//===--- ModuleFile.h - Info about a loaded serialized module ---*- C++ -*-===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2015 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See http://swift.org/LICENSE.txt for license information
// See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//

#ifndef SWIFT_SERIALIZATION_MODULEFILE_H
#define SWIFT_SERIALIZATION_MODULEFILE_H

#include "ModuleFormat.h"
#include "swift/AST/Decl.h"
#include "swift/AST/Identifier.h"
#include "swift/AST/TypeLoc.h"
#include "swift/Basic/Fixnum.h"
#include "swift/Basic/LLVM.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/OwningPtr.h"
#include "llvm/ADT/TinyPtrVector.h"
#include "llvm/Bitcode/BitstreamReader.h"

namespace llvm {
  class BitstreamCursor;
  class BitstreamReader;
  class MemoryBuffer;
}

namespace swift {
class Module;
class Pattern;
class ProtocolConformance;

/// Describes whether a loaded module can be used.
enum class ModuleStatus {
  /// The module is valid.
  Valid,

  /// The module contains pointers to source files, which should be loaded
  /// instead.
  ///
  /// This is a bring-up hack and will eventually go away.
  FallBackToTranslationUnit,

  /// The module file format is too new to be used by this version of the
  /// compiler.
  FormatTooNew,

  /// The module file depends on another module that can't be loaded.
  MissingDependency,

  /// The module file is malformed in some way.
  Malformed
};

/// A serialized module, along with the tools to access it.
class ModuleFile {
  /// A reference back to the AST representation of the module.
  Module *ModuleContext;

  /// The module file data.
  llvm::OwningPtr<llvm::MemoryBuffer> InputFile;

  /// The reader attached to InputFile.
  llvm::BitstreamReader InputReader;

  /// The cursor used to lazily load things from the file.
  llvm::BitstreamCursor DeclTypeCursor;

  /// The data blob containing all of the module's identifiers.
  StringRef IdentifierData;

  /// Paths to the source files used to build this module.
  SmallVector<StringRef, 4> SourcePaths;

public:
  /// Represents another module that has been imported as a dependency.
  ///
  /// If \c Mod is null, the dependency hasn't been resolved yet.
  class Dependency {
  public:
    Module *Mod;
    StringRef Name;

    /*implicit*/ Dependency(StringRef name) : Mod(nullptr), Name(name) {}
  };

private:
  /// All modules this module depends on.
  SmallVector<Dependency, 8> Dependencies;

  template <typename T>
  class Serialized {
  private:
    using RawBitOffset = decltype(DeclTypeCursor.GetCurrentBitNo());

    using ImplTy = PointerUnion<T, serialization::BitOffset>;
    ImplTy Value;

  public:
    /*implicit*/ Serialized(serialization::BitOffset offset) : Value(offset) {}

    bool isComplete() const {
      return Value.template is<T>();
    }

    T get() const {
      return Value.template get<T>();
    }

    /*implicit*/ operator T() const {
      return get();
    }

    /*implicit*/ operator serialization::BitOffset() const {
      return Value.template get<serialization::BitOffset>();
    }

    /*implicit*/ operator RawBitOffset() const {
      return Value.template get<serialization::BitOffset>();
    }

    template <typename Derived>
    Serialized &operator=(Derived deserialized) {
      assert(!isComplete() || ImplTy(deserialized) == Value);
      Value = deserialized;
      return *this;
    }
  };

  /// Decls referenced by this module.
  std::vector<Serialized<Decl*>> Decls;

  /// Types referenced by this module.
  std::vector<Serialized<Type>> Types;

  /// Represents an identifier that may or may not have been deserialized yet.
  ///
  /// If \c Offset is non-zero, the identifier has not been loaded yet.
  class SerializedIdentifier {
  public:
    Identifier Ident;
    serialization::BitOffset Offset;

    template <typename IntTy>
    /*implicit*/ SerializedIdentifier(IntTy rawOffset)
      : Offset(rawOffset) {}
  };

  /// Identifiers referenced by this module.
  std::vector<SerializedIdentifier> Identifiers;

  /// All top-level decls in this module.
  llvm::DenseMap<Identifier, TinyPtrVector<ValueDecl *>> TopLevelDecls;

  /// An array of the top-level decl IDs.
  // FIXME: We don't really want to deserialize all of these at once.
  std::vector<serialization::DeclID> RawTopLevelIDs;

  using OperatorKey = std::pair<Identifier, serialization::OperatorKind>;
  friend struct llvm::DenseMapInfo<OperatorKey>;

  /// All the operators in the module.
  llvm::DenseMap<OperatorKey, OperatorDecl *> Operators;

  /// An array of the top-level decl IDs.
  // FIXME: We don't really want to deserialize all of these at once.
  std::vector<serialization::DeclID> RawOperatorIDs;

  /// Whether this module file can be used.
  ModuleStatus Status;

  /// Constructs an new module and validates it.
  ModuleFile(llvm::OwningPtr<llvm::MemoryBuffer> &&input);

  /// Convenience function for module loading.
  void error(ModuleStatus issue = ModuleStatus::Malformed) {
    assert(issue != ModuleStatus::Valid &&
           issue != ModuleStatus::FallBackToTranslationUnit);
    Status = issue;
  }

  /// Recursively reads a pattern from \c DeclTypeCursor.
  ///
  /// If the record at the cursor is not a pattern, returns null.
  Pattern *maybeReadPattern();

  /// Recursively reads a protocol conformance from \c DeclTypeCursor.
  ///
  /// If the record at the cursor is not a protocol conformance, returns
  /// Nothing. Note that a null pointer is a valid conformance value.
  Optional<std::pair<ProtocolDecl *, ProtocolConformance *>>
  maybeReadConformance();

  /// Reads a generic param list from \c DeclTypeCursor.
  ///
  /// If the record at the cursor is not a generic param list, returns null
  /// without moving the cursor.
  GenericParamList *maybeReadGenericParams(DeclContext *DC);

  /// Creates an array of types from the given IDs.
  ///
  /// The returned array is owned by the ASTContext.
  ///
  /// \param rawTypeIDs An array of TypeID values, but using \c uint64_t for
  ///                   compatibility with BitstreamReader.
  /// \param[out] classType If non-null, and one of the type IDs resolves to a
  ///                       class type, this will be set to that type.
  MutableArrayRef<TypeLoc> getTypes(ArrayRef<uint64_t> rawTypeIDs,
                                    Type *classType = nullptr);

  /// Reads members of a DeclContext from \c DeclTypeCursor.
  ///
  /// The returned array is owned by the ASTContext.
  /// Returns Nothing if there is an error.
  ///
  /// Note: this destroys the cursor's position in the stream. Furthermore,
  /// because it reads from the cursor, it is not possible to reset the cursor
  /// after reading. Nothing should ever follow a DECL_CONTEXT block.
  Optional<MutableArrayRef<Decl *>> readMembers();

  /// Returns the decl context with the given ID, deserializing it if needed.
  DeclContext *getDeclContext(serialization::DeclID DID);

  Optional<Decl *> requestDecl(serialization::DeclID);

  Optional<Type> requestType(serialization::TypeID);

  /// Returns the decl with the given ID, deserializing it if needed.
  ///
  /// \param DID The ID for the decl within this module.
  /// \param ForcedContext Optional override for the decl context of certain
  ///                      kinds of decls, used to avoid re-entrant
  ///                      deserialization.
  /// \param DidRecord Optional callback, called at some point after the decl
  ///                  has been recorded in the decl table (but not necessarily
  ///                  completed).
  Decl *getDecl(serialization::DeclID DID,
                Optional<DeclContext *> ForcedContext = {},
                Optional<std::function<void(Decl*)>> DidRecord = {});

  /// Returns the type with the given ID, deserializing it if needed.
  Type getType(serialization::TypeID TID);

  /// Returns the identifier with the given ID, deserializing it if needed.
  Identifier getIdentifier(serialization::IdentifierID IID);

  /// Populates TopLevelIDs for name lookup.
  void buildTopLevelDeclMap();

public:
  /// Loads a module from the given memory buffer.
  ///
  /// \param input A memory buffer containing the serialized module data.
  ///              The created module takes ownership of the buffer, even if
  ///              there's an error in loading.
  /// \param[out] module The loaded module.
  /// \returns Whether the module was successfully loaded, or what went wrong
  ///          if it was not.
  static ModuleStatus load(llvm::OwningPtr<llvm::MemoryBuffer> &&input,
                           llvm::OwningPtr<ModuleFile> &module) {
    module.reset(new ModuleFile(std::move(input)));
    return module->getStatus();
  }

  /// Associates this module file with an AST module.
  ///
  /// Returns false if the association failed.
  bool associateWithModule(Module *module);

  /// Checks whether this module can be used.
  ModuleStatus getStatus() const { return Status; }

  /// Returns paths to the source files that were used to build this module.
  ArrayRef<StringRef> getInputSourcePaths() const {
    assert(getStatus() == ModuleStatus::Valid ||
           getStatus() == ModuleStatus::FallBackToTranslationUnit);
    return SourcePaths;
  }

  /// Returns the list of modules this module depends on.
  ArrayRef<Dependency> getDependencies() const {
    return Dependencies;
  }

  /// Searches the module's top-level decls for the given identifier.
  void lookupValue(Identifier name, SmallVectorImpl<ValueDecl*> &results);

  /// Searches the module's operators for one with the given name and fixity.
  ///
  /// If none is found, returns null.
  OperatorDecl *lookupOperator(Identifier name, DeclKind fixity);
};

} // end namespace swift

namespace llvm {
  template<> struct DenseMapInfo<swift::ModuleFile::OperatorKey> {
    using OperatorKey = swift::ModuleFile::OperatorKey;
    using Identifier = swift::Identifier;
    
    static OperatorKey getEmptyKey() {
      return OperatorKey(Identifier(), swift::serialization::Prefix);
    }
    static OperatorKey getTombstoneKey() {
      return OperatorKey(Identifier(), swift::serialization::Postfix);
    }
    static unsigned getHashValue(OperatorKey Val) {
      using RawPair = std::pair<Identifier, unsigned>;
      return DenseMapInfo<RawPair>::getHashValue(RawPair(Val));
    }
    static bool isEqual(OperatorKey LHS, OperatorKey RHS) {
      return LHS == RHS;
    }
  };
}

#endif