/// <summary>
/// Given two byte arrays representing a pairwise alignment, shift them so
/// that all deletions start as early as possible. For example:
///
/// <code>
/// TTTTAAAATTTT -> Converts to -> TTTTAAAATTTT
/// TTTTAA--TTTT TTTT--AATTTT
/// </code>
///
/// This function takes a IPairwiseSequenceAlignment and assumes that the first sequence is the reference and second
/// sequence is the query. It returns a new Pairwise sequence alignment with all of the indels left aligned as well as a list of variants.
/// </summary>
/// <param name="aln">Aln. The second sequence should be of type QualitativeSequence or Sequence</param>
/// <param name="callVariants">callVariants. If true, it will call variants, otherwise the second half of tuple will be null. </param>
public static Tuple <IPairwiseSequenceAlignment, List <Variant> > LeftAlignIndelsAndCallVariants(IPairwiseSequenceAlignment aln, bool callVariants = true)
{
if (aln == null)
{
throw new NullReferenceException("aln");
}
if (aln.PairwiseAlignedSequences == null || aln.PairwiseAlignedSequences.Count != 1)
{
throw new ArgumentException("The pairwise aligned sequence should only have one alignment");
}
var frstAln = aln.PairwiseAlignedSequences.First();
var seq1 = frstAln.FirstSequence;
var seq2 = frstAln.SecondSequence;
if (seq1 == null)
{
throw new NullReferenceException("seq1");
}
else if (seq2 == null)
{
throw new NullReferenceException("seq2");
}
//TODO: Might implement an ambiguity check later.
#if FALSE
if (seq1.Alphabet.HasAmbiguity || seq2.Alphabet.HasAmbiguity)
{
throw new ArgumentException("Cannot left align sequences with ambiguous symbols.");
}
#endif
// Note we have to copy unless we can guarantee the array will not be mutated.
byte[] refseq = seq1.ToArray();
ISequence newQuery;
List <Variant> variants = null;
// Call variants for a qualitative sequence
if (seq2 is QualitativeSequence)
{
var qs = seq2 as QualitativeSequence;
var query = Enumerable.Zip(qs, qs.GetQualityScores(), (bp, qv) => new BPandQV(bp, (byte)qv, false)).ToArray();
AlignmentUtils.LeftAlignIndels(refseq, query);
AlignmentUtils.VerifyNoGapsOnEnds(refseq, query);
if (callVariants)
{
variants = VariantCaller.CallVariants(refseq, query, seq2.IsMarkedAsReverseComplement());
}
var newQueryQS = new QualitativeSequence(qs.Alphabet,
qs.FormatType,
query.Select(z => z.BP).ToArray(),
query.Select(p => p.QV).ToArray(),
false);
newQueryQS.Metadata = seq2.Metadata;
newQuery = newQueryQS;
}
else if (seq2 is Sequence) // For a sequence with no QV values.
{
var qs = seq2 as Sequence;
var query = qs.Select(v => new BPandQV(v, 0, false)).ToArray();
AlignmentUtils.LeftAlignIndels(refseq, query);
AlignmentUtils.VerifyNoGapsOnEnds(refseq, query);
// ISequence does not have a setable metadata
var newQueryS = new Sequence(qs.Alphabet, query.Select(z => z.BP).ToArray(), false);
newQueryS.Metadata = seq2.Metadata;
if (callVariants)
{
variants = VariantCaller.CallVariants(refseq, query, seq2.IsMarkedAsReverseComplement());
}
newQuery = newQueryS;
}
else
{
throw new ArgumentException("Can only left align indels if the query sequence is of type Sequence or QualitativeSequence.");
}
if (aln.FirstSequence != null && aln.FirstSequence.ID != null)
{
foreach (var v in variants)
{
v.RefName = aln.FirstSequence.ID;
}
}
var newRef = new Sequence(seq1.Alphabet, refseq, false);
newRef.ID = seq1.ID;
newRef.Metadata = seq1.Metadata;
newQuery.ID = seq2.ID;
var newaln = new PairwiseSequenceAlignment(aln.FirstSequence, aln.SecondSequence);
var pas = new PairwiseAlignedSequence();
pas.FirstSequence = newRef;
pas.SecondSequence = newQuery;
newaln.Add(pas);
return(new Tuple <IPairwiseSequenceAlignment, List <Variant> > (newaln, variants));
}
/// <summary>
/// Calls the variants.
///
/// Should only be used internally as assumptions are made that the alignments are left-aligned and fulfill certain criteria.
/// </summary>
/// <returns>The variants.</returns>
/// <param name="refSeq">Reference seq.</param>
/// <param name="querySeq">Query seq.</param>
/// <param name="originallyReverseComplemented">If set to <c>true</c> the query sequence was originally reverse complemented. (this affects QV value scoring)</param>
internal static List <Variant> CallVariants(byte[] refSeq, BPandQV[] querySeq, bool originallyReverseComplemented)
{
if (originallyReverseComplemented)
{
AlignmentUtils.ReverseQVValuesForHomopolymers(querySeq);
}
List <Variant> variants = new List <Variant>();
// Now call variants.
var gap = DnaAlphabet.Instance.Gap;
int i = 0;
int refPos = 0;
int queryPos = 0;
while (i < refSeq.Length)
{
if (refSeq[i] == gap)
{
int len = AlignmentUtils.GetGapLength(i, refSeq);
var nextBasePos = (i + len);
// Should alway be true as we don't end in gaps
Debug.Assert(nextBasePos < refSeq.Length);
var hplenAndChar = determineHomoPolymerLength(nextBasePos, refSeq);
var bases = getBases(querySeq, i, len);
var newVariant = new IndelVariant(refPos - 1, len, bases, IndelType.Insertion,
hplenAndChar.Item2, hplenAndChar.Item1,
(i == 0 || (i + len + hplenAndChar.Item1) >= refSeq.Length));
newVariant.QV = querySeq[queryPos].QV;
variants.Add(newVariant);
i += len;
queryPos += len;
}
else if (querySeq[i].BP == gap)
{
int len = AlignmentUtils.GetGapLength(i, querySeq);
var bases = getBases(refSeq, i, len);
var hplenAndChar = determineHomoPolymerLength(i, refSeq);
var newVariant = new IndelVariant(refPos - 1, len, bases,
IndelType.Deletion, hplenAndChar.Item2,
hplenAndChar.Item1, (i == 0 || (i + len + hplenAndChar.Item1) >= refSeq.Length));
/* An insertion mutation occurs BEFORE pos, so normally we get the next base
* or the last one if it's a reverse complemented alignment. However, this is not true if
* it is a homopolymer because what would have been the previous position is the next position
* after left aligning and reversing the position of the QV value.
*
* Consider the following
* --*- -*--
* A-TA --> TA-T
* AGTA TACT
*
* However,
* --*-- --*--
* A-TTA ----> T-AAT
* ATTTA TAAAT
*
*/
if ((i + len) < querySeq.Length)
{
var qc_pos = originallyReverseComplemented ? i - 1 : i + len;
if (newVariant.InHomopolymer)
{
qc_pos = i + len;
}
newVariant.QV = querySeq[qc_pos].QV;
}
variants.Add(newVariant);
i += len;
refPos += len;
}
else
{
if (querySeq[i].BP != refSeq[i])
{
var newVariant = new SNPVariant(refPos, (char)querySeq[i].BP, (char)refSeq[i], (i == 0 || i == (refSeq.Length - 1)));
newVariant.QV = querySeq [queryPos].QV;
variants.Add(newVariant);
}
i++; refPos++; queryPos++;
}
}
return(variants);
}
