//===--- NestedNameSpecifier.h - C++ nested name specifiers -----*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
//  This file defines the NestedNameSpecifier class, which represents
//  a C++ nested-name-specifier.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_CLANG_AST_NESTEDNAMESPECIFIER_H
#define LLVM_CLANG_AST_NESTEDNAMESPECIFIER_H

#include "llvm/ADT/FoldingSet.h"
#include "llvm/ADT/PointerIntPair.h"

namespace llvm {
  class raw_ostream;
}

namespace clang {

class ASTContext;
class NamespaceDecl;
class IdentifierInfo;
class PrintingPolicy;
class Type;

/// \brief Represents a C++ nested name specifier, such as
/// "::std::vector<int>::".
///
/// C++ nested name specifiers are the prefixes to qualified
/// namespaces. For example, "foo::" in "foo::x" is a nested name
/// specifier. Nested name specifiers are made up of a sequence of
/// specifiers, each of which can be a namespace, type, identifier
/// (for dependent names), or the global specifier ('::', must be the
/// first specifier).
class NestedNameSpecifier : public llvm::FoldingSetNode {
  /// \brief The nested name specifier that precedes this nested name
  /// specifier.
  ///
  /// The pointer is the nested-name-specifier that precedes this
  /// one. The integer stores one of the first four values of type
  /// SpecifierKind.
  llvm::PointerIntPair<NestedNameSpecifier *, 2> Prefix;

  /// \brief The last component in the nested name specifier, which
  /// can be an identifier, a declaration, or a type.
  ///
  /// When the pointer is NULL, this specifier represents the global
  /// specifier '::'. Otherwise, the pointer is one of
  /// IdentifierInfo*, Namespace*, or Type*, depending on the kind of
  /// specifier as encoded within the prefix.
  void* Specifier;

public:
  /// \brief The kind of specifier that completes this nested name
  /// specifier.
  enum SpecifierKind {
    /// \brief An identifier, stored as an IdentifierInfo*.
    Identifier = 0,
    /// \brief A namespace, stored as a Namespace*.
    Namespace = 1,
    /// \brief A type, stored as a Type*.
    TypeSpec = 2,
    /// \brief A type that was preceded by the 'template' keyword,
    /// stored as a Type*.
    TypeSpecWithTemplate = 3,
    /// \brief The global specifier '::'. There is no stored value.
    Global = 4
  };

private:
  /// \brief Builds the global specifier.
  NestedNameSpecifier() : Prefix(0, 0), Specifier(0) { }

  /// \brief Copy constructor used internally to clone nested name
  /// specifiers.
  NestedNameSpecifier(const NestedNameSpecifier &Other) 
    : llvm::FoldingSetNode(Other), Prefix(Other.Prefix), 
      Specifier(Other.Specifier) {
  }

  NestedNameSpecifier &operator=(const NestedNameSpecifier &); // do not implement

  /// \brief Either find or insert the given nested name specifier
  /// mockup in the given context.
  static NestedNameSpecifier *FindOrInsert(ASTContext &Context, 
                                           const NestedNameSpecifier &Mockup);

public:
  /// \brief Builds a specifier combining a prefix and an identifier.
  ///
  /// The prefix must be dependent, since nested name specifiers
  /// referencing an identifier are only permitted when the identifier
  /// cannot be resolved.
  static NestedNameSpecifier *Create(ASTContext &Context, 
                                     NestedNameSpecifier *Prefix, 
                                     IdentifierInfo *II);

  /// \brief Builds a nested name specifier that names a namespace.
  static NestedNameSpecifier *Create(ASTContext &Context, 
                                     NestedNameSpecifier *Prefix, 
                                     NamespaceDecl *NS);

  /// \brief Builds a nested name specifier that names a type.
  static NestedNameSpecifier *Create(ASTContext &Context, 
                                     NestedNameSpecifier *Prefix, 
                                     bool Template, Type *T);

  /// \brief Returns the nested name specifier representing the global
  /// scope.
  static NestedNameSpecifier *GlobalSpecifier(ASTContext &Context);

  /// \brief Return the prefix of this nested name specifier.
  ///
  /// The prefix contains all of the parts of the nested name
  /// specifier that preced this current specifier. For example, for a
  /// nested name specifier that represents "foo::bar::", the current
  /// specifier will contain "bar::" and the prefix will contain
  /// "foo::".
  NestedNameSpecifier *getPrefix() const { return Prefix.getPointer(); }

  /// \brief Determine what kind of nested name specifier is stored.
  SpecifierKind getKind() const { 
    if (Specifier == 0)
      return Global;
    return (SpecifierKind)Prefix.getInt(); 
  }

  /// \brief Retrieve the identifier stored in this nested name
  /// specifier.
  IdentifierInfo *getAsIdentifier() const {
    if (Prefix.getInt() == Identifier)
      return (IdentifierInfo *)Specifier;

    return 0;
  }
  
  /// \brief Retrieve the namespace stored in this nested name
  /// specifier.
  NamespaceDecl *getAsNamespace() const {
    if (Prefix.getInt() == Namespace)
      return (NamespaceDecl *)Specifier;

    return 0;
  }

  /// \brief Retrieve the type stored in this nested name specifier.
  Type *getAsType() const {
    if (Prefix.getInt() == TypeSpec || 
        Prefix.getInt() == TypeSpecWithTemplate)
      return (Type *)Specifier;

    return 0;
  }

  /// \brief Whether this nested name specifier refers to a dependent
  /// type or not.
  bool isDependent() const;

  /// \brief Print this nested name specifier to the given output
  /// stream.
  void print(llvm::raw_ostream &OS, const PrintingPolicy &Policy) const;

  void Profile(llvm::FoldingSetNodeID &ID) const {
    ID.AddPointer(Prefix.getOpaqueValue());
    ID.AddPointer(Specifier);
  }

  void Destroy(ASTContext &Context);

  /// \brief Dump the nested name specifier to standard output to aid
  /// in debugging.
  void dump();
};

}

#endif