//===- 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/FileManager.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/SmallString.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/Support/FileSystem.h"
#include "llvm/Support/raw_ostream.h"
#include <cassert>
#include <iterator>
#include <map>
#include <memory>
#include <system_error>
#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.startswith(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.startswith(startSpace))
      RB.InsertText(offs, indent, /*InsertAfter=*/false);
  }

  return false;
}

namespace {

// A wrapper for a file stream that atomically overwrites the target.
//
// Creates a file output stream for a temporary file in the constructor,
// which is later accessible via getStream() if ok() return true.
// Flushes the stream and moves the temporary file to the target location
// in the destructor.
class AtomicallyMovedFile {
public:
  AtomicallyMovedFile(DiagnosticsEngine &Diagnostics, StringRef Filename,
                      bool &AllWritten)
      : Diagnostics(Diagnostics), Filename(Filename), AllWritten(AllWritten) {
    TempFilename = Filename;
    TempFilename += "-%%%%%%%%";
    int FD;
    if (llvm::sys::fs::createUniqueFile(TempFilename, FD, TempFilename)) {
      AllWritten = false;
      Diagnostics.Report(clang::diag::err_unable_to_make_temp)
        << TempFilename;
    } else {
      FileStream.reset(new llvm::raw_fd_ostream(FD, /*shouldClose=*/true));
    }
  }

  ~AtomicallyMovedFile() {
    if (!ok()) return;

    // Close (will also flush) theFileStream.
    FileStream->close();
    if (std::error_code ec = llvm::sys::fs::rename(TempFilename, Filename)) {
      AllWritten = false;
      Diagnostics.Report(clang::diag::err_unable_to_rename_temp)
        << TempFilename << Filename << ec.message();
      // If the remove fails, there's not a lot we can do - this is already an
      // error.
      llvm::sys::fs::remove(TempFilename);
    }
  }

  bool ok() { return (bool)FileStream; }
  raw_ostream &getStream() { return *FileStream; }

private:
  DiagnosticsEngine &Diagnostics;
  StringRef Filename;
  SmallString<128> TempFilename;
  std::unique_ptr<llvm::raw_fd_ostream> FileStream;
  bool &AllWritten;
};

} // namespace

bool Rewriter::overwriteChangedFiles() {
  bool AllWritten = true;
  for (buffer_iterator I = buffer_begin(), E = buffer_end(); I != E; ++I) {
    const FileEntry *Entry =
        getSourceMgr().getFileEntryForID(I->first);
    AtomicallyMovedFile File(getSourceMgr().getDiagnostics(), Entry->getName(),
                             AllWritten);
    if (File.ok()) {
      I->second.write(File.getStream());
    }
  }
  return !AllWritten;
}