//=============================================================================
//  MuseScore
//  Music Composition & Notation
//
//  Copyright (C) 2018 Werner Schweer
//
//  This program is free software; you can redistribute it and/or modify
//  it under the terms of the GNU General Public License version 2
//  as published by the Free Software Foundation and appearing in
//  the file LICENCE.GPL
//=============================================================================

#include "scorediff.h"

#include "duration.h"
#include "measure.h"
#include "score.h"
#include "staff.h"
#include "xml.h"

#include "dtl/dtl.hpp"

#include <algorithm>
#include <utility>

namespace Ms {
//---------------------------------------------------------
//   MscxModeDiff
//---------------------------------------------------------

class MscxModeDiff
{
    static constexpr const char* tagRegExpStr = "</?(?<name>[A-z_][A-z_0-9\\-.:]*)( [A-z_0-9\\-.:\\s=\"]*)?/?>";
    const QRegularExpression tagRegExp;

    enum TagType {
        START_TAG, END_TAG
    };
    struct Tag {
        int line;
        TagType type;
        QString name;

        Tag(int l, TagType t, const QString& n)
            : line(l), type(t), name(n) {}
    };

    static DiffType fromDtlDiffType(dtl::edit_t dtlType);

    void adjustSemanticsMscx(std::vector<TextDiff>&);
    int adjustSemanticsMscxOneDiff(std::vector<TextDiff>& diffs, int index);
    int nextDiffOnShiftIndex(const std::vector<TextDiff>& diffs, int index, bool down);
    static QString getOuterLines(const QString& str, int lines, bool start);
    bool assessShiftDiff(const std::vector<TextDiff>&, const std::vector<Tag>& extraTags, int index, int lines);
    int performShiftDiff(std::vector<TextDiff>&, int index, int lines);
    void readMscx(const QString& xml, std::vector<Tag>& extraTags);
    void handleTag(int line, TagType type, const QString& name, std::vector<Tag>& extraTags);

public:
    MscxModeDiff();

    std::vector<TextDiff> lineModeDiff(const QString& s1, const QString& s2);
    std::vector<TextDiff> mscxModeDiff(const QString& s1, const QString& s2);
};

//---------------------------------------------------------
//   TextDiffParser
//    Used by ScoreDiff class during parsing MSCX text diff
//---------------------------------------------------------

class TextDiffParser
{
    const int iScore;
    const int iOtherScore;

    int tagLevel = 0;
    int currentDiffTagLevel = 0;
    std::vector<const ScoreElement*> contextsStack;
    std::vector<bool> tagIsElement;
    const ScoreElement* lastElementEnded = nullptr;
    QString markupContext;

    BaseDiff* handleToken(const QXmlStreamReader& r, const ScoreElement* newElement, bool saveDiff);
    bool insideDiffTag() const { return currentDiffTagLevel != 0; }

public:
    TextDiffParser(int iScore);

    void makeDiffs(const QString& mscx, const std::vector<std::pair<const ScoreElement*, QString> >& elements,
                   const std::vector<TextDiff>& textDiffs, std::vector<BaseDiff*>& diffs);
};

//---------------------------------------------------------
//   MscxModeDiff::MscxModeDiff
//---------------------------------------------------------

MscxModeDiff::MscxModeDiff()
    : tagRegExp(tagRegExpStr)
{}

//---------------------------------------------------------
//   MscxModeDiff::fromDtlDiffType
//---------------------------------------------------------

DiffType MscxModeDiff::fromDtlDiffType(dtl::edit_t dtlType)
{
    switch (dtlType) {
    case dtl::SES_DELETE:
        return DiffType::DELETE;
    case dtl::SES_COMMON:
        return DiffType::EQUAL;
    case dtl::SES_ADD:
        return DiffType::INSERT;
    }
    Q_ASSERT(false);   // dtlType must have one of the values handled above.
    return DiffType::EQUAL;
}

//---------------------------------------------------------
//   MscxModeDiff::lineModeDiff
//---------------------------------------------------------

std::vector<TextDiff> MscxModeDiff::lineModeDiff(const QString& s1, const QString& s2)
{
    // type declarations for dtl library
    typedef QStringRef elem;
    typedef std::pair<elem, dtl::elemInfo> sesElem;
    typedef std::vector<sesElem> sesElemVec;

    const QVector<QStringRef> linesVec1 = s1.splitRef('\n');
    std::vector<QStringRef> lines1(linesVec1.begin(), linesVec1.end());
    const QVector<QStringRef> linesVec2 = s2.splitRef('\n');
    std::vector<QStringRef> lines2(linesVec2.begin(), linesVec2.end());
    dtl::Diff<QStringRef, std::vector<QStringRef> > diff(lines1, lines2);

    diff.compose();

    const sesElemVec changes = diff.getSes().getSequence();
    std::vector<TextDiff> diffs;
    int line[2][2] { { 1, 1 }, { 1, 1 } }; // for correct assigning line numbers to
                                           // DELETE and INSERT diffs we need to
                                           // count lines separately for these diff
                                           // types (EQUAL can use both counters).

    for (const sesElem& ch : changes) {
        DiffType type = fromDtlDiffType(ch.second.type);
        const int iThis = (type == DiffType::DELETE) ? 0 : 1;     // for EQUAL doesn't matter

        if (diffs.empty() || diffs.back().type != type) {
            if (!diffs.empty()) {
                // sync line numbers
                DiffType prevType = diffs.back().type;
                const int prevThis = (prevType == DiffType::DELETE) ? 0 : 1;
                const int prevOther = (prevThis == 1) ? 0 : 1;
                if (prevType == DiffType::EQUAL) {
                    std::copy_n(line[prevThis], 2, line[prevOther]);
                } else {
                    line[prevThis][prevOther] = line[prevOther][prevOther];
                }

                if (type == DiffType::EQUAL) {
                    const int iOther = (iThis == 1) ? 0 : 1;
                    line[iThis][iOther] = line[iOther][iOther];
                }
            }

            diffs.emplace_back();
            TextDiff& d = diffs.back();
            d.type = type;
            std::copy_n(line[iThis], 2, d.start);
            d.end[0] = line[iThis][0] - 1;       // equal line numbers would mean an actual change in that line.
            d.end[1] = line[iThis][1] - 1;
        }

        TextDiff& d = diffs.back();
        d.end[iThis] = (line[iThis][iThis]++);
        d.text[iThis].append(ch.first).append('\n');
        if (type == DiffType::EQUAL) {
            const int iOther = (iThis == 1) ? 0 : 1;
            d.end[iOther] = (line[iThis][iOther]++);
            d.text[iOther].append(ch.first).append('\n');
        }
    }

    return diffs;
}

//---------------------------------------------------------
//   MscxModeDiff::mscxModeDiff
//---------------------------------------------------------

std::vector<TextDiff> MscxModeDiff::mscxModeDiff(const QString& s1, const QString& s2)
{
    std::vector<TextDiff> diffs = lineModeDiff(s1, s2);
    adjustSemanticsMscx(diffs);
    return diffs;
}

//---------------------------------------------------------
//   MscxModeDiff::adjustSemanticsMscx
//---------------------------------------------------------

void MscxModeDiff::adjustSemanticsMscx(std::vector<TextDiff>& diffs)
{
    for (unsigned i = 0; i < diffs.size(); ++i) {
        i = adjustSemanticsMscxOneDiff(diffs, i);
    }
}

//---------------------------------------------------------
//   MscxModeDiff::adjustSemanticsMscx
//    Returns new index of the given diff
//---------------------------------------------------------

int MscxModeDiff::adjustSemanticsMscxOneDiff(std::vector<TextDiff>& diffs, int index)
{
    TextDiff* diff = &diffs[index];
    int iScore;
    switch (diff->type) {
    case DiffType::EQUAL:
    case DiffType::REPLACE:
        // TODO: split a REPLACE diff, though they should not be here
        return index;
    case DiffType::INSERT:
        iScore = 1;
        break;
    case DiffType::DELETE:
    default:
        iScore = 0;
        break;
    }

    std::vector<Tag> extraTags;
    readMscx(diff->text[iScore], extraTags);

    if (extraTags.empty()) {
        return index;     // good, nothing to adjust
    }
    auto firstStartExtra = extraTags.begin();
    auto lastStartExtra = extraTags.begin();
    auto firstEndExtra = extraTags.begin();
    auto lastEndExtra = extraTags.begin();
    for (auto tag = extraTags.begin(); tag != extraTags.end(); ++tag) {
        TagType type = tag->type;
        switch (type) {
        case START_TAG:
            if (firstStartExtra->type != START_TAG) {
                firstStartExtra = tag;
            }
            lastStartExtra = tag;
            break;
        case END_TAG:
            if (firstStartExtra->type != END_TAG) {
                firstEndExtra = tag;
            }
            lastEndExtra = tag;
            break;
        default:
            break;
        }
    }

    // Try to shift current diff up and down and see whether this helps
    int lines = lastEndExtra->line - firstEndExtra->line + 1;
    if (assessShiftDiff(diffs, extraTags, index, lines)) {
        return performShiftDiff(diffs, index, lines);
    } else {
        lines = -(lastStartExtra->line - firstStartExtra->line + 1);
        if (assessShiftDiff(diffs, extraTags, index, lines)) {
            return performShiftDiff(diffs, index, lines);
        }
    }

    return index;
}

//---------------------------------------------------------
//   MscxModeDiff::assessShiftDiff
//    Returns true if shift of the diff with the given
//    index is possible and there would be no extra tags
//    left after such a shift.
//---------------------------------------------------------

bool MscxModeDiff::assessShiftDiff(const std::vector<TextDiff>& diffs, const std::vector<Tag>& origExtraTags, int index,
                                   int lines)
{
    if (lines == 0) {
        return diffs.empty();
    }
    const bool down = (lines > 0);
    const int nextDiffIdx = nextDiffOnShiftIndex(diffs, index, down);
    if (nextDiffIdx == index) {
        return false;
    }

    const TextDiff& diff = diffs[index];
    const TextDiff& nextDiff = diffs[nextDiffIdx];

    Q_ASSERT(diff.type == DiffType::DELETE || diff.type == DiffType::INSERT);
    const int iScore = (diff.type == DiffType::DELETE ? 0 : 1);

    const QString& diffTxt = diff.text[iScore];
    const QString& nextTxt = nextDiff.text[iScore];
    const QString diffChunk = getOuterLines(diffTxt, lines, down);
    const QString nextChunk = getOuterLines(nextTxt, lines, down);

    if (diffChunk == nextChunk) {
        std::vector<Tag> extraTags(origExtraTags);
        std::vector<Tag> diffExtraTags;
        readMscx(diffChunk, diffExtraTags);

        // merge diff chunk reading result with the result
        // for the whole chunk
        while (!diffExtraTags.empty()) {
            auto tag = down ? diffExtraTags.begin() : (diffExtraTags.end() - 1);

            if (extraTags.size() < 2) {     // would normally erase 2 tags
                return false;
            }

            auto firstExtra = extraTags.begin();
            if ((firstExtra->type == END_TAG)
                && (firstExtra->name == tag->name)) {
                extraTags.erase(firstExtra);
            } else {
                return false;
            }
            auto lastExtra = extraTags.end() - 1;
            if ((lastExtra->type == START_TAG)
                && (lastExtra->name == tag->name)) {
                extraTags.erase(lastExtra);
            } else {
                return false;
            }

            diffExtraTags.erase(tag);
        }

        if (extraTags.empty()) {
            // We have succeeded
            return true;
        }
    }
    return false;
}

//---------------------------------------------------------
//   MscxModeDiff::performShiftDiff
//    Perform a shift of the diff with the given index and
//    return a new index of the diff.
//---------------------------------------------------------

int MscxModeDiff::performShiftDiff(std::vector<TextDiff>& diffs, int index, int lines)
{
    if (lines == 0) {
        return index;
    }
    const bool down = (lines > 0);
    const int absLines = qAbs(lines);
    const int nextDiffIdx = nextDiffOnShiftIndex(diffs, index, down);
    if (nextDiffIdx == index) {
        return index;
    }

    TextDiff& diff = diffs[index];
    TextDiff& nextDiff = diffs[nextDiffIdx];

    Q_ASSERT(diff.type == DiffType::DELETE || diff.type == DiffType::INSERT);
    const int iScore = (diff.type == DiffType::DELETE ? 0 : 1);
    QString& diffTxt = diff.text[iScore];

    const QString diffChunk = getOuterLines(diffTxt, absLines, down);

    Q_ASSERT(nextDiff.type == DiffType::EQUAL);
    int chunkStart[2];   // line numbers of diffChunk in two scores
    int chunkEnd[2];
    if (down) {
        std::copy(diff.start, diff.start + 2, chunkStart);
        chunkEnd[0] = diff.start[0] + absLines - 1;
        chunkEnd[1] = diff.start[1] + absLines - 1;
    } else {
        chunkStart[0] = diff.end[0] - (absLines - 1);
        chunkStart[1] = diff.end[1] - (absLines - 1);
        std::copy(diff.end, diff.end + 2, chunkEnd);
    }

    if (down) {
        diffTxt.remove(0, diffChunk.size());
        diffTxt.append(diffChunk);
        nextDiff.text[0].remove(0, diffChunk.size());
        nextDiff.text[1].remove(0, diffChunk.size());
    } else {
        diffTxt.chop(diffChunk.size());
        diffTxt.prepend(diffChunk);
        nextDiff.text[0].chop(diffChunk.size());
        nextDiff.text[1].chop(diffChunk.size());
    }
    // shift line numbers: needed both for shifted diff and for diffs
    // between the shifted diff and nextDiff
    const int inc = down ? 1 : -1;
    for (int i = index; i != nextDiffIdx; i += inc) {
        TextDiff& d = diffs[i];
        Q_UNUSED(d);
        Q_ASSERT(d.type != DiffType::EQUAL);     // nextDiff should be the first EQUAL diff in that direction
        diff.start[0] += lines;
        diff.end[0] += lines;
        diff.start[1] += lines;
        diff.end[1] += lines;
    }
    int* nextChunkLines = down ? nextDiff.start : nextDiff.end;
    nextChunkLines[0] += lines;
    nextChunkLines[1] += lines;

    TextDiff eqDiff;
    eqDiff.type = DiffType::EQUAL;
    eqDiff.text[0] = diffChunk;
    eqDiff.text[1] = diffChunk;
    std::copy(chunkStart, chunkStart + 2, eqDiff.start);
    std::copy(chunkEnd, chunkEnd + 2, eqDiff.end);

    const int prevDiffIdx = index + (down ? -1 : 1);
    bool merged = false;
    if (diffs[prevDiffIdx].type == DiffType::EQUAL) {
        merged = diffs[prevDiffIdx].merge(eqDiff);
    }

    if (!merged) {
        const int insertIdx = down ? index : (index + 1);
        diffs.insert(diffs.begin() + insertIdx, eqDiff);
        if (down) {
            ++index;
        }
    }

    return index;
}

//---------------------------------------------------------
//   MscxModeDiff::getOuterLines
//---------------------------------------------------------

QString MscxModeDiff::getOuterLines(const QString& str, int lines, bool start)
{
    lines = qAbs(lines);
    const int secIdxStart = start ? 0 : (-1 - (lines - 1));
    const int secIdxEnd = start ? (lines - 1) : -1;
    constexpr auto secFlags = QString::SectionIncludeTrailingSep | QString::SectionSkipEmpty;
    return str.section('\n', secIdxStart, secIdxEnd, secFlags);
}

//---------------------------------------------------------
//   MscxModeDiff::nextDiffOnShiftIndex
//---------------------------------------------------------

int MscxModeDiff::nextDiffOnShiftIndex(const std::vector<TextDiff>& diffs, int index, bool down)
{
    const DiffType diffType = diffs[index].type;
    Q_ASSERT(diffType == DiffType::DELETE || diffType == DiffType::INSERT);
    int nextDiffIdx = index + (down ? 1 : -1);
    while (nextDiffIdx >= 0 && nextDiffIdx < int(diffs.size())) {
        const TextDiff& d = diffs[nextDiffIdx];
        if (d.type == diffType) {
            // Two INSERT or DELETE diffs in a row, probably shouldn't happen
            return index;
        }
        if (d.type == DiffType::EQUAL) {
            return nextDiffIdx;
        }
        // REPLACE is not here, the other type can be skipped
        Q_ASSERT(d.type != DiffType::REPLACE);
        nextDiffIdx += (down ? 1 : -1);
    }
    return index;
}

//---------------------------------------------------------
//   MscxModeDiff::readMscx
//---------------------------------------------------------

void MscxModeDiff::readMscx(const QString& xml, std::vector<Tag>& extraTags)
{
    int line = 0;
    int nextLineIndex = xml.indexOf('\n');
    QRegularExpressionMatchIterator m = tagRegExp.globalMatch(xml);
    while (m.hasNext()) {
        QRegularExpressionMatch match = m.next();
        QStringRef tag(match.capturedRef("name"));
        while ((match.capturedStart("name") > nextLineIndex) && (nextLineIndex > 0)) {
            ++line;
            nextLineIndex = xml.indexOf('\n', nextLineIndex + 1);
        }
        if (match.capturedRef().startsWith("</")) {
            // end element
            handleTag(line, END_TAG, tag.toString(), extraTags);
            if (tag == "Tuplet") {
                // special case: <Tuplet> / <endTuplet/> pair
                handleTag(line, START_TAG, "__tupletBound", extraTags);
            }
        } else if (match.capturedRef().endsWith("/>")) {
            // empty element: do nothing
            if (tag == "endTuplet") {
                // special case: <Tuplet> / <endTuplet/> pair
                handleTag(line, END_TAG, "__tupletBound", extraTags);
            }
        } else {
            // start element
            handleTag(line, START_TAG, tag.toString(), extraTags);
        }
    }
}

//---------------------------------------------------------
//   MscxModeDiff::handleTag
//---------------------------------------------------------

void MscxModeDiff::handleTag(int line, TagType type, const QString& name, std::vector<Tag>& extraTags)
{
    switch (type) {
    case START_TAG:
        extraTags.emplace_back(line, type, name);
        break;
    case END_TAG:
    {
        auto lastTag = extraTags.empty() ? nullptr : &extraTags.back();
        if (lastTag
            && lastTag->type == START_TAG && lastTag->name == name) {
            extraTags.pop_back();
        } else {
            extraTags.emplace_back(line, type, name);
        }
    }
    break;
    }
}

//---------------------------------------------------------
//   TextDiffParser
//---------------------------------------------------------

TextDiffParser::TextDiffParser(int iScore)
    : iScore(iScore), iOtherScore(iScore == 1 ? 0 : 1)
{
    contextsStack.push_back(nullptr);
}

//---------------------------------------------------------
//   TextDiffParser::makeDiffs
//---------------------------------------------------------

void TextDiffParser::makeDiffs(const QString& mscx, const std::vector<std::pair<const ScoreElement*,
                                                                                QString> >& elements,
                               const std::vector<TextDiff>& textDiffs,
                               std::vector<BaseDiff*>& diffs)
{
    QXmlStreamReader r(mscx);
    r.readNext();   // read first tag
    auto textDiff = textDiffs.begin();
    auto textDiffEnd = textDiffs.end();
    auto nextElement = elements.begin();
    auto nextElementEnd = elements.end();
    while (!r.atEnd()) {
        // Scroll to the correct diff to be handled now
        while (textDiff != textDiffEnd
               && textDiff->end[iScore] < r.lineNumber()) {
            // Save ContextChange when leaving equal chunk
            if (textDiff->type == DiffType::EQUAL) {
                ContextChange* c = new ContextChange;
                c->type = textDiff->type;
                c->textDiff = &(*textDiff);
                c->ctx[iScore] = contextsStack.back();
                c->ctx[iOtherScore] = nullptr;
                c->before[iScore] = lastElementEnded;
                c->before[iOtherScore] = nullptr;
                diffs.push_back(c);
            }

            ++textDiff;
        }
        if (textDiff == textDiffEnd) {
            break;
        }

        bool saveDiff = false;
        if (!insideDiffTag()
            && (textDiff->type == DiffType::DELETE || textDiff->type == DiffType::INSERT)
            ) {
            const int iDiffScore = (textDiff->type == DiffType::DELETE) ? 0 : 1;
            if (iScore == iDiffScore) {
                saveDiff = true;
            }
        }

        const ScoreElement* newElement = nullptr;
        if (r.isStartElement()) {
            if (nextElement != nextElementEnd
                && nextElement->second == r.name()) {
                newElement = (nextElement++)->first;
            }

            ++tagLevel;
            tagIsElement.push_back(newElement);
        }

        BaseDiff* diff = handleToken(r, newElement, saveDiff);

        if (diff) {
            diff->type = textDiff->type;
            diff->textDiff = &(*textDiff);
            diff->before[iScore] = lastElementEnded;
            diff->before[iOtherScore] = nullptr;
            diffs.push_back(diff);

            if (saveDiff) {
                // It is assumed that diff items are created in handleToken
                // only for start tags
                Q_ASSERT(r.isStartElement());
                ItemType type = diff->itemType();
                if (type == ItemType::ELEMENT || type == ItemType::PROPERTY) {
                    currentDiffTagLevel = tagLevel;
                    if (type == ItemType::ELEMENT && contextsStack.back()->isSpanner()) {
                        // Consider <Spanner> tag as the current differing tag
                        --currentDiffTagLevel;
                    }
                }
            }
        }

        if (r.isEndElement()) {
            if (currentDiffTagLevel == tagLevel) {
                currentDiffTagLevel = 0;
            }
            --tagLevel;
            tagIsElement.pop_back();
        }

        r.readNext();
    }
    if (r.hasError()) {
        qWarning("TextDiffParser::makeDiffs: error while reading MSCX output: %s",
                 r.errorString().toLatin1().constData());
    }
}

//---------------------------------------------------------
//   TextDiffParser::handleToken
//    Returns nullptr or a newly allocated BaseDiff with
//    properly filled context and fields that are unique to
//    descendants of BaseDiff (e.g. el[2] for ElementDiff).
//    Type and textDiff are left unfilled.
//---------------------------------------------------------

BaseDiff* TextDiffParser::handleToken(const QXmlStreamReader& r, const ScoreElement* newElement, bool saveDiff)
{
    if (!r.isStartElement() && !r.isEndElement()) {
        return nullptr;
    }
    BaseDiff* diff = nullptr;
    const QStringRef tag(r.name());

    if (r.isStartElement()) {
        if (newElement) {
            if (saveDiff) {
                ElementDiff* d = new ElementDiff;
                diff = d;
                d->ctx[iScore] = contextsStack.back();
                d->el[iScore] = newElement;
                d->el[iOtherScore] = nullptr;
            }
            contextsStack.push_back(newElement);
        } else if (tag == "Spanner") {
            markupContext = tag.toString();
        } else if (saveDiff) {
            const ScoreElement* ctx = contextsStack.back();
            if (markupContext == "Spanner" && !(ctx && ctx->isSpanner())) {
                // some property inside the end of a spanner
            } else if (tag == "prev" || tag == "next") {
                // Ignore these tags
            } else if (tag == "location" || tag == "voice") {
                if (ctx && ctx->isMeasure()) {
                    MarkupDiff* d = new MarkupDiff;
                    diff = d;
                    d->ctx[iScore] = ctx;
                    d->name = tag.toString();
                    const ScoreElement* widerCtx = *(contextsStack.end() - 2);
                    if (widerCtx && widerCtx->isStaff()) {
                        d->info = toStaff(widerCtx)->idx();
                    }
                }
            } else {
                Pid propId = ctx ? ctx->propertyId(tag) : Pid::END;
                if (propId != Pid::END) {
                    PropertyDiff* d = new PropertyDiff;
                    diff = d;
                    d->ctx[iScore] = contextsStack.back();
                    d->pid = propId;
                } else {
                    MarkupDiff* d = new MarkupDiff;
                    diff = d;
                    d->ctx[iScore] = contextsStack.back();
                    d->name = tag.toString();
                    if (tag == "metaTag") {
                        d->info = r.attributes().value("name").toString();
                    }
                }
            }
        }
    } else { // end element
        if ((tagIsElement.back() && !contextsStack.back()->isSpanner())
            || (tag == "Spanner" && contextsStack.back()->isSpanner())
            ) {
            lastElementEnded = contextsStack.back();
            contextsStack.pop_back();
        }
        if (!markupContext.isEmpty() && tag == markupContext) {
            markupContext.clear();
        }
    }

    if (diff) {
        diff->ctx[iOtherScore] = nullptr;
    }
    return diff;
}

//---------------------------------------------------------
//   lineNumberSort
//---------------------------------------------------------

static bool lineNumberSort(BaseDiff* d1, BaseDiff* d2)
{
    const TextDiff* t1 = d1->textDiff;
    const TextDiff* t2 = d2->textDiff;
    return (t1->end[0] < t2->end[0]) || (t1->end[1] < t2->end[1]);
}

//---------------------------------------------------------
//   positionSort
//---------------------------------------------------------

static bool positionSort(BaseDiff* d1, BaseDiff* d2)
{
    return d1->afrac(0) < d2->afrac(0) || d1->afrac(1) < d2->afrac(1);
}

//---------------------------------------------------------
//   scoreToMscx
//---------------------------------------------------------

static QString scoreToMscx(Score* s, XmlWriter& xml)
{
    QString mscx;
    xml.setString(&mscx, QIODevice::WriteOnly);
    xml.setRecordElements(true);
    s->write(xml, /* onlySelection */ false);
    xml.flush();
    return mscx;
}

//---------------------------------------------------------
//   ScoreDiff
//    s1, s2 are scores to compare.
//    ScoreDiff does NOT take ownership of the scores.
//---------------------------------------------------------

ScoreDiff::ScoreDiff(Score* s1, Score* s2, bool textDiffOnly)
    : _s1(s1), _s2(s2), _textDiffOnly(textDiffOnly)
{
    update();
}

//---------------------------------------------------------
//   makeDiffs
//---------------------------------------------------------

static void makeDiffs(const QString& mscx1, const QString& mscx2, const XmlWriter& xml1, const XmlWriter& xml2,
                      const std::vector<TextDiff>& textDiffs, std::vector<BaseDiff*>& diffs)
{
    TextDiffParser p1(0);
    p1.makeDiffs(mscx1, xml1.elements(), textDiffs, diffs);
    TextDiffParser p2(1);
    p2.makeDiffs(mscx2, xml2.elements(), textDiffs, diffs);

    std::stable_sort(diffs.begin(), diffs.end(), lineNumberSort);

    // Fill correct contexts for diffs
    const ScoreElement* lastCtx[2] {};
    const ScoreElement* lastBefore[2] {};
    for (BaseDiff* diff : diffs) {
        for (int i = 0; i < 2; ++i) {
            if (diff->ctx[i]) {
                lastCtx[i] = diff->ctx[i];
            } else {
                diff->ctx[i] = lastCtx[i];
            }

            if (diff->before[i]) {
                lastBefore[i] = diff->before[i];
            } else {
                diff->before[i] = lastBefore[i];
            }
        }
    }

    // Filter out EQUAL diffs and dummy ContextChange items
    std::vector<BaseDiff*> filteredDiffs;
    for (BaseDiff* diff : diffs) {
        if ((diff->itemType() == ItemType::CONTEXTCHANGE)
            || (diff->type == DiffType::EQUAL)) {
            delete diff;
        } else {
            filteredDiffs.push_back(diff);
        }
    }
    std::swap(diffs, filteredDiffs);
}

//---------------------------------------------------------
//   ScoreDiff::update
//    Updates the diff according to the current state of
//    the compared scores.
//---------------------------------------------------------

void ScoreDiff::update()
{
    if (updated()) {
        return;
    }

    qDeleteAll(_diffs);
    _diffs.clear();
    _textDiffs.clear();
    qDeleteAll(_mergedTextDiffs);
    _mergedTextDiffs.clear();

    XmlWriter xml1(_s1);
    XmlWriter xml2(_s2);
    QString mscx1(scoreToMscx(_s1, xml1));
    QString mscx2(scoreToMscx(_s2, xml2));

    _textDiffs = MscxModeDiff().mscxModeDiff(mscx1, mscx2);

    if (!_textDiffOnly) {
        makeDiffs(mscx1, mscx2, xml1, xml2, _textDiffs, _diffs);

        processMarkupDiffs();
        mergeInsertDeleteDiffs();
        mergeElementDiffs();
        editPropertyDiffs();

        std::stable_sort(_diffs.begin(), _diffs.end(), positionSort);
    }

    _scoreState1 = _s1->state();
    _scoreState2 = _s2->state();
}

//---------------------------------------------------------
//   ~ScoreDiff
//---------------------------------------------------------

ScoreDiff::~ScoreDiff()
{
    qDeleteAll(_mergedTextDiffs);
    qDeleteAll(_diffs);
}

//---------------------------------------------------------
//   deleteDiffs
//---------------------------------------------------------

static void deleteDiffs(std::vector<BaseDiff*>& diffsList, const std::vector<BaseDiff*>& toDelete)
{
    for (BaseDiff* diff : toDelete) {
        for (auto it = diffsList.begin(); it != diffsList.end(); ++it) {
            if (*it == diff) {
                diffsList.erase(it);
                break;
            }
        }
        delete diff;
    }
}

//---------------------------------------------------------
//   measureToMscx
//---------------------------------------------------------

static QString measureToMscx(const Measure* m, XmlWriter& xml, int staff)
{
    QString mscx;
    xml.setString(&mscx, QIODevice::WriteOnly);
    xml.setRecordElements(true);
    m->write(xml, staff, false, false);
    xml.flush();
    return mscx;
}

//---------------------------------------------------------
//   measureInfo
//---------------------------------------------------------

struct MeasureInfo {
    const Measure* m1;
    const Measure* m2;
    int staff;

    MeasureInfo(const Measure* m1, const Measure* m2, int staff)
        : m1(m1), m2(m2), staff(staff) {}

    bool operator==(const MeasureInfo& other) { return m1 == other.m1 && m2 == other.m2 && staff == other.staff; }
    bool operator!=(const MeasureInfo& other) { return !(*this == other); }
};

//---------------------------------------------------------
//   ScoreDiff::processMarkupDiffs
//    Find MarkupDiffs and convert them to the appropriate
//    diffs of other types if needed.
//---------------------------------------------------------

void ScoreDiff::processMarkupDiffs()
{
    std::vector<BaseDiff*> abandonedDiffs;
    std::vector<MeasureInfo> measuresToProcess;
    Pid pids[] { Pid::TRACK, Pid::POSITION };   // list of pids to be accepted on measures processing
    for (BaseDiff* diff : _diffs) {
        if (diff->itemType() != ItemType::MARKUP) {
            continue;
        }

        MarkupDiff* d = static_cast<MarkupDiff*>(diff);
        const QString& name = d->name;

        if (name == "voice" || name == "location") {
            if (d->ctx[0]->isMeasure() && d->ctx[1]->isMeasure()) {
                MeasureInfo m(toMeasure(d->ctx[0]), toMeasure(d->ctx[1]), d->info.toInt());
                bool add = true;
                for (auto& mScheduled : measuresToProcess) {
                    if (mScheduled == m) {
                        add = false;
                        break;
                    }
                }
                if (add) {
                    measuresToProcess.push_back(m);
                }
                abandonedDiffs.push_back(d);
            }
        }
    }

    std::vector<BaseDiff*> newDiffs;
    for (auto& m : measuresToProcess) {
        XmlWriter xml1(m.m1->score());
        xml1.setWriteTrack(true);
        xml1.setWritePosition(true);
        QString mscx1 = measureToMscx(m.m1, xml1, m.staff);

        XmlWriter xml2(m.m2->score());
        xml2.setWriteTrack(true);
        xml2.setWritePosition(true);
        QString mscx2 = measureToMscx(m.m2, xml2, m.staff);

        std::vector<TextDiff> textDiffs = MscxModeDiff().mscxModeDiff(mscx1, mscx2);
        makeDiffs(mscx1, mscx2, xml1, xml2, textDiffs, newDiffs);
    }

    for (BaseDiff* newDiff : newDiffs) {
        bool save = false;
        if (newDiff->itemType() == ItemType::PROPERTY) {
            PropertyDiff* pDiff = static_cast<PropertyDiff*>(newDiff);
            for (Pid pid : pids) {
                if (pDiff->pid == pid) {
                    save = true;
                    break;
                }
            }
            if (pDiff->pid == Pid::TRACK) {
                pDiff->pid = Pid::VOICE;
            }

            if (pDiff->ctx[0]->isMeasure() || pDiff->ctx[1]->isMeasure()) {
                save = false;
            }
        }

        if (save) {
            newDiff->textDiff = nullptr;
            _diffs.push_back(newDiff);
        } else {
            delete newDiff;
        }
    }

    deleteDiffs(_diffs, abandonedDiffs);
}

//---------------------------------------------------------
//   ScoreDiff::mergeInsertDeleteDiffs
//    Merge INSERT and DELETE diffs to REPLACE diffs where
//    possible.
//---------------------------------------------------------

void ScoreDiff::mergeInsertDeleteDiffs()
{
    const ScoreElement* lastCtx1 = _s1;
    const ScoreElement* lastCtx2 = _s2;
    std::vector<BaseDiff*> diffsToMerge;
    std::vector<BaseDiff*> abandonedDiffs;
    for (BaseDiff* diff : _diffs) {
        if ((diff->ctx[0] != lastCtx1) || (diff->ctx[1] != lastCtx2)) {
            diffsToMerge.clear();
            lastCtx1 = diff->ctx[0];
            lastCtx2 = diff->ctx[1];
        }
        bool merge = false;
        for (auto diff2It = diffsToMerge.begin(); diff2It != diffsToMerge.end(); ++diff2It) {
            BaseDiff* diff2 = (*diff2It);
            if (diff->type == DiffType::DELETE) {
                if ((diff2->type == DiffType::INSERT) && diff->sameItem(*diff2)) {
                    merge = true;
                }
            } else if (diff->type == DiffType::INSERT) {
                if ((diff2->type == DiffType::DELETE) && diff->sameItem(*diff2)) {
                    merge = true;
                }
            }

            if (merge) {
                // To preserve the correct order of diffs, we should
                // leave diff2 in place since it appeared earlier in
                // the _diffs list.
                diff2->type = DiffType::REPLACE;

                if (diff->textDiff && diff2->textDiff) {
                    TextDiff* mergedTextDiff = new TextDiff(*diff2->textDiff);
                    mergedTextDiff->merge(*diff->textDiff);
                    _mergedTextDiffs.push_back(mergedTextDiff);
                    diff2->textDiff = mergedTextDiff;
                } else if (!diff2->textDiff) {
                    diff2->textDiff = diff->textDiff;
                }

                int idx1 = (diff->type == DiffType::DELETE) ? 0 : 1;
                switch (diff2->itemType()) {
                case ItemType::ELEMENT:
                {
                    ElementDiff* d = static_cast<ElementDiff*>(diff);
                    ElementDiff* d2 = static_cast<ElementDiff*>(diff2);
                    // d2->el[idx2] is already filled
                    d2->el[idx1] = d->el[idx1];
                }
                break;
                case ItemType::PROPERTY:
                case ItemType::MARKUP:
                    // nothing to fill
                    break;
                case ItemType::CONTEXTCHANGE:
                    break;
                }

                abandonedDiffs.push_back(diff);
                diffsToMerge.erase(diff2It);
                break;         // loop on diffsToMerge
            }
        }

        if (!merge) {
            diffsToMerge.push_back(diff);
        }
    }

    deleteDiffs(_diffs, abandonedDiffs);
}

//---------------------------------------------------------
//   ScoreDiff::mergeElementDiffs
//    Merge element diffs with equal elements
//---------------------------------------------------------

void ScoreDiff::mergeElementDiffs()
{
    std::map<const ScoreElement*, ElementDiff*> elementDiffs;
    std::vector<BaseDiff*> abandonedDiffs;
    for (BaseDiff* diff : _diffs) {
        if (diff->itemType() != ItemType::ELEMENT) {
            continue;
        }

        ElementDiff* elDiff = static_cast<ElementDiff*>(diff);
        auto foundDiffIt1 = elementDiffs.find(elDiff->el[0]);
        auto foundDiffIt2 = elementDiffs.find(elDiff->el[1]);
        ElementDiff* foundDiff = nullptr;
        if (foundDiffIt1 != elementDiffs.end()) {
            foundDiff = foundDiffIt1->second;
        } else if (foundDiffIt2 != elementDiffs.end()) {
            foundDiff = foundDiffIt2->second;
        }

        if (foundDiff && foundDiff->type == elDiff->type
            && foundDiff->el[0] == elDiff->el[0]
            && foundDiff->el[1] == elDiff->el[1]) {
            for (int i = 0; i < 2; ++i) {
                const ScoreElement* se = foundDiff->el[i];
                if (!se) {
                    continue;
                }
                if (!se->isMeasure() && se->isElement()) {
                    const Element* m = toElement(se)->findMeasure();
                    if (m) {
                        foundDiff->ctx[i] = m;
                    } else {
                        foundDiff->ctx[i] = se->score();
                    }
                } else {
                    foundDiff->ctx[i] = se->score();
                }
            }
            abandonedDiffs.push_back(elDiff);
        } else {
            for (int i = 0; i < 2; ++i) {
                if (const ScoreElement* se = elDiff->el[i]) {
                    elementDiffs[se] = elDiff;
                }
            }
        }
    }

    deleteDiffs(_diffs, abandonedDiffs);
}

//---------------------------------------------------------
//   ScoreDiff::editPropertyDiffs
//    Merge property diffs with equal elements, edit some
//    diffs if necessary
//---------------------------------------------------------

void ScoreDiff::editPropertyDiffs()
{
    std::multimap<const ScoreElement*, PropertyDiff*> propertyDiffs;
    std::vector<BaseDiff*> abandonedDiffs;
    for (BaseDiff* diff : _diffs) {
        if (diff->itemType() != ItemType::PROPERTY) {
            continue;
        }

        PropertyDiff* pDiff = static_cast<PropertyDiff*>(diff);

        if (pDiff->pid == Pid::TPC1 || pDiff->pid == Pid::TPC2) {
            // Special case: "tpc" and "pitch" properties are partially
            // overlapped so we will mark tpc changes as pitch changes
            pDiff->pid = Pid::PITCH;
        }

        auto foundRange = propertyDiffs.equal_range(pDiff->ctx[0]);
        bool merged = false;
        for (auto it = foundRange.first; it != foundRange.second; ++it) {
            PropertyDiff* foundDiff = it->second;
            if (foundDiff && foundDiff->type == pDiff->type
                && foundDiff->ctx[0] == pDiff->ctx[0]
                && foundDiff->ctx[1] == pDiff->ctx[1]
                && foundDiff->pid == pDiff->pid
                ) {
                abandonedDiffs.push_back(pDiff);
                merged = true;
                break;
            }
        }

        if (!merged) {
            propertyDiffs.emplace(pDiff->ctx[0], pDiff);
        }
    }

    deleteDiffs(_diffs, abandonedDiffs);
}

//---------------------------------------------------------
//   ScoreDiff::equal
//---------------------------------------------------------

bool ScoreDiff::equal() const
{
    for (const TextDiff& td : _textDiffs) {
        if (td.type != DiffType::EQUAL) {
            return false;
        }
    }
    return true;
}

//---------------------------------------------------------
//   ScoreDiff::rawDiff
//---------------------------------------------------------

QString ScoreDiff::rawDiff(bool skipEqual) const
{
    QStringList list;
    for (const TextDiff& td : _textDiffs) {
        if (!skipEqual || td.type != DiffType::EQUAL) {
            list.push_back(td.toString(true));
        }
    }
    return list.join('\n');
}

//---------------------------------------------------------
//   ScoreDiff::userDiff
//---------------------------------------------------------

QString ScoreDiff::userDiff() const
{
    QStringList list;
    for (const BaseDiff* d : _diffs) {
        list.push_back(d->toString());
    }
    return list.join('\n');
}

//---------------------------------------------------------
//   TextDiff::merge
//---------------------------------------------------------

bool TextDiff::merge(const TextDiff& other)
{
    if (type == other.type) {
        if (other.end[0] == (start[0] - 1) && other.end[1] == (start[1] - 1)) {
            start[0] = other.start[0];
            start[1] = other.start[1];
            text[0].prepend(other.text[0]);
            text[1].prepend(other.text[1]);
        } else if ((end[0] + 1) == other.start[0] && (end[1] + 1) == other.start[1]) {
            end[0] = other.end[0];
            end[1] = other.end[1];
            text[0].append(other.text[0]);
            text[1].append(other.text[1]);
        } else {
            qWarning("TextDiff:merge: invalid argument: wrong line numbers");
            return false;
        }
    } else if ((type == DiffType::INSERT && other.type == DiffType::DELETE)
               || (type == DiffType::DELETE && other.type == DiffType::INSERT)
               ) {
        type = DiffType::REPLACE;
        const int iOther = (other.type == DiffType::DELETE) ? 0 : 1;
        start[iOther] = other.start[iOther];
        end[iOther] = other.end[iOther];
        text[iOther] = other.text[iOther];
    } else {
        qWarning("TextDiff:merge: invalid argument: wrong types");
        return false;
    }

    return true;
}

//---------------------------------------------------------
//   addLinePrefix
//---------------------------------------------------------

static QString addLinePrefix(const QString& str, const QString& prefix)
{
    if (prefix.isEmpty()) {
        return str;
    }
    QVector<QStringRef> lines = str.splitRef('\n');
    if (lines.back().isEmpty()) {
        lines.pop_back();
    }
    QStringList processedLines;
    for (QStringRef& line : lines) {
        processedLines.push_back(QString(prefix).append(line));
    }
    return processedLines.join('\n');
}

//---------------------------------------------------------
//   TextDiff::toString
//    type argument allows to define which part of diff
//    should be printed. For example, it allows to print
//    only deleted chunk for REPLACE diff item.
//---------------------------------------------------------

QString TextDiff::toString(DiffType dt, bool prefixLines) const
{
    if (dt == DiffType::REPLACE) {
        QStringList l;
        l.push_back(toString(DiffType::DELETE, prefixLines));
        l.push_back(toString(DiffType::INSERT, prefixLines));
        return l.join('\n');
    }

    int idx = (dt == DiffType::INSERT) ? 1 : 0;
    const char* prefix = (dt == DiffType::INSERT) ? ">" : "<";

    QString lines[2];
    for (int i = 0; i < 2; ++i) {
        if ((i != idx && dt != DiffType::EQUAL)
            || end[i] <= start[i]
            ) {
            lines[i] = QString::number(start[i]);
        } else {
            lines[i] = QString("%1--%2")
                       .arg(start[i]).arg(end[i]);
        }
    }

    return QString("@%1;%2\n%3")
           .arg(lines[0]).arg(lines[1])
           .arg(prefixLines ? addLinePrefix(text[idx], prefix) : text[idx]);
}

//---------------------------------------------------------
//   BaseDiff::sameItem
//---------------------------------------------------------

bool BaseDiff::sameItem(const BaseDiff& other) const
{
    if (itemType() != other.itemType()
        || ctx[0] != other.ctx[0] || ctx[1] != other.ctx[1]) {
        return false;
    }
    if (textDiff == other.textDiff) {
        return true;
    } else if (!textDiff || !other.textDiff) {
        return false;
    }
    return textDiff->start[0] == other.textDiff->start[0]
           && textDiff->start[1] == other.textDiff->start[1]
    ;
}

//---------------------------------------------------------
//   BaseDiff::afrac
//    Returns position of the changed chunk
//---------------------------------------------------------

Fraction BaseDiff::afrac(int score) const
{
    Q_ASSERT(score == 0 || score == 1);
    if (ctx[score] && ctx[score]->isElement()) {
        return toElement(ctx[score])->tick();
    }
    if (before[score] && before[score]->isElement()) {
        const Element* bef = toElement(before[score]);
        Fraction f = bef->tick();
        if (bef->isDurationElement()) {
            const DurationElement* de = toDurationElement(bef);
            return f + de->actualTicks();
        }
        return f;
    }
    return Fraction(0,1);
}

//---------------------------------------------------------
//   describeContext
//---------------------------------------------------------

static QString describeContext(const ScoreElement* ctx)
{
    if (!ctx) {
        return QString("no context");
    }
    QString descr;
    if (ctx->isElement()) {
        const Element* e = toElement(ctx);
        if (const Measure* m = toMeasure(e->findMeasure())) {
            descr += QString("%1 %2").arg(m->userName()).arg(m->no() + 1);
        }
    }
    if (!ctx->isMeasure()) {
        if (!descr.isEmpty()) {
            descr += ": ";
        }
        descr += ctx->userName();
        // TODO: add more info
    }
    return descr;
}

//---------------------------------------------------------
//   ContextChange::toString
//    ContextChange elements are not intended to be shown
//    to user, this function is for debugging purposes.
//---------------------------------------------------------

QString ContextChange::toString() const
{
    return QString("Context change: ctx1 (%1), ctx2(%2)").arg(describeContext(ctx[0])).arg(describeContext(ctx[1]));
}

//---------------------------------------------------------
//   ElementDiff::sameItem
//---------------------------------------------------------

bool ElementDiff::sameItem(const BaseDiff& other) const
{
    return BaseDiff::sameItem(other);
}

//---------------------------------------------------------
//   ElementDiff::afrac
//    Returns position of the changed chunk
//---------------------------------------------------------

Fraction ElementDiff::afrac(int score) const
{
    Q_ASSERT(score == 0 || score == 1);
    const ScoreElement* se = el[score];
    if (se && se->isElement()) {
        return toElement(se)->tick();
    }
    return BaseDiff::afrac(score);
}

//---------------------------------------------------------
//   ElementDiff::toString
//---------------------------------------------------------

QString ElementDiff::toString() const
{
    QString ctxDescr = describeContext(ctx[0]);
    switch (type) {
    case DiffType::DELETE:
        return QObject::tr("%1: removed element %2", "scorediff").arg(ctxDescr).arg(el[0]->userName());
    case DiffType::INSERT:
        return QObject::tr("%1: inserted element %2", "scorediff").arg(ctxDescr).arg(el[1]->userName());
    case DiffType::REPLACE:
        return QObject::tr("%1: replaced element %2 with element %3",
                           "scorediff").arg(ctxDescr).arg(el[0]->userName()).arg(el[1]->userName());
    case DiffType::EQUAL:
        Q_ASSERT(el[0]->type() == el[1]->type());
        return QObject::tr("%1: equal element %2", "scorediff").arg(ctxDescr).arg(el[0]->userName());
    }
    return ctxDescr;
}

//---------------------------------------------------------
//   PropertyDiff::sameItem
//---------------------------------------------------------

bool PropertyDiff::sameItem(const BaseDiff& otherBase) const
{
    if (!BaseDiff::sameItem(otherBase)) {
        return false;
    }
    if (itemType() != otherBase.itemType()) {
        return false;
    }
    const PropertyDiff& other = static_cast<const PropertyDiff&>(otherBase);
    return pid == other.pid;
}

//---------------------------------------------------------
//   PropertyDiff::toString
//---------------------------------------------------------

QString PropertyDiff::toString() const
{
    QString ctxDescr = describeContext(ctx[0]);
    QString propName = propertyUserName(pid);
    switch (propertyType(pid)) {
    case P_TYPE::BOOL:
    {
        bool b1 = ctx[0]->getProperty(pid).toBool();
        Q_ASSERT(b1 != ctx[1]->getProperty(pid).toBool());
        QString t;
        if (b1) {
            t = QObject::tr("%1: property %2 is turned off", "scorediff");
        } else {
            t = QObject::tr("%1: property %2 is turned on", "scorediff");
        }
        return t.arg(ctxDescr).arg(propName);
    }
    default:
    {
        QString val1 = ctx[0]->propertyUserValue(pid);
        QString val2 = ctx[1]->propertyUserValue(pid);
        QString t = QObject::tr("%1: property %2 changed from %3 to %4", "scorediff");
        return t.arg(ctxDescr).arg(propName).arg(val1).arg(val2);
    }
    }
}

//---------------------------------------------------------
//   MarkupDiff::sameItem
//---------------------------------------------------------

bool MarkupDiff::sameItem(const BaseDiff& otherBase) const
{
    if (!BaseDiff::sameItem(otherBase)) {
        return false;
    }
    if (itemType() != otherBase.itemType()) {
        return false;
    }
    const MarkupDiff& other = static_cast<const MarkupDiff&>(otherBase);
    return name == other.name;
}

//---------------------------------------------------------
//   MarkupDiff::toString
//---------------------------------------------------------

QString MarkupDiff::toString() const
{
    QString ctxDescr = describeContext(ctx[0]);
    if (name == "metaTag") {
        QString tagName = info.toString();
        return QObject::tr("%1: %2 changed from %3 to %4", "scorediff")
               .arg(ctxDescr).arg(tagName)
               .arg(ctx[0]->score()->metaTag(tagName))
               .arg(ctx[1]->score()->metaTag(tagName));
    }
    return QObject::tr("%1: markup changes: %2", "scorediff")
           .arg(ctxDescr).arg(name);
}
}