/* Copyright 2016 Applied Defense Solutions (ADS)
    * 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.
    * ADS 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.io.IOException;
  import java.util.Date;
  import java.util.List;
  
  import org.hipparchus.linear.RealMatrix;
  import org.orekit.data.DataContext;
  import org.orekit.errors.OrekitException;
  import org.orekit.errors.OrekitMessages;
  import org.orekit.files.ccsds.definitions.TimeSystem;
  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.CommonMetadataKey;
  import org.orekit.files.ccsds.ndm.odm.OdmHeader;
  import org.orekit.files.ccsds.ndm.odm.OdmMetadataKey;
  import org.orekit.files.ccsds.ndm.odm.StateVectorKey;
  import org.orekit.files.ccsds.section.HeaderKey;
  import org.orekit.files.ccsds.section.KvnStructureKey;
  import org.orekit.files.ccsds.section.MetadataKey;
  import org.orekit.files.ccsds.section.XmlStructureKey;
  import org.orekit.files.ccsds.utils.ContextBinding;
  import org.orekit.files.ccsds.utils.FileFormat;
  import org.orekit.files.ccsds.utils.generation.AbstractMessageWriter;
  import org.orekit.files.ccsds.utils.generation.Generator;
  import org.orekit.time.AbsoluteDate;
  import org.orekit.utils.CartesianDerivativesFilter;
  import org.orekit.utils.IERSConventions;
  import org.orekit.utils.TimeStampedPVCoordinates;
  import org.orekit.utils.units.Unit;
  
  /**
   * A writer for Orbit Ephemeris Message (OEM) files.
   *
   * <h2> Metadata </h2>
   *
   * <p> The OEM metadata used by this writer is described in the following table. Many
   * metadata items are optional or have default values so they do not need to be specified.
   * At a minimum the user must supply those values that are required and for which no
   * default exits: {@link OdmMetadataKey#OBJECT_NAME}, and {@link CommonMetadataKey#OBJECT_ID}. The usage
   * column in the table indicates where the metadata item is used, either in the OEM header
   * or in the metadata section at the start of an OEM ephemeris segment.
   *
   * <table>
   * <caption>OEM metadata</caption>
   *     <thead>
   *         <tr>
   *             <th>Keyword</th>
   *             <th>Usage</th>
   *             <th>Obligatory</th>
   *             <th>Default</th>
   *             <th>Reference</th>
   *    </thead>
   *    <tbody>
   *        <tr>
   *            <td>{@code CCSDS_OEM_VERS}</td>
   *            <td>Header</td>
   *            <td>Yes</td>
   *            <td>{@link Oem#FORMAT_VERSION_KEY}</td>
   *            <td>Table 5-2</td>
   *        <tr>
   *            <td>{@code COMMENT}</td>
   *            <td>Header</td>
   *            <td>No</td>
   *            <td></td>
   *            <td>Table 5-2</td>
   *        <tr>
   *            <td>{@link HeaderKey#CREATION_DATE}</td>
   *            <td>Header</td>
   *            <td>Yes</td>
   *            <td>{@link Date#Date() Now}</td>
   *            <td>Table 5.2, 6.5.9</td>
   *        <tr>
   *            <td>{@link HeaderKey#ORIGINATOR}</td>
   *            <td>Header</td>
   *            <td>Yes</td>
   *            <td>{@link #DEFAULT_ORIGINATOR}</td>
   *            <td>Table 5-2</td>
   *        <tr>
   *            <td>{@link OdmMetadataKey#OBJECT_NAME}</td>
   *            <td>Segment</td>
  *            <td>Yes</td>
  *            <td></td>
  *            <td>Table 5-3</td>
  *        <tr>
  *            <td>{@link CommonMetadataKey#OBJECT_ID}</td>
  *            <td>Segment</td>
  *            <td>Yes</td>
  *            <td></td>
  *            <td>Table 5-3</td>
  *        <tr>
  *            <td>{@link CommonMetadataKey#CENTER_NAME}</td>
  *            <td>Segment</td>
  *            <td>Yes</td>
  *            <td></td>
  *            <td>Table 5-3</td>
  *        <tr>
  *            <td>{@link CommonMetadataKey#REF_FRAME}</td>
  *            <td>Segment</td>
  *            <td>Yes</td>
  *            <td></td>
  *            <td>Table 5-3, Annex A</td>
  *        <tr>
  *            <td>{@link CommonMetadataKey#REF_FRAME_EPOCH}</td>
  *            <td>Segment</td>
  *            <td>No</td>
  *            <td></td>
  *            <td>Table 5-3, 6.5.9</td>
  *        <tr>
  *            <td>{@link MetadataKey#TIME_SYSTEM}</td>
  *            <td>Segment</td>
  *            <td>Yes</td>
  *            <td></td>
  *        <tr>
  *            <td>{@link OemMetadataKey#START_TIME}</td>
  *            <td>Segment</td>
  *            <td>Yes</td>
  *            <td></td>
  *            <td>Table 5-3, 6.5.9</td>
  *        <tr>
  *            <td>{@link OemMetadataKey#USEABLE_START_TIME}</td>
  *            <td>Segment</td>
  *            <td>No</td>
  *            <td></td>
  *            <td>Table 5-3, 6.5.9</td>
  *        <tr>
  *            <td>{@link OemMetadataKey#STOP_TIME}</td>
  *            <td>Segment</td>
  *            <td>Yes</td>
  *            <td></td>
  *            <td>Table 5-3, 6.5.9</td>
  *        <tr>
  *            <td>{@link OemMetadataKey#USEABLE_STOP_TIME}</td>
  *            <td>Segment</td>
  *            <td>No</td>
  *            <td></td>
  *            <td>Table 5-3, 6.5.9</td>
  *        <tr>
  *            <td>{@link OemMetadataKey#INTERPOLATION}</td>
  *            <td>Segment</td>
  *            <td>No</td>
  *            <td></td>
  *            <td>Table 5-3</td>
  *        <tr>
  *            <td>{@link OemMetadataKey#INTERPOLATION_DEGREE}</td>
  *            <td>Segment</td>
  *            <td>No</td>
  *            <td></td>
  *            <td>Table 5-3</td>
  *    </tbody>
  *</table>
  *
  * <p> The {@link MetadataKey#TIME_SYSTEM} must be constant for the whole file and is used
  * to interpret all dates except {@link HeaderKey#CREATION_DATE} which is always in {@link
  * TimeSystem#UTC UTC}. The guessing algorithm is not guaranteed to work so it is recommended
  * to provide values for {@link CommonMetadataKey#CENTER_NAME} and {@link MetadataKey#TIME_SYSTEM}
  * to avoid any bugs associated with incorrect guesses.
  *
  * <p> Standardized values for {@link MetadataKey#TIME_SYSTEM} are GMST, GPS, MET, MRT, SCLK,
  * TAI, TCB, TDB, TT, UT1, and UTC. Standardized values for reference frames
  * are EME2000, GTOD, ICRF, ITRF2000, ITRF-93, ITRF-97, LVLH, RTN, QSW, TOD, TNW, NTW and RSW.
  * Additionally ITRF followed by a four digit year may be used.
  *
  * @author Hank Grabowski
  * @author Evan Ward
  * @since 9.0
  * @see <a href="https://public.ccsds.org/Pubs/502x0b2c1.pdf">CCSDS 502.0-B-2 Orbit Data
  *      Messages</a>
  * @see <a href="https://public.ccsds.org/Pubs/500x0g4.pdf">CCSDS 500.0-G-4 Navigation
  *      Data Definitions and Conventions</a>
  * @see StreamingOemWriter
  */
 public class OemWriter extends AbstractMessageWriter<OdmHeader, OemSegment, Oem> {
 
     /** Version number implemented. **/
     public static final double CCSDS_OEM_VERS = 3.0;
 
     /** Default file name for error messages. */
     public static final String DEFAULT_FILE_NAME = "<OEM output>";
 
     /** Padding width for aligning the '=' sign. */
     public static final int KVN_PADDING_WIDTH = 20;
 
     /**
      * Constructor used to create a new OEM writer configured with the necessary parameters
      * to successfully fill in all required fields that aren't part of a standard object.
      * <p>
      * If the mandatory header entries are not present (or if header is null),
      * built-in defaults will be used
      * </p>
      * <p>
      * The writer is built from the complete header and partial metadata. The template
      * metadata is used to initialize and independent local copy, that will be updated
      * as new segments are written (with at least the segment start and stop will change,
      * but some other parts may change too). The {@code template} argument itself is not
      * changed.
      * </p>
      * <p>
      * Calling this constructor directly is not recommended. Users should rather use
      * {@link org.orekit.files.ccsds.ndm.WriterBuilder#buildOemWriter()
      * writerBuilder.buildOemWriter()}.
      * </p>
      * @param conventions IERS Conventions
      * @param dataContext used to retrieve frames, time scales, etc.
      * @param missionReferenceDate reference date for Mission Elapsed Time or Mission Relative Time time systems
      * @since 11.0
      * @see #DEFAULT_FILE_NAME
      */
     public OemWriter(final IERSConventions conventions, final DataContext dataContext,
                      final AbsoluteDate missionReferenceDate) {
         super(Oem.ROOT, Oem.FORMAT_VERSION_KEY, CCSDS_OEM_VERS,
               new ContextBinding(
                   () -> conventions, () -> true, () -> dataContext,
                   () -> ParsedUnitsBehavior.STRICT_COMPLIANCE,
                   () -> missionReferenceDate, () -> TimeSystem.UTC, () -> 0.0, () -> 1.0));
     }
 
     /** {@inheritDoc} */
     @Override
     protected void writeSegmentContent(final Generator generator, final double formatVersion,
                                        final OemSegment segment)
         throws IOException {
 
         final OemMetadata metadata = segment.getMetadata();
         writeMetadata(generator, metadata);
 
         startData(generator);
 
         // write data comments
         generator.writeComments(segment.getData().getComments());
 
         // Loop on orbit data
         final CartesianDerivativesFilter filter = segment.getAvailableDerivatives();
         if (filter == CartesianDerivativesFilter.USE_P) {
             throw new OrekitException(OrekitMessages.MISSING_VELOCITY);
         }
         final boolean useAcceleration = filter.equals(CartesianDerivativesFilter.USE_PVA);
         for (final TimeStampedPVCoordinates coordinates : segment.getCoordinates()) {
             writeOrbitEphemerisLine(generator, metadata, coordinates, useAcceleration);
         }
 
         // output covariance data
         writeCovariances(generator, segment.getMetadata(), segment.getData().getCovarianceMatrices());
 
         endData(generator);
 
     }
 
     /** Write an ephemeris segment metadata.
      * @param generator generator to use for producing output
      * @param metadata metadata to write
      * @throws IOException if the output stream throws one while writing.
      */
     void writeMetadata(final Generator generator, final OemMetadata metadata)
         throws IOException {
 
         // add an empty line for presentation
         generator.newLine();
 
         final ContextBinding oldContext = getContext();
         setContext(new ContextBinding(oldContext::getConventions,
                                       oldContext::isSimpleEOP,
                                       oldContext::getDataContext,
                                       oldContext::getParsedUnitsBehavior,
                                       oldContext::getReferenceDate,
                                       metadata::getTimeSystem,
                                       oldContext::getClockCount,
                                       oldContext::getClockRate));
 
         // Start metadata
         generator.enterSection(generator.getFormat() == FileFormat.KVN ?
                                KvnStructureKey.META.name() :
                                XmlStructureKey.metadata.name());
 
         generator.writeComments(metadata.getComments());
 
         // objects
         generator.writeEntry(OdmMetadataKey.OBJECT_NAME.name(),    metadata.getObjectName(),       null, true);
         generator.writeEntry(CommonMetadataKey.OBJECT_ID.name(),   metadata.getObjectID(),         null, true);
         generator.writeEntry(CommonMetadataKey.CENTER_NAME.name(), metadata.getCenter().getName(), null, false);
 
         // frames
         generator.writeEntry(CommonMetadataKey.REF_FRAME.name(), metadata.getReferenceFrame().getName(), null, true);
         generator.writeOptionalDateEntry(CommonMetadataKey.REF_FRAME_EPOCH.name(), getTimeConverter(), metadata.getFrameEpoch(), true, false);
 
         // time
         generator.writeEntry(MetadataKey.TIME_SYSTEM.name(), metadata.getTimeSystem(), true);
         generator.writeEntry(OemMetadataKey.START_TIME.name(), getTimeConverter(), metadata.getStartTime(), false, true);
         generator.writeOptionalDateEntry(OemMetadataKey.USEABLE_START_TIME.name(), getTimeConverter(), metadata.getUseableStartTime(), false, false);
         generator.writeOptionalDateEntry(OemMetadataKey.USEABLE_STOP_TIME.name(), getTimeConverter(), metadata.getUseableStopTime(), false, false);
         generator.writeEntry(OemMetadataKey.STOP_TIME.name(), getTimeConverter(), metadata.getStopTime(), false, true);
 
         // interpolation
         generator.writeOptionalEnumEntry(OemMetadataKey.INTERPOLATION.name(), metadata.getInterpolationMethod(), false);
         // treat degree < 0 as equivalent to null
         if (metadata.getInterpolationDegree() >= 0) {
             generator.writeEntry(OemMetadataKey.INTERPOLATION_DEGREE.name(),
                     Integer.toString(metadata.getInterpolationDegree()),
                     null, false);
         }
 
         // Stop metadata
         generator.exitSection();
 
         // add an empty line for presentation
         generator.newLine();
 
     }
 
     /**
      * Write a single orbit ephemeris line .
      * @param generator generator to use for producing output
      * @param metadata metadata to use for interpreting data
      * @param coordinates orbit information for a given date
      * @param useAcceleration is true, the acceleration data must be used
      * @throws IOException if the output stream throws one while writing.
      */
     void writeOrbitEphemerisLine(final Generator generator, final OemMetadata metadata,
                                  final TimeStampedPVCoordinates coordinates,
                                  final boolean useAcceleration)
         throws IOException {
 
         if (generator.getFormat() == FileFormat.KVN) {
 
             // Epoch
             generator.writeRawData(generator.dateToString(getTimeConverter(), coordinates.getDate()));
 
             // Position data in km
             generator.writeRawData(' ');
             generator.writeRawData(generator.doubleToString(Unit.KILOMETRE.fromSI(coordinates.getPosition().getX())));
             generator.writeRawData(' ');
             generator.writeRawData(generator.doubleToString(Unit.KILOMETRE.fromSI(coordinates.getPosition().getY())));
             generator.writeRawData(' ');
             generator.writeRawData(generator.doubleToString(Unit.KILOMETRE.fromSI(coordinates.getPosition().getZ())));
 
             // Velocity data in km/s
             generator.writeRawData(' ');
             generator.writeRawData(generator.doubleToString(Units.KM_PER_S.fromSI(coordinates.getVelocity().getX())));
             generator.writeRawData(' ');
             generator.writeRawData(generator.doubleToString(Units.KM_PER_S.fromSI(coordinates.getVelocity().getY())));
             generator.writeRawData(' ');
             generator.writeRawData(generator.doubleToString(Units.KM_PER_S.fromSI(coordinates.getVelocity().getZ())));
 
             // Acceleration data in km/s²
             if (useAcceleration) {
                 generator.writeRawData(' ');
                 generator.writeRawData(generator.doubleToString(Units.KM_PER_S2.fromSI(coordinates.getAcceleration().getX())));
                 generator.writeRawData(' ');
                 generator.writeRawData(generator.doubleToString(Units.KM_PER_S2.fromSI(coordinates.getAcceleration().getY())));
                 generator.writeRawData(' ');
                 generator.writeRawData(generator.doubleToString(Units.KM_PER_S2.fromSI(coordinates.getAcceleration().getZ())));
             }
 
             // end the line
             generator.newLine();
         } else {
             generator.enterSection(OemDataSubStructureKey.stateVector.name());
 
             // Epoch
             generator.writeEntry(StateVectorKey.EPOCH.name(), getTimeConverter(), coordinates.getDate(), false, true);
 
             // Position data in km
             generator.writeEntry(StateVectorKey.X.name(), coordinates.getPosition().getX(), Unit.KILOMETRE, true);
             generator.writeEntry(StateVectorKey.Y.name(), coordinates.getPosition().getY(), Unit.KILOMETRE, true);
             generator.writeEntry(StateVectorKey.Z.name(), coordinates.getPosition().getZ(), Unit.KILOMETRE, true);
 
             // Velocity data in km/s
             generator.writeEntry(StateVectorKey.X_DOT.name(), coordinates.getVelocity().getX(), Units.KM_PER_S, true);
             generator.writeEntry(StateVectorKey.Y_DOT.name(), coordinates.getVelocity().getY(), Units.KM_PER_S, true);
             generator.writeEntry(StateVectorKey.Z_DOT.name(), coordinates.getVelocity().getZ(), Units.KM_PER_S, true);
 
             // Acceleration data in km/s²
             if (useAcceleration) {
                 generator.writeEntry(StateVectorKey.X_DDOT.name(), coordinates.getAcceleration().getX(), Units.KM_PER_S2, true);
                 generator.writeEntry(StateVectorKey.Y_DDOT.name(), coordinates.getAcceleration().getY(), Units.KM_PER_S2, true);
                 generator.writeEntry(StateVectorKey.Z_DDOT.name(), coordinates.getAcceleration().getZ(), Units.KM_PER_S2, true);
             }
 
             generator.exitSection();
 
         }
     }
 
     /**
      * Write a covariance matrices.
      * @param generator generator to use for producing output
      * @param metadata metadata to use for interpreting data
      * @param covariances covariances to write
      * @throws IOException if the output stream throws one while writing.
      */
     void writeCovariances(final Generator generator, final OemMetadata metadata,
                           final List<CartesianCovariance> covariances)
         throws IOException {
         if (covariances != null && !covariances.isEmpty()) {
 
             // enter the global covariance section in KVN
             if (generator.getFormat() == FileFormat.KVN) {
                 generator.enterSection(OemDataSubStructureKey.COVARIANCE.name());
             }
 
             for (final CartesianCovariance covariance : covariances) {
                 writeCovariance(generator, metadata, covariance);
             }
 
             // exit the global covariance section in KVN
             if (generator.getFormat() == FileFormat.KVN) {
                 generator.exitSection();
             }
 
         }
     }
 
     /**
      * Write a single covariance matrix.
      * @param generator generator to use for producing output
      * @param metadata metadata to use for interpreting data
      * @param covariance covariance to write
      * @throws IOException if the output stream throws one while writing.
      */
     private void writeCovariance(final Generator generator, final OemMetadata metadata,
                                  final CartesianCovariance covariance)
         throws IOException {
 
         // wrapper for a single matrix in XML
         if (generator.getFormat() == FileFormat.XML) {
             generator.enterSection(OemDataSubStructureKey.covarianceMatrix.name());
         }
 
         // epoch
         generator.writeEntry(CartesianCovarianceKey.EPOCH.name(), getTimeConverter(), covariance.getEpoch(), false, true);
 
         // reference frame
         if (covariance.getReferenceFrame() != metadata.getReferenceFrame()) {
             generator.writeEntry(CartesianCovarianceKey.COV_REF_FRAME.name(), covariance.getReferenceFrame().getName(), null, false);
         }
 
         // matrix data
         final RealMatrix m = covariance.getCovarianceMatrix();
         if (generator.getFormat() == FileFormat.KVN) {
             for (int i = 0; i < m.getRowDimension(); ++i) {
 
                 // write triangular matrix entries
                 for (int j = 0; j <= i; ++j) {
                     if (j > 0) {
                         generator.writeRawData(' ');
                     }
                     generator.writeRawData(generator.doubleToString(Units.KM2.fromSI(m.getEntry(i, j))));
                 }
 
                 // end the line
                 generator.newLine();
 
             }
         } else {
             generator.writeEntry(CartesianCovarianceKey.CX_X.name(),         m.getEntry(0, 0), Units.KM2,        true);
             generator.writeEntry(CartesianCovarianceKey.CY_X.name(),         m.getEntry(1, 0), Units.KM2,        true);
             generator.writeEntry(CartesianCovarianceKey.CY_Y.name(),         m.getEntry(1, 1), Units.KM2,        true);
             generator.writeEntry(CartesianCovarianceKey.CZ_X.name(),         m.getEntry(2, 0), Units.KM2,        true);
             generator.writeEntry(CartesianCovarianceKey.CZ_Y.name(),         m.getEntry(2, 1), Units.KM2,        true);
             generator.writeEntry(CartesianCovarianceKey.CZ_Z.name(),         m.getEntry(2, 2), Units.KM2,        true);
             generator.writeEntry(CartesianCovarianceKey.CX_DOT_X.name(),     m.getEntry(3, 0), Units.KM2_PER_S,  true);
             generator.writeEntry(CartesianCovarianceKey.CX_DOT_Y.name(),     m.getEntry(3, 1), Units.KM2_PER_S,  true);
             generator.writeEntry(CartesianCovarianceKey.CX_DOT_Z.name(),     m.getEntry(3, 2), Units.KM2_PER_S,  true);
             generator.writeEntry(CartesianCovarianceKey.CX_DOT_X_DOT.name(), m.getEntry(3, 3), Units.KM2_PER_S2, true);
             generator.writeEntry(CartesianCovarianceKey.CY_DOT_X.name(),     m.getEntry(4, 0), Units.KM2_PER_S,  true);
             generator.writeEntry(CartesianCovarianceKey.CY_DOT_Y.name(),     m.getEntry(4, 1), Units.KM2_PER_S,  true);
             generator.writeEntry(CartesianCovarianceKey.CY_DOT_Z.name(),     m.getEntry(4, 2), Units.KM2_PER_S,  true);
             generator.writeEntry(CartesianCovarianceKey.CY_DOT_X_DOT.name(), m.getEntry(4, 3), Units.KM2_PER_S2, true);
             generator.writeEntry(CartesianCovarianceKey.CY_DOT_Y_DOT.name(), m.getEntry(4, 4), Units.KM2_PER_S2, true);
             generator.writeEntry(CartesianCovarianceKey.CZ_DOT_X.name(),     m.getEntry(5, 0), Units.KM2_PER_S,  true);
             generator.writeEntry(CartesianCovarianceKey.CZ_DOT_Y.name(),     m.getEntry(5, 1), Units.KM2_PER_S,  true);
             generator.writeEntry(CartesianCovarianceKey.CZ_DOT_Z.name(),     m.getEntry(5, 2), Units.KM2_PER_S,  true);
             generator.writeEntry(CartesianCovarianceKey.CZ_DOT_X_DOT.name(), m.getEntry(5, 3), Units.KM2_PER_S2, true);
             generator.writeEntry(CartesianCovarianceKey.CZ_DOT_Y_DOT.name(), m.getEntry(5, 4), Units.KM2_PER_S2, true);
             generator.writeEntry(CartesianCovarianceKey.CZ_DOT_Z_DOT.name(), m.getEntry(5, 5), Units.KM2_PER_S2, true);
         }
 
         // wrapper for a single matrix in XML
         if (generator.getFormat() == FileFormat.XML) {
             generator.exitSection();
         }
 
     }
 
     /** Start of a data block.
      * @param generator generator to use for producing output
      * @throws IOException if the output stream throws one while writing.
      */
     void startData(final Generator generator) throws IOException {
         if (generator.getFormat() == FileFormat.XML) {
             generator.enterSection(XmlStructureKey.data.name());
         }
     }
 
     /** End of a data block.
      * @param generator generator to use for producing output
      * @throws IOException if the output stream throws one while writing.
      */
     void endData(final Generator generator) throws IOException {
         if (generator.getFormat() == FileFormat.XML) {
             generator.exitSection();
         }
     }
 
 }