//===- CIndexUSR.cpp - Clang-C Source Indexing Library --------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the generation and use of USRs from CXEntities.
//
//===----------------------------------------------------------------------===//

#include "CIndexer.h"
#include "CXCursor.h"
#include "clang/AST/DeclVisitor.h"
#include "clang/Frontend/ASTUnit.h"
#include "clang/Lex/PreprocessingRecord.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/Support/raw_ostream.h"

using namespace clang;
using namespace clang::cxstring;

//===----------------------------------------------------------------------===//
// USR generation.
//===----------------------------------------------------------------------===//

namespace {
class USRGenerator : public DeclVisitor<USRGenerator> {
  llvm::raw_ostream &Out;
  bool IgnoreResults;
  ASTUnit *AU;
public:
  USRGenerator(ASTUnit *au, llvm::raw_ostream &out)
    : Out(out), IgnoreResults(false), AU(au) {}

  bool ignoreResults() const { return IgnoreResults; }

  // Visitation methods from generating USRs from AST elements.
  void VisitBlockDecl(BlockDecl *D);
  void VisitDeclContext(DeclContext *D);
  void VisitFieldDecl(FieldDecl *D);
  void VisitFunctionDecl(FunctionDecl *D);
  void VisitNamedDecl(NamedDecl *D);
  void VisitNamespaceDecl(NamespaceDecl *D);
  void VisitObjCClassDecl(ObjCClassDecl *CD);
  void VisitObjCContainerDecl(ObjCContainerDecl *CD);
  void VisitObjCForwardProtocolDecl(ObjCForwardProtocolDecl *P);
  void VisitObjCMethodDecl(ObjCMethodDecl *MD);
  void VisitObjCPropertyDecl(ObjCPropertyDecl *D);
  void VisitObjCPropertyImplDecl(ObjCPropertyImplDecl *D);
  void VisitTagDecl(TagDecl *D);
  void VisitTypedefDecl(TypedefDecl *D);
  void VisitVarDecl(VarDecl *D);

  /// Generate the string component containing the location of the
  ///  declaration.
  void GenLoc(const Decl *D);

  /// String generation methods used both by the visitation methods
  /// and from other clients that want to directly generate USRs.  These
  /// methods do not construct complete USRs (which incorporate the parents
  /// of an AST element), but only the fragments concerning the AST element
  /// itself.

  /// Generate a USR fragment for a named declaration.  This does
  /// not include the USR component for the parent.
  void GenNamedDecl(llvm::StringRef name);

  /// Generate a USR for an Objective-C class.
  void GenObjCClass(llvm::StringRef cls);
  /// Generate a USR for an Objective-C class category.
  void GenObjCCategory(llvm::StringRef cls, llvm::StringRef cat);
  /// Generate a USR fragment for an Objective-C instance variable.  The
  /// complete USR can be created by concatenating the USR for the
  /// encompassing class with this USR fragment.
  void GenObjCIvar(llvm::StringRef ivar);
  /// Generate a USR fragment for an Objective-C method.
  void GenObjCMethod(llvm::StringRef sel, bool isInstanceMethod);
  /// Generate a USR fragment for an Objective-C property.
  void GenObjCProperty(llvm::StringRef prop);
  /// Generate a USR for an Objective-C protocol.
  void GenObjCProtocol(llvm::StringRef prot);
};

class StringUSRGenerator {
private:
  llvm::SmallString<1024> StrBuf;
  llvm::raw_svector_ostream Out;
  USRGenerator UG;
public:
  StringUSRGenerator(const CXCursor *C = 0)
    : Out(StrBuf), UG(C ? cxcursor::getCursorASTUnit(*C) : 0, Out) {
    // Add the USR space prefix.
    Out << "c:";
  }

  llvm::StringRef str() {
    return Out.str();
  }

  USRGenerator* operator->() { return &UG; }

  template <typename T>
  llvm::raw_svector_ostream &operator<<(const T &x) {
    Out << x;
    return Out;
  }
};

} // end anonymous namespace

//===----------------------------------------------------------------------===//
// Generating USRs from ASTS.
//===----------------------------------------------------------------------===//

void USRGenerator::VisitBlockDecl(BlockDecl *D) {
  VisitDeclContext(D->getDeclContext());
  // FIXME: Better support for anonymous blocks.
  Out << "@B@anon";
}

void USRGenerator::VisitDeclContext(DeclContext *DC) {
  if (NamedDecl *D = dyn_cast<NamedDecl>(DC))
    Visit(D);
}

void USRGenerator::VisitFieldDecl(FieldDecl *D) {
  const std::string &s = D->getNameAsString();
  if (s.empty()) {
    // Bit fields can be anonymous.
    IgnoreResults = true;
    return;
  }
  VisitDeclContext(D->getDeclContext());
  Out << (isa<ObjCIvarDecl>(D) ? "@" : "@FI@") << s;
}

void USRGenerator::VisitFunctionDecl(FunctionDecl *D) {
  VisitDeclContext(D->getDeclContext());
  Out << "@F@" << D;
}

void USRGenerator::VisitNamedDecl(NamedDecl *D) {
  VisitDeclContext(D->getDeclContext());
  const std::string &s = D->getNameAsString();
  // The string can be empty if the declaration has no name; e.g., it is
  // the ParmDecl with no name for declaration of a function pointer type, e.g.:
  //  	void  (*f)(void *);
  // In this case, don't generate a USR.
  if (s.empty())
    IgnoreResults = true;
  else
    GenNamedDecl(s);
}

void USRGenerator::VisitVarDecl(VarDecl *D) {
  // VarDecls can be declared 'extern' within a function or method body,
  // but their enclosing DeclContext is the function, not the TU.  We need
  // to check the storage class to correctly generate the USR.
  if (!D->hasExternalStorage())
    VisitDeclContext(D->getDeclContext());

  const std::string &s = D->getNameAsString();
  // The string can be empty if the declaration has no name; e.g., it is
  // the ParmDecl with no name for declaration of a function pointer type, e.g.:
  //  	void  (*f)(void *);
  // In this case, don't generate a USR.
  if (s.empty())
    IgnoreResults = true;
  else
    GenNamedDecl(s);
}

void USRGenerator::VisitNamespaceDecl(NamespaceDecl *D) {
  VisitDeclContext(D->getDeclContext());
  Out << "@N@" << D;
}

void USRGenerator::VisitObjCMethodDecl(ObjCMethodDecl *D) {
  Visit(cast<Decl>(D->getDeclContext()));
  GenObjCMethod(DeclarationName(D->getSelector()).getAsString(),
                D->isInstanceMethod());
}

void USRGenerator::VisitObjCClassDecl(ObjCClassDecl *D) {
  // FIXME: @class declarations can refer to multiple classes.  We need
  //  to be able to traverse these.
  IgnoreResults = true;
}

void USRGenerator::VisitObjCForwardProtocolDecl(ObjCForwardProtocolDecl *D) {
  // FIXME: @protocol declarations can refer to multiple protocols.  We need
  //  to be able to traverse these.
  IgnoreResults = true;
}

void USRGenerator::VisitObjCContainerDecl(ObjCContainerDecl *D) {
  switch (D->getKind()) {
    default:
      assert(false && "Invalid ObjC container.");
    case Decl::ObjCInterface:
    case Decl::ObjCImplementation:
      GenObjCClass(D->getName());
      break;
    case Decl::ObjCCategory: {
      ObjCCategoryDecl *CD = cast<ObjCCategoryDecl>(D);
      ObjCInterfaceDecl *ID = CD->getClassInterface();
      if (!ID) {
        // Handle invalid code where the @interface might not
        // have been specified.
        // FIXME: We should be able to generate this USR even if the
        // @interface isn't available.
        IgnoreResults = true;
        return;
      }
      GenObjCCategory(ID->getName(), CD->getName());
      break;
    }
    case Decl::ObjCCategoryImpl: {
      ObjCCategoryImplDecl *CD = cast<ObjCCategoryImplDecl>(D);
      ObjCInterfaceDecl *ID = CD->getClassInterface();
      if (!ID) {
        // Handle invalid code where the @interface might not
        // have been specified.
        // FIXME: We should be able to generate this USR even if the
        // @interface isn't available.
        IgnoreResults = true;
        return;
      }
      GenObjCCategory(ID->getName(), CD->getName());
      break;
    }
    case Decl::ObjCProtocol:
      GenObjCProtocol(cast<ObjCProtocolDecl>(D)->getName());
      break;
  }
}

void USRGenerator::VisitObjCPropertyDecl(ObjCPropertyDecl *D) {
  Visit(cast<Decl>(D->getDeclContext()));
  GenObjCProperty(D->getName());
}

void USRGenerator::VisitObjCPropertyImplDecl(ObjCPropertyImplDecl *D) {
  if (ObjCPropertyDecl *PD = D->getPropertyDecl()) {
    VisitObjCPropertyDecl(PD);
    return;
  }

  IgnoreResults = true;
}

void USRGenerator::VisitTagDecl(TagDecl *D) {
  D = D->getCanonicalDecl();
  VisitDeclContext(D->getDeclContext());
  switch (D->getTagKind()) {
    case TagDecl::TK_struct: Out << "@S"; break;
    case TagDecl::TK_class:  Out << "@C"; break;
    case TagDecl::TK_union:  Out << "@U"; break;
    case TagDecl::TK_enum:   Out << "@E"; break;
  }

  const std::string &s = D->getNameAsString();
  const TypedefDecl *TD = 0;
  if (s.empty()) {
    TD = D->getTypedefForAnonDecl();
    Out << (TD ? 'A' : 'a');
  }

  // Add the location of the tag decl to handle resolution across
  // translation units.
  if (D->getLinkage() == NoLinkage) {
    Out << '@';
    GenLoc(D);
    if (IgnoreResults)
      return;
  }

  if (s.empty()) {
    if (TD)
      Out << '@' << TD;
  }
  else
    Out << '@' << s;
}

void USRGenerator::VisitTypedefDecl(TypedefDecl *D) {
  DeclContext *DC = D->getDeclContext();
  if (NamedDecl *DCN = dyn_cast<NamedDecl>(DC))
    Visit(DCN);
  Out << "@T@";
  if (D->getLinkage() == NoLinkage) {
    GenLoc(D);
    if (IgnoreResults)
      return;
    Out << '@';
  }
  Out << D->getName();
}

void USRGenerator::GenLoc(const Decl *D) {
  const SourceManager &SM = AU->getSourceManager();
  SourceLocation L = D->getLocStart();
  if (L.isInvalid()) {
    IgnoreResults = true;
    return;
  }
  L = SM.getInstantiationLoc(L);
  const std::pair<FileID, unsigned> &Decomposed = SM.getDecomposedLoc(L);
  const FileEntry *FE = SM.getFileEntryForID(Decomposed.first);
  if (FE) {
    llvm::sys::Path P(FE->getName());
    Out << P.getLast();
  }
  else {
    // This case really isn't interesting.
    IgnoreResults = true;
    return;
  }
  Out << '@'
      << SM.getLineNumber(Decomposed.first, Decomposed.second) << ':'
      << SM.getColumnNumber(Decomposed.first, Decomposed.second);
}

//===----------------------------------------------------------------------===//
// General purpose USR generation methods.
//===----------------------------------------------------------------------===//

void USRGenerator::GenNamedDecl(llvm::StringRef name) {
  Out << "@" << name;
}

void USRGenerator::GenObjCClass(llvm::StringRef cls) {
  Out << "objc(cs)" << cls;
}

void USRGenerator::GenObjCCategory(llvm::StringRef cls, llvm::StringRef cat) {
  Out << "objc(cy)" << cls << '@' << cat;
}

void USRGenerator::GenObjCIvar(llvm::StringRef ivar) {
  GenNamedDecl(ivar);
}

void USRGenerator::GenObjCMethod(llvm::StringRef meth, bool isInstanceMethod) {
  Out << (isInstanceMethod ? "(im)" : "(cm)") << meth;
}

void USRGenerator::GenObjCProperty(llvm::StringRef prop) {
  Out << "(py)" << prop;
}

void USRGenerator::GenObjCProtocol(llvm::StringRef prot) {
  Out << "objc(pl)" << prot;
}

//===----------------------------------------------------------------------===//
// API hooks.
//===----------------------------------------------------------------------===//

static inline llvm::StringRef extractUSRSuffix(llvm::StringRef s) {
  return s.startswith("c:") ? s.substr(2) : "";
}

static CXString getDeclCursorUSR(const CXCursor &C) {
  Decl *D = cxcursor::getCursorDecl(C);

  // Don't generate USRs for things with invalid locations.
  if (!D || D->getLocStart().isInvalid())
    return createCXString("");

  // Check if the cursor has 'NoLinkage'.
  if (const NamedDecl *ND = dyn_cast<NamedDecl>(D))
    switch (ND->getLinkage()) {
      case ExternalLinkage:
        // Generate USRs for all entities with external linkage.
        break;
      case NoLinkage:
        // We allow enums, typedefs, and structs that have no linkage to
        // have USRs that are anchored to the file they were defined in
        // (e.g., the header).  This is a little gross, but in principal
        // enums/anonymous structs/etc. defined in a common header file
        // are referred to across multiple translation units.
        if (isa<TagDecl>(ND) || isa<TypedefDecl>(ND) ||
            isa<EnumConstantDecl>(ND) || isa<FieldDecl>(ND))
          break;
        // Fall-through.
      case InternalLinkage:
      case UniqueExternalLinkage:
        return createCXString("");
    }

  StringUSRGenerator SUG(&C);
  SUG->Visit(D);

  if (SUG->ignoreResults())
    return createCXString("");

  // For development testing.
  // assert(SUG.str().size() > 2);

    // Return a copy of the string that must be disposed by the caller.
  return createCXString(SUG.str(), true);
}

extern "C" {

CXString clang_getCursorUSR(CXCursor C) {
  const CXCursorKind &K = clang_getCursorKind(C);

  if (clang_isDeclaration(K))
      return getDeclCursorUSR(C);

  if (K == CXCursor_MacroDefinition) {
    StringUSRGenerator SUG(&C);
    SUG << "macro@"
        << cxcursor::getCursorMacroDefinition(C)->getName()->getNameStart();
    return createCXString(SUG.str(), true);
  }

  return createCXString("");
}

CXString clang_constructUSR_ObjCIvar(const char *name, CXString classUSR) {
  StringUSRGenerator SUG;
  SUG << extractUSRSuffix(clang_getCString(classUSR));
  SUG->GenObjCIvar(name);
  return createCXString(SUG.str(), true);
}

CXString clang_constructUSR_ObjCMethod(const char *name,
                                       unsigned isInstanceMethod,
                                       CXString classUSR) {
  StringUSRGenerator SUG;
  SUG << extractUSRSuffix(clang_getCString(classUSR));
  SUG->GenObjCMethod(name, isInstanceMethod);
  return createCXString(SUG.str(), true);
}

CXString clang_constructUSR_ObjCClass(const char *name) {
  StringUSRGenerator SUG;
  SUG->GenObjCClass(name);
  return createCXString(SUG.str(), true);
}

CXString clang_constructUSR_ObjCProtocol(const char *name) {
  StringUSRGenerator SUG;
  SUG->GenObjCProtocol(name);
  return createCXString(SUG.str(), true);
}

CXString clang_constructUSR_ObjCCategory(const char *class_name,
                                         const char *category_name) {
  StringUSRGenerator SUG;
  SUG->GenObjCCategory(class_name, category_name);
  return createCXString(SUG.str(), true);
}

CXString clang_constructUSR_ObjCProperty(const char *property,
                                         CXString classUSR) {
  StringUSRGenerator SUG;
  SUG << extractUSRSuffix(clang_getCString(classUSR));
  SUG->GenObjCProperty(property);
  return createCXString(SUG.str(), true);
}

} // end extern "C"