package jalview.ext.ensembl;

import jalview.datamodel.Alignment;
import jalview.datamodel.AlignmentI;
import jalview.datamodel.DBRefEntry;
import jalview.datamodel.DBRefSource;
import jalview.datamodel.Mapping;
import jalview.datamodel.SequenceFeature;
import jalview.datamodel.SequenceI;
import jalview.exceptions.JalviewException;
import jalview.io.FastaFile;
import jalview.io.FileParse;
import jalview.io.gff.SequenceOntology;
import jalview.util.DBRefUtils;
import jalview.util.MapList;

import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;

/**
 * Base class for Ensembl sequence fetchers
 * 
 * @author gmcarstairs
 */
public abstract class EnsemblSeqProxy extends EnsemblRestClient
{
  protected static final String PARENT = "Parent";

  protected static final String ID = "ID";

  public enum EnsemblSeqType
  {
    /**
     * type=genomic for the full dna including introns
     */
    GENOMIC("genomic"),

    /**
     * type=cdna for transcribed dna including UTRs
     */
    CDNA("cdna"),

    /**
     * type=cds for coding dna excluding UTRs
     */
    CDS("cds"),

    /**
     * type=protein for the peptide product sequence
     */
    PROTEIN("protein");

    /*
     * the value of the 'type' parameter to fetch this version of 
     * an Ensembl sequence
     */
    private String type;

    EnsemblSeqType(String t)
    {
      type = t;
    }

    public String getType()
    {
      return type;
    }

  }

  /**
   * A comparator to sort ranges into ascending start position order
   */
  private class RangeSorter implements Comparator<int[]>
  {
    boolean forwards;

    RangeSorter(boolean forward)
    {
      forwards = forward;
    }

    @Override
    public int compare(int[] o1, int[] o2)
    {
      return (forwards ? 1 : -1) * Integer.compare(o1[0], o2[0]);
    }

  };

  /**
   * Constructor
   */
  public EnsemblSeqProxy()
  {
  }

  /**
   * Makes the sequence queries to Ensembl's REST service and returns an
   * alignment consisting of the returned sequences
   */
  @Override
  public AlignmentI getSequenceRecords(String query) throws Exception
  {
    long now = System.currentTimeMillis();
    // TODO use a String... query vararg instead?

    // danger: accession separator used as a regex here, a string elsewhere
    // in this case it is ok (it is just a space), but (e.g.) '\' would not be
    List<String> allIds = Arrays.asList(query.split(getAccessionSeparator()));
    AlignmentI alignment = null;
    inProgress = true;

    /*
     * execute queries, if necessary in batches of the
     * maximum allowed number of ids
     */
    int maxQueryCount = getMaximumQueryCount();
    for (int v = 0, vSize = allIds.size(); v < vSize; v += maxQueryCount)
    {
      int p = Math.min(vSize, v + maxQueryCount);
      List<String> ids = allIds.subList(v, p);
      try
      {
        alignment = fetchSequences(ids, alignment);
      } catch (Throwable r)
      {
        inProgress = false;
        String msg = "Aborting ID retrieval after " + v
                + " chunks. Unexpected problem (" + r.getLocalizedMessage()
                + ")";
        System.err.println(msg);
        if (alignment != null)
        {
          break; // return what we got
        }
        else
        {
          throw new JalviewException(msg, r);
        }
      }
    }

    /*
     * fetch and transfer genomic sequence features
     */
    for (String accId : allIds)
    {
      addFeaturesAndProduct(accId, alignment);
    }

    inProgress = false;
    System.out.println(getClass().getName() + " took "
            + (System.currentTimeMillis() - now) + "ms to fetch");
    return alignment;
  }

  /**
   * Fetches Ensembl features using the /overlap REST endpoint, and adds them to
   * the sequence in the alignment. Also fetches the protein product, maps it
   * from the CDS features of the sequence, and saves it as a cross-reference of
   * the dna sequence.
   * 
   * @param accId
   * @param alignment
   */
  protected void addFeaturesAndProduct(String accId, AlignmentI alignment)
  {
    try
    {
      /*
       * get 'dummy' genomic sequence with exon, cds and variation features
       */
      EnsemblOverlap gffFetcher = new EnsemblOverlap();
      EnsemblFeatureType[] features = getFeaturesToFetch();
      AlignmentI geneFeatures = gffFetcher.getSequenceRecords(accId,
              features);
      if (geneFeatures.getHeight() > 0)
      {
        /*
         * transfer features to the query sequence
         */
        SequenceI genomicSequence = geneFeatures.getSequenceAt(0);
        SequenceI querySeq = alignment.findName(accId);
        transferFeatures(accId, genomicSequence, querySeq);

        /*
         * fetch and map protein product, and add it as a cross-reference
         * of the retrieved sequence
         */
        addProteinProduct(querySeq);
      }
    } catch (IOException e)
    {
      System.err.println("Error transferring Ensembl features: "
              + e.getMessage());
    }
  }

  /**
   * Returns those sequence feature types to fetch from Ensembl. We may want
   * features either because they are of interest to the user, or as means to
   * identify the locations of the sequence on the genomic sequence (CDS
   * features identify CDS, exon features identify cDNA etc).
   * 
   * @return
   */
  protected abstract EnsemblFeatureType[] getFeaturesToFetch();

  /**
   * Fetches and maps the protein product, and adds it as a cross-reference of
   * the retrieved sequence
   */
  protected void addProteinProduct(SequenceI querySeq)
  {
    String accId = querySeq.getName();
    try
    {
      AlignmentI protein = new EnsemblProtein().getSequenceRecords(accId);
      if (protein == null || protein.getHeight() == 0)
      {
        System.out.println("Failed to retrieve protein for " + accId);
        return;
      }
      SequenceI proteinSeq = protein.getSequenceAt(0);

      /*
       * need dataset sequences (to be the subject of mappings)
       */
      proteinSeq.createDatasetSequence();
      querySeq.createDatasetSequence();

      MapList mapList = mapCdsToProtein(querySeq, proteinSeq);
      if (mapList != null)
      {
        Mapping map = new Mapping(proteinSeq.getDatasetSequence(), mapList);
        DBRefEntry dbr = new DBRefEntry(getDbSource(), getDbVersion(),
                accId, map);
        querySeq.getDatasetSequence().addDBRef(dbr);
      }
    } catch (Exception e)
    {
      System.err
              .println(String.format("Error retrieving protein for %s: %s",
                      accId, e.getMessage()));
    }
  }

  /**
   * Returns a mapping from dna to protein by inspecting sequence features of
   * type "CDS" on the dna.
   * 
   * @param dnaSeq
   * @param proteinSeq
   * @return
   */
  protected MapList mapCdsToProtein(SequenceI dnaSeq, SequenceI proteinSeq)
  {
    SequenceFeature[] sfs = dnaSeq.getSequenceFeatures();
    if (sfs == null)
    {
      return null;
    }

    List<int[]> ranges = new ArrayList<int[]>(50);
    SequenceOntology so = SequenceOntology.getInstance();

    int mappedDnaLength = 0;
    
    /*
     * Map CDS columns of dna to peptide. No need to worry about reverse strand
     * dna here since the retrieved sequence is as transcribed (reverse
     * complement for reverse strand), i.e in the same sense as the peptide. 
     */
    for (SequenceFeature sf : sfs)
    {
      /*
       * process a CDS feature (or a sub-type of CDS)
       */
      if (so.isA(sf.getType(), SequenceOntology.CDS))
      {
        ranges.add(new int[] { sf.getBegin(), sf.getEnd() });
        mappedDnaLength += Math.abs(sf.getEnd() - sf.getBegin()) + 1;
      }
    }
    int proteinLength = proteinSeq.getLength();
    List<int[]> proteinRange = new ArrayList<int[]>();
    proteinRange.add(new int[] { 1, proteinLength });

    /*
     * dna length should map to protein (or protein minus stop codon)
     */
    if (mappedDnaLength == 3 * proteinLength
            || mappedDnaLength == 3 * (proteinLength + 1))
    {
      return new MapList(ranges, proteinRange, 3, 1);
    }
    return null;
  }

  /**
   * Fetches sequences for the list of accession ids and adds them to the
   * alignment. Returns the extended (or created) alignment.
   * 
   * @param ids
   * @param alignment
   * @return
   * @throws JalviewException
   * @throws IOException
   */
  protected AlignmentI fetchSequences(List<String> ids, AlignmentI alignment)
          throws JalviewException, IOException
  {
    if (!isEnsemblAvailable())
    {
      inProgress = false;
      throw new JalviewException("ENSEMBL Rest API not available.");
    }
    FileParse fp = getSequenceReader(ids);
    FastaFile fr = new FastaFile(fp);
    if (fr.hasWarningMessage())
    {
      System.out.println(String.format(
              "Warning when retrieving %d ids %s\n%s", ids.size(),
              ids.toString(), fr.getWarningMessage()));
    }
    else if (fr.getSeqs().size() != ids.size())
    {
      System.out.println(String.format(
              "Only retrieved %d sequences for %d query strings", fr
                      .getSeqs().size(), ids.size()));
    }
    if (fr.getSeqs().size() > 0)
    {
      AlignmentI seqal = new Alignment(
              fr.getSeqsAsArray());
      for (SequenceI sq:seqal.getSequences())
      {
        if (sq.getDescription() == null)
        {
          sq.setDescription(getDbName());
        }
        String name = sq.getName();
        if (ids.contains(name)
                || ids.contains(name.replace("ENSP", "ENST")))
        {
          DBRefUtils.parseToDbRef(sq, DBRefSource.ENSEMBL, "0", name);
        }
      }
      if (alignment == null)
      {
        alignment = seqal;
      }
      else
      {
        alignment.append(seqal);
      }
    }
    return alignment;
  }

  /**
   * Returns the URL for the REST call
   * 
   * @return
   * @throws MalformedURLException
   */
  @Override
  protected URL getUrl(List<String> ids) throws MalformedURLException
  {
    // ids are not used - they go in the POST body instead
    StringBuffer urlstring = new StringBuffer(128);
    urlstring.append(SEQUENCE_ID_URL);

    // @see https://github.com/Ensembl/ensembl-rest/wiki/Output-formats
    urlstring.append("?type=").append(getSourceEnsemblType().getType());
    urlstring.append(("&Accept=text/x-fasta"));

    URL url = new URL(urlstring.toString());
    return url;
  }

  /**
   * A sequence/id POST request currently allows up to 50 queries
   * 
   * @see http://rest.ensembl.org/documentation/info/sequence_id_post
   */
  @Override
  public int getMaximumQueryCount()
  {
    return 50;
  }

  @Override
  public boolean useGetRequest()
  {
    return false;
  }

  @Override
  public String getRequestMimeType()
  {
    return "application/json";
  }

  @Override
  public String getResponseMimeType()
  {
    return "text/x-fasta";
  }

  /**
   * 
   * @return the configured sequence return type for this source
   */
  protected abstract EnsemblSeqType getSourceEnsemblType();

  /**
   * Returns a list of [start, end] genomic ranges corresponding to the sequence
   * being retrieved.
   * 
   * The correspondence between the frames of reference is made by locating
   * those features on the genomic sequence which identify the retrieved
   * sequence. Specifically
   * <ul>
   * <li>genomic sequence is identified by "transcript" features with
   * ID=transcript:transcriptId</li>
   * <li>cdna sequence is identified by "exon" features with
   * Parent=transcript:transcriptId</li>
   * <li>cds sequence is identified by "CDS" features with
   * Parent=transcript:transcriptId</li>
   * </ul>
   * 
   * The returned ranges are sorted to run forwards (for positive strand) or
   * backwards (for negative strand). Aborts and returns null if both positive
   * and negative strand are found (this should not normally happen).
   * 
   * @param sfs
   * @param accId
   * @return
   */
  protected MapList getGenomicRanges(SequenceFeature[] sfs, String accId)
  {
    /*
     * generously size for initial number of cds regions
     * (worst case titin Q8WZ42 has c. 313 exons)
     */
    List<int[]> regions = new ArrayList<int[]>(100);
    int mappedLength = 0;
    int direction = 1; // forward
    boolean directionSet = false;
  
    for (SequenceFeature sf : sfs)
    {
      /*
       * accept the target feature type or a specialisation of it
       * (e.g. coding_exon for exon)
       */
      if (identifiesSequence(sf, accId))
      {
          int strand = sf.getStrand();
  
          if (directionSet && strand != direction)
          {
            // abort - mix of forward and backward
          System.err.println("Error: forward and backward strand for "
                  + accId);
            return null;
          }
          direction = strand;
          directionSet = true;
  
          /*
           * add to CDS ranges, semi-sorted forwards/backwards
           */
          if (strand < 0)
          {
            regions.add(0, new int[] { sf.getEnd(), sf.getBegin() });
          }
          else
          {
            regions.add(new int[] { sf.getBegin(), sf.getEnd() });
          }
          mappedLength += Math.abs(sf.getEnd() - sf.getBegin() + 1);
        }
    }
  
    /*
     * a final sort is needed since Ensembl returns CDS sorted within source
     * (havana / ensembl_havana)
     */
    Collections.sort(regions, new RangeSorter(direction == 1));
  
    List<int[]> to = new ArrayList<int[]>();
    to.add(new int[] { 1, mappedLength });
  
    return new MapList(regions, to, 1, 1);
  }

  /**
   * Returns true if the sequence feature identifies positions of the genomic
   * sequence feature which are within the sequence being retrieved.
   * 
   * @param sf
   * @param accId
   * @return
   */
  protected abstract boolean identifiesSequence(SequenceFeature sf,
          String accId);

  /**
   * Transfers the sequence feature to the target sequence, adjusting its start
   * and end range based on the 'overlap' ranges. Features which do not overlap
   * the target sequence are ignored, as are features with a parent other than
   * the target sequence id.
   * 
   * @param sf
   * @param targetSequence
   * @param overlap
   */
  protected void transferFeature(SequenceFeature sf,
          SequenceI targetSequence, MapList overlap)
  {
    String parent = (String) sf.getValue(PARENT);
    if (parent != null && !parent.contains(targetSequence.getName()))
    {
      // this genomic feature belongs to a different transcript
      return;
    }

    int start = sf.getBegin();
    int end = sf.getEnd();
    int[] mappedRange = overlap.locateInTo(start, end);
  
    if (mappedRange != null)
    {
      SequenceFeature copy = new SequenceFeature(sf);
      int offset = targetSequence.getStart() - 1;
      copy.setBegin(offset + Math.min(mappedRange[0], mappedRange[1]));
      copy.setEnd(offset + Math.max(mappedRange[0], mappedRange[1]));
      targetSequence.addSequenceFeature(copy);

      /*
       * for sequence_variant, make an additional feature with consequence
       */
      if (SequenceOntology.getInstance().isSequenceVariant(sf.getType()))
      {
        String consequence = (String) sf.getValue("consequence_type");
        if (consequence != null)
        {
          SequenceFeature sf2 = new SequenceFeature("consequence",
                  consequence, copy.getBegin(), copy.getEnd(), 0f,
                  null);
          targetSequence.addSequenceFeature(sf2);
        }
      }
    }
  
  }

  /**
   * Transfers features from sourceSequence to targetSequence
   * 
   * @param accessionId
   * @param sourceSequence
   * @param targetSequence
   */
  protected void transferFeatures(String accessionId,
          SequenceI sourceSequence, SequenceI targetSequence)
  {
    if (sourceSequence == null || targetSequence == null)
    {
      return;
    }

    SequenceFeature[] sfs = sourceSequence.getSequenceFeatures();
    MapList overlap = getGenomicRanges(sfs, accessionId);

    final boolean forwardStrand = overlap.isFromForwardStrand();

    /*
     * sort features by start position (descending if reverse strand) 
     * before transferring (in forwards order) to the target sequence
     */
    Arrays.sort(sfs, new Comparator<SequenceFeature>()
    {
      @Override
      public int compare(SequenceFeature o1, SequenceFeature o2)
      {
        int c = Integer.compare(o1.getBegin(), o2.getBegin());
        return forwardStrand ? c : -c;
      }
    });

    for (SequenceFeature sf : sfs)
    {
      if (retainFeature(sf.getType()))
      {
        transferFeature(sf, targetSequence, overlap);
      }
    }
  }

  /**
   * Answers true if the feature type is one to attach to the retrieved sequence
   * 
   * @param type
   * @return
   */
  protected boolean retainFeature(@SuppressWarnings("unused") String type)
  {
    return true; // default is to keep all
  }
}