//===- Rewriter.cpp - Code rewriting interface ----------------------------===//

//

// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.

// See https://llvm.org/LICENSE.txt for license information.

// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception

//

//===----------------------------------------------------------------------===//

//

//  This file defines the Rewriter class, which is used for code

//  transformations.

//

//===----------------------------------------------------------------------===//

#include "clang/Rewrite/Core/Rewriter.h"

#include "clang/Basic/Diagnostic.h"

#include "clang/Basic/DiagnosticIDs.h"

#include "clang/Basic/SourceLocation.h"

#include "clang/Basic/SourceManager.h"

#include "clang/Lex/Lexer.h"

#include "clang/Rewrite/Core/RewriteBuffer.h"

#include "clang/Rewrite/Core/RewriteRope.h"

#include "llvm/ADT/SmallVector.h"

#include "llvm/ADT/StringRef.h"

#include "llvm/Support/Error.h"

#include "llvm/Support/raw_ostream.h"

#include <cassert>

#include <iterator>

#include <map>

#include <utility>

using namespace clang;

raw_ostream &RewriteBuffer::write(raw_ostream &os) const {

  // Walk RewriteRope chunks efficiently using MoveToNextPiece() instead of the

  // character iterator.

  for (RopePieceBTreeIterator I = begin(), E = end(); I != E;

       I.MoveToNextPiece())

    os << I.piece();

  return os;

}

/// Return true if this character is non-new-line whitespace:

/// ' ', '\\t', '\\f', '\\v', '\\r'.

static inline bool isWhitespaceExceptNL(unsigned char c) {

  switch (c) {

  case ' ':

  case '\t':

  case '\f':

  case '\v':

  case '\r':

    return true;

  default:

    return false;

  }

}

void RewriteBuffer::RemoveText(unsigned OrigOffset, unsigned Size,

                               bool removeLineIfEmpty) {

  // Nothing to remove, exit early.

  if (Size == 0) return;

  unsigned RealOffset = getMappedOffset(OrigOffset, true);

  assert(RealOffset+Size <= Buffer.size() && "Invalid location");

  // Remove the dead characters.

  Buffer.erase(RealOffset, Size);

  // Add a delta so that future changes are offset correctly.

  AddReplaceDelta(OrigOffset, -Size);

  if (removeLineIfEmpty) {

    // Find the line that the remove occurred and if it is completely empty

    // remove the line as well.

    iterator curLineStart = begin();

    unsigned curLineStartOffs = 0;

    iterator posI = begin();

    for (unsigned i = 0; i != RealOffset; ++i) {

      if (*posI == '\n') {

        curLineStart = posI;

        ++curLineStart;

        curLineStartOffs = i + 1;

      }

      ++posI;

    }

    unsigned lineSize = 0;

    posI = curLineStart;

    while (posI != end() && isWhitespaceExceptNL(*posI)) {

      ++posI;

      ++lineSize;

    }

    if (posI != end() && *posI == '\n') {

      Buffer.erase(curLineStartOffs, lineSize + 1/* + '\n'*/);

      // FIXME: Here, the offset of the start of the line is supposed to be

      // expressed in terms of the original input not the "real" rewrite

      // buffer.  How do we compute that reliably?  It might be tempting to use

      // curLineStartOffs + OrigOffset - RealOffset, but that assumes the

      // difference between the original and real offset is the same at the

      // removed text and at the start of the line, but that's not true if

      // edits were previously made earlier on the line.  This bug is also

      // documented by a FIXME on the definition of

      // clang::Rewriter::RewriteOptions::RemoveLineIfEmpty.  A reproducer for

      // the implementation below is the test RemoveLineIfEmpty in

      // clang/unittests/Rewrite/RewriteBufferTest.cpp.

      AddReplaceDelta(curLineStartOffs, -(lineSize + 1/* + '\n'*/));

    }

  }

}

void RewriteBuffer::InsertText(unsigned OrigOffset, StringRef Str,

                               bool InsertAfter) {

  // Nothing to insert, exit early.

  if (Str.empty()) return;

  unsigned RealOffset = getMappedOffset(OrigOffset, InsertAfter);

  Buffer.insert(RealOffset, Str.begin(), Str.end());

  // Add a delta so that future changes are offset correctly.

  AddInsertDelta(OrigOffset, Str.size());

}

/// ReplaceText - This method replaces a range of characters in the input

/// buffer with a new string.  This is effectively a combined "remove+insert"

/// operation.

void RewriteBuffer::ReplaceText(unsigned OrigOffset, unsigned OrigLength,

                                StringRef NewStr) {

  unsigned RealOffset = getMappedOffset(OrigOffset, true);

  Buffer.erase(RealOffset, OrigLength);

  Buffer.insert(RealOffset, NewStr.begin(), NewStr.end());

  if (OrigLength != NewStr.size())

    AddReplaceDelta(OrigOffset, NewStr.size() - OrigLength);

}

//===----------------------------------------------------------------------===//

// Rewriter class

//===----------------------------------------------------------------------===//

/// getRangeSize - Return the size in bytes of the specified range if they

/// are in the same file.  If not, this returns -1.

int Rewriter::getRangeSize(const CharSourceRange &Range,

                           RewriteOptions opts) const {

  if (!isRewritable(Range.getBegin()) ||

      !isRewritable(Range.getEnd())) return -1;

  FileID StartFileID, EndFileID;

  unsigned StartOff = getLocationOffsetAndFileID(Range.getBegin(), StartFileID);

  unsigned EndOff = getLocationOffsetAndFileID(Range.getEnd(), EndFileID);

  if (StartFileID != EndFileID)

    return -1;

  // If edits have been made to this buffer, the delta between the range may

  // have changed.

  std::map<FileID, RewriteBuffer>::const_iterator I =

    RewriteBuffers.find(StartFileID);

  if (I != RewriteBuffers.end()) {

    const RewriteBuffer &RB = I->second;

    EndOff = RB.getMappedOffset(EndOff, opts.IncludeInsertsAtEndOfRange);

    StartOff = RB.getMappedOffset(StartOff, !opts.IncludeInsertsAtBeginOfRange);

  }

  // Adjust the end offset to the end of the last token, instead of being the

  // start of the last token if this is a token range.

  if (Range.isTokenRange())

    EndOff += Lexer::MeasureTokenLength(Range.getEnd(), *SourceMgr, *LangOpts);

  return EndOff-StartOff;

}

int Rewriter::getRangeSize(SourceRange Range, RewriteOptions opts) const {

  return getRangeSize(CharSourceRange::getTokenRange(Range), opts);

}

/// getRewrittenText - Return the rewritten form of the text in the specified

/// range.  If the start or end of the range was unrewritable or if they are

/// in different buffers, this returns an empty string.

///

/// Note that this method is not particularly efficient.

std::string Rewriter::getRewrittenText(CharSourceRange Range) const {

  if (!isRewritable(Range.getBegin()) ||

      !isRewritable(Range.getEnd()))

    return {};

  FileID StartFileID, EndFileID;

  unsigned StartOff, EndOff;

  StartOff = getLocationOffsetAndFileID(Range.getBegin(), StartFileID);

  EndOff   = getLocationOffsetAndFileID(Range.getEnd(), EndFileID);

  if (StartFileID != EndFileID)

    return {}; // Start and end in different buffers.

  // If edits have been made to this buffer, the delta between the range may

  // have changed.

  std::map<FileID, RewriteBuffer>::const_iterator I =

    RewriteBuffers.find(StartFileID);

  if (I == RewriteBuffers.end()) {

    // If the buffer hasn't been rewritten, just return the text from the input.

    const char *Ptr = SourceMgr->getCharacterData(Range.getBegin());

    // Adjust the end offset to the end of the last token, instead of being the

    // start of the last token.

    if (Range.isTokenRange())

      EndOff +=

          Lexer::MeasureTokenLength(Range.getEnd(), *SourceMgr, *LangOpts);

    return std::string(Ptr, Ptr+EndOff-StartOff);

  }

  const RewriteBuffer &RB = I->second;

  EndOff = RB.getMappedOffset(EndOff, true);

  StartOff = RB.getMappedOffset(StartOff);

  // Adjust the end offset to the end of the last token, instead of being the

  // start of the last token.

  if (Range.isTokenRange())

    EndOff += Lexer::MeasureTokenLength(Range.getEnd(), *SourceMgr, *LangOpts);

  // Advance the iterators to the right spot, yay for linear time algorithms.

  RewriteBuffer::iterator Start = RB.begin();

  std::advance(Start, StartOff);

  RewriteBuffer::iterator End = Start;

  assert(EndOff >= StartOff && "Invalid iteration distance");

  std::advance(End, EndOff-StartOff);

  return std::string(Start, End);

}

unsigned Rewriter::getLocationOffsetAndFileID(SourceLocation Loc,

                                              FileID &FID) const {

  assert(Loc.isValid() && "Invalid location");

  std::pair<FileID, unsigned> V = SourceMgr->getDecomposedLoc(Loc);

  FID = V.first;

  return V.second;

}

/// getEditBuffer - Get or create a RewriteBuffer for the specified FileID.

RewriteBuffer &Rewriter::getEditBuffer(FileID FID) {

  std::map<FileID, RewriteBuffer>::iterator I =

    RewriteBuffers.lower_bound(FID);

  if (I != RewriteBuffers.end() && I->first == FID)

    return I->second;

  I = RewriteBuffers.insert(I, std::make_pair(FID, RewriteBuffer()));

  StringRef MB = SourceMgr->getBufferData(FID);

  I->second.Initialize(MB.begin(), MB.end());

  return I->second;

}

/// InsertText - Insert the specified string at the specified location in the

/// original buffer.

bool Rewriter::InsertText(SourceLocation Loc, StringRef Str,

                          bool InsertAfter, bool indentNewLines) {

  if (!isRewritable(Loc)) return true;

  FileID FID;

  unsigned StartOffs = getLocationOffsetAndFileID(Loc, FID);

  SmallString<128> indentedStr;

  if (indentNewLines && Str.contains('\n')) {

    StringRef MB = SourceMgr->getBufferData(FID);

    unsigned lineNo = SourceMgr->getLineNumber(FID, StartOffs) - 1;

    const SrcMgr::ContentCache *Content =

        &SourceMgr->getSLocEntry(FID).getFile().getContentCache();

    unsigned lineOffs = Content->SourceLineCache[lineNo];

    // Find the whitespace at the start of the line.

    StringRef indentSpace;

    {

      unsigned i = lineOffs;

      while (isWhitespaceExceptNL(MB[i]))

        ++i;

      indentSpace = MB.substr(lineOffs, i-lineOffs);

    }

    SmallVector<StringRef, 4> lines;

    Str.split(lines, "\n");

    for (unsigned i = 0, e = lines.size(); i != e; ++i) {

      indentedStr += lines[i];

      if (i < e-1) {

        indentedStr += '\n';

        indentedStr += indentSpace;

      }

    }

    Str = indentedStr.str();

  }

  getEditBuffer(FID).InsertText(StartOffs, Str, InsertAfter);

  return false;

}

bool Rewriter::InsertTextAfterToken(SourceLocation Loc, StringRef Str) {

  if (!isRewritable(Loc)) return true;

  FileID FID;

  unsigned StartOffs = getLocationOffsetAndFileID(Loc, FID);

  RewriteOptions rangeOpts;

  rangeOpts.IncludeInsertsAtBeginOfRange = false;

  StartOffs += getRangeSize(SourceRange(Loc, Loc), rangeOpts);

  getEditBuffer(FID).InsertText(StartOffs, Str, /*InsertAfter*/true);

  return false;

}

/// RemoveText - Remove the specified text region.

bool Rewriter::RemoveText(SourceLocation Start, unsigned Length,

                          RewriteOptions opts) {

  if (!isRewritable(Start)) return true;

  FileID FID;

  unsigned StartOffs = getLocationOffsetAndFileID(Start, FID);

  getEditBuffer(FID).RemoveText(StartOffs, Length, opts.RemoveLineIfEmpty);

  return false;

}

/// ReplaceText - This method replaces a range of characters in the input

/// buffer with a new string.  This is effectively a combined "remove/insert"

/// operation.

bool Rewriter::ReplaceText(SourceLocation Start, unsigned OrigLength,

                           StringRef NewStr) {

  if (!isRewritable(Start)) return true;

  FileID StartFileID;

  unsigned StartOffs = getLocationOffsetAndFileID(Start, StartFileID);

  getEditBuffer(StartFileID).ReplaceText(StartOffs, OrigLength, NewStr);

  return false;

}

bool Rewriter::ReplaceText(SourceRange range, SourceRange replacementRange) {

  if (!isRewritable(range.getBegin())) return true;

  if (!isRewritable(range.getEnd())) return true;

  if (replacementRange.isInvalid()) return true;

  SourceLocation start = range.getBegin();

  unsigned origLength = getRangeSize(range);

  unsigned newLength = getRangeSize(replacementRange);

  FileID FID;

  unsigned newOffs = getLocationOffsetAndFileID(replacementRange.getBegin(),

                                                FID);

  StringRef MB = SourceMgr->getBufferData(FID);

  return ReplaceText(start, origLength, MB.substr(newOffs, newLength));

}

bool Rewriter::IncreaseIndentation(CharSourceRange range,

                                   SourceLocation parentIndent) {

  if (range.isInvalid()) return true;

  if (!isRewritable(range.getBegin())) return true;

  if (!isRewritable(range.getEnd())) return true;

  if (!isRewritable(parentIndent)) return true;

  FileID StartFileID, EndFileID, parentFileID;

  unsigned StartOff, EndOff, parentOff;

  StartOff = getLocationOffsetAndFileID(range.getBegin(), StartFileID);

  EndOff   = getLocationOffsetAndFileID(range.getEnd(), EndFileID);

  parentOff = getLocationOffsetAndFileID(parentIndent, parentFileID);

  if (StartFileID != EndFileID || StartFileID != parentFileID)

    return true;

  if (StartOff > EndOff)

    return true;

  FileID FID = StartFileID;

  StringRef MB = SourceMgr->getBufferData(FID);

  unsigned parentLineNo = SourceMgr->getLineNumber(FID, parentOff) - 1;

  unsigned startLineNo = SourceMgr->getLineNumber(FID, StartOff) - 1;

  unsigned endLineNo = SourceMgr->getLineNumber(FID, EndOff) - 1;

  const SrcMgr::ContentCache *Content =

      &SourceMgr->getSLocEntry(FID).getFile().getContentCache();

  // Find where the lines start.

  unsigned parentLineOffs = Content->SourceLineCache[parentLineNo];

  unsigned startLineOffs = Content->SourceLineCache[startLineNo];

  // Find the whitespace at the start of each line.

  StringRef parentSpace, startSpace;

  {

    unsigned i = parentLineOffs;

    while (isWhitespaceExceptNL(MB[i]))

      ++i;

    parentSpace = MB.substr(parentLineOffs, i-parentLineOffs);

    i = startLineOffs;

    while (isWhitespaceExceptNL(MB[i]))

      ++i;

    startSpace = MB.substr(startLineOffs, i-startLineOffs);

  }

  if (parentSpace.size() >= startSpace.size())

    return true;

  if (!startSpace.starts_with(parentSpace))

    return true;

  StringRef indent = startSpace.substr(parentSpace.size());

  // Indent the lines between start/end offsets.

  RewriteBuffer &RB = getEditBuffer(FID);

  for (unsigned lineNo = startLineNo; lineNo <= endLineNo; ++lineNo) {

    unsigned offs = Content->SourceLineCache[lineNo];

    unsigned i = offs;

    while (isWhitespaceExceptNL(MB[i]))

      ++i;

    StringRef origIndent = MB.substr(offs, i-offs);

    if (origIndent.starts_with(startSpace))

      RB.InsertText(offs, indent, /*InsertAfter=*/false);

  }

  return false;

}

bool Rewriter::overwriteChangedFiles() {

  bool AllWritten = true;

  auto& Diag = getSourceMgr().getDiagnostics();

  unsigned OverwriteFailure = Diag.getCustomDiagID(

      DiagnosticsEngine::Error, "unable to overwrite file %0: %1");

  for (buffer_iterator I = buffer_begin(), E = buffer_end(); I != E; ++I) {

    OptionalFileEntryRef Entry = getSourceMgr().getFileEntryRefForID(I->first);

    llvm::SmallString<128> Path(Entry->getName());

    getSourceMgr().getFileManager().makeAbsolutePath(Path);

    if (auto Error = llvm::writeToOutput(Path, [&](llvm::raw_ostream &OS) {

          I->second.write(OS);

          return llvm::Error::success();

        })) {

      Diag.Report(OverwriteFailure)

          << Entry->getName() << llvm::toString(std::move(Error));

      AllWritten = false;

    }

  }

  return !AllWritten;

}