//===--- Extract.cpp - Clang refactoring library --------------------------===//

//

// 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

//

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

///

/// \file

/// Implements the "extract" refactoring that can pull code into

/// new functions, methods or declare new variables.

///

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

#include "clang/Tooling/Refactoring/Extract/Extract.h"

#include "clang/AST/ASTContext.h"

#include "clang/AST/DeclCXX.h"

#include "clang/AST/Expr.h"

#include "clang/AST/ExprObjC.h"

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

#include "clang/Tooling/Refactoring/Extract/SourceExtraction.h"

#include <optional>

namespace clang {

namespace tooling {

namespace {

/// Returns true if \c E is a simple literal or a reference expression that

/// should not be extracted.

bool isSimpleExpression(const Expr *E) {

  if (!E)

    return false;

  switch (E->IgnoreParenCasts()->getStmtClass()) {

  case Stmt::DeclRefExprClass:

  case Stmt::PredefinedExprClass:

  case Stmt::IntegerLiteralClass:

  case Stmt::FloatingLiteralClass:

  case Stmt::ImaginaryLiteralClass:

  case Stmt::CharacterLiteralClass:

  case Stmt::StringLiteralClass:

    return true;

  default:

    return false;

  }

}

SourceLocation computeFunctionExtractionLocation(const Decl *D) {

  if (isa<CXXMethodDecl>(D)) {

    // Code from method that is defined in class body should be extracted to a

    // function defined just before the class.

    while (const auto *RD = dyn_cast<CXXRecordDecl>(D->getLexicalDeclContext()))

      D = RD;

  }

  return D->getBeginLoc();

}

} // end anonymous namespace

const RefactoringDescriptor &ExtractFunction::describe() {

  static const RefactoringDescriptor Descriptor = {

      "extract-function",

      "Extract Function",

      "(WIP action; use with caution!) Extracts code into a new function",

  };

  return Descriptor;

}

Expected<ExtractFunction>

ExtractFunction::initiate(RefactoringRuleContext &Context,

                          CodeRangeASTSelection Code,

                          std::optional<std::string> DeclName) {

  // We would like to extract code out of functions/methods/blocks.

  // Prohibit extraction from things like global variable / field

  // initializers and other top-level expressions.

  if (!Code.isInFunctionLikeBodyOfCode())

    return Context.createDiagnosticError(

        diag::err_refactor_code_outside_of_function);

  if (Code.size() == 1) {

    // Avoid extraction of simple literals and references.

    if (isSimpleExpression(dyn_cast<Expr>(Code[0])))

      return Context.createDiagnosticError(

          diag::err_refactor_extract_simple_expression);

    // Property setters can't be extracted.

    if (const auto *PRE = dyn_cast<ObjCPropertyRefExpr>(Code[0])) {

      if (!PRE->isMessagingGetter())

        return Context.createDiagnosticError(

            diag::err_refactor_extract_prohibited_expression);

    }

  }

  return ExtractFunction(std::move(Code), DeclName);

}

// FIXME: Support C++ method extraction.

// FIXME: Support Objective-C method extraction.

Expected<AtomicChanges>

ExtractFunction::createSourceReplacements(RefactoringRuleContext &Context) {

  const Decl *ParentDecl = Code.getFunctionLikeNearestParent();

  assert(ParentDecl && "missing parent");

  // Compute the source range of the code that should be extracted.

  SourceRange ExtractedRange(Code[0]->getBeginLoc(),

                             Code[Code.size() - 1]->getEndLoc());

  // FIXME (Alex L): Add code that accounts for macro locations.

  ASTContext &AST = Context.getASTContext();

  SourceManager &SM = AST.getSourceManager();

  const LangOptions &LangOpts = AST.getLangOpts();

  Rewriter ExtractedCodeRewriter(SM, LangOpts);

  // FIXME: Capture used variables.

  // Compute the return type.

  QualType ReturnType = AST.VoidTy;

  // FIXME (Alex L): Account for the return statement in extracted code.

  // FIXME (Alex L): Check for lexical expression instead.

  bool IsExpr = Code.size() == 1 && 
isa<Expr>(Code[0])25
;

  if (IsExpr) {

    // FIXME (Alex L): Get a more user-friendly type if needed.

    ReturnType = cast<Expr>(Code[0])->getType();

  }

  // FIXME: Rewrite the extracted code performing any required adjustments.

  // FIXME: Capture any field if necessary (method -> function extraction).

  // FIXME: Sort captured variables by name.

  // FIXME: Capture 'this' / 'self' if necessary.

  // FIXME: Compute the actual parameter types.

  // Compute the location of the extracted declaration.

  SourceLocation ExtractedDeclLocation =

      computeFunctionExtractionLocation(ParentDecl);

  // FIXME: Adjust the location to account for any preceding comments.

  // FIXME: Adjust with PP awareness like in Sema to get correct 'bool'

  // treatment.

  PrintingPolicy PP = AST.getPrintingPolicy();

  // FIXME: PP.UseStdFunctionForLambda = true;

  PP.SuppressStrongLifetime = true;

  PP.SuppressLifetimeQualifiers = true;

  PP.SuppressUnwrittenScope = true;

  ExtractionSemicolonPolicy Semicolons = ExtractionSemicolonPolicy::compute(

      Code[Code.size() - 1], ExtractedRange, SM, LangOpts);

  AtomicChange Change(SM, ExtractedDeclLocation);

  // Create the replacement for the extracted declaration.

  {

    std::string ExtractedCode;

    llvm::raw_string_ostream OS(ExtractedCode);

    // FIXME: Use 'inline' in header.

    OS << "static ";

    ReturnType.print(OS, PP, DeclName);

    OS << '(';

    // FIXME: Arguments.

    OS << ')';

    // Function body.

    OS << " {\n";

    if (IsExpr && 
!ReturnType->isVoidType()7
)

      OS << "return ";

    OS << ExtractedCodeRewriter.getRewrittenText(ExtractedRange);

    if (Semicolons.isNeededInExtractedFunction())

      OS << ';';

    OS << "\n}\n\n";

    auto Err = Change.insert(SM, ExtractedDeclLocation, OS.str());

    if (Err)

      return std::move(Err);

  }

  // Create the replacement for the call to the extracted declaration.

  {

    std::string ReplacedCode;

    llvm::raw_string_ostream OS(ReplacedCode);

    OS << DeclName << '(';

    // FIXME: Forward arguments.

    OS << ')';

    if (Semicolons.isNeededInOriginalFunction())

      OS << ';';

    auto Err = Change.replace(

        SM, CharSourceRange::getTokenRange(ExtractedRange), OS.str());

    if (Err)

      return std::move(Err);

  }

  // FIXME: Add support for assocciated symbol location to AtomicChange to mark

  // the ranges of the name of the extracted declaration.

  return AtomicChanges{std::move(Change)};

}

} // end namespace tooling

} // end namespace clang