JAL-2418 source formatting
[jalview.git] / src / jalview / analysis / AlignmentUtils.java
index aa7cb18..1b8f84f 100644 (file)
@@ -39,8 +39,10 @@ import jalview.io.gff.SequenceOntologyFactory;
 import jalview.io.gff.SequenceOntologyI;
 import jalview.schemes.ResidueProperties;
 import jalview.util.Comparison;
+import jalview.util.DBRefUtils;
 import jalview.util.MapList;
 import jalview.util.MappingUtils;
+import jalview.util.RangeComparator;
 import jalview.util.StringUtils;
 
 import java.io.UnsupportedEncodingException;
@@ -59,6 +61,7 @@ import java.util.Map;
 import java.util.Map.Entry;
 import java.util.NoSuchElementException;
 import java.util.Set;
+import java.util.SortedMap;
 import java.util.TreeMap;
 
 /**
@@ -71,22 +74,26 @@ import java.util.TreeMap;
 public class AlignmentUtils
 {
 
+  private static final int CODON_LENGTH = 3;
+
   private static final String SEQUENCE_VARIANT = "sequence_variant:";
+
   private static final String ID = "ID";
 
   /**
    * A data model to hold the 'normal' base value at a position, and an optional
    * sequence variant feature
    */
-  static class DnaVariant
+  static final class DnaVariant
   {
-    String base;
+    final String base;
 
     SequenceFeature variant;
 
     DnaVariant(String nuc)
     {
       base = nuc;
+      variant = null;
     }
 
     DnaVariant(String nuc, SequenceFeature var)
@@ -94,6 +101,11 @@ public class AlignmentUtils
       base = nuc;
       variant = var;
     }
+
+    public String getSource()
+    {
+      return variant == null ? null : variant.getFeatureGroup();
+    }
   }
 
   /**
@@ -159,10 +171,12 @@ public class AlignmentUtils
         }
       }
       // TODO use Character.toLowerCase to avoid creating String objects?
-      char[] upstream = new String(ds.getSequence(s.getStart() - 1
-              - ustream_ds, s.getStart() - 1)).toLowerCase().toCharArray();
-      char[] downstream = new String(ds.getSequence(s_end - 1, s_end
-              + dstream_ds)).toLowerCase().toCharArray();
+      char[] upstream = new String(ds
+              .getSequence(s.getStart() - 1 - ustream_ds, s.getStart() - 1))
+                      .toLowerCase().toCharArray();
+      char[] downstream = new String(
+              ds.getSequence(s_end - 1, s_end + dstream_ds)).toLowerCase()
+                      .toCharArray();
       char[] coreseq = s.getSequence();
       char[] nseq = new char[offset + upstream.length + downstream.length
               + coreseq.length];
@@ -177,8 +191,8 @@ public class AlignmentUtils
       System.arraycopy(upstream, 0, nseq, p, upstream.length);
       System.arraycopy(coreseq, 0, nseq, p + upstream.length,
               coreseq.length);
-      System.arraycopy(downstream, 0, nseq, p + coreseq.length
-              + upstream.length, downstream.length);
+      System.arraycopy(downstream, 0, nseq,
+              p + coreseq.length + upstream.length, downstream.length);
       s.setSequence(new String(nseq));
       s.setStart(s.getStart() - ustream_ds);
       s.setEnd(s_end + downstream.length);
@@ -305,9 +319,9 @@ public class AlignmentUtils
    * @return
    */
   protected static boolean mapProteinToCdna(
-          final AlignmentI proteinAlignment,
-          final AlignmentI cdnaAlignment, Set<SequenceI> mappedDna,
-          Set<SequenceI> mappedProtein, boolean xrefsOnly)
+          final AlignmentI proteinAlignment, final AlignmentI cdnaAlignment,
+          Set<SequenceI> mappedDna, Set<SequenceI> mappedProtein,
+          boolean xrefsOnly)
   {
     boolean mappingExistsOrAdded = false;
     List<SequenceI> thisSeqs = proteinAlignment.getSequences();
@@ -336,9 +350,8 @@ public class AlignmentUtils
          * Don't map non-xrefd sequences more than once each. This heuristic
          * allows us to pair up similar sequences in ordered alignments.
          */
-        if (!xrefsOnly
-                && (mappedProtein.contains(aaSeq) || mappedDna
-                        .contains(cdnaSeq)))
+        if (!xrefsOnly && (mappedProtein.contains(aaSeq)
+                || mappedDna.contains(cdnaSeq)))
         {
           continue;
         }
@@ -391,7 +404,8 @@ public class AlignmentUtils
   /**
    * Builds a mapping (if possible) of a cDNA to a protein sequence.
    * <ul>
-   * <li>first checks if the cdna translates exactly to the protein sequence</li>
+   * <li>first checks if the cdna translates exactly to the protein
+   * sequence</li>
    * <li>else checks for translation after removing a STOP codon</li>
    * <li>else checks for translation after removing a START codon</li>
    * <li>if that fails, inspect CDS features on the cDNA sequence</li>
@@ -413,8 +427,9 @@ public class AlignmentUtils
      * String objects.
      */
     final SequenceI proteinDataset = proteinSeq.getDatasetSequence();
-    char[] aaSeqChars = proteinDataset != null ? proteinDataset
-            .getSequence() : proteinSeq.getSequence();
+    char[] aaSeqChars = proteinDataset != null
+            ? proteinDataset.getSequence()
+            : proteinSeq.getSequence();
     final SequenceI cdnaDataset = cdnaSeq.getDatasetSequence();
     char[] cdnaSeqChars = cdnaDataset != null ? cdnaDataset.getSequence()
             : cdnaSeq.getSequence();
@@ -426,7 +441,7 @@ public class AlignmentUtils
     /*
      * cdnaStart/End, proteinStartEnd are base 1 (for dataset sequence mapping)
      */
-    final int mappedLength = 3 * aaSeqChars.length;
+    final int mappedLength = CODON_LENGTH * aaSeqChars.length;
     int cdnaLength = cdnaSeqChars.length;
     int cdnaStart = cdnaSeq.getStart();
     int cdnaEnd = cdnaSeq.getEnd();
@@ -438,14 +453,14 @@ public class AlignmentUtils
      */
     if (cdnaLength != mappedLength && cdnaLength > 2)
     {
-      String lastCodon = String.valueOf(cdnaSeqChars, cdnaLength - 3, 3)
-              .toUpperCase();
+      String lastCodon = String.valueOf(cdnaSeqChars,
+              cdnaLength - CODON_LENGTH, CODON_LENGTH).toUpperCase();
       for (String stop : ResidueProperties.STOP)
       {
         if (lastCodon.equals(stop))
         {
-          cdnaEnd -= 3;
-          cdnaLength -= 3;
+          cdnaEnd -= CODON_LENGTH;
+          cdnaLength -= CODON_LENGTH;
           break;
         }
       }
@@ -455,14 +470,13 @@ public class AlignmentUtils
      * If lengths still don't match, try ignoring start codon.
      */
     int startOffset = 0;
-    if (cdnaLength != mappedLength
-            && cdnaLength > 2
-            && String.valueOf(cdnaSeqChars, 0, 3).toUpperCase()
+    if (cdnaLength != mappedLength && cdnaLength > 2
+            && String.valueOf(cdnaSeqChars, 0, CODON_LENGTH).toUpperCase()
                     .equals(ResidueProperties.START))
     {
-      startOffset += 3;
-      cdnaStart += 3;
-      cdnaLength -= 3;
+      startOffset += CODON_LENGTH;
+      cdnaStart += CODON_LENGTH;
+      cdnaLength -= CODON_LENGTH;
     }
 
     if (translatesAs(cdnaSeqChars, startOffset, aaSeqChars))
@@ -470,8 +484,9 @@ public class AlignmentUtils
       /*
        * protein is translation of dna (+/- start/stop codons)
        */
-      MapList map = new MapList(new int[] { cdnaStart, cdnaEnd }, new int[]
-      { proteinStart, proteinEnd }, 3, 1);
+      MapList map = new MapList(new int[] { cdnaStart, cdnaEnd },
+              new int[]
+              { proteinStart, proteinEnd }, CODON_LENGTH, 1);
       return map;
     }
 
@@ -502,9 +517,9 @@ public class AlignmentUtils
     int aaPos = 0;
     int dnaPos = cdnaStart;
     for (; dnaPos < cdnaSeqChars.length - 2
-            && aaPos < aaSeqChars.length; dnaPos += 3, aaPos++)
+            && aaPos < aaSeqChars.length; dnaPos += CODON_LENGTH, aaPos++)
     {
-      String codon = String.valueOf(cdnaSeqChars, dnaPos, 3);
+      String codon = String.valueOf(cdnaSeqChars, dnaPos, CODON_LENGTH);
       final String translated = ResidueProperties.codonTranslate(codon);
 
       /*
@@ -540,9 +555,9 @@ public class AlignmentUtils
     {
       return true;
     }
-    if (dnaPos == cdnaSeqChars.length - 3)
+    if (dnaPos == cdnaSeqChars.length - CODON_LENGTH)
     {
-      String codon = String.valueOf(cdnaSeqChars, dnaPos, 3);
+      String codon = String.valueOf(cdnaSeqChars, dnaPos, CODON_LENGTH);
       if ("STOP".equals(ResidueProperties.codonTranslate(codon)))
       {
         return true;
@@ -621,10 +636,9 @@ public class AlignmentUtils
    * @param preserveUnmappedGaps
    * @param preserveMappedGaps
    */
-  public static void alignSequenceAs(SequenceI alignTo,
-          SequenceI alignFrom, AlignedCodonFrame mapping, String myGap,
-          char sourceGap, boolean preserveMappedGaps,
-          boolean preserveUnmappedGaps)
+  public static void alignSequenceAs(SequenceI alignTo, SequenceI alignFrom,
+          AlignedCodonFrame mapping, String myGap, char sourceGap,
+          boolean preserveMappedGaps, boolean preserveUnmappedGaps)
   {
     // TODO generalise to work for Protein-Protein, dna-dna, dna-protein
 
@@ -819,8 +833,9 @@ public class AlignmentUtils
         }
         else
         {
-          gapsToAdd = Math.min(intronLength + trailingGapLength
-                  - sourceGapMappedLength, trailingGapLength);
+          gapsToAdd = Math.min(
+                  intronLength + trailingGapLength - sourceGapMappedLength,
+                  trailingGapLength);
         }
       }
     }
@@ -850,6 +865,11 @@ public class AlignmentUtils
    */
   public static int alignProteinAsDna(AlignmentI protein, AlignmentI dna)
   {
+    if (protein.isNucleotide() || !dna.isNucleotide())
+    {
+      System.err.println("Wrong alignment type in alignProteinAsDna");
+      return 0;
+    }
     List<SequenceI> unmappedProtein = new ArrayList<SequenceI>();
     Map<AlignedCodon, Map<SequenceI, AlignedCodon>> alignedCodons = buildCodonColumnsMap(
             protein, dna, unmappedProtein);
@@ -857,6 +877,179 @@ public class AlignmentUtils
   }
 
   /**
+   * Realigns the given dna to match the alignment of the protein, using codon
+   * mappings to translate aligned peptide positions to codons.
+   * 
+   * Always produces a padded CDS alignment.
+   * 
+   * @param dna
+   *          the alignment whose sequences are realigned by this method
+   * @param protein
+   *          the protein alignment whose alignment we are 'copying'
+   * @return the number of sequences that were realigned
+   */
+  public static int alignCdsAsProtein(AlignmentI dna, AlignmentI protein)
+  {
+    if (protein.isNucleotide() || !dna.isNucleotide())
+    {
+      System.err.println("Wrong alignment type in alignProteinAsDna");
+      return 0;
+    }
+    // todo: implement this
+    List<AlignedCodonFrame> mappings = protein.getCodonFrames();
+    int alignedCount = 0;
+    int width = 0; // alignment width for padding CDS
+    for (SequenceI dnaSeq : dna.getSequences())
+    {
+      if (alignCdsSequenceAsProtein(dnaSeq, protein, mappings,
+              dna.getGapCharacter()))
+      {
+        alignedCount++;
+      }
+      width = Math.max(dnaSeq.getLength(), width);
+    }
+    int oldwidth;
+    int diff;
+    for (SequenceI dnaSeq : dna.getSequences())
+    {
+      oldwidth = dnaSeq.getLength();
+      diff = width - oldwidth;
+      if (diff > 0)
+      {
+        dnaSeq.insertCharAt(oldwidth, diff, dna.getGapCharacter());
+      }
+    }
+    return alignedCount;
+  }
+
+  /**
+   * Helper method to align (if possible) the dna sequence to match the
+   * alignment of a mapped protein sequence. This is currently limited to
+   * handling coding sequence only.
+   * 
+   * @param cdsSeq
+   * @param protein
+   * @param mappings
+   * @param gapChar
+   * @return
+   */
+  static boolean alignCdsSequenceAsProtein(SequenceI cdsSeq,
+          AlignmentI protein, List<AlignedCodonFrame> mappings,
+          char gapChar)
+  {
+    SequenceI cdsDss = cdsSeq.getDatasetSequence();
+    if (cdsDss == null)
+    {
+      System.err
+              .println("alignCdsSequenceAsProtein needs aligned sequence!");
+      return false;
+    }
+
+    List<AlignedCodonFrame> dnaMappings = MappingUtils
+            .findMappingsForSequence(cdsSeq, mappings);
+    for (AlignedCodonFrame mapping : dnaMappings)
+    {
+      SequenceI peptide = mapping.findAlignedSequence(cdsSeq, protein);
+      if (peptide != null)
+      {
+        int peptideLength = peptide.getLength();
+        Mapping map = mapping.getMappingBetween(cdsSeq, peptide);
+        if (map != null)
+        {
+          MapList mapList = map.getMap();
+          if (map.getTo() == peptide.getDatasetSequence())
+          {
+            mapList = mapList.getInverse();
+          }
+          int cdsLength = cdsDss.getLength();
+          int mappedFromLength = MappingUtils
+                  .getLength(mapList.getFromRanges());
+          int mappedToLength = MappingUtils
+                  .getLength(mapList.getToRanges());
+          boolean addStopCodon = (cdsLength == mappedFromLength
+                  * CODON_LENGTH + CODON_LENGTH)
+                  || (peptide.getDatasetSequence()
+                          .getLength() == mappedFromLength - 1);
+          if (cdsLength != mappedToLength && !addStopCodon)
+          {
+            System.err.println(String.format(
+                    "Can't align cds as protein (length mismatch %d/%d): %s",
+                    cdsLength, mappedToLength, cdsSeq.getName()));
+          }
+
+          /*
+           * pre-fill the aligned cds sequence with gaps
+           */
+          char[] alignedCds = new char[peptideLength * CODON_LENGTH
+                  + (addStopCodon ? CODON_LENGTH : 0)];
+          Arrays.fill(alignedCds, gapChar);
+
+          /*
+           * walk over the aligned peptide sequence and insert mapped 
+           * codons for residues in the aligned cds sequence 
+           */
+          char[] alignedPeptide = peptide.getSequence();
+          char[] nucleotides = cdsDss.getSequence();
+          int copiedBases = 0;
+          int cdsStart = cdsDss.getStart();
+          int proteinPos = peptide.getStart() - 1;
+          int cdsCol = 0;
+          for (char residue : alignedPeptide)
+          {
+            if (Comparison.isGap(residue))
+            {
+              cdsCol += CODON_LENGTH;
+            }
+            else
+            {
+              proteinPos++;
+              int[] codon = mapList.locateInTo(proteinPos, proteinPos);
+              if (codon == null)
+              {
+                // e.g. incomplete start codon, X in peptide
+                cdsCol += CODON_LENGTH;
+              }
+              else
+              {
+                for (int j = codon[0]; j <= codon[1]; j++)
+                {
+                  char mappedBase = nucleotides[j - cdsStart];
+                  alignedCds[cdsCol++] = mappedBase;
+                  copiedBases++;
+                }
+              }
+            }
+          }
+
+          /*
+           * append stop codon if not mapped from protein,
+           * closing it up to the end of the mapped sequence
+           */
+          if (copiedBases == nucleotides.length - CODON_LENGTH)
+          {
+            for (int i = alignedCds.length - 1; i >= 0; i--)
+            {
+              if (!Comparison.isGap(alignedCds[i]))
+              {
+                cdsCol = i + 1; // gap just after end of sequence
+                break;
+              }
+            }
+            for (int i = nucleotides.length
+                    - CODON_LENGTH; i < nucleotides.length; i++)
+            {
+              alignedCds[cdsCol++] = nucleotides[i];
+            }
+          }
+          cdsSeq.setSequence(new String(alignedCds));
+          return true;
+        }
+      }
+    }
+    return false;
+  }
+
+  /**
    * Builds a map whose key is an aligned codon position (3 alignment column
    * numbers base 0), and whose value is a map from protein sequence to each
    * protein's peptide residue for that codon. The map generates an ordering of
@@ -899,8 +1092,8 @@ public class AlignmentUtils
         if (prot != null)
         {
           Mapping seqMap = mapping.getMappingForSequence(dnaSeq);
-          addCodonPositions(dnaSeq, prot, protein.getGapCharacter(),
-                  seqMap, alignedCodons);
+          addCodonPositions(dnaSeq, prot, protein.getGapCharacter(), seqMap,
+                  alignedCodons);
           unmappedProtein.remove(prot);
         }
       }
@@ -913,7 +1106,7 @@ public class AlignmentUtils
     // TODO resolve JAL-2022 so this fudge can be removed
     int mappedSequenceCount = protein.getHeight() - unmappedProtein.size();
     addUnmappedPeptideStarts(alignedCodons, mappedSequenceCount);
-    
+
     return alignedCodons;
   }
 
@@ -953,8 +1146,8 @@ public class AlignmentUtils
         AlignedCodon codon = sequenceCodon.getValue();
         if (codon.peptideCol > 1)
         {
-          System.err
-                  .println("Problem mapping protein with >1 unmapped start positions: "
+          System.err.println(
+                  "Problem mapping protein with >1 unmapped start positions: "
                           + seq.getName());
         }
         else if (codon.peptideCol == 1)
@@ -965,8 +1158,8 @@ public class AlignmentUtils
           if (lastCodon != null)
           {
             AlignedCodon firstPeptide = new AlignedCodon(lastCodon.pos1,
-                    lastCodon.pos2, lastCodon.pos3, String.valueOf(seq
-                            .getCharAt(0)), 0);
+                    lastCodon.pos2, lastCodon.pos3,
+                    String.valueOf(seq.getCharAt(0)), 0);
             toAdd.put(seq, firstPeptide);
           }
           else
@@ -1115,7 +1308,8 @@ public class AlignmentUtils
    * <ul>
    * <li>One alignment must be nucleotide, and the other protein</li>
    * <li>At least one pair of sequences must be already mapped, or mappable</li>
-   * <li>Mappable means the nucleotide translation matches the protein sequence</li>
+   * <li>Mappable means the nucleotide translation matches the protein
+   * sequence</li>
    * <li>The translation may ignore start and stop codons if present in the
    * nucleotide</li>
    * </ul>
@@ -1171,9 +1365,10 @@ public class AlignmentUtils
       return false;
     }
 
-    SequenceI dnaDs = dnaSeq.getDatasetSequence() == null ? dnaSeq : dnaSeq
-            .getDatasetSequence();
-    SequenceI proteinDs = proteinSeq.getDatasetSequence() == null ? proteinSeq
+    SequenceI dnaDs = dnaSeq.getDatasetSequence() == null ? dnaSeq
+            : dnaSeq.getDatasetSequence();
+    SequenceI proteinDs = proteinSeq.getDatasetSequence() == null
+            ? proteinSeq
             : proteinSeq.getDatasetSequence();
 
     for (AlignedCodonFrame mapping : mappings)
@@ -1210,8 +1405,7 @@ public class AlignmentUtils
    *          the alignment to check for presence of annotations
    */
   public static void findAddableReferenceAnnotations(
-          List<SequenceI> sequenceScope,
-          Map<String, String> labelForCalcId,
+          List<SequenceI> sequenceScope, Map<String, String> labelForCalcId,
           final Map<SequenceI, List<AlignmentAnnotation>> candidates,
           AlignmentI al)
   {
@@ -1315,8 +1509,8 @@ public class AlignmentUtils
 
   /**
    * Set visibility of alignment annotations of specified types (labels), for
-   * specified sequences. This supports controls like
-   * "Show all secondary structure", "Hide all Temp factor", etc.
+   * specified sequences. This supports controls like "Show all secondary
+   * structure", "Hide all Temp factor", etc.
    * 
    * @al the alignment to scan for annotations
    * @param types
@@ -1340,9 +1534,8 @@ public class AlignmentUtils
       {
         if (anyType || types.contains(aa.label))
         {
-          if ((aa.sequenceRef != null)
-                  && (forSequences == null || forSequences
-                          .contains(aa.sequenceRef)))
+          if ((aa.sequenceRef != null) && (forSequences == null
+                  || forSequences.contains(aa.sequenceRef)))
           {
             aa.visible = doShow;
           }
@@ -1404,9 +1597,9 @@ public class AlignmentUtils
    * added to the alignment dataset.
    * 
    * @param dna
-   *          aligned dna sequences
+   *          aligned nucleotide (dna or cds) sequences
    * @param dataset
-   *          - throws error if not given a dataset
+   *          the alignment dataset the sequences belong to
    * @param products
    *          (optional) to restrict results to CDS that map to specified
    *          protein products
@@ -1414,45 +1607,54 @@ public class AlignmentUtils
    *         sequences (or null if no mappings are found)
    */
   public static AlignmentI makeCdsAlignment(SequenceI[] dna,
-          AlignmentI dataset, AlignmentI products)
+          AlignmentI dataset, SequenceI[] products)
   {
-    if (dataset.getDataset() != null)
+    if (dataset == null || dataset.getDataset() != null)
     {
-      throw new Error(
+      throw new IllegalArgumentException(
               "IMPLEMENTATION ERROR: dataset.getDataset() must be null!");
     }
+    List<SequenceI> foundSeqs = new ArrayList<SequenceI>();
     List<SequenceI> cdsSeqs = new ArrayList<SequenceI>();
     List<AlignedCodonFrame> mappings = dataset.getCodonFrames();
     HashSet<SequenceI> productSeqs = null;
     if (products != null)
     {
       productSeqs = new HashSet<SequenceI>();
-      for (SequenceI seq : products.getSequences())
+      for (SequenceI seq : products)
       {
-        productSeqs.add(seq.getDatasetSequence() == null ? seq : seq
-                .getDatasetSequence());
+        productSeqs.add(seq.getDatasetSequence() == null ? seq
+                : seq.getDatasetSequence());
       }
     }
 
     /*
-     * construct CDS sequences from the (cds-to-protein) mappings made earlier;
-     * this makes it possible to model multiple products from dna (e.g. EMBL); 
-     * however it does mean we don't have the EMBL protein_id (a property on 
-     * the CDS features) in order to make the CDS sequence name :-( 
+     * Construct CDS sequences from mappings on the alignment dataset.
+     * The logic is:
+     * - find the protein product(s) mapped to from each dna sequence
+     * - if the mapping covers the whole dna sequence (give or take start/stop
+     *   codon), take the dna as the CDS sequence
+     * - else search dataset mappings for a suitable dna sequence, i.e. one
+     *   whose whole sequence is mapped to the protein 
+     * - if no sequence found, construct one from the dna sequence and mapping
+     *   (and add it to dataset so it is found if this is repeated)
      */
-    for (SequenceI seq : dna)
+    for (SequenceI dnaSeq : dna)
     {
-      SequenceI seqDss = seq.getDatasetSequence() == null ? seq : seq
-              .getDatasetSequence();
+      SequenceI dnaDss = dnaSeq.getDatasetSequence() == null ? dnaSeq
+              : dnaSeq.getDatasetSequence();
+
       List<AlignedCodonFrame> seqMappings = MappingUtils
-              .findMappingsForSequence(seq, mappings);
+              .findMappingsForSequence(dnaSeq, mappings);
       for (AlignedCodonFrame mapping : seqMappings)
       {
-        List<Mapping> mappingsFromSequence = mapping.getMappingsFromSequence(seq);
+        List<Mapping> mappingsFromSequence = mapping
+                .getMappingsFromSequence(dnaSeq);
 
         for (Mapping aMapping : mappingsFromSequence)
         {
-          if (aMapping.getMap().getFromRatio() == 1)
+          MapList mapList = aMapping.getMap();
+          if (mapList.getFromRatio() == 1)
           {
             /*
              * not a dna-to-protein mapping (likely dna-to-cds)
@@ -1461,55 +1663,33 @@ public class AlignmentUtils
           }
 
           /*
-           * check for an existing CDS sequence i.e. a 3:1 mapping to 
-           * the dna mapping's product
+           * skip if mapping is not to one of the target set of proteins
            */
-          SequenceI cdsSeq = null;
-
-          // TODO better mappings collection data model so we can do
-          // a direct lookup instead of double loops to find mappings
-
           SequenceI proteinProduct = aMapping.getTo();
-
-          /*
-           * skip if not mapped to one of a specified set of proteins
-           */
           if (productSeqs != null && !productSeqs.contains(proteinProduct))
           {
             continue;
           }
 
-          for (AlignedCodonFrame acf : MappingUtils
-                  .findMappingsForSequence(proteinProduct, mappings))
+          /*
+           * try to locate the CDS from the dataset mappings;
+           * guard against duplicate results (for the case that protein has
+           * dbrefs to both dna and cds sequences)
+           */
+          SequenceI cdsSeq = findCdsForProtein(mappings, dnaSeq,
+                  seqMappings, aMapping);
+          if (cdsSeq != null)
           {
-            for (SequenceToSequenceMapping map : acf.getMappings())
+            if (!foundSeqs.contains(cdsSeq))
             {
-              if (map.getMapping().getMap().getFromRatio() == 3
-                      && proteinProduct == map.getMapping().getTo()
-                      && seqDss != map.getFromSeq())
+              foundSeqs.add(cdsSeq);
+              SequenceI derivedSequence = cdsSeq.deriveSequence();
+              cdsSeqs.add(derivedSequence);
+              if (!dataset.getSequences().contains(cdsSeq))
               {
-                /*
-                 * found a 3:1 mapping to the protein product which is not
-                 * from the dna sequence...assume it is from the CDS sequence
-                 * TODO mappings data model that brings together related
-                 * dna-cds-protein mappings in one object
-                 */
-                cdsSeq = map.getFromSeq();
+                dataset.addSequence(cdsSeq);
               }
             }
-          }
-          if (cdsSeq != null)
-          {
-            /*
-             * mappings are always to dataset sequences so create an aligned
-             * sequence to own it; add the dataset sequence to the dataset
-             */
-            SequenceI derivedSequence = cdsSeq.deriveSequence();
-            cdsSeqs.add(derivedSequence);
-            if (!dataset.getSequences().contains(cdsSeq))
-            {
-              dataset.addSequence(cdsSeq);
-            }
             continue;
           }
 
@@ -1517,24 +1697,35 @@ public class AlignmentUtils
            * didn't find mapped CDS sequence - construct it and add
            * its dataset sequence to the dataset
            */
-          cdsSeq = makeCdsSequence(seq.getDatasetSequence(), aMapping);
-          SequenceI cdsSeqDss = cdsSeq.createDatasetSequence();
+          cdsSeq = makeCdsSequence(dnaSeq.getDatasetSequence(), aMapping,
+                  dataset).deriveSequence();
+          // cdsSeq has a name constructed as CDS|<dbref>
+          // <dbref> will be either the accession for the coding sequence,
+          // marked in the /via/ dbref to the protein product accession
+          // or it will be the original nucleotide accession.
+          SequenceI cdsSeqDss = cdsSeq.getDatasetSequence();
+
           cdsSeqs.add(cdsSeq);
+
           if (!dataset.getSequences().contains(cdsSeqDss))
           {
+            // check if this sequence is a newly created one
+            // so needs adding to the dataset
             dataset.addSequence(cdsSeqDss);
           }
 
           /*
            * add a mapping from CDS to the (unchanged) mapped to range
            */
-          List<int[]> cdsRange = Collections.singletonList(new int[] { 1,
-              cdsSeq.getLength() });
-          MapList map = new MapList(cdsRange, aMapping.getMap()
-                  .getToRanges(), aMapping.getMap().getFromRatio(),
-                  aMapping.getMap().getToRatio());
+          List<int[]> cdsRange = Collections
+                  .singletonList(new int[]
+                  { 1, cdsSeq.getLength() });
+          MapList cdsToProteinMap = new MapList(cdsRange,
+                  mapList.getToRanges(), mapList.getFromRatio(),
+                  mapList.getToRatio());
           AlignedCodonFrame cdsToProteinMapping = new AlignedCodonFrame();
-          cdsToProteinMapping.addMap(cdsSeq, proteinProduct, map);
+          cdsToProteinMapping.addMap(cdsSeqDss, proteinProduct,
+                  cdsToProteinMap);
 
           /*
            * guard against duplicating the mapping if repeating this action
@@ -1544,44 +1735,173 @@ public class AlignmentUtils
             mappings.add(cdsToProteinMapping);
           }
 
+          propagateDBRefsToCDS(cdsSeqDss, dnaSeq.getDatasetSequence(),
+                  proteinProduct, aMapping);
           /*
            * add another mapping from original 'from' range to CDS
            */
-          AlignedCodonFrame dnaToProteinMapping = new AlignedCodonFrame();
-          map = new MapList(aMapping.getMap().getFromRanges(), cdsRange, 1,
-                  1);
-          dnaToProteinMapping.addMap(seq.getDatasetSequence(), cdsSeq, map);
-          if (!mappings.contains(dnaToProteinMapping))
+          AlignedCodonFrame dnaToCdsMapping = new AlignedCodonFrame();
+          MapList dnaToCdsMap = new MapList(mapList.getFromRanges(),
+                  cdsRange, 1, 1);
+          dnaToCdsMapping.addMap(dnaSeq.getDatasetSequence(), cdsSeqDss,
+                  dnaToCdsMap);
+          if (!mappings.contains(dnaToCdsMapping))
           {
-            mappings.add(dnaToProteinMapping);
+            mappings.add(dnaToCdsMapping);
           }
 
+          /*
+           * add DBRef with mapping from protein to CDS
+           * (this enables Get Cross-References from protein alignment)
+           * This is tricky because we can't have two DBRefs with the
+           * same source and accession, so need a different accession for
+           * the CDS from the dna sequence
+           */
+
+          // specific use case:
+          // Genomic contig ENSCHR:1, contains coding regions for ENSG01,
+          // ENSG02, ENSG03, with transcripts and products similarly named.
+          // cannot add distinct dbrefs mapping location on ENSCHR:1 to ENSG01
+
+          // JBPNote: ?? can't actually create an example that demonstrates we
+          // need to
+          // synthesize an xref.
+
+          for (DBRefEntry primRef : dnaDss.getPrimaryDBRefs())
+          {
+            // creates a complementary cross-reference to the source sequence's
+            // primary reference.
+
+            DBRefEntry cdsCrossRef = new DBRefEntry(primRef.getSource(),
+                    primRef.getSource() + ":" + primRef.getVersion(),
+                    primRef.getAccessionId());
+            cdsCrossRef
+                    .setMap(new Mapping(dnaDss, new MapList(dnaToCdsMap)));
+            cdsSeqDss.addDBRef(cdsCrossRef);
+
+            // problem here is that the cross-reference is synthesized -
+            // cdsSeq.getName() may be like 'CDS|dnaaccession' or
+            // 'CDS|emblcdsacc'
+            // assuming cds version same as dna ?!?
+
+            DBRefEntry proteinToCdsRef = new DBRefEntry(primRef.getSource(),
+                    primRef.getVersion(), cdsSeq.getName());
+            //
+            proteinToCdsRef.setMap(
+                    new Mapping(cdsSeqDss, cdsToProteinMap.getInverse()));
+            proteinProduct.addDBRef(proteinToCdsRef);
+          }
 
           /*
            * transfer any features on dna that overlap the CDS
            */
-          transferFeatures(seq, cdsSeq, map, null, SequenceOntologyI.CDS);
+          transferFeatures(dnaSeq, cdsSeq, dnaToCdsMap, null,
+                  SequenceOntologyI.CDS);
         }
       }
     }
 
-    AlignmentI cds = new Alignment(cdsSeqs.toArray(new SequenceI[cdsSeqs
-            .size()]));
+    AlignmentI cds = new Alignment(
+            cdsSeqs.toArray(new SequenceI[cdsSeqs.size()]));
     cds.setDataset(dataset);
 
     return cds;
   }
 
   /**
+   * A helper method that finds a CDS sequence in the alignment dataset that is
+   * mapped to the given protein sequence, and either is, or has a mapping from,
+   * the given dna sequence.
+   * 
+   * @param mappings
+   *          set of all mappings on the dataset
+   * @param dnaSeq
+   *          a dna (or cds) sequence we are searching from
+   * @param seqMappings
+   *          the set of mappings involving dnaSeq
+   * @param aMapping
+   *          an initial candidate from seqMappings
+   * @return
+   */
+  static SequenceI findCdsForProtein(List<AlignedCodonFrame> mappings,
+          SequenceI dnaSeq, List<AlignedCodonFrame> seqMappings,
+          Mapping aMapping)
+  {
+    /*
+     * TODO a better dna-cds-protein mapping data representation to allow easy
+     * navigation; until then this clunky looping around lists of mappings
+     */
+    SequenceI seqDss = dnaSeq.getDatasetSequence() == null ? dnaSeq
+            : dnaSeq.getDatasetSequence();
+    SequenceI proteinProduct = aMapping.getTo();
+
+    /*
+     * is this mapping from the whole dna sequence (i.e. CDS)?
+     * allowing for possible stop codon on dna but not peptide
+     */
+    int mappedFromLength = MappingUtils
+            .getLength(aMapping.getMap().getFromRanges());
+    int dnaLength = seqDss.getLength();
+    if (mappedFromLength == dnaLength
+            || mappedFromLength == dnaLength - CODON_LENGTH)
+    {
+      return seqDss;
+    }
+
+    /*
+     * looks like we found the dna-to-protein mapping; search for the
+     * corresponding cds-to-protein mapping
+     */
+    List<AlignedCodonFrame> mappingsToPeptide = MappingUtils
+            .findMappingsForSequence(proteinProduct, mappings);
+    for (AlignedCodonFrame acf : mappingsToPeptide)
+    {
+      for (SequenceToSequenceMapping map : acf.getMappings())
+      {
+        Mapping mapping = map.getMapping();
+        if (mapping != aMapping
+                && mapping.getMap().getFromRatio() == CODON_LENGTH
+                && proteinProduct == mapping.getTo()
+                && seqDss != map.getFromSeq())
+        {
+          mappedFromLength = MappingUtils
+                  .getLength(mapping.getMap().getFromRanges());
+          if (mappedFromLength == map.getFromSeq().getLength())
+          {
+            /*
+            * found a 3:1 mapping to the protein product which covers
+            * the whole dna sequence i.e. is from CDS; finally check it
+            * is from the dna start sequence
+            */
+            SequenceI cdsSeq = map.getFromSeq();
+            List<AlignedCodonFrame> dnaToCdsMaps = MappingUtils
+                    .findMappingsForSequence(cdsSeq, seqMappings);
+            if (!dnaToCdsMaps.isEmpty())
+            {
+              return cdsSeq;
+            }
+          }
+        }
+      }
+    }
+    return null;
+  }
+
+  /**
    * Helper method that makes a CDS sequence as defined by the mappings from the
    * given sequence i.e. extracts the 'mapped from' ranges (which may be on
    * forward or reverse strand).
    * 
    * @param seq
    * @param mapping
+   * @param dataset
+   *          - existing dataset. We check for sequences that look like the CDS
+   *          we are about to construct, if one exists already, then we will
+   *          just return that one.
    * @return CDS sequence (as a dataset sequence)
    */
-  static SequenceI makeCdsSequence(SequenceI seq, Mapping mapping)
+  static SequenceI makeCdsSequence(SequenceI seq, Mapping mapping,
+          AlignmentI dataset)
   {
     char[] seqChars = seq.getSequence();
     List<int[]> fromRanges = mapping.getMap().getFromRanges();
@@ -1609,12 +1929,132 @@ public class AlignmentUtils
       }
     }
 
-    SequenceI newSeq = new Sequence(seq.getName() + "|"
-            + mapping.getTo().getName(), newSeqChars, 1, newPos);
+    /*
+     * assign 'from id' held in the mapping if set (e.g. EMBL protein_id),
+     * else generate a sequence name
+     */
+    String mapFromId = mapping.getMappedFromId();
+    String seqId = "CDS|" + (mapFromId != null ? mapFromId : seq.getName());
+    SequenceI newSeq = new Sequence(seqId, newSeqChars, 1, newPos);
+    if (dataset != null)
+    {
+      SequenceI[] matches = dataset.findSequenceMatch(newSeq.getName());
+      if (matches != null)
+      {
+        boolean matched = false;
+        for (SequenceI mtch : matches)
+        {
+          if (mtch.getStart() != newSeq.getStart())
+          {
+            continue;
+          }
+          if (mtch.getEnd() != newSeq.getEnd())
+          {
+            continue;
+          }
+          if (!Arrays.equals(mtch.getSequence(), newSeq.getSequence()))
+          {
+            continue;
+          }
+          if (!matched)
+          {
+            matched = true;
+            newSeq = mtch;
+          }
+          else
+          {
+            System.err.println(
+                    "JAL-2154 regression: warning - found (and ignnored a duplicate CDS sequence):"
+                            + mtch.toString());
+          }
+        }
+      }
+    }
+    // newSeq.setDescription(mapFromId);
+
     return newSeq;
   }
 
   /**
+   * add any DBRefEntrys to cdsSeq from contig that have a Mapping congruent to
+   * the given mapping.
+   * 
+   * @param cdsSeq
+   * @param contig
+   * @param mapping
+   * @return list of DBRefEntrys added.
+   */
+  public static List<DBRefEntry> propagateDBRefsToCDS(SequenceI cdsSeq,
+          SequenceI contig, SequenceI proteinProduct, Mapping mapping)
+  {
+
+    // gather direct refs from contig congrent with mapping
+    List<DBRefEntry> direct = new ArrayList<DBRefEntry>();
+    HashSet<String> directSources = new HashSet<String>();
+    if (contig.getDBRefs() != null)
+    {
+      for (DBRefEntry dbr : contig.getDBRefs())
+      {
+        if (dbr.hasMap() && dbr.getMap().getMap().isTripletMap())
+        {
+          MapList map = dbr.getMap().getMap();
+          // check if map is the CDS mapping
+          if (mapping.getMap().equals(map))
+          {
+            direct.add(dbr);
+            directSources.add(dbr.getSource());
+          }
+        }
+      }
+    }
+    DBRefEntry[] onSource = DBRefUtils.selectRefs(
+            proteinProduct.getDBRefs(),
+            directSources.toArray(new String[0]));
+    List<DBRefEntry> propagated = new ArrayList<DBRefEntry>();
+
+    // and generate appropriate mappings
+    for (DBRefEntry cdsref : direct)
+    {
+      // clone maplist and mapping
+      MapList cdsposmap = new MapList(
+              Arrays.asList(new int[][]
+              { new int[] { cdsSeq.getStart(), cdsSeq.getEnd() } }),
+              cdsref.getMap().getMap().getToRanges(), 3, 1);
+      Mapping cdsmap = new Mapping(cdsref.getMap().getTo(),
+              cdsref.getMap().getMap());
+
+      // create dbref
+      DBRefEntry newref = new DBRefEntry(cdsref.getSource(),
+              cdsref.getVersion(), cdsref.getAccessionId(),
+              new Mapping(cdsmap.getTo(), cdsposmap));
+
+      // and see if we can map to the protein product for this mapping.
+      // onSource is the filtered set of accessions on protein that we are
+      // tranferring, so we assume accession is the same.
+      if (cdsmap.getTo() == null && onSource != null)
+      {
+        List<DBRefEntry> sourceRefs = DBRefUtils.searchRefs(onSource,
+                cdsref.getAccessionId());
+        if (sourceRefs != null)
+        {
+          for (DBRefEntry srcref : sourceRefs)
+          {
+            if (srcref.getSource().equalsIgnoreCase(cdsref.getSource()))
+            {
+              // we have found a complementary dbref on the protein product, so
+              // update mapping's getTo
+              newref.getMap().setTo(proteinProduct);
+            }
+          }
+        }
+      }
+      cdsSeq.addDBRef(newref);
+      propagated.add(newref);
+    }
+    return propagated;
+  }
+
+  /**
    * Transfers co-located features on 'fromSeq' to 'toSeq', adjusting the
    * feature start/end ranges, optionally omitting specified feature types.
    * Returns the number of features copied.
@@ -1743,7 +2183,7 @@ public class AlignmentUtils
     /*
      * dna length should map to protein (or protein plus stop codon)
      */
-    int codesForResidues = mappedDnaLength / 3;
+    int codesForResidues = mappedDnaLength / CODON_LENGTH;
     if (codesForResidues == (proteinLength + 1))
     {
       // assuming extra codon is for STOP and not in peptide
@@ -1752,7 +2192,7 @@ public class AlignmentUtils
     if (codesForResidues == proteinLength)
     {
       proteinRange.add(new int[] { proteinStart, proteinEnd });
-      return new MapList(ranges, proteinRange, 3, 1);
+      return new MapList(ranges, proteinRange, CODON_LENGTH, 1);
     }
     return null;
   }
@@ -1806,8 +2246,8 @@ public class AlignmentUtils
           if (begin > end)
           {
             // shouldn't happen!
-            System.err
-                    .println("Error: start phase extends beyond start CDS in "
+            System.err.println(
+                    "Error: start phase extends beyond start CDS in "
                             + dnaSeq.getName());
           }
         }
@@ -1832,14 +2272,7 @@ public class AlignmentUtils
      * ranges are assembled in order. Other cases should not use this method,
      * but instead construct an explicit mapping for CDS (e.g. EMBL parsing).
      */
-    Collections.sort(result, new Comparator<int[]>()
-    {
-      @Override
-      public int compare(int[] o1, int[] o2)
-      {
-        return Integer.compare(o1[0], o2[0]);
-      }
-    });
+    Collections.sort(result, new RangeComparator(true));
     return result;
   }
 
@@ -2028,8 +2461,8 @@ public class AlignmentUtils
      * are currently ignored here
      */
     String trans = codon.contains("-") ? "-"
-            : (codon.length() > 3 ? null : ResidueProperties
-                    .codonTranslate(codon));
+            : (codon.length() > CODON_LENGTH ? null
+                    : ResidueProperties.codonTranslate(codon));
     if (trans != null && !trans.equals(residue))
     {
       String residue3Char = StringUtils
@@ -2040,7 +2473,7 @@ public class AlignmentUtils
       // set score to 0f so 'graduated colour' option is offered! JAL-2060
       SequenceFeature sf = new SequenceFeature(
               SequenceOntologyI.SEQUENCE_VARIANT, desc, peptidePos,
-              peptidePos, 0f, "Jalview");
+              peptidePos, 0f, var.getSource());
       StringBuilder attributes = new StringBuilder(32);
       String id = (String) var.variant.getValue(ID);
       if (id != null)
@@ -2051,12 +2484,12 @@ public class AlignmentUtils
         }
         sf.setValue(ID, id);
         attributes.append(ID).append("=").append(id);
-        // TODO handle other species variants
+        // TODO handle other species variants JAL-2064
         StringBuilder link = new StringBuilder(32);
         try
         {
-          link.append(desc).append(" ").append(id)
-                  .append("|http://www.ensembl.org/Homo_sapiens/Variation/Summary?v=")
+          link.append(desc).append(" ").append(id).append(
+                  "|http://www.ensembl.org/Homo_sapiens/Variation/Summary?v=")
                   .append(URLEncoder.encode(id, "UTF-8"));
           sf.addLink(link.toString());
         } catch (UnsupportedEncodingException e)
@@ -2064,8 +2497,7 @@ public class AlignmentUtils
           // as if
         }
       }
-      String clinSig = (String) var.variant
-              .getValue(CLINICAL_SIGNIFICANCE);
+      String clinSig = (String) var.variant.getValue(CLINICAL_SIGNIFICANCE);
       if (clinSig != null)
       {
         sf.setValue(CLINICAL_SIGNIFICANCE, clinSig);
@@ -2090,6 +2522,7 @@ public class AlignmentUtils
    * @param dnaToProtein
    * @return
    */
+  @SuppressWarnings("unchecked")
   static LinkedHashMap<Integer, List<DnaVariant>[]> buildDnaVariantsMap(
           SequenceI dnaSeq, MapList dnaToProtein)
   {
@@ -2133,7 +2566,7 @@ public class AlignmentUtils
         List<DnaVariant>[] codonVariants = variants.get(peptidePosition);
         if (codonVariants == null)
         {
-          codonVariants = new ArrayList[3];
+          codonVariants = new ArrayList[CODON_LENGTH];
           codonVariants[0] = new ArrayList<DnaVariant>();
           codonVariants[1] = new ArrayList<DnaVariant>();
           codonVariants[2] = new ArrayList<DnaVariant>();
@@ -2159,18 +2592,18 @@ public class AlignmentUtils
          * get this peptide's codon positions e.g. [3, 4, 5] or [4, 7, 10]
          */
         int[] codon = peptidePosition == lastPeptidePostion ? lastCodon
-                : MappingUtils.flattenRanges(dnaToProtein.locateInFrom(
-                        peptidePosition, peptidePosition));
+                : MappingUtils.flattenRanges(dnaToProtein
+                        .locateInFrom(peptidePosition, peptidePosition));
         lastPeptidePostion = peptidePosition;
         lastCodon = codon;
 
         /*
          * save nucleotide (and any variant) for each codon position
          */
-        for (int codonPos = 0; codonPos < 3; codonPos++)
+        for (int codonPos = 0; codonPos < CODON_LENGTH; codonPos++)
         {
-          String nucleotide = String.valueOf(
-                  dnaSeq.getCharAt(codon[codonPos] - dnaStart))
+          String nucleotide = String
+                  .valueOf(dnaSeq.getCharAt(codon[codonPos] - dnaStart))
                   .toUpperCase();
           List<DnaVariant> codonVariant = codonVariants[codonPos];
           if (codon[codonPos] == dnaCol)
@@ -2220,7 +2653,7 @@ public class AlignmentUtils
   {
     AlignmentI copy = new Alignment(new Alignment(seqs));
     copy.setDataset(dataset);
-
+    boolean isProtein = !copy.isNucleotide();
     SequenceIdMatcher matcher = new SequenceIdMatcher(seqs);
     if (xrefs != null)
     {
@@ -2231,7 +2664,8 @@ public class AlignmentUtils
         {
           for (DBRefEntry dbref : dbrefs)
           {
-            if (dbref.getMap() == null || dbref.getMap().getTo() == null)
+            if (dbref.getMap() == null || dbref.getMap().getTo() == null
+                    || dbref.getMap().getTo().isProtein() != isProtein)
             {
               continue;
             }
@@ -2265,19 +2699,32 @@ public class AlignmentUtils
    */
   public static int alignAs(AlignmentI unaligned, AlignmentI aligned)
   {
+    /*
+     * easy case - aligning a copy of aligned sequences
+     */
+    if (alignAsSameSequences(unaligned, aligned))
+    {
+      return unaligned.getHeight();
+    }
+
+    /*
+     * fancy case - aligning via mappings between sequences
+     */
     List<SequenceI> unmapped = new ArrayList<SequenceI>();
     Map<Integer, Map<SequenceI, Character>> columnMap = buildMappedColumnsMap(
             unaligned, aligned, unmapped);
     int width = columnMap.size();
     char gap = unaligned.getGapCharacter();
     int realignedCount = 0;
+    // TODO: verify this loop scales sensibly for very wide/high alignments
 
     for (SequenceI seq : unaligned.getSequences())
     {
       if (!unmapped.contains(seq))
       {
         char[] newSeq = new char[width];
-        Arrays.fill(newSeq, gap);
+        Arrays.fill(newSeq, gap); // JBPComment - doubt this is faster than the
+                                  // Integer iteration below
         int newCol = 0;
         int lastCol = 0;
 
@@ -2299,7 +2746,7 @@ public class AlignmentUtils
           }
           newCol++;
         }
-        
+
         /*
          * trim trailing gaps
          */
@@ -2309,6 +2756,7 @@ public class AlignmentUtils
           System.arraycopy(newSeq, 0, tmp, 0, lastCol + 1);
           newSeq = tmp;
         }
+        // TODO: optimise SequenceI to avoid char[]->String->char[]
         seq.setSequence(String.valueOf(newSeq));
         realignedCount++;
       }
@@ -2317,6 +2765,72 @@ public class AlignmentUtils
   }
 
   /**
+   * If unaligned and aligned sequences share the same dataset sequences, then
+   * simply copies the aligned sequences to the unaligned sequences and returns
+   * true; else returns false
+   * 
+   * @param unaligned
+   *          - sequences to be aligned based on aligned
+   * @param aligned
+   *          - 'guide' alignment containing sequences derived from same dataset
+   *          as unaligned
+   * @return
+   */
+  static boolean alignAsSameSequences(AlignmentI unaligned,
+          AlignmentI aligned)
+  {
+    if (aligned.getDataset() == null || unaligned.getDataset() == null)
+    {
+      return false; // should only pass alignments with datasets here
+    }
+
+    // map from dataset sequence to alignment sequence(s)
+    Map<SequenceI, List<SequenceI>> alignedDatasets = new HashMap<SequenceI, List<SequenceI>>();
+    for (SequenceI seq : aligned.getSequences())
+    {
+      SequenceI ds = seq.getDatasetSequence();
+      if (alignedDatasets.get(ds) == null)
+      {
+        alignedDatasets.put(ds, new ArrayList<SequenceI>());
+      }
+      alignedDatasets.get(ds).add(seq);
+    }
+
+    /*
+     * first pass - check whether all sequences to be aligned share a dataset
+     * sequence with an aligned sequence
+     */
+    for (SequenceI seq : unaligned.getSequences())
+    {
+      if (!alignedDatasets.containsKey(seq.getDatasetSequence()))
+      {
+        return false;
+      }
+    }
+
+    /*
+     * second pass - copy aligned sequences;
+     * heuristic rule: pair off sequences in order for the case where 
+     * more than one shares the same dataset sequence 
+     */
+    for (SequenceI seq : unaligned.getSequences())
+    {
+      List<SequenceI> alignedSequences = alignedDatasets
+              .get(seq.getDatasetSequence());
+      // TODO: getSequenceAsString() will be deprecated in the future
+      // TODO: need to leave to SequenceI implementor to update gaps
+      seq.setSequence(alignedSequences.get(0).getSequenceAsString());
+      if (alignedSequences.size() > 0)
+      {
+        // pop off aligned sequences (except the last one)
+        alignedSequences.remove(0);
+      }
+    }
+
+    return true;
+  }
+
+  /**
    * Returns a map whose key is alignment column number (base 1), and whose
    * values are a map of sequence characters in that column.
    * 
@@ -2325,15 +2839,16 @@ public class AlignmentUtils
    * @param unmapped
    * @return
    */
-  static Map<Integer, Map<SequenceI, Character>> buildMappedColumnsMap(
-          AlignmentI unaligned, AlignmentI aligned, List<SequenceI> unmapped)
+  static SortedMap<Integer, Map<SequenceI, Character>> buildMappedColumnsMap(
+          AlignmentI unaligned, AlignmentI aligned,
+          List<SequenceI> unmapped)
   {
     /*
      * Map will hold, for each aligned column position, a map of
      * {unalignedSequence, characterPerSequence} at that position.
      * TreeMap keeps the entries in ascending column order. 
      */
-    Map<Integer, Map<SequenceI, Character>> map = new TreeMap<Integer, Map<SequenceI, Character>>();
+    SortedMap<Integer, Map<SequenceI, Character>> map = new TreeMap<Integer, Map<SequenceI, Character>>();
 
     /*
      * record any sequences that have no mapping so can't be realigned
@@ -2361,7 +2876,8 @@ public class AlignmentUtils
   }
 
   /**
-   * Helper method that adds to a map the mapped column positions of a sequence. <br>
+   * Helper method that adds to a map the mapped column positions of a sequence.
+   * <br>
    * For example if aaTT-Tg-gAAA is mapped to TTTAAA then the map should record
    * that columns 3,4,6,10,11,12 map to characters T,T,T,A,A,A of the mapped to
    * sequence.
@@ -2390,8 +2906,8 @@ public class AlignmentUtils
      */
     if (seqMap.getTo() == fromSeq.getDatasetSequence())
     {
-      seqMap = new Mapping(seq.getDatasetSequence(), seqMap.getMap()
-              .getInverse());
+      seqMap = new Mapping(seq.getDatasetSequence(),
+              seqMap.getMap().getInverse());
     }
 
     char[] fromChars = fromSeq.getSequence();