//===--- GlobalModuleIndex.h - Global Module Index --------------*- 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 GlobalModuleIndex class, which manages a global index
// containing all of the identifiers with namespace-scope bindings attached to
// them as well as all of the selectors that name methods, across all of the
// modules within a given subdirectory of the module cache. It is used to
// improve the performance of queries such as "does this identifier have any
// top-level bindings in any module?"
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_CLANG_SERIALIZATION_GLOBAL_MODULE_INDEX_H
#define LLVM_CLANG_SERIALIZATION_GLOBAL_MODULE_INDEX_H

#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringRef.h"
#include <utility>

namespace clang {

class DeclarationName;
class DirectoryEntry;
class FileEntry;
class FileManager;

using llvm::SmallVector;
using llvm::SmallVectorImpl;
using llvm::StringRef;

/// \brief A global index for a set of module files, providing information about
/// the top-level identifiers and selectors within those module files.
///
/// The global index is an aid for name lookup into modules, offering a central
/// place where one can look for identifiers or selectors to determine which
/// module files contain a namespace-scope identity with that identifier or
/// a method with that selector, respectively. This allows the client to
/// restrict the search to only those module files known to have a binding for
/// that identifier or selector, improving performance. Moreover, the global
/// module index may know about module files that have not been imported, and
/// can be queried to determine which modules the currently translation could
/// or should load to fix a problem.
class GlobalModuleIndex {
  /// \brief Internal constructor. Use \c readIndex() to read an index.
  explicit GlobalModuleIndex(FileManager &FileMgr);

public:
  /// \brief An error code returned when trying to read an index.
  enum ErrorCode {
    /// \brief No error occurred.
    EC_None,
    /// \brief The index found was out-of-date, meaning that some of the
    /// module files are newer than the index.
    ///
    /// This error code is not actually fatal, because if the index is
    /// up-to-date for any module files, it is 
    EC_OutOfDate,
    /// \brief No index was found.
    EC_NotFound,
    /// \brief Some other process is currently building the index; it is not
    /// available yet.
    EC_Building,
    /// \brief There was an unspecified I/O error reading or writing the index.
    EC_IOError
  };

  /// \brief Read a global index file for the given directory.
  ///
  /// \param FileMgr The file manager to use for reading files.
  ///
  /// \param Path The path to the specific module cache where the module files
  /// for the intended configuration reside.
  ///
  /// \returns A pair containing the global module index (if it exists) and
  /// the error code.
  static std::pair<GlobalModuleIndex *, ErrorCode>
  readIndex(FileManager &FileMgr, StringRef Path);

  /// \brief Retrieve the set of modules that have up-to-date indexes.
  ///
  /// \param ModuleFiles Will be populated with the set of module files that
  /// have been indexed.
  void getKnownModules(SmallVectorImpl<const FileEntry *> &ModuleFiles);

  /// \brief Retrieve the set of module files on which the given module file
  /// directly depends.
  void getModuleDependencies(const FileEntry *ModuleFile,
                             SmallVectorImpl<const FileEntry *> &Dependencies);

  /// \brief Look for all of the module files with a namespace-scope binding
  /// for the given name, e.g., a global function, variable, or type with that
  /// name, or declare a method with the selector.
  ///
  /// \param Name The name or selector to look for.
  ///
  /// \param DeclaringModuleFiles Will be populated with the list of module
  /// files that declare entities with the given name.
  ///
  /// \returns true if any module files were found, false otherwise.
  bool lookupName(DeclarationName Name,
                  SmallVectorImpl<const FileEntry *> &DeclaringModuleFiles);

  /// \brief Write a global index into the given
  ///
  /// \param FileMgr The file manager to use to load module files.
  ///
  /// \param Path The path to the directory containing module files, into
  /// which the global index will be written.
  static ErrorCode writeIndex(FileManager &FileMgr, StringRef Path);
};

}

#endif