// ==========================================================================
//                 SeqAn - The Library for Sequence Analysis
// ==========================================================================
// Copyright (c) 2006-2026, Knut Reinert, FU Berlin
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
//     * Redistributions of source code must retain the above copyright
//       notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above copyright
//       notice, this list of conditions and the following disclaimer in the
//       documentation and/or other materials provided with the distribution.
//     * Neither the name of Knut Reinert or the FU Berlin nor the names of
//       its contributors may be used to endorse or promote products derived
//       from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
// ARE DISCLAIMED. IN NO EVENT SHALL KNUT REINERT OR THE FU BERLIN BE LIABLE
// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
// LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
// OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
// DAMAGE.
//
// ==========================================================================
// Author: David Weese <david.weese@fu-berlin.de>
// ==========================================================================

#include <iostream>

#ifndef SEQAN_HEADER_STORE_IO_SAM_H
#define SEQAN_HEADER_STORE_IO_SAM_H

namespace seqan2
{

// ============================================================================
// Forwards
// ============================================================================

template <typename TSpec, typename TConfig>
class FragmentStore;

// ============================================================================
// Classes
// ============================================================================

struct FragStoreImportFlags
{
    bool importRead:1;
    bool importReadSeq:1;
    bool importReadName:1;
    bool importReadAlignment:1;
    bool importReadAlignmentQuality:1;
    bool importReadAlignmentTags:1;

    FragStoreImportFlags():
        importRead(true),
        importReadSeq(true),
        importReadName(true),
        importReadAlignment(true),
        importReadAlignmentQuality(true),
        importReadAlignmentTags(true)
    {}
};

template <typename TFragmentStore>
struct FragStoreSAMContext
{
    typedef typename Id<TFragmentStore>::Type                                   TId;
    typedef typename Value<typename TFragmentStore::TAlignedReadStore>::Type    TAlignedElement;
    typedef typename TAlignedElement::TGapAnchors                               TReadGapAnchors;
    typedef String<typename TFragmentStore::TContigGapAnchor>                   TContigAnchorGaps;
    typedef typename TFragmentStore::TReadSeq                                   TReadSeq;

    TId                 readId;
    TReadGapAnchors     readGapAnchors;
    TContigAnchorGaps   contigGapAnchors;

    // Buffer for the read sequence.
    TReadSeq readSeq;

    // Buffer for the current BamAlignmentRecord.
    BamAlignmentRecord bamRecord;
};

template <typename TId>
struct MatchMateInfo_
{
    TId     readId;
    int32_t contigId;
    TId     pairMatchId;
    TId     matePairId;//:(sizeof(TId)*8-1);
    int32_t beginPos;
    bool    reversed;
};

// ============================================================================
// Functors
// ============================================================================

template <typename TFragStore>
struct AlignedMateLess_
{
    TFragStore &fragStore;

    AlignedMateLess_(TFragStore &fragStore_) :
        fragStore(fragStore_) {}

    template <typename TAlignedRead>
    inline bool
    operator() (TAlignedRead const& a, TAlignedRead const& b) const
    {
        if (a.contigId < b.contigId) return true;
        if (a.contigId > b.contigId) return false;

        typename TFragStore::TContigPos posA = _min(a.beginPos, a.endPos);
        typename TFragStore::TContigPos posB = _min(b.beginPos, b.endPos);
        if (posA < posB) return true;
        if (posA > posB) return false;

        bool reversedA = (a.endPos < a.beginPos);
        bool reversedB = (b.endPos < b.beginPos);
        if (reversedA != reversedB) return reversedB;

        typedef typename TFragStore::TMatePairStore     TMatePairStore;
        typedef typename Value<TMatePairStore>::Type    TMatePair;
        typename TMatePair::TId matePairIdB = TMatePair::INVALID_ID;

        if (a.readId >= length(fragStore.readStore))
            return false;

        if (b.readId < length(fragStore.readStore))
            matePairIdB = fragStore.readStore[b.readId].matePairId;

        return (fragStore.readStore[a.readId].matePairId < matePairIdB);
    }
};

struct MatchMateInfoLess_
{
    template <typename TMInfo>
    inline bool
    operator() (TMInfo const &a, TMInfo const &b) const
    {
        if (a.contigId < b.contigId) return true;
        if (a.contigId > b.contigId) return false;
        if (a.beginPos < b.beginPos) return true;
        if (a.beginPos > b.beginPos) return false;
        if (a.reversed != b.reversed) return b.reversed;
        if (a.matePairId < b.matePairId) return true;
        if (a.matePairId > b.matePairId) return false;
        return (a.pairMatchId < b.pairMatchId);
    }
};

// ============================================================================
// Metafunctions
// ============================================================================

template <typename TDirection, typename TSpec, typename TConfig, typename TStorageSpec>
struct FormattedFileContext<FormattedFile<Bam, TDirection, FragmentStore<TSpec, TConfig> >, TStorageSpec>
{
    typedef FragmentStore<TSpec, TConfig>                           TFragmentStore;
    typedef typename TFragmentStore::TContigNameStore               TNameStore;
    typedef NameStoreCache<TNameStore, CharString>                  TNameStoreCache;
    typedef BamIOContext<TNameStore, TNameStoreCache, Dependent<> > Type;
};

// ============================================================================
// Read Functions
// ============================================================================

// --------------------------------------------------------------------------
// Function clear()
// --------------------------------------------------------------------------

inline void
clear(FragStoreImportFlags & flags)
{
    flags.importRead = false;
    flags.importReadSeq = false;
    flags.importReadName = false;
    flags.importReadAlignment = false;
    flags.importReadAlignmentQuality = false;
    flags.importReadAlignmentTags = false;
}

// --------------------------------------------------------------------------
// Function appendAlignment()
// --------------------------------------------------------------------------

template<typename TSpec, typename TConfig, typename TContigId, typename TId, typename TPos, typename TGaps>
inline typename Size<typename FragmentStore<TSpec, TConfig>::TAlignedReadStore>::Type
appendAlignment(
    FragmentStore<TSpec, TConfig> & fragStore,
    TId readId,
    TContigId contigId,
    TPos beginPos,
    TPos endPos,
    TGaps const & gaps)
{
    typedef FragmentStore<TSpec, TConfig> TFragmentStore;
    typedef typename Value<typename TFragmentStore::TAlignedReadStore>::Type TAlignedElement;

    TId id = length(fragStore.alignedReadStore);
    TAlignedElement alignedElem = TAlignedElement(id, readId, contigId, beginPos, endPos, gaps);
    appendValue(fragStore.alignedReadStore, alignedElem);

    return id;
}

// --------------------------------------------------------------------------
// Function _compareAlignedReadAndMateInfo()
// --------------------------------------------------------------------------

template <typename TAlignedRead, typename TMInfo, typename TFragStore>
inline int
_compareAlignedReadAndMateInfo(TAlignedRead const &a, TMInfo const &b, TFragStore const &fragStore)
{
    typedef typename TAlignedRead::TId  TId;
    typedef typename TAlignedRead::TPos TPos;

    if (a.contigId < (TId)b.contigId) return -1;
    if (a.contigId > (TId)b.contigId) return 1;

    TPos posA = _min(a.beginPos, a.endPos);
    if (posA < (TPos)b.beginPos) return -1;
    if (posA > (TPos)b.beginPos) return 1;

    bool reversedA = (a.endPos < a.beginPos);
    if (!reversedA &&  b.reversed) return -1;
    if ( reversedA && !b.reversed) return 1;

    typedef typename TFragStore::TMatePairStore     TMatePairStore;
    typedef typename Value<TMatePairStore>::Type    TMatePair;
    typename TMatePair::TId matePairIdA = TMatePair::INVALID_ID;

    if (a.readId < length(fragStore.readStore))
        matePairIdA = fragStore.readStore[a.readId].matePairId;

    if (matePairIdA < b.matePairId) return -1;
    if (matePairIdA > b.matePairId) return 1;
    return 0;
}

// --------------------------------------------------------------------------
// Function _generatePairMatchIds()
// --------------------------------------------------------------------------

template<typename TSpec, typename TConfig, typename TMatchMateInfos>
inline void
_generatePairMatchIds (
    FragmentStore<TSpec, TConfig> & fragStore,
    TMatchMateInfos & matchMateInfos)
{
    typedef FragmentStore<TSpec, TConfig>                           TFragmentStore;
    typedef typename TFragmentStore::TAlignedReadStore              TAlignedReadStore;
    typedef typename Iterator<TAlignedReadStore, Standard>::Type    TIter;
    typedef typename Iterator<TMatchMateInfos, Standard>::Type      TMIter;

    TIter it = begin(fragStore.alignedReadStore, Standard());
    TIter itEnd = end(fragStore.alignedReadStore, Standard());
    TMIter mit = begin(matchMateInfos, Standard());
    TMIter mitEnd = end(matchMateInfos, Standard());

    if (it == itEnd || mit == mitEnd) return;

    // sort the aligned read store by: begin position, contig name
    std::sort(it,  itEnd,  AlignedMateLess_<TFragmentStore>(fragStore));
    std::sort(mit, mitEnd, MatchMateInfoLess_());

    while (true)
    {
        int cmp = _compareAlignedReadAndMateInfo(*it, *mit, fragStore);

        if (cmp == 0)   // both are equal -> link them
            if (it->pairMatchId > mit->pairMatchId)     // avoid id swap and instead decide for
                it->pairMatchId = mit->pairMatchId;     // the smaller of both ids

        if (cmp >= 0)   // MateInfo is less or equal
            if (++mit == mitEnd)
                return;

        if (cmp <= 0)   // AlignedRead is less or equal
            if (++it == itEnd)
                return;
    }
}

// --------------------------------------------------------------------------
// Function readRecords()
// --------------------------------------------------------------------------

template <typename TSpec, typename TConfig, typename TNameStore, typename TNameStoreCache,
          typename TStorageSpec, typename TForwardIter, typename TFormat>
inline void
readRecords(FragmentStore<TSpec, TConfig> & store,
            BamIOContext<TNameStore, TNameStoreCache, TStorageSpec> & ctx,
            TForwardIter & iter,
            TFormat const & format,
            FragStoreImportFlags const & importFlags)
{
    typedef FragmentStore<TSpec, TConfig> TFragmentStore;
    typedef typename Id<TFragmentStore>::Type TId;

    // data structure to temporarily store the gaps that need to be inserted in the contig sequences
    typedef MatchMateInfo_<TId> TMatchMateInfo;
    typedef String<TMatchMateInfo> TMatchMateInfos;
    typedef StringSet<String<typename TFragmentStore::TContigGapAnchor>, Owner<ConcatDirect<> > > TContigAnchorGaps;

    // data structure to temporarily store information about match mates
    TMatchMateInfos matchMateInfos;
    TContigAnchorGaps contigAnchorGaps;

    // Read in the header.  We will subsequently ignore it and use the information indirectly just using the
    // sequence names if any.
    BamHeader bamHeader;
    readHeader(bamHeader, ctx, iter, format);

    // fill up contig entries for each contig name that appears in the header
    resize(store.contigStore, length(store.contigNameStore));

    // Read in alignments section
    _readAlignments(store, contigAnchorGaps, matchMateInfos, ctx, iter, format, importFlags);

    if (importFlags.importReadAlignment)
    {
        // set the match mate IDs using the information stored in matchMateInfos
        _generatePairMatchIds(store, matchMateInfos);
        convertPairWiseToGlobalAlignment(store, contigAnchorGaps);
    }
}

template <typename TFSSpec, typename TConfig, typename TDirection, typename TSpec>
inline void
readRecords(FragmentStore<TFSSpec, TConfig> & store,
            FormattedFile<Bam, TDirection, TSpec> & bamFile,
            FragStoreImportFlags const & importFlags)
{
    typedef FragmentStore<TFSSpec, TConfig>                 TFragmentStore;
    typedef typename TFragmentStore::TContigNameStore       TContigNameStore;
    typedef NameStoreCache<TContigNameStore, CharString>    TContigNameStoreCache;

    BamIOContext<TContigNameStore, TContigNameStoreCache, Dependent<> > ctx;

    // Make sure that the BAM I/O context refers to the name cache of the FragmentStore
    setContigNames(ctx, store.contigNameStore);
    setContigNamesCache(ctx, store.contigNameStoreCache);
    setContigLengths(ctx, contigLengths(context(bamFile)));
    std::swap(ctx.buffer, context(bamFile).buffer);
    std::swap(ctx.translateFile2GlobalRefId, context(bamFile).translateFile2GlobalRefId);

    refresh(contigNamesCache(ctx));
    readRecords(store, ctx, directionIterator(bamFile, Input()), format(bamFile), importFlags);
//for(size_t i=0;i<length(contigNames(ctx));++i)
//std::cout<<contigNames(ctx)[i]<<std::endl;
    std::swap(ctx.buffer, context(bamFile).buffer);
    std::swap(ctx.translateFile2GlobalRefId, context(bamFile).translateFile2GlobalRefId);
}

template <typename TFSSpec, typename TConfig, typename TDirection, typename TSpec>
inline void
readRecords(FragmentStore<TFSSpec, TConfig> & store,
            FormattedFile<Bam, TDirection, TSpec> & bamFile)
{
    readRecords(store, bamFile, FragStoreImportFlags());
}

//template <typename TSpec, typename TConfig>
//inline void
//readRecords(FragmentStore<TSpec, TConfig> & store,
//            FormattedFile<Bam, Input, FragmentStore<TSpec, TConfig> > & bamFile)
//{
//    readRecord(record, context(file), file.iter, file.format);
//}
//readRecord(BamAlignmentRecord & record,
//           BamIOContext<TNameStore, TNameStoreCache, TStorageSpec> & context,
//           TForwardIter & iter,
//           TagSelector<TTagList> const & format)


// --------------------------------------------------------------------------
// Function _readAlignments()
// --------------------------------------------------------------------------
// reads all alignements from a SAM/BAM file into FragmentStore

template <typename TSpec, typename TConfig, typename TContigAnchorGaps, typename TMatchMateInfos,
          typename TNameStore, typename TNameStoreCache,
          typename TStorageSpec, typename TForwardIter, typename TFormat>
inline void
_readAlignments(
    FragmentStore<TSpec, TConfig> & fragStore,
    TContigAnchorGaps & contigAnchorGaps,
    TMatchMateInfos & matchMateInfos,
    BamIOContext<TNameStore, TNameStoreCache, TStorageSpec> & ctx,
    TForwardIter & iter,
    TFormat const & format,
    FragStoreImportFlags const & importFlags)
{
//IOREV _nodoc_ docusmentation in code, but unclear
    // create dummy entries in Sam specific aligned read quality store and aligned read tag store
    // is needed so the ID in the aligned store can be use to access the other stores
    // even if there exists previous entries without
    typedef FragmentStore<TSpec, TConfig> TFragmentStore;
    typedef typename TFragmentStore::TAlignQualityStore TAlignQualityStore;
    typedef typename TFragmentStore::TReadSeqStore TReadSeqStore;
    typedef typename Size<TReadSeqStore>::Type TReadSeqStoreSize;
    typedef typename Value<TAlignQualityStore>::Type TAlignQuality;

    // sync sizes of alignQualityStore and alignedReadTagStore with alignedReadStore
    TAlignQuality q;
    q.score = std::numeric_limits<decltype(q.score)>::max();
    resize(fragStore.alignQualityStore, length(fragStore.alignedReadStore), q);
    resize(fragStore.alignedReadTagStore, length(fragStore.alignedReadStore));

    // read in alignments
    FragStoreSAMContext<TFragmentStore> contextSAM;
//        refresh(fragStore.contigNameStoreCache);  // was done for the BamIOContext already
    refresh(fragStore.readNameStoreCache);

    uint64_t recNo = 0;
    while (!atEnd(iter))
    {
        try
        {
            ++recNo;
            _readOneAlignment(fragStore, contigAnchorGaps, matchMateInfos, ctx, iter, format, contextSAM, importFlags);
        }
        catch (IOError &e)
        {
            std::stringstream sstr;
            sstr << "Error in SAM/BAM record #" << recNo << ": " << e.what();
            SEQAN_THROW(IOError(sstr.str()));
        }
    }

    if (importFlags.importReadSeq)
    {
        TReadSeqStoreSize emptyReads = 0;
        for(TReadSeqStoreSize i = 0; i < length(fragStore.alignedReadStore); ++i)
            if (empty(fragStore.readSeqStore[fragStore.alignedReadStore[i].readId]))
            {
                ++emptyReads;
//                std::cerr << "Read sequence empty for " << fragStore.readNameStore[fragStore.alignedReadStore[i].readId] << std::endl;
            }
        if (emptyReads != 0)
            std::cerr << "Warning: " << emptyReads << " read sequences are empty." << std::endl;
    }
}

// --------------------------------------------------------------------------
// Function _bamAppendAlignment()
// --------------------------------------------------------------------------

template <typename TReadSeq, typename TCigar, typename TPos, typename TContigId, typename TId, typename TFragmentStore>
inline void
_bamAppendAlignment(
    TFragmentStore &fragStore,
    TReadSeq const &readSeq,
    TCigar &cigar,
    TPos &beginPos, TPos &endPos,
    TContigId contigId,
    TId &pairMatchId,
    FragStoreSAMContext<TFragmentStore> & contextSAM)
{
    typedef typename TFragmentStore::TAlignedReadStore                      TAlignedReadStore;
    typedef typename Value<TAlignedReadStore>::Type                         TAlignedRead;
    typedef Gaps<TReadSeq, AnchorGaps<typename TAlignedRead::TGapAnchors> > TReadGaps;

    // insert alignment gaps
    clear(contextSAM.readGapAnchors);
    TReadGaps readGaps(readSeq, contextSAM.readGapAnchors);
    unsigned beginGaps = cigarToGapAnchorRead(readGaps, cigar);

    // adapt start or end (on reverse strand) position if alignment begins with gaps
    if (beginPos > endPos)
        endPos += beginGaps;
    else
        beginPos += beginGaps;

    // create a new entry in the aligned read store
    pairMatchId = appendAlignment(fragStore, contextSAM.readId, contigId, beginPos, endPos, contextSAM.readGapAnchors);
}

// --------------------------------------------------------------------------
// Function _bamAppendAlignmentWithoutSeq()
// --------------------------------------------------------------------------

template <typename TCigar, typename TPos, typename TContigId, typename TId, typename TFragmentStore>
inline void
_bamAppendAlignmentWithoutSeq(
    TFragmentStore &fragStore,
    TCigar &cigar,
    TPos &beginPos, TPos &endPos,
    TContigId contigId,
    TId &pairMatchId,
    FragStoreSAMContext<TFragmentStore> & contextSAM)
{
    typedef typename TFragmentStore::TAlignedReadStore                      TAlignedReadStore;
    typedef typename Value<TAlignedReadStore>::Type                         TAlignedRead;
    typedef Gaps<Nothing, AnchorGaps<typename TAlignedRead::TGapAnchors> >  TReadGaps;
    Nothing nothing;

    // insert alignment gaps
    clear(contextSAM.readGapAnchors);
    TReadGaps readGaps(nothing, contextSAM.readGapAnchors);
    unsigned beginGaps = cigarToGapAnchorRead(readGaps, cigar);

    // adapt start or end (on reverse strand) position if alignment begins with gaps
    if (beginPos > endPos)
        endPos += beginGaps;
    else
        beginPos += beginGaps;

    // create a new entry in the aligned read store
    pairMatchId = appendAlignment(fragStore, contextSAM.readId, contigId, beginPos, endPos, contextSAM.readGapAnchors);
}

// --------------------------------------------------------------------------
// Function _readAlignments()
// --------------------------------------------------------------------------
// read one alignment record from SAM/BAM file into FragmentStore

template <
    typename TSpec,
    typename TConfig,
    typename TContigAnchorGaps,
    typename TMatchMateInfos,
    typename TNameStore, typename TNameStoreCache,
    typename TStorageSpec, typename TForwardIter, typename TFormat>
inline void
_readOneAlignment(
    FragmentStore<TSpec, TConfig> & fragStore,
    TContigAnchorGaps & contigAnchorGaps,
    TMatchMateInfos & matchMateInfos,
    BamIOContext<TNameStore, TNameStoreCache, TStorageSpec> & ctx,
    TForwardIter & iter,
    TFormat const & format,
    FragStoreSAMContext<FragmentStore<TSpec, TConfig> > & contextSAM,
    FragStoreImportFlags const & importFlags)
{
    // Basic types
    typedef FragmentStore<TSpec, TConfig>                                       TFragmentStore;
    typedef FragStoreSAMContext<TFragmentStore>                                 TSAMContext;
    typedef typename Id<TFragmentStore>::Type                                   TId;
    //typedef typename Size<TFragmentStore>::Type                                 TSize;

    // All fragment store element types
    //typedef typename Value<typename TFragmentStore::TContigStore>::Type         TContigElement;
    //typedef typename Value<typename TFragmentStore::TLibraryStore>::Type        TLibraryStoreElement;
    //typedef typename Value<typename TFragmentStore::TReadStore>::Type           TReadStoreElement;
    typedef typename Value<typename TFragmentStore::TAlignQualityStore>::Type   TAlignQualityElement;

    // Type for sequence in readstore
    typedef typename TFragmentStore::TReadSeq                                   TReadSeq;

    // Type for gap anchor
    typedef typename TFragmentStore::TContigPos                                 TContigPos;
    typedef Gaps<Nothing, AnchorGaps<typename TSAMContext::TContigAnchorGaps> > TContigGapsPW;

    // Type to temporarily store information about match mates
    typedef typename Value<TMatchMateInfos>::Type                               TMatchMateInfo;

    // Read next BamAlignmentRecord and get shortcut.
    BamAlignmentRecord & record = contextSAM.bamRecord;
    readRecord(record, ctx, iter, format);

    // Get element of align quality store.
    TAlignQualityElement mapQ;
    mapQ.score = record.mapQ;

    // Get begin and end position.
    TContigPos beginPos = record.beginPos;
    TContigPos endPos = 0;
    _getLengthInRef(endPos, record.cigar);
    endPos = beginPos + endPos;
    if (hasFlagRC(record))
        std::swap(beginPos, endPos);

    // Put read sequence and qualities into readSeq and reverseComplement if necessary.
    TReadSeq & readSeq = contextSAM.readSeq;
    readSeq = record.seq;
    assignQualities(readSeq, record.qual);
    if (hasFlagRC(record))
        reverseComplement(readSeq);

    // Check if read sequence is already in the store.  If so get the ID, otherwise create new entries in the read
    // then read name and mate pair store.
    contextSAM.readId = -1;
    if (importFlags.importRead)
    {
        if (!importFlags.importReadName)
            clear(record.qName);

        bool newRead = _storeAppendRead(fragStore, contextSAM.readId, record.qName, readSeq, record.flag,
                                        contextSAM);
        (void)newRead;
        SEQAN_ASSERT_NOT(newRead && empty(readSeq));
    }

    // Stop here if read is unaligned.
    if (record.rID == BamAlignmentRecord::INVALID_REFID || record.beginPos == BamAlignmentRecord::INVALID_POS)
        return;

    // Sync contigStore with size of contigNameStore (if a new contig was added)
    resize(fragStore.contigStore, length(fragStore.contigNameStore));

    // Stop if no alignment in CIGAR string.
    if (empty(record.cigar))
        return;

    // Handle read alignment import.
    TId pairMatchId = 0;
    if (importFlags.importReadAlignment)
    {
        // generate gap anchor string for the read
        if (importFlags.importReadSeq)
            _bamAppendAlignment(fragStore, fragStore.readSeqStore[contextSAM.readId], record.cigar, beginPos, endPos,
                                record.rID, pairMatchId, contextSAM);
        else
            _bamAppendAlignmentWithoutSeq(fragStore, record.cigar, beginPos, endPos, record.rID, pairMatchId,
                                          contextSAM);

        clear(contextSAM.contigGapAnchors);
        TContigGapsPW contigGaps(contextSAM.contigGapAnchors);
        cigarToGapAnchorContig(contigGaps, record.cigar);
        appendValue(contigAnchorGaps, contextSAM.contigGapAnchors);
    }

    // Import tags and remove some tags.
    if (importFlags.importReadAlignmentTags || importFlags.importReadAlignmentQuality)
    {
        // extract and delete some tags
        if (!empty(record.tags))
        {
            BamTagsDict tags(record.tags);
            int tagId = -1;
            if (findTagKey(tagId, tags, "MD"))
                eraseTag(tags, tagId);
            if (findTagKey(tagId, tags, "NM") && extractTagValue(mapQ.errors, tags, tagId))
                eraseTag(tags, tagId);
        }
    }

    // Create entries in Sam specific stores.
    if (importFlags.importReadAlignmentQuality)
        appendValue(fragStore.alignQualityStore, mapQ, Generous());

    if (importFlags.importReadAlignmentTags)
        appendValue(fragStore.alignedReadTagStore, record.tags, Generous());

    // Store additional data about match mate temporarily.
    // used in the end of the read function to generate match mate IDs.
    if (importFlags.importRead && importFlags.importReadAlignment && record.rNextId != BamAlignmentRecord::INVALID_REFID)
    {
        if (contextSAM.readId < length(fragStore.readStore))
        {
            // insert match mate info for the mate record
            TMatchMateInfo matchMateInfo =
            {
                /* .readId      = */  contextSAM.readId,
                /* .contigId    = */  record.rNextId,
                /* .pairMatchId = */  pairMatchId,
                /* .matePairId  = */  fragStore.readStore[contextSAM.readId].matePairId,
                /* .beginPos    = */  record.pNext,
                /* .reversed    = */  hasFlagNextRC(record)
            };
            appendValue(matchMateInfos, matchMateInfo);
            back(fragStore.alignedReadStore).pairMatchId = pairMatchId;
        }
    }
}

// ============================================================================
// Write Functions
// ============================================================================

// --------------------------------------------------------------------------
// Function _fillHeader()
// --------------------------------------------------------------------------

template <typename TSpec, typename TConfig, typename TBamIOFunctor>
inline void
_fillHeader(BamHeader & header,
            FragmentStore<TSpec, TConfig> & store,
            TBamIOFunctor & /* functor */)
{
    typedef FragmentStore<TSpec, TConfig>                       TFragmentStore;
    typedef typename TFragmentStore::TLibraryStore              TLibraryStore;
    typedef typename TFragmentStore::TContigStore               TContigStore;

    typedef typename Value<TContigStore>::Type                  TContig;
    typedef typename Iterator<TLibraryStore, Standard>::Type    TLibraryIter;
    typedef typename Id<TContig>::Type                          TId;

    typedef BamHeaderRecord::TTag                               TTag;

    // Fill first header line.
    BamHeaderRecord firstRecord;
    firstRecord.type = BAM_HEADER_FIRST;
    appendValue(firstRecord.tags, TTag("VN", "1.4"));
    appendValue(firstRecord.tags, TTag("SO", "unsorted"));
    appendValue(header, firstRecord);

    // Fill program header line.
    BamHeaderRecord pgRecord;
    pgRecord.type = BAM_HEADER_PROGRAM;
    appendValue(pgRecord.tags, TTag("ID", "SeqAn"));
    appendValue(header, pgRecord);

    // Fill library info header line.
    BamHeaderRecord rgRecord;
    rgRecord.type = BAM_HEADER_READ_GROUP;

    TLibraryIter lit    = begin(store.libraryStore, Standard());
    TLibraryIter litEnd = end(store.libraryStore, Standard());

    for (TId id = 0; lit != litEnd; ++lit, ++id)
    {
        CharString buffer;
        appendNumber(buffer, id + 1);
        appendValue(pgRecord.tags, TTag("ID", buffer));
        appendValue(pgRecord.tags, TTag("LB", store.libraryNameStore[id]));
        clear(buffer);
        appendNumber(buffer, (int)store.libraryStore[id].mean);
        appendValue(pgRecord.tags, TTag("PI", buffer));
        // Sample name needs to be included into fragment store.
        appendValue(pgRecord.tags, TTag("SM", "none"));
    }
}

// --------------------------------------------------------------------------
// Function fillHeader()
// --------------------------------------------------------------------------

template <typename TSpec, typename TFSSpec, typename TFSConfig, typename TBamIOFunctor>
inline void
fillHeader(BamHeader & header,
           FormattedFile<Bam, Output, TSpec> & bamFile,
           FragmentStore<TFSSpec, TFSConfig> & store,
           TBamIOFunctor & functor)
{
    // Make sure that the BAM I/O context refers to the name cache of the FragmentStore
    setContigNames(context(bamFile), store.contigNameStore);
    setContigNamesCache(context(bamFile), store.contigNameStoreCache);

    // Fill header with information from fragment store.
    _fillHeader(header, store, functor);

    // Fill sequence lengths.
    resize(contigLengths(context(bamFile)), length(store.contigStore));
    for (size_t i = 0; i != length(store.contigStore); ++i)
        contigLengths(context(bamFile))[i] = length(store.contigStore[i].seq);
}

template <typename TSpec, typename TFSSpec, typename TFSConfig>
inline void
fillHeader(BamHeader & header,
           FormattedFile<Bam, Output, TSpec> & bamFile,
           FragmentStore<TFSSpec, TFSConfig> & store)
{
    Nothing nothing;
    fillHeader(header, bamFile, store, nothing);
}

// --------------------------------------------------------------------------
// Function writeHeader()
// --------------------------------------------------------------------------

template <typename TSpec, typename TFSSpec, typename TFSConfig, typename TBamIOFunctor>
inline void writeHeader(FormattedFile<Bam, Output, TSpec> & bamFile,
                        FragmentStore<TFSSpec, TFSConfig> & store,
                        TBamIOFunctor & functor)
{
    BamHeader header;

    // Fill header with information from fragment store.
    fillHeader(header, bamFile, store, functor);

    // Write header to target.
    writeHeader(bamFile, header);
}

template <typename TSpec, typename TFSSpec, typename TFSConfig>
inline void writeHeader(FormattedFile<Bam, Output, TSpec> & bamFile,
                        FragmentStore<TFSSpec, TFSConfig> & store)
{
    Nothing nothing;
    writeHeader(bamFile, store, nothing);
}

// --------------------------------------------------------------------------
// Function _fillBamSeqAndQual()
// --------------------------------------------------------------------------

template <typename TSeq, typename TQual, typename TRead>
inline void
_fillBamSeqAndQual(TSeq &bamSeq, TQual &bamQual, TRead const &read)
{
    bamSeq = read;

    resize(bamQual, length(read));
    typename Iterator<TQual, Standard>::Type       tIt    = begin(bamQual, Standard());
    typename Iterator<TRead const, Standard>::Type sIt    = begin(read, Standard());
    typename Iterator<TRead const, Standard>::Type sItEnd = end(read, Standard());

    for (; sIt != sItEnd; ++sIt, ++tIt)
        *tIt = (char)(getQualityValue(*sIt) + '!');
}

// --------------------------------------------------------------------------
// Function setPrimaryMatch()
// --------------------------------------------------------------------------

template <typename TSpec, typename TConfig, typename TAlignedRead, typename TAlignQuality, typename TBamIOFunctor>
inline void
setPrimaryMatch(BamAlignmentRecord & record,
                FragmentStore<TSpec, TConfig> & store,
                TAlignedRead const & alignedRead,       // read alignment to transform into a BamAlignmentRecord
                TAlignQuality const & alignQuality,     // read alignment quality
                TBamIOFunctor & functor,                // functor that extracts/computes alignment for cigar/md strings
                bool secondaryAlignment)                // is this a secondary alignment?
{
    typedef FragmentStore<TSpec, TConfig>                           TFragmentStore;

    typedef typename TFragmentStore::TContigStore                   TContigStore;
    typedef typename Value<TContigStore>::Type                      TContig;
    typedef typename TContig::TGapAnchors                           TContigGapAnchors;

    typedef Iterator<CharString, Standard>::Type                    TCharStringIterator;

    typedef Gaps<Nothing, AnchorGaps<TContigGapAnchors> >           TContigGaps;

    // Fill QNAME with read name.
    clear(record.qName);
    TCharStringIterator it = begin(store.readNameStore[alignedRead.readId], Standard());
    TCharStringIterator itEnd = end(store.readNameStore[alignedRead.readId], Standard());
    for (; it != itEnd && *it != ' ' && *it != '\t'; ++it)
        appendValue(record.qName, *it);

    // Fill FLAG.
    unsigned short flag = 0;

    if (alignedRead.beginPos > alignedRead.endPos)
        flag |= BAM_FLAG_RC;
    if (secondaryAlignment)
        flag |= BAM_FLAG_SECONDARY;     // we've already output an alignment for this read (this one is secondary)

    signed char mateNo = getMateNo(store, alignedRead.readId);
    if (mateNo == 0)
        flag |= BAM_FLAG_FIRST;        // this read is the first in the pair
    else if (mateNo == 1)
        flag |= BAM_FLAG_LAST;         // this read is the second in the pair

    // Set flags regarding mate alignment.

    // We disinguish 3 cases:
    //  1) We have no mate (single-end read)
    //  2) We might have a mate, but it wasn't aligned properly
    //  3) We have a mate which was aligned properly
    //
    // wich are encoded as follows:
    //  1) alignedRead and alignedMate have the same address in _fillRecord
    //  2) alignedMate has an invalid contigId (== INVALID_ID)
    //  3) alignedRead and alignedMate have valid readIds

    if (mateNo >= 0)
        flag |=   BAM_FLAG_MULTIPLE | BAM_FLAG_NEXT_UNMAPPED;   // there is a mate
    else
        flag &= ~(BAM_FLAG_MULTIPLE | BAM_FLAG_NEXT_UNMAPPED);  // there is no mate

    record.flag = flag;

    // Fill RNAME by providing contig id.
    record.rID = alignedRead.contigId;

    // Fill POS with start position.
    TContigGaps contigGaps(/*store.contigStore[alignedRead.contigId].seq, */store.contigStore[alignedRead.contigId].gaps);
    record.beginPos = positionGapToSeq(contigGaps, std::min(alignedRead.beginPos, alignedRead.endPos));

    // Fill MAPQ with mapping quality.
//    if (alignQuality.score != TAlignedReadQualityElement::INVALID_SCORE)
    if (alignQuality.score > 0)
        record.mapQ = alignQuality.score;
    else
        record.mapQ = 255;

//    // Fill CIGAR using aligned read.
//    SEQAN_IF_CONSTEXPR (!IsSameType<TAlignFunctor, Nothing>::VALUE)
//        getCigarString(record.cigar, row(align, 0), row(align, 1));

    // Retrieve number of errors from quality store.
    int errors = -1;
    if (alignQuality.errors != std::numeric_limits<unsigned char>::max())
        errors = alignQuality.errors;

    // Use record.qual as a temporary for the md string.
    alignAndGetCigarString(record.cigar, record.qual, store.contigStore[alignedRead.contigId],
            store.readSeqStore[alignedRead.readId], alignedRead, errors, functor);

    if (alignQuality.errors != std::numeric_limits<unsigned char>::max())
    {
//        if (errors > (int)alignQuality.errors)
//            std::cerr << "WARNING: More errors in the alignment (" << errors << ") than given in NM tag / alignQuality ("
//                      << (int)alignQuality.errors << ") for read " << record.qName << std::endl;

        // To output the same NM value if a SAM file is loaded and saved, we overwrite error with the original value
        // TODO(weese): This can be changed if desired (uncomment the following line) but now even the ex1.sam example
        //              of the SAMtools have NM values that are inconsistent to their CIGAR/MD strings
        errors = alignQuality.errors;
    }

    // Fill tags here to release record.qual
    if (errors != -1)
        appendTagValue(record.tags, "NM", errors);
    if (!empty(record.tags))
        appendTagValue(record.tags, "MD", record.qual, 'Z');

    record.rNextId = BamAlignmentRecord::INVALID_REFID;
    record.pNext = BamAlignmentRecord::INVALID_POS;
    record.tLen = BamAlignmentRecord::INVALID_LEN;

    if (!secondaryAlignment)
    {
        // Fill SEQ and QUAL with read sequence and quality values.
        if (alignedRead.beginPos <= alignedRead.endPos)
            _fillBamSeqAndQual(record.seq, record.qual, store.readSeqStore[alignedRead.readId]);
        else
            _fillBamSeqAndQual(record.seq, record.qual, reverseComplementString(store.readSeqStore[alignedRead.readId]));
    }
    else
    {
        clear(record.seq);
        clear(record.qual);
    }
}

// --------------------------------------------------------------------------
// Function setMateMatch()
// --------------------------------------------------------------------------

template <typename TSpec, typename TConfig, typename TAlignedRead>
inline void
setMateMatch(BamAlignmentRecord & record,
             FragmentStore<TSpec, TConfig> & store,
             TAlignedRead const & alignedRead,       // read alignment to transform into a BamAlignmentRecord
             TAlignedRead const & alignedMate)       // alignment of the mate
{
    typedef FragmentStore<TSpec, TConfig>                           TFragmentStore;

    typedef typename TFragmentStore::TContigStore                   TContigStore;
    typedef typename Value<TContigStore>::Type                      TContig;
    typedef typename TContig::TGapAnchors                           TContigGapAnchors;

    typedef typename TFragmentStore::TReadStore                     TReadStore;
    typedef typename Value<TReadStore>::Type                        TReadStoreElement;

    typedef Gaps<Nothing, AnchorGaps<TContigGapAnchors> >           TContigGaps;


    record.flag &= ~(BAM_FLAG_ALL_PROPER | BAM_FLAG_NEXT_RC | BAM_FLAG_NEXT_UNMAPPED);
    if (alignedMate.contigId != TReadStoreElement::INVALID_ID)
    {
        record.flag |= BAM_FLAG_ALL_PROPER;    // mate is mapped properly

        if (alignedMate.beginPos > alignedMate.endPos)
            record.flag |= BAM_FLAG_NEXT_RC;   // mate is mapped on reverse strand
    }
    else
    {
        record.flag |= BAM_FLAG_NEXT_UNMAPPED; // mate is unmapped
    }

    record.rNextId = (alignedMate.contigId != TContig::INVALID_ID)? alignedMate.contigId : BamAlignmentRecord::INVALID_REFID;

    // Fill PNEXT with mate start position
    // Fill TLEN with outer distance of the read alignments
    if (alignedMate.contigId < length(store.contigStore))
    {
        TContigGaps contigGaps(store.contigStore[alignedMate.contigId].gaps);
        record.pNext = positionGapToSeq(contigGaps, std::min(alignedMate.beginPos, alignedMate.endPos));

        if (alignedMate.contigId == alignedRead.contigId)
        {
            if (alignedRead.beginPos < alignedMate.beginPos)
                record.tLen = positionGapToSeq(contigGaps, std::max(alignedMate.beginPos, alignedMate.endPos) - 1) - record.beginPos + 1;
            else
                record.tLen = record.pNext - positionGapToSeq(contigGaps, std::max(alignedRead.beginPos, alignedRead.endPos) - 1) - 1;
        }
        else
        {
            record.tLen = BamAlignmentRecord::INVALID_LEN;
        }
    }
    else
    {
        record.pNext = BamAlignmentRecord::INVALID_POS;
        record.tLen = BamAlignmentRecord::INVALID_LEN;
    }
}

// --------------------------------------------------------------------------
// Function writeAlignments()
// --------------------------------------------------------------------------

template <typename TSpec, typename TFSSpec, typename TFSConfig, typename TBamIOFunctor>
inline void
writeAlignments(FormattedFile<Bam, Output, TSpec> & bamFile,
                FragmentStore<TFSSpec, TFSConfig> & store,
                TBamIOFunctor & functor)
{
    typedef FragmentStore<TFSSpec, TFSConfig>                       TFragmentStore;

    typedef typename TFragmentStore::TReadStore                     TReadStore;
    typedef typename Value<TReadStore>::Type                        TReadStoreElement;

    typedef typename TFragmentStore::TAlignedReadStore              TAlignedReadStore;
    typedef typename Iterator<TAlignedReadStore, Standard>::Type    TAlignedReadStoreIterator;
    typedef typename Value<TAlignedReadStore>::Type                 TAlignedReadStoreElement;
    typedef typename Id<TAlignedReadStoreElement>::Type             TAlignedReadStoreElementId;

    typedef typename TFragmentStore::TAlignQualityStore             TAlignQualityStore;
    typedef typename Value<TAlignQualityStore>::Type                TAlignQualityStoreElement;

    typedef TAlignQualityStoreElement *                             TAlignQualityStoreElementPtr;

    // Store outer library size for each pair match (indexed by pairMatchId)
    String<TAlignedReadStoreElementId> mateIndices;
    calculateMateIndices(mateIndices, store);

    // Bitset to signal wether a read was aligned at least once.
    String<bool, Packed<> > readAligned;
    resize(readAligned, length(store.readStore), false);

    // Dummy store elements to cope with missing information.
    TAlignQualityStoreElement       noAlignQuality;
    TAlignQualityStoreElementPtr    alignQualityPtr;

    TAlignedReadStoreIterator it    = begin(store.alignedReadStore, Standard());
    TAlignedReadStoreIterator itEnd = end(store.alignedReadStore, Standard());

    BamAlignmentRecord record;

    for (; it != itEnd; ++it)
    {
        TAlignedReadStoreElement &alignedRead = *it;

        // Try to get quality.
        if (alignedRead.id < length(store.alignQualityStore))
            alignQualityPtr = &store.alignQualityStore[alignedRead.id];
        else
            alignQualityPtr = &noAlignQuality;

        // Try to get a mate.

        // We disinguish 3 cases:
        //  1) We have no mate (single-end read)
        //  2) We might have a mate, but it wasn't aligned properly
        //  3) We have a mate which was aligned properly

        // Test for secondary alignment and mark read as seen.
        bool secondary = getValue(readAligned, alignedRead.readId);
        assignValue(readAligned, alignedRead.readId, true);

        // Fill record.
        clear(record);

        // case 1 or 2 is handled here
        setPrimaryMatch(record, store, alignedRead, *alignQualityPtr, functor, secondary);

        if (alignedRead.pairMatchId != TReadStoreElement::INVALID_ID)
        {
            // case 3
            TAlignedReadStoreElementId mateIndex = mateIndices[2 * alignedRead.pairMatchId + getMateNo(store, alignedRead.readId)];
            if (mateIndex < length(store.alignedReadStore))
                setMateMatch(record, store, alignedRead, store.alignedReadStore[mateIndex]);
        }

        // Append additional tags.
        if (alignedRead.id < length(store.alignedReadTagStore))
            append(record.tags, store.alignedReadTagStore[alignedRead.id]);

        // Write record to target.
        writeRecord(bamFile, record);
    }
}

// --------------------------------------------------------------------------
// Function writeRecords()
// --------------------------------------------------------------------------

template <typename TSpec, typename TFSSpec, typename TFSConfig, typename TBamIOFunctor>
inline void
writeRecords(FormattedFile<Bam, Output, TSpec> & bamFile,
             FragmentStore<TFSSpec, TFSConfig> & store,
             TBamIOFunctor & functor)
{
    // 1. write header
    writeHeader(bamFile, store, functor);

    // 2. write aligments
    writeAlignments(bamFile, store, functor);
}

template <typename TSpec, typename TFSSpec, typename TFSConfig>
inline void
writeRecords(FormattedFile<Bam, Output, TSpec> & bamFile,
             FragmentStore<TFSSpec, TFSConfig> & store)
{
    BamAlignFunctorDefault functor;
    writeRecords(bamFile, store, functor);
}

}// namespace seqan2

#endif //#ifndef SEQAN_HEADER_...
