+ * 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 - 3)
+ {
+ 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() == 3
+ && 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;
+ }
+
+ /**