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#include "clangformatbaseindenter.h"

#include <clang/Tooling/Core/Replacement.h>

#include <utils/algorithm.h>
#include <utils/fileutils.h>
#include <utils/textutils.h>
#include <utils/qtcassert.h>

#include <QTextDocument>

namespace ClangFormat {

static void adjustFormatStyleForLineBreak(clang::format::FormatStyle &style,
                                          ReplacementsToKeep replacementsToKeep)
{
    if (replacementsToKeep == ReplacementsToKeep::All)
        return;

    style.MaxEmptyLinesToKeep = 2;
    style.SortIncludes = false;
    style.SortUsingDeclarations = false;

    // This is a separate pass, don't do it unless it's the full formatting.
    style.FixNamespaceComments = false;

    if (replacementsToKeep == ReplacementsToKeep::IndentAndBefore)
        return;

    style.DisableFormat = false;
    style.ColumnLimit = 0;
#ifdef KEEP_LINE_BREAKS_FOR_NON_EMPTY_LINES_BACKPORTED
    style.KeepLineBreaksForNonEmptyLines = true;
#endif
}

static llvm::StringRef clearExtraNewline(llvm::StringRef text)
{
    while (text.startswith("\n\n"))
        text = text.drop_front();
    return text;
}

static clang::tooling::Replacements filteredReplacements(
    const clang::tooling::Replacements &replacements,
    int offset,
    int utf8LineLengthBeforeCursor,
    int extraEmptySpaceOffset,
    ReplacementsToKeep replacementsToKeep)
{
    clang::tooling::Replacements filtered;
    for (const clang::tooling::Replacement &replacement : replacements) {
        int replacementOffset = static_cast<int>(replacement.getOffset());
        const bool replacementDoesNotMatchRestriction
            = (replacementsToKeep == ReplacementsToKeep::OnlyIndent
               && replacementOffset != offset - 1)
              || (replacementsToKeep == ReplacementsToKeep::IndentAndBefore
                  && replacementOffset > offset + utf8LineLengthBeforeCursor - 1);
        if (replacementDoesNotMatchRestriction)
            continue;

        if (replacementOffset >= offset - 1)
            replacementOffset += extraEmptySpaceOffset;

        llvm::StringRef text = replacementsToKeep == ReplacementsToKeep::OnlyIndent
                                   ? clearExtraNewline(replacement.getReplacementText())
                                   : replacement.getReplacementText();

        llvm::Error error = filtered.add(
            clang::tooling::Replacement(replacement.getFilePath(),
                                        static_cast<unsigned int>(replacementOffset),
                                        replacement.getLength(),
                                        text));
        // Throws if error is not checked.
        if (error) {
            error = llvm::handleErrors(std::move(error),
                                       [](const llvm::ErrorInfoBase &) -> llvm::Error {
                                           return llvm::Error::success();
                                       });
            QTC_CHECK(!error && "Error must be a \"success\" at this point");
            break;
        }
    }
    return filtered;
}

static void trimFirstNonEmptyBlock(const QTextBlock &currentBlock)
{
    QTextBlock prevBlock = currentBlock.previous();
    while (prevBlock.position() > 0 && prevBlock.text().trimmed().isEmpty())
        prevBlock = prevBlock.previous();

    if (prevBlock.text().trimmed().isEmpty())
        return;

    const QString initialText = prevBlock.text();
    if (!initialText.at(initialText.size() - 1).isSpace())
        return;

    auto lastNonSpace = std::find_if_not(initialText.rbegin(),
                                         initialText.rend(),
                                         [](const QChar &letter) { return letter.isSpace(); });
    const int extraSpaceCount = static_cast<int>(std::distance(initialText.rbegin(), lastNonSpace));

    QTextCursor cursor(prevBlock);
    cursor.beginEditBlock();
    cursor.movePosition(QTextCursor::Right,
                        QTextCursor::MoveAnchor,
                        initialText.size() - extraSpaceCount);
    cursor.movePosition(QTextCursor::Right, QTextCursor::KeepAnchor, extraSpaceCount);
    cursor.removeSelectedText();
    cursor.endEditBlock();
}

// Returns the total langth of previous lines with pure whitespace.
static int previousEmptyLinesLength(const QTextBlock &currentBlock)
{
    int length{0};
    QTextBlock prevBlock = currentBlock.previous();
    while (prevBlock.position() > 0 && prevBlock.text().trimmed().isEmpty()) {
        length += prevBlock.text().length() + 1;
        prevBlock = prevBlock.previous();
    }

    return length;
}

static void modifyToIndentEmptyLines(
    QByteArray &buffer, int offset, int &length, const QTextBlock &block, bool secondTry)
{
    const QString blockText = block.text();
    int firstNonWhitespace = Utils::indexOf(blockText,
                                            [](const QChar &ch) { return !ch.isSpace(); });
    if (firstNonWhitespace > 0)
        offset += firstNonWhitespace;

    const bool closingParenBlock = firstNonWhitespace >= 0
                                   && blockText.at(firstNonWhitespace) == ')';

    if (firstNonWhitespace < 0 || closingParenBlock) {
        //This extra text works for the most cases.
        QByteArray dummyText("a;a;");

        // Search for previous character
        QTextBlock prevBlock = block.previous();
        bool prevBlockIsEmpty = prevBlock.position() > 0 && prevBlock.text().trimmed().isEmpty();
        while (prevBlockIsEmpty) {
            prevBlock = prevBlock.previous();
            prevBlockIsEmpty = prevBlock.position() > 0 && prevBlock.text().trimmed().isEmpty();
        }
        if (closingParenBlock || prevBlock.text().endsWith(','))
            dummyText = "&& a";

        length += dummyText.length();
        buffer.insert(offset, dummyText);
    }

    if (secondTry) {
        int nextLinePos = buffer.indexOf('\n', offset);
        if (nextLinePos < 0)
            nextLinePos = buffer.size() - 1;

        if (nextLinePos > 0) {
            // If first try was not successful try to put ')' in the end of the line to close possibly
            // unclosed parentheses.
            // TODO: Does it help to add different endings depending on the context?
            buffer.insert(nextLinePos, ')');
            length += 1;
        }
    }
}

static Utils::LineColumn utf16LineColumn(const QTextBlock &block,
                                         int blockOffsetUtf8,
                                         const QByteArray &utf8Buffer,
                                         int utf8Offset)
{
    // If lastIndexOf('\n') returns -1 then we are fine to add 1 and get 0 offset.
    const int lineStartUtf8Offset = utf8Offset == 0
                                        ? 0
                                        : utf8Buffer.lastIndexOf('\n', utf8Offset - 1) + 1;
    int line = block.blockNumber() + 1; // Init with the line corresponding the block.

    if (utf8Offset < blockOffsetUtf8) {
        line -= static_cast<int>(std::count(utf8Buffer.begin() + lineStartUtf8Offset,
                                            utf8Buffer.begin() + blockOffsetUtf8,
                                            '\n'));
    } else {
        line += static_cast<int>(std::count(utf8Buffer.begin() + blockOffsetUtf8,
                                            utf8Buffer.begin() + lineStartUtf8Offset,
                                            '\n'));
    }

    const QByteArray lineText = utf8Buffer.mid(lineStartUtf8Offset,
                                               utf8Offset - lineStartUtf8Offset);
    return Utils::LineColumn(line, QString::fromUtf8(lineText).size() + 1);
}

static TextEditor::Replacements utf16Replacements(const QTextBlock &block,
                                                  int blockOffsetUtf8,
                                                  const QByteArray &utf8Buffer,
                                                  const clang::tooling::Replacements &replacements)
{
    TextEditor::Replacements convertedReplacements;
    convertedReplacements.reserve(replacements.size());
    for (const clang::tooling::Replacement &replacement : replacements) {
        const Utils::LineColumn lineColUtf16 = utf16LineColumn(block,
                                                               blockOffsetUtf8,
                                                               utf8Buffer,
                                                               static_cast<int>(
                                                                   replacement.getOffset()));
        if (!lineColUtf16.isValid())
            continue;
        const int utf16Offset = Utils::Text::positionInText(block.document(),
                                                            lineColUtf16.line,
                                                            lineColUtf16.column);
        const int utf16Length = QString::fromUtf8(
                                    utf8Buffer.mid(static_cast<int>(replacement.getOffset()),
                                                   static_cast<int>(replacement.getLength())))
                                    .size();
        convertedReplacements.emplace_back(utf16Offset,
                                           utf16Length,
                                           QString::fromStdString(replacement.getReplacementText()));
    }

    return convertedReplacements;
}

static void applyReplacements(const QTextBlock &block, const TextEditor::Replacements &replacements)
{
    if (replacements.empty())
        return;

    int fullOffsetShift = 0;
    QTextCursor editCursor(block);
    for (const TextEditor::Replacement &replacement : replacements) {
        editCursor.beginEditBlock();
        editCursor.setPosition(replacement.offset + fullOffsetShift);
        editCursor.movePosition(QTextCursor::NextCharacter,
                                QTextCursor::KeepAnchor,
                                replacement.length);
        editCursor.removeSelectedText();
        editCursor.insertText(replacement.text);
        editCursor.endEditBlock();
        fullOffsetShift += replacement.text.length() - replacement.length;
    }
}

static QString selectedLines(QTextDocument *doc,
                             const QTextBlock &startBlock,
                             const QTextBlock &endBlock)
{
    QString text = Utils::Text::textAt(QTextCursor(doc),
                                       startBlock.position(),
                                       std::max(0,
                                                endBlock.position() + endBlock.length()
                                                    - startBlock.position() - 1));
    while (!text.isEmpty() && text.rbegin()->isSpace())
        text.chop(1);
    return text;
}

ClangFormatBaseIndenter::ClangFormatBaseIndenter(QTextDocument *doc)
    : TextEditor::Indenter(doc)
{}

TextEditor::IndentationForBlock ClangFormatBaseIndenter::indentationForBlocks(
    const QVector<QTextBlock> &blocks,
    const TextEditor::TabSettings & /*tabSettings*/,
    int cursorPositionInEditor)
{
    TextEditor::IndentationForBlock ret;
    for (QTextBlock block : blocks)
        ret.insert(block.blockNumber(), indentFor(block, cursorPositionInEditor));
    return ret;
}

void ClangFormatBaseIndenter::indent(const QTextCursor &cursor,
                                     const QChar &typedChar,
                                     int cursorPositionInEditor)
{
    if (cursor.hasSelection()) {
        // Calling currentBlock.next() might be unsafe because we change the document.
        // Let's operate with block numbers instead.
        const int startNumber = m_doc->findBlock(cursor.selectionStart()).blockNumber();
        const int endNumber = m_doc->findBlock(cursor.selectionEnd()).blockNumber();
        for (int currentBlockNumber = startNumber; currentBlockNumber <= endNumber;
             ++currentBlockNumber) {
            const QTextBlock currentBlock = m_doc->findBlockByNumber(currentBlockNumber);
            if (currentBlock.isValid()) {
                const int blocksAmount = m_doc->blockCount();
                indentBlock(currentBlock, typedChar, cursorPositionInEditor);

                // Only blocks before current might be added/removed, so it's safe to modify the index.
                if (blocksAmount != m_doc->blockCount())
                    currentBlockNumber += (m_doc->blockCount() - blocksAmount);
            }
        }
    } else {
        indentBlock(cursor.block(), typedChar, cursorPositionInEditor);
    }
}

void ClangFormatBaseIndenter::indent(const QTextCursor &cursor,
                                     const QChar &typedChar,
                                     const TextEditor::TabSettings & /*tabSettings*/,
                                     int cursorPositionInEditor)
{
    indent(cursor, typedChar, cursorPositionInEditor);
}

void ClangFormatBaseIndenter::reindent(const QTextCursor &cursor,
                                       const TextEditor::TabSettings & /*tabSettings*/,
                                       int cursorPositionInEditor)
{
    indent(cursor, QChar::Null, cursorPositionInEditor);
}

TextEditor::Replacements ClangFormatBaseIndenter::format(const QTextCursor &cursor,
                                                         int cursorPositionInEditor)
{
    int utf8Offset;
    int utf8Length;
    QTextBlock block;

    const QByteArray buffer = m_doc->toPlainText().toUtf8();
    if (cursor.hasSelection()) {
        block = m_doc->findBlock(cursor.selectionStart());
        const QTextBlock end = m_doc->findBlock(cursor.selectionEnd());
        utf8Offset = Utils::Text::utf8NthLineOffset(m_doc, buffer, block.blockNumber() + 1);
        QTC_ASSERT(utf8Offset >= 0, return TextEditor::Replacements(););
        utf8Length = selectedLines(m_doc, block, end).toUtf8().size();
    } else {
        block = cursor.block();
        utf8Offset = Utils::Text::utf8NthLineOffset(m_doc, buffer, block.blockNumber() + 1);
        QTC_ASSERT(utf8Offset >= 0, return TextEditor::Replacements(););

        utf8Length = block.text().toUtf8().size();
    }

    const TextEditor::Replacements toReplace = replacements(buffer,
                                                            utf8Offset,
                                                            utf8Length,
                                                            block,
                                                            cursorPositionInEditor,
                                                            ReplacementsToKeep::All,
                                                            QChar::Null);
    applyReplacements(block, toReplace);

    return toReplace;
}

TextEditor::Replacements ClangFormatBaseIndenter::format(
    const QTextCursor &cursor,
    const TextEditor::TabSettings & /*tabSettings*/,
    int cursorPositionInEditor)
{
    return format(cursor, cursorPositionInEditor);
}

void ClangFormatBaseIndenter::indentBeforeCursor(const QTextBlock &block,
                                                 const QChar &typedChar,
                                                 int cursorPositionInEditor)
{
    const QByteArray buffer = m_doc->toPlainText().toUtf8();
    const int utf8Offset = Utils::Text::utf8NthLineOffset(m_doc, buffer, block.blockNumber() + 1);
    QTC_ASSERT(utf8Offset >= 0, return;);
    const TextEditor::Replacements toReplace = replacements(buffer,
                                                            utf8Offset,
                                                            0,
                                                            block,
                                                            cursorPositionInEditor,
                                                            ReplacementsToKeep::IndentAndBefore,
                                                            typedChar);
    applyReplacements(block, toReplace);
}

static bool doNotIndentInContext(QTextDocument *doc, int pos)
{
    const QChar character = doc->characterAt(pos);
    const QTextBlock currentBlock = doc->findBlock(pos);
    const QString text = currentBlock.text().left(pos - currentBlock.position());
    switch (character.toLatin1()) {
    default:
        break;
    case ':':
        // Do not indent when it's the first ':' and it's not the 'case' line.
        if (text.contains(QLatin1String("case")) || text.contains(QLatin1String("default"))
            || text.contains(QLatin1String("public")) || text.contains(QLatin1String("private"))
            || text.contains(QLatin1String("protected")) || text.contains(QLatin1String("signals"))
            || text.contains(QLatin1String("Q_SIGNALS"))) {
            return false;
        }
        if (pos > 0 && doc->characterAt(pos - 1) != ':')
            return true;
        break;
    case '<':
    case '>':
        // "<<" and ">>" could be problematic
        if (pos > 0 && doc->characterAt(pos - 1) == character)
            return true;
        break;
    }

    return false;
}

void ClangFormatBaseIndenter::indentBlock(const QTextBlock &block,
                                          const QChar &typedChar,
                                          int cursorPositionInEditor)
{
    QTextBlock currentBlock = block;
    const int blockPosition = currentBlock.position();
    trimFirstNonEmptyBlock(currentBlock);

    if (typedChar != QChar::Null && cursorPositionInEditor > 0
        && m_doc->characterAt(cursorPositionInEditor - 1) == typedChar
        && doNotIndentInContext(m_doc, cursorPositionInEditor - 1)) {
        return;
    }

    if (formatWhileTyping()
        && (cursorPositionInEditor == -1 || cursorPositionInEditor >= blockPosition)
        && (typedChar == QChar::Null || typedChar == ';' || typedChar == '}')) {
        // Format before current position only in case the cursor is inside the indented block.
        // So if cursor position is less then the block position then the current line is before
        // the indented block - don't trigger extra formatting in this case.
        // cursorPositionInEditor == -1 means the consition matches automatically.

        // Format only before newline or complete statement not to break code.
        if (cursorPositionInEditor >= 0)
            cursorPositionInEditor += currentBlock.position() - blockPosition;
        else
            cursorPositionInEditor = currentBlock.position();

        indentBeforeCursor(currentBlock, typedChar, cursorPositionInEditor);
        return;
    }

    const QByteArray buffer = m_doc->toPlainText().toUtf8();
    const int utf8Offset = Utils::Text::utf8NthLineOffset(m_doc, buffer, block.blockNumber() + 1);
    QTC_ASSERT(utf8Offset >= 0, return;);

    applyReplacements(currentBlock,
                      replacements(buffer,
                                   utf8Offset,
                                   0,
                                   currentBlock,
                                   cursorPositionInEditor,
                                   ReplacementsToKeep::OnlyIndent,
                                   typedChar));
}

void ClangFormatBaseIndenter::indentBlock(const QTextBlock &block,
                                          const QChar &typedChar,
                                          const TextEditor::TabSettings & /*tabSettings*/,
                                          int cursorPositionInEditor)
{
    indentBlock(block, typedChar, cursorPositionInEditor);
}

int ClangFormatBaseIndenter::indentFor(const QTextBlock &block, int cursorPositionInEditor)
{
    trimFirstNonEmptyBlock(block);
    const QByteArray buffer = m_doc->toPlainText().toUtf8();
    const int utf8Offset = Utils::Text::utf8NthLineOffset(m_doc, buffer, block.blockNumber() + 1);
    QTC_ASSERT(utf8Offset >= 0, return 0;);

    const TextEditor::Replacements toReplace = replacements(buffer,
                                                            utf8Offset,
                                                            0,
                                                            block,
                                                            cursorPositionInEditor,
                                                            ReplacementsToKeep::OnlyIndent);

    if (toReplace.empty())
        return -1;

    const TextEditor::Replacement &replacement = toReplace.front();
    int afterLineBreak = replacement.text.lastIndexOf('\n');
    afterLineBreak = (afterLineBreak < 0) ? 0 : afterLineBreak + 1;
    return static_cast<int>(replacement.text.size() - afterLineBreak);
}

int ClangFormatBaseIndenter::indentFor(const QTextBlock &block,
                                       const TextEditor::TabSettings & /*tabSettings*/,
                                       int cursorPositionInEditor)
{
    return indentFor(block, cursorPositionInEditor);
}

bool ClangFormatBaseIndenter::isElectricCharacter(const QChar &ch) const
{
    switch (ch.toLatin1()) {
    case '{':
    case '}':
    case ':':
    case '#':
    case '<':
    case '>':
    case ';':
    case '(':
    case ')':
        return true;
    }
    return false;
}

void ClangFormatBaseIndenter::formatOrIndent(const QTextCursor &cursor,
                                             const TextEditor::TabSettings & /*tabSettings*/,
                                             int cursorPositionInEditor)
{
    if (formatCodeInsteadOfIndent())
        format(cursor, cursorPositionInEditor);
    else
        indent(cursor, QChar::Null, cursorPositionInEditor);
}

clang::format::FormatStyle ClangFormatBaseIndenter::styleForFile() const
{
    llvm::Expected<clang::format::FormatStyle> style
        = clang::format::getStyle("file", m_fileName.toString().toStdString(), "none");
    if (style)
        return *style;

    handleAllErrors(style.takeError(), [](const llvm::ErrorInfoBase &) {
        // do nothing
    });

    return clang::format::getLLVMStyle();
}

static int formattingRangeStart(const QTextBlock &currentBlock,
                                const QByteArray &buffer,
                                int documentRevision)
{
    QTextBlock prevBlock = currentBlock.previous();
    while ((prevBlock.position() > 0 || prevBlock.length() > 0)
           && prevBlock.revision() != documentRevision) {
        // Find the first block with not matching revision.
        prevBlock = prevBlock.previous();
    }
    if (prevBlock.revision() == documentRevision)
        prevBlock = prevBlock.next();

    return Utils::Text::utf8NthLineOffset(prevBlock.document(), buffer, prevBlock.blockNumber() + 1);
}

TextEditor::Replacements ClangFormatBaseIndenter::replacements(QByteArray buffer,
                                                               int utf8Offset,
                                                               int utf8Length,
                                                               const QTextBlock &block,
                                                               int cursorPositionInEditor,
                                                               ReplacementsToKeep replacementsToKeep,
                                                               const QChar &typedChar,
                                                               bool secondTry) const
{
    clang::format::FormatStyle style = styleForFile();

    int originalOffsetUtf8 = utf8Offset;
    int originalLengthUtf8 = utf8Length;
    QByteArray originalBuffer = buffer;

    int utf8LineLengthBeforeCursor = 0;
    if (cursorPositionInEditor > 0 && typedChar != QChar::Null) {
        // Format starting with the electric character if it's present.
        utf8LineLengthBeforeCursor
            = block.text().left(cursorPositionInEditor - block.position()).toUtf8().size();
    }

    int extraEmptySpaceOffset = 0;
    int rangeStart = 0;
    if (replacementsToKeep != ReplacementsToKeep::All) {
        if (replacementsToKeep == ReplacementsToKeep::IndentAndBefore)
            rangeStart = formattingRangeStart(block, buffer, lastSaveRevision());

        extraEmptySpaceOffset = previousEmptyLinesLength(block);
        utf8Offset -= extraEmptySpaceOffset;
        buffer.remove(utf8Offset, extraEmptySpaceOffset);

        adjustFormatStyleForLineBreak(style, replacementsToKeep);
        modifyToIndentEmptyLines(buffer, utf8Offset, utf8Length, block, secondTry);

        if (replacementsToKeep == ReplacementsToKeep::IndentAndBefore) {
            buffer.insert(utf8Offset - 1, " //");
            extraEmptySpaceOffset -= 3;
            utf8Offset += 3;
        }
    }

    if (replacementsToKeep != ReplacementsToKeep::IndentAndBefore || utf8Offset < rangeStart)
        rangeStart = utf8Offset;

    unsigned int rangeLength = static_cast<unsigned int>(utf8Offset + utf8Length - rangeStart);

    std::vector<clang::tooling::Range> ranges{{static_cast<unsigned int>(rangeStart), rangeLength}};

    clang::format::FormattingAttemptStatus status;

    clang::tooling::Replacements clangReplacements = reformat(style,
                                                              buffer.data(),
                                                              ranges,
                                                              m_fileName.toString().toStdString(),
                                                              &status);

    clang::tooling::Replacements filtered;
    if (status.FormatComplete) {
        filtered = filteredReplacements(clangReplacements,
                                        utf8Offset,
                                        utf8LineLengthBeforeCursor,
                                        extraEmptySpaceOffset,
                                        replacementsToKeep);
    }
    const bool canTryAgain = replacementsToKeep == ReplacementsToKeep::OnlyIndent
                             && typedChar == QChar::Null && !secondTry;
    if (canTryAgain && filtered.empty()) {
        return replacements(originalBuffer,
                            originalOffsetUtf8,
                            originalLengthUtf8,
                            block,
                            cursorPositionInEditor,
                            replacementsToKeep,
                            typedChar,
                            true);
    }

    return utf16Replacements(block, originalOffsetUtf8, originalBuffer, filtered);
}

} // namespace ClangFormat