//===- ComputeReplacements.cpp --------------------------------*- C++ -*-=====//

//

// 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

//

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

#include "clang/Tooling/Core/Replacement.h"

#include "clang/Tooling/Syntax/Mutations.h"

#include "clang/Tooling/Syntax/Tokens.h"

#include "llvm/Support/Error.h"

using namespace clang;

namespace {

using ProcessTokensFn = llvm::function_ref<void(llvm::ArrayRef<syntax::Token>,

                                                bool /*IsOriginal*/)>;

/// Enumerates spans of tokens from the tree consecutively laid out in memory.

void enumerateTokenSpans(const syntax::Tree *Root, ProcessTokensFn Callback) {

  struct Enumerator {

    Enumerator(ProcessTokensFn Callback)

        : SpanBegin(nullptr), SpanEnd(nullptr), SpanIsOriginal(false),

          Callback(Callback) {}

    void run(const syntax::Tree *Root) {

      process(Root);

      // Report the last span to the user.

      if (SpanBegin)

        Callback(llvm::makeArrayRef(SpanBegin, SpanEnd), SpanIsOriginal);

    }

  private:

    void process(const syntax::Node *N) {

      if (auto *T = dyn_cast<syntax::Tree>(N)) {

        for (const auto *C = T->getFirstChild(); C != nullptr;

             C = C->getNextSibling())

          process(C);

        return;

      }

      auto *L = cast<syntax::Leaf>(N);

      if (SpanEnd == L->getToken() && 
SpanIsOriginal == L->isOriginal()322
) {

        // Extend the current span.

        ++SpanEnd;

        return;

      }

      // Report the current span to the user.

      if (SpanBegin)

        Callback(llvm::makeArrayRef(SpanBegin, SpanEnd), SpanIsOriginal);

      // Start recording a new span.

      SpanBegin = L->getToken();

      SpanEnd = SpanBegin + 1;

      SpanIsOriginal = L->isOriginal();

    }

    const syntax::Token *SpanBegin;

    const syntax::Token *SpanEnd;

    bool SpanIsOriginal;

    ProcessTokensFn Callback;

  };

  return Enumerator(Callback).run(Root);

}

syntax::FileRange rangeOfExpanded(const syntax::Arena &A,

                                  llvm::ArrayRef<syntax::Token> Expanded) {

  const auto &Buffer = A.getTokenBuffer();

  const auto &SM = A.getSourceManager();

  // Check that \p Expanded actually points into expanded tokens.

  assert(Buffer.expandedTokens().begin() <= Expanded.begin());

  assert(Expanded.end() < Buffer.expandedTokens().end());

  if (Expanded.empty())

    // (!) empty tokens must always point before end().

    return syntax::FileRange(

        SM, SM.getExpansionLoc(Expanded.begin()->location()), /*Length=*/0);

  auto Spelled = Buffer.spelledForExpanded(Expanded);

  assert(Spelled && "could not find spelled tokens for expanded");

  return syntax::Token::range(SM, Spelled->front(), Spelled->back());

}

} // namespace

tooling::Replacements

syntax::computeReplacements(const syntax::Arena &A,

                            const syntax::TranslationUnit &TU) {

  const auto &Buffer = A.getTokenBuffer();

  const auto &SM = A.getSourceManager();

  tooling::Replacements Replacements;

  // Text inserted by the replacement we are building now.

  std::string Replacement;

  auto emitReplacement = [&](llvm::ArrayRef<syntax::Token> ReplacedRange) {

    if (ReplacedRange.empty() && 
Replacement.empty()84
)

      return;

    llvm::cantFail(Replacements.add(tooling::Replacement(

        SM, rangeOfExpanded(A, ReplacedRange).toCharRange(SM), Replacement)));

    Replacement = "";

  };

  const syntax::Token *NextOriginal = Buffer.expandedTokens().begin();

  enumerateTokenSpans(

      &TU, [&](llvm::ArrayRef<syntax::Token> Tokens, bool IsOriginal) {

        if (!IsOriginal) {

          Replacement +=

              syntax::Token::range(SM, Tokens.front(), Tokens.back()).text(SM);

          return;

        }

        assert(NextOriginal <= Tokens.begin());

        // We are looking at a span of original tokens.

        if (NextOriginal != Tokens.begin()) {

          // There is a gap, record a replacement or deletion.

          emitReplacement(llvm::makeArrayRef(NextOriginal, Tokens.begin()));

        } else {

          // No gap, but we may have pending insertions. Emit them now.

          emitReplacement(llvm::makeArrayRef(NextOriginal, /*Length=*/0));

        }

        NextOriginal = Tokens.end();

      });

  // We might have pending replacements at the end of file. If so, emit them.

  emitReplacement(llvm::makeArrayRef(

      NextOriginal, Buffer.expandedTokens().drop_back().end()));

  return Replacements;

}