/* Copyright 2002-2026 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.oem;
  
  import java.util.ArrayList;
  import java.util.List;
  import java.util.function.Function;
  import java.util.regex.Pattern;
  
  import org.orekit.data.DataContext;
  import org.orekit.data.DataSource;
  import org.orekit.errors.OrekitException;
  import org.orekit.errors.OrekitMessages;
  import org.orekit.files.ccsds.definitions.CcsdsFrameMapper;
  import org.orekit.files.ccsds.definitions.Units;
  import org.orekit.files.ccsds.ndm.ParsedUnitsBehavior;
  import org.orekit.files.ccsds.ndm.odm.CartesianCovariance;
  import org.orekit.files.ccsds.ndm.odm.CartesianCovarianceKey;
  import org.orekit.files.ccsds.ndm.odm.OdmCommonMetadata;
  import org.orekit.files.ccsds.ndm.odm.CommonMetadataKey;
  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.StateVector;
  import org.orekit.files.ccsds.ndm.odm.StateVectorKey;
  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.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.parsing.ProcessingState;
  import org.orekit.files.general.EphemerisFileParser;
  import org.orekit.frames.Frame;
  import org.orekit.time.AbsoluteDate;
  import org.orekit.utils.IERSConventions;
  import org.orekit.utils.units.Unit;
  
  /**
   * A parser for the CCSDS OEM (Orbit Ephemeris 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 sports
   * @since 6.1
   */
  public class OemParser extends OdmParser<Oem, OemParser> implements EphemerisFileParser<Oem> {
  
      /** Comment marker. */
      private static final String COMMENT = "COMMENT";
  
                      /** Pattern for splitting strings at blanks. */
      private static final Pattern SPLIT_AT_BLANKS = Pattern.compile("\\s+");
  
      /** File header. */
      private OdmHeader header;
  
      /** File segments. */
      private List<OemSegment> segments;
  
      /** Metadata for current observation block. */
      private OemMetadata metadata;
  
      /** Context binding valid for current metadata. */
      private ContextBinding context;
  
      /** Current Ephemerides block being parsed. */
      private OemData currentBlock;
  
      /** Indicator for covariance parsing. */
      private boolean inCovariance;
  
      /** Current covariance matrix being parsed. */
      private CartesianCovariance currentCovariance;
  
      /** Current row number in covariance matrix. */
      private int currentRow;
 
     /** Default interpolation degree. */
     private final int defaultInterpolationDegree;
 
     /** Processor for global message structure. */
     private ProcessingState structureProcessor;
 
     /** State vector logical block being read. */
     private StateVector stateVectorBlock;
 
     /**
      * Complete constructor.
      * <p>
      * Calling this constructor directly is not recommended. Users should rather use
      * {@link org.orekit.files.ccsds.ndm.ParserBuilder#buildOemParser()
      * parserBuilder.buildOemParser()}.
      * </p>
      * @param conventions IERS Conventions
      * @param simpleEOP if true, tidal effects are ignored when interpolating EOP
      * @param dataContext used to retrieve frames, time scales, etc.
      * @param missionReferenceDate reference date for Mission Elapsed Time or Mission Relative Time time systems
      * (may be null if time system is absolute)
      * @param mu gravitational coefficient
      * @param defaultInterpolationDegree default interpolation degree
      * @param parsedUnitsBehavior behavior to adopt for handling parsed units
      * @param filters filters to apply to parse tokens
      * @param frameMapper for creating an Orekit {@link Frame}.
      * @since 13.1.5
      */
     public OemParser(final IERSConventions conventions, final boolean simpleEOP,
                      final DataContext dataContext,
                      final AbsoluteDate missionReferenceDate, final double mu,
                      final int defaultInterpolationDegree, final ParsedUnitsBehavior parsedUnitsBehavior,
                      final Function<ParseToken, List<ParseToken>>[] filters,
                      final CcsdsFrameMapper frameMapper) {
         super(Oem.ROOT, Oem.FORMAT_VERSION_KEY, conventions, simpleEOP, dataContext,
                 missionReferenceDate, mu, parsedUnitsBehavior, filters,
                 frameMapper);
         this.defaultInterpolationDegree  = defaultInterpolationDegree;
     }
 
     /** {@inheritDoc} */
     @Override
     public Oem 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();
         segments          = new ArrayList<>();
         metadata          = null;
         context           = null;
         currentBlock      = null;
         inCovariance      = false;
         currentCovariance = null;
         currentRow        = -1;
         if (fileFormat == FileFormat.XML) {
             structureProcessor = new XmlStructureProcessingState(Oem.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 (currentBlock != null) {
             // we have started a new segment, we need to finalize the previous one
             finalizeData();
         }
         metadata = new OemMetadata(defaultInterpolationDegree, getFrameMapper());
         context  = new ContextBinding(this::getConventions, this::isSimpleEOP,
                                       this::getDataContext, this::getParsedUnitsBehavior,
                                       this::getMissionReferenceDate,
                                       metadata::getTimeSystem, () -> 0.0, () -> 1.0);
         anticipateNext(this::processMetadataToken);
         return true;
     }
 
     /** {@inheritDoc} */
     @Override
     public boolean inMetadata() {
         anticipateNext(structureProcessor);
         return true;
     }
 
     /** {@inheritDoc} */
     @Override
     public boolean finalizeMetadata() {
         metadata.finalizeMetadata(context);
         metadata.validate(header.getFormatVersion());
         if (metadata.getCenter().getBody() != null) {
             setMuCreated(metadata.getCenter().getBody().getGM());
         }
         anticipateNext(getFileFormat() == FileFormat.XML ? structureProcessor : this::processKvnDataToken);
         return true;
     }
 
     /** {@inheritDoc} */
     @Override
     public boolean prepareData() {
         currentBlock = new OemData();
         anticipateNext(getFileFormat() == FileFormat.XML ? this::processXmlSubStructureToken : this::processMetadataToken);
         return true;
     }
 
     /** {@inheritDoc} */
     @Override
     public boolean inData() {
         anticipateNext(getFileFormat() == FileFormat.XML ? structureProcessor : this::processKvnCovarianceToken);
         return true;
     }
 
     /** {@inheritDoc} */
     @Override
     public boolean finalizeData() {
         if (metadata != null) {
             currentBlock.validate(header.getFormatVersion());
             segments.add(new OemSegment(metadata, currentBlock, getSelectedMu()));
         }
         metadata          = null;
         context           = null;
         currentBlock      = null;
         inCovariance      = false;
         currentCovariance = null;
         currentRow        = -1;
         return true;
     }
 
     /** {@inheritDoc} */
     @Override
     public Oem build() {
         // OEM KVN file lack a DATA_STOP keyword, hence we can't call finalizeData()
         // automatically before the end of the file
         finalizeData();
         final Oem file = new Oem(header, segments, getConventions(), getDataContext(), getSelectedMu());
         file.checkTimeSystems();
         return file;
     }
 
     /** Manage state vector section in a XML message.
      * @param starting if true, parser is entering the section
      * otherwise it is leaving the section
      * @return always return true
      */
     boolean manageXmlStateVectorSection(final boolean starting) {
         if (starting) {
             stateVectorBlock = new StateVector();
             anticipateNext(this::processXmlStateVectorToken);
         } else {
             currentBlock.addData(stateVectorBlock.toTimeStampedPVCoordinates(),
                                  stateVectorBlock.hasAcceleration());
             stateVectorBlock = null;
             anticipateNext(structureProcessor);
         }
         return true;
     }
 
     /** Manage covariance matrix section.
      * @param starting if true, parser is entering the section
      * otherwise it is leaving the section
      * @return always return true
      */
     boolean manageCovarianceSection(final boolean starting) {
         if (starting) {
             // save the current metadata for later retrieval of reference frame
             final OdmCommonMetadata savedMetadata = metadata;
             currentCovariance = new CartesianCovariance(
                     savedMetadata::getReferenceFrame,
                     savedMetadata.getFrameMapper());
             anticipateNext(getFileFormat() == FileFormat.XML ?
                         this::processXmlCovarianceToken :
                         this::processKvnCovarianceToken);
         } else {
             currentBlock.addCovarianceMatrix(currentCovariance);
             currentCovariance = null;
             anticipateNext(structureProcessor);
         }
         return true;
     }
 
     /** 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 CommonMetadataKey.valueOf(token.getName()).process(token, context, metadata);
                 } catch (IllegalArgumentException iaeC) {
                     try {
                         return OemMetadataKey.valueOf(token.getName()).process(token, context, metadata);
                     } catch (IllegalArgumentException iaeE) {
                         // token has not been recognized
                         return false;
                     }
                 }
             }
         }
     }
 
     /** Process one XML data substructure token.
      * @param token token to process
      * @return true if token was processed, false otherwise
      */
     private boolean processXmlSubStructureToken(final ParseToken token) {
         if (COMMENT.equals(token.getName())) {
             return token.getType() == TokenType.ENTRY ? currentBlock.addComment(token.getContentAsNormalizedString()) : true;
         } else {
             try {
                 return token.getName() != null &&
                                 OemDataSubStructureKey.valueOf(token.getName()).process(token, this);
             } catch (IllegalArgumentException iae) {
                 // token has not been recognized
                 return false;
             }
         }
     }
 
     /** Process one data token in a KVN message.
      * @param token token to process
      * @return true if token was processed, false otherwise
      */
     private boolean processKvnDataToken(final ParseToken token) {
         if (currentBlock == null) {
             // OEM KVN file lack a DATA_START keyword, hence we can't call prepareData()
             // automatically before the first data token arrives
             prepareData();
         }
         inData();
         if (COMMENT.equals(token.getName())) {
             return token.getType() == TokenType.ENTRY ? currentBlock.addComment(token.getContentAsNormalizedString()) : true;
         } else if (token.getType() == TokenType.RAW_LINE) {
             try {
                 final String[] fields = SPLIT_AT_BLANKS.split(token.getRawContent().trim());
                 if (fields.length != 7 && fields.length != 10) {
                     throw new OrekitException(OrekitMessages.UNABLE_TO_PARSE_LINE_IN_FILE,
                                               token.getLineNumber(), token.getFileName(), token.getContentAsNormalizedString());
                 }
                 stateVectorBlock = new StateVector();
                 stateVectorBlock.setEpoch(context.getTimeSystem().getConverter(context).parse(fields[0]));
                 stateVectorBlock.setP(0, Unit.KILOMETRE.toSI(Double.parseDouble(fields[1])));
                 stateVectorBlock.setP(1, Unit.KILOMETRE.toSI(Double.parseDouble(fields[2])));
                 stateVectorBlock.setP(2, Unit.KILOMETRE.toSI(Double.parseDouble(fields[3])));
                 stateVectorBlock.setV(0, Units.KM_PER_S.toSI(Double.parseDouble(fields[4])));
                 stateVectorBlock.setV(1, Units.KM_PER_S.toSI(Double.parseDouble(fields[5])));
                 stateVectorBlock.setV(2, Units.KM_PER_S.toSI(Double.parseDouble(fields[6])));
                 if (fields.length == 10) {
                     stateVectorBlock.setA(0, Units.KM_PER_S2.toSI(Double.parseDouble(fields[7])));
                     stateVectorBlock.setA(1, Units.KM_PER_S2.toSI(Double.parseDouble(fields[8])));
                     stateVectorBlock.setA(2, Units.KM_PER_S2.toSI(Double.parseDouble(fields[9])));
                 }
                 return currentBlock.addData(stateVectorBlock.toTimeStampedPVCoordinates(),
                                             stateVectorBlock.hasAcceleration());
             } catch (NumberFormatException nfe) {
                 throw new OrekitException(nfe, OrekitMessages.UNABLE_TO_PARSE_LINE_IN_FILE,
                                           token.getLineNumber(), token.getFileName(), token.getRawContent());
             }
         } else {
             // not a raw line, it is most probably either the end of the data section or a covariance section
             return false;
         }
     }
 
     /** Process one state vector data token in a XML message.
      * @param token token to process
      * @return true if token was processed, false otherwise
      */
     private boolean processXmlStateVectorToken(final ParseToken token) {
         anticipateNext(this::processXmlSubStructureToken);
         try {
             return token.getName() != null &&
                    StateVectorKey.valueOf(token.getName()).process(token, context, stateVectorBlock);
         } catch (IllegalArgumentException iae) {
             // token has not been recognized
             return false;
         }
     }
 
     /** Process one covariance token in a KVN message.
      * @param token token to process
      * @return true if token was processed, false otherwise
      */
     private boolean processKvnCovarianceToken(final ParseToken token) {
         anticipateNext(getFileFormat() == FileFormat.XML ? structureProcessor : this::processMetadataToken);
         if (token.getName() != null) {
             if (OemDataSubStructureKey.COVARIANCE.name().equals(token.getName()) ||
                 OemDataSubStructureKey.covarianceMatrix.name().equals(token.getName())) {
                 // we are entering/leaving covariance section
                 inCovariance = token.getType() == TokenType.START;
                 return true;
             } else if (!inCovariance) {
                 // this is not a covariance token
                 return false;
             } else {
                 // named tokens in covariance section must be at the start, before the raw lines
                 if (currentRow > 0) {
                     // the previous covariance matrix was not completed
                     throw new OrekitException(OrekitMessages.UNABLE_TO_PARSE_ELEMENT_IN_FILE,
                                               token.getName(), token.getLineNumber(), token.getFileName());
                 }
 
                 if (currentCovariance == null) {
                     // save the current metadata for later retrieval of reference frame
                     final OdmCommonMetadata savedMetadata = metadata;
                     currentCovariance = new CartesianCovariance(
                             savedMetadata::getReferenceFrame,
                             savedMetadata.getFrameMapper());
                     currentRow        = 0;
                 }
 
                 // parse the token
                 try {
                     return CartesianCovarianceKey.valueOf(token.getName()).
                            process(token, context, currentCovariance);
                 } catch (IllegalArgumentException iae) {
                     // token not recognized
                     return false;
                 }
 
             }
         } else {
             // this is a raw line
             try {
                 final String[] fields = SPLIT_AT_BLANKS.split(token.getContentAsNormalizedString().trim());
                 if (fields.length != currentRow + 1) {
                     throw new OrekitException(OrekitMessages.UNABLE_TO_PARSE_LINE_IN_FILE,
                                               token.getLineNumber(), token.getFileName(), token.getContentAsNormalizedString());
                 }
                 for (int j = 0; j < fields.length; ++j) {
                     currentCovariance.setCovarianceMatrixEntry(currentRow, j, 1.0e6 * Double.parseDouble(fields[j]));
                 }
                 if (++currentRow == 6) {
                     // this was the last row
                     currentBlock.addCovarianceMatrix(currentCovariance);
                     currentCovariance = null;
                     currentRow        = -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 covariance matrix data token in a XML message.
      * @param token token to process
      * @return true if token was processed, false otherwise
      */
     private boolean processXmlCovarianceToken(final ParseToken token) {
         anticipateNext(this::processXmlSubStructureToken);
         try {
             return token.getName() != null &&
                    CartesianCovarianceKey.valueOf(token.getName()).process(token, context, currentCovariance);
         } catch (IllegalArgumentException iae) {
             // token has not been recognized
             return false;
         }
     }
 
 }