }
         } else {
             // we are in the section data part
             if (currentManeuverHistory.isEmpty()) {
                 // we are starting the real data section, we can now check metadata is complete
                 currentManeuverHistoryMetadata.validate(header.getFormatVersion());
                 anticipateNext(this::processDataSubStructureToken);
             }
             if (token.getType() == TokenType.START || token.getType() == TokenType.STOP) {
                 return true;
             }
             try {
                 final String[] fields = SPLIT_AT_BLANKS.split(token.getRawContent().trim());
                 final List<ManeuverFieldType> types = currentManeuverHistoryMetadata.getManComposition();
                 if (fields.length != types.size()) {
                     throw new OrekitException(OrekitMessages.UNABLE_TO_PARSE_LINE_IN_FILE,
                                               token.getLineNumber(), token.getFileName(), token.getContentAsNormalizedString());
                 }
                 final OrbitManeuver maneuver = new OrbitManeuver();
                 for (int i = 0; i < fields.length; ++i) {
                     types.get(i).process(fields[i], context, maneuver, token.getLineNumber(), token.getFileName());
                 }
                 currentManeuverHistory.add(maneuver);
                 return true;
             } catch (NumberFormatException nfe) {
                 throw new OrekitException(nfe, OrekitMessages.UNABLE_TO_PARSE_LINE_IN_FILE,
                                           token.getLineNumber(), token.getFileName(), token.getContentAsNormalizedString());
             }
         }
     }
 
     /** Process one perturbation parameter data token.
      * @param token token to process
      * @return true if token was processed, false otherwise
      */
     private boolean processPerturbationToken(final ParseToken token) {
         anticipateNext(this::processDataSubStructureToken);
         try {
             return token.getName() != null &&
                    PerturbationsKey.valueOf(token.getName()).process(token, context, perturbationsBlock);
         } catch (IllegalArgumentException iae) {
             // token has not been recognized
             return false;
         }
     }
 
     /** Process one orbit determination data token.
      * @param token token to process
      * @return true if token was processed, false otherwise
      */
     private boolean processOrbitDeterminationToken(final ParseToken token) {
         if (orbitDeterminationBlock == null) {
             orbitDeterminationBlock = new OrbitDetermination();
         }
         anticipateNext(this::processDataSubStructureToken);
         try {
             return token.getName() != null &&
                    OrbitDeterminationKey.valueOf(token.getName()).process(token, context, orbitDeterminationBlock);
         } catch (IllegalArgumentException iae) {
             // token has not been recognized
             return false;
         }
     }
 
     /** Process one user-defined parameter data token.
      * @param token token to process
      * @return true if token was processed, false otherwise
      */
     private boolean processUserDefinedToken(final ParseToken token) {
         if (userDefinedBlock == null) {
             userDefinedBlock = new UserDefined();
         }
         anticipateNext(this::processDataSubStructureToken);
         if ("COMMENT".equals(token.getName())) {
             return token.getType() == TokenType.ENTRY ? userDefinedBlock.addComment(token.getContentAsNormalizedString()) : true;
         } else if (token.getName().startsWith(UserDefined.USER_DEFINED_PREFIX)) {
             if (token.getType() == TokenType.ENTRY) {
                 userDefinedBlock.addEntry(token.getName().substring(UserDefined.USER_DEFINED_PREFIX.length()),
                                           token.getContentAsNormalizedString());
             }
             return true;
         } else {
             // the token was not processed
             return false;
         }
     }
 
 }